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TDMS Study 88070-03 Pathology Tables

NTP                                        STATISTICAL ANALYSIS OF PRIMARY TUMORS                              REPORT: PEIRPT08
LAB: Battelle Northwest                                        ISOBUTENE                                       DATE: 06/19/97

EXPERIMENT: 88070 TEST: 03                                                                                     TIME: 12:22:01
TEST TYPE:  CHRONIC                             CAGES FROM 0000 TO LAST CAGE                                   PAGE:
CONT: N01-ES-15313                              ROUTE: RESPIRATORY EXPOSURE WHOLE BODY                         NTP C#: C88070
PATHOLOGIST: GRUMBEIN, S.                                                                                      CAS: 115-11-0007
                

Rats(FISCHER344)
-----------------------------
FOR ALL DOSES THE TUMOR RATES IN THE FOLLOWING TISSUES/ORGANS ARE BASED ON NUMBER OF TISSUES EXAMINED.
IN OTHER TISSUES/ORGANS, RATES ARE BASED ON NUMBER OF ANIMALS NECROPSIED.

                                                 ----------------
                                                 Adrenal Gland
                                                 Adrenal Medulla
                                                 Bone Marrow
                                                 Brain
                                                 Clitoral Gland
                                                 Clitoral/Preputial Gland
                                                 Epididymis
                                                 Heart
                                                 Islets, Pancreatic
                                                 Kidney
                                                 Liver
                                                 Lung
                                                 Nose
                                                 Ovary
                                                 Pancreas
                                                 Parathyroid Gland
                                                 Pituitary Gland
                                                 Preputial Gland
                                                 Prostate
                                                 Salivary Glands
                                                 Spleen
                                                 Testes
                                                 Thymus
                                                 Thyroid Gland
                                                 Urinary Bladder
NTP                                        STATISTICAL ANALYSIS OF PRIMARY TUMORS                              REPORT: PEIRPT08   
LAB: Battelle Northwest                                        ISOBUTENE                                       DATE: 06/19/97     
EXPERIMENT: 88070 TEST: 03                                                                                     TIME: 12:22:01     
TEST TYPE:  CHRONIC                             CAGES FROM 0000 TO LAST CAGE                                   PAGE:              
CONT: N01-ES-15313                              ROUTE: RESPIRATORY EXPOSURE WHOLE BODY                         NTP C#: C88070     
PATHOLOGIST: GRUMBEIN, S.                                                                                      CAS: 115-11-0007   



SUMMARY OF STATISTICALLY SIGNIFICANT (P<=.05) RESULTS
IN THE ANALYSIS OF               ISOBUTENE
===============================================================

Male Rats
------------
Organ                                 Morphology
-----                                 ----------
Islets, Pancreatic                     Carcinoma or Adenoma
Skin                                   Basal Cell Adenoma
Thyroid Gland: Follicular Cell         Carcinoma
All Organs                             Leukemia: Lymphocytic, Monocytic, Mononuclear, or Undifferentiated
                                       Malignant Tumors
===============================================================
Female Rats
------------
Organ                                  Morphology
-----                                  ----------
Adrenal Medulla                        Pheochromocytoma Benign
Clitoral/Preputial Gland               Carcinoma or Adenoma
Pituitary Gland: Pars Distalis or UnspeAdenomaSite
All Organs                             Benign Tumors
                                       Malignant and Benign Tumors
===============================================================
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 1
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)        -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Adrenal Medulla                                                                                                                  |
|     Pheochromocytoma Benign                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     23/50 (46%)  18/49 (37%)  16/50 (32%)  23/50 (46%) |3/50 (6%)    3/50 (6%)    10/49 (20%)  4/49 (8%)    |
|POLY-3 ADJUSTED (b)|     60.0%        52.1%        46.2%        56.9%       |7.5%         8.2%         22.7%        10.2%        |
|TERMINAL (d)       |     6/7 (86%)    4/5 (80%)    4/6 (67%)    6/8 (75%)   |3/23 (13%)   2/19 (11%)   7/33 (21%)   2/22 (9%)    |
|FIRST INCIDENCE    |     539          526          496          525         |733 (T)      722          626          650          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.426N     P=0.524      P=0.328N     P=0.432N    |P=0.544      P=0.570      P=0.115      P=0.476      |
|POLY 3             |     P=0.497      P=0.309N     P=0.146N     P=0.476N    |P=0.589      P=0.625      P=0.050      P=0.493      |
|POLY 1.5           |     P=0.410      P=0.270N     P=0.124N     P=0.515N    |P=0.571      P=0.636      P=0.042 *    P=0.489      |
|POLY 6             |     P=0.544N     P=0.405N     P=0.205N     P=0.447N    |P=0.588N     P=0.611      P=0.063      P=0.493      |
|LOGISTIC REGRESSION|     P=0.506N     P=0.360N     P=0.205N     P=0.401N    |P=0.554      P=0.571      P=0.055      P=0.474      |
|COCH-ARM / FISHERS |     P=0.307      P=0.232N     P=0.109N     P=0.579N    |P=0.545      P=0.661N     P=0.033 *    P=0.489      |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Adrenal Medulla                                                                                                                  |
|     Pheochromocytoma Malignant                                                                                                  |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/50 (0%)    1/49 (2%)    1/50 (2%)    3/50 (6%)   |0/50 (0%)    0/50 (0%)    0/49 (0%)    0/49 (0%)    |
|POLY-3 ADJUSTED (b)|     0.0%         3.2%         3.2%         8.3%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     1/8 (13%)   |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     ---          664          453          631         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.118      P=0.471      P=0.500      P=0.142     |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.085      P=0.485      P=0.489      P=0.132     |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.080      P=0.490      P=0.494      P=0.127     |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.093      P=0.476      P=0.480      P=0.137     |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.075      P=0.477      P=0.562      P=0.134     |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.072      P=0.495      P=0.500      P=0.121     |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 2
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Adrenal Medulla                                                                                                                  |
|     Pheochromocytoma: Benign, Complex, Malignant, NOS                                                                           |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     23/50 (46%)  18/49 (37%)  17/50 (34%)  24/50 (48%) |4/50 (8%)    3/50 (6%)    10/49 (20%)  4/49 (8%)    |
|POLY-3 ADJUSTED (b)|     60.0%        52.1%        48.0%        59.1%       |10.0%        8.2%         22.7%        10.2%        |
|TERMINAL (d)       |     6/7 (86%)    4/5 (80%)    4/6 (67%)    6/8 (75%)   |4/23 (17%)   2/19 (11%)   7/33 (21%)   2/22 (9%)    |
|FIRST INCIDENCE    |     539          526          453          525         |733 (T)      722          626          650          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.493N     P=0.524      P=0.397N     P=0.498N    |P=0.559N     P=0.608N     P=0.206      P=0.620      |
|POLY 3             |     P=0.399      P=0.309N     P=0.187N     P=0.564N    |P=0.516N     P=0.545N     P=0.101      P=0.638      |
|POLY 1.5           |     P=0.323      P=0.270N     P=0.166N     P=0.580     |P=0.531N     P=0.532N     P=0.086      P=0.633      |
|POLY 6             |     P=0.515      P=0.405N     P=0.245N     P=0.539N    |P=0.507N     P=0.563N     P=0.124      P=0.639      |
|LOGISTIC REGRESSION|     P=0.512      P=0.360N     P=0.262N     P=0.481N    |P=0.549N     P=0.612N     P=0.110      P=0.617      |
|COCH-ARM / FISHERS |     P=0.237      P=0.232N     P=0.154N     P=0.500     |P=0.554N     P=0.500N     P=0.068      P=0.631      |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Brain                                                                                                                            |
|     Oligodendroglioma, Glioma, or Astrocytoma                                                                                   |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     2/50 (4%)    0/50 (0%)    0/50 (0%)    0/50 (0%)   |0/50 (0%)    0/50 (0%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     5.8%         0.0%         0.0%         0.0%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     379          ---          ---          ---         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.296N     P=0.253N     P=0.275N     P=0.230N    |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.272N     P=0.263N     P=0.263N     P=0.229N    |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.287N     P=0.252N     P=0.251N     P=0.232N    |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.249N     P=0.282N     P=0.282N     P=0.229N    |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.414N     P=0.149N     P=0.184N     P=0.445N    |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.308N     P=0.247N     P=0.247N     P=0.247N    |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 3
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Clitoral/Preputial Gland                                                                                                         |
|     Adenoma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     4/50 (8%)    2/50 (4%)    2/49 (4%)    1/50 (2%)   |3/50 (6%)    3/49 (6%)    6/47 (13%)   0/48 (0%)    |
|POLY-3 ADJUSTED (b)|     11.4%        6.4%         6.4%         2.8%        |7.5%         8.4%         14.2%        0.0%         |
|TERMINAL (d)       |     1/7 (14%)    1/5 (20%)    0/6 (0%)     0/8 (0%)    |3/23 (13%)   3/18 (17%)   4/31 (13%)   0/22 (0%)    |
|FIRST INCIDENCE    |     467          583          628          700         |733 (T)      733 (T)      620          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.156N     P=0.416N     P=0.428N     P=0.167N    |P=0.072N     P=0.547      P=0.388      P=0.127N     |
|POLY 3             |     P=0.170N     P=0.386N     P=0.390N     P=0.167N    |P=0.080N     P=0.611      P=0.269      P=0.129N     |
|POLY 1.5           |     P=0.185N     P=0.364N     P=0.370N     P=0.171N    |P=0.082N     P=0.624      P=0.245      P=0.129N     |
|POLY 6             |     P=0.154N     P=0.423N     P=0.420N     P=0.166N    |P=0.082N     P=0.593      P=0.299      P=0.132N     |
|LOGISTIC REGRESSION|     P=0.191N     P=0.344N     P=0.346N     P=0.187N    |P=0.084N     P=0.547      P=0.281      (e)          |
|COCH-ARM / FISHERS |     P=0.207N     P=0.339N     P=0.349N     P=0.181N    |P=0.086N     P=0.651      P=0.213      P=0.129N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Clitoral/Preputial Gland                                                                                                         |
|     Carcinoma                                                                                                                   |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    3/50 (6%)    2/49 (4%)    3/50 (6%)   |1/50 (2%)    0/49 (0%)    5/47 (11%)   1/48 (2%)    |
|POLY-3 ADJUSTED (b)|     2.9%         9.4%         6.3%         8.2%        |2.5%         0.0%         12.0%        2.7%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/18 (0%)    4/31 (13%)   1/22 (5%)    |
|FIRST INCIDENCE    |     560          526          520          540         |664          ---          720          733 (T)      |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.455      P=0.225      P=0.471      P=0.339     |P=0.633N     P=0.525N     P=0.177      P=0.752      |
|POLY 3             |     P=0.431      P=0.278      P=0.474      P=0.331     |P=0.622N     P=0.523N     P=0.109      P=0.746      |
|POLY 1.5           |     P=0.411      P=0.290      P=0.483      P=0.321     |P=0.627N     P=0.517N     P=0.100      P=0.747      |
|POLY 6             |     P=0.455      P=0.260      P=0.461      P=0.340     |P=0.625N     P=0.532N     P=0.119      P=0.740      |
|LOGISTIC REGRESSION|     P=0.352      P=0.303      P=0.538      P=0.279     |P=0.640      P=0.510N     P=0.125      P=0.748      |
|COCH-ARM / FISHERS |     P=0.381      P=0.309      P=0.492      P=0.309     |P=0.636N     P=0.505N     P=0.088      P=0.742      |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 4
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Clitoral/Preputial Gland                                                                                                         |
|     Carcinoma or Adenoma                                                                                                        |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     5/50 (10%)   5/50 (10%)   4/49 (8%)    4/50 (8%)   |4/50 (8%)    3/49 (6%)    11/47 (23%)  1/48 (2%)    |
|POLY-3 ADJUSTED (b)|     14.1%        15.5%        12.4%        10.9%       |10.0%        8.4%         26.1%        2.7%         |
|TERMINAL (d)       |     1/7 (14%)    1/5 (20%)    0/6 (0%)     0/8 (0%)    |3/23 (13%)   3/18 (17%)   8/31 (26%)   1/22 (5%)    |
|FIRST INCIDENCE    |     467          526          520          540         |664          733 (T)      620          733 (T)      |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.335N     P=0.502      P=0.590N     P=0.457N    |P=0.113N     P=0.625N     P=0.130      P=0.192N     |
|POLY 3             |     P=0.383N     P=0.572      P=0.562N     P=0.477N    |P=0.115N     P=0.564N     P=0.051      P=0.199N     |
|POLY 1.5           |     P=0.407N     P=0.597      P=0.540N     P=0.484N    |P=0.118N     P=0.547N     P=0.043 *    P=0.197N     |
|POLY 6             |     P=0.359N     P=0.531      P=0.593N     P=0.476N    |P=0.118N     P=0.588N     P=0.063      P=0.206N     |
|LOGISTIC REGRESSION|     P=0.444N     P=0.624      P=0.483N     P=0.529N    |P=0.132N     P=0.607N     P=0.062      P=0.210N     |
|COCH-ARM / FISHERS |     P=0.444N     P=0.630N     P=0.513N     P=0.500N    |P=0.132N     P=0.511N     P=0.034 *    P=0.194N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Islets, Pancreatic                                                                                                               |
|     Adenoma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     4/50 (8%)    0/49 (0%)    1/50 (2%)    4/50 (8%)   |1/50 (2%)    0/50 (0%)    0/49 (0%)    0/49 (0%)    |
|POLY-3 ADJUSTED (b)|     11.8%        0.0%         3.2%         10.8%       |2.5%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     1/7 (14%)    0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     666          ---          714          618         |726          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.306      P=0.123N     P=0.246N     P=0.608N    |P=0.549N     P=0.547N     P=0.436N     P=0.508N     |
|POLY 3             |     P=0.276      P=0.071N     P=0.203N     P=0.599N    |P=0.548N     P=0.517N     P=0.484N     P=0.505N     |
|POLY 1.5           |     P=0.249      P=0.067N     P=0.191N     P=0.617N    |P=0.548N     P=0.512N     P=0.492N     P=0.505N     |
|POLY 6             |     P=0.324      P=0.079N     P=0.225N     P=0.580N    |P=0.549N     P=0.523N     P=0.476N     P=0.507N     |
|LOGISTIC REGRESSION|     P=0.293      P=0.092N     P=0.238N     P=0.600N    |P=0.554N     P=0.533N     P=0.465N     P=0.515N     |
|COCH-ARM / FISHERS |     P=0.218      P=0.061N     P=0.181N     P=0.643N    |P=0.550N     P=0.500N     P=0.505N     P=0.505N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 5
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Islets, Pancreatic                                                                                                               |
|     Carcinoma                                                                                                                   |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     4/50 (8%)    2/49 (4%)    1/50 (2%)    4/50 (8%)   |0/50 (0%)    0/50 (0%)    0/49 (0%)    0/49 (0%)    |
|POLY-3 ADJUSTED (b)|     11.6%        6.4%         3.2%         10.8%       |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     1/7 (14%)    0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     477          664          620          534         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.490      P=0.473N     P=0.257N     P=0.610N    |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.451      P=0.383N     P=0.206N     P=0.609N    |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.422      P=0.367N     P=0.193N     P=0.622N    |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.491      P=0.413N     P=0.227N     P=0.598N    |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.433      P=0.378N     P=0.191N     P=0.632N    |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.385      P=0.349N     P=0.181N     P=0.643N    |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Islets, Pancreatic                                                                                                               |
|     Carcinoma or Adenoma                                                                                                        |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     8/50 (16%)   2/49 (4%)    2/50 (4%)    8/50 (16%)  |1/50 (2%)    0/50 (0%)    0/49 (0%)    0/49 (0%)    |
|POLY-3 ADJUSTED (b)|     22.8%        6.4%         6.4%         21.0%       |2.5%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     2/7 (29%)    0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     477          664          620          534         |726          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.287      P=0.131N     P=0.101N     P=0.556N    |P=0.549N     P=0.547N     P=0.436N     P=0.508N     |
|POLY 3             |     P=0.238      P=0.060N     P=0.058N     P=0.540N    |P=0.548N     P=0.517N     P=0.484N     P=0.505N     |
|POLY 1.5           |     P=0.201      P=0.055N     P=0.052N     P=0.568N    |P=0.548N     P=0.512N     P=0.492N     P=0.505N     |
|POLY 6             |     P=0.306      P=0.071N     P=0.071N     P=0.506N    |P=0.549N     P=0.523N     P=0.476N     P=0.507N     |
|LOGISTIC REGRESSION|     P=0.237      P=0.070N     P=0.068N     P=0.557N    |P=0.554N     P=0.533N     P=0.465N     P=0.515N     |
|COCH-ARM / FISHERS |     P=0.163      P=0.049N*    P=0.046N*    P=0.607N    |P=0.550N     P=0.500N     P=0.505N     P=0.505N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 6
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Kidney: Renal Tubule                                                                                                             |
|     Adenoma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     2/50 (4%)    1/50 (2%)    0/50 (0%)    2/50 (4%)   |0/50 (0%)    0/50 (0%)    0/49 (0%)    0/49 (0%)    |
|POLY-3 ADJUSTED (b)|     6.0%         3.2%         0.0%         5.5%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     1/8 (13%)   |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     719          684          ---          610         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.563      P=0.682N     P=0.353N     P=0.691N    |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.525      P=0.527N     P=0.255N     P=0.669N    |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.505      P=0.516N     P=0.246N     P=0.678N    |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.552      P=0.547N     P=0.268N     P=0.660N    |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.550      P=0.606N     P=0.280N     P=0.668N    |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.479      P=0.500N     P=0.247N     P=0.691N    |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Kidney: Renal Tubule                                                                                                             |
|     Carcinoma                                                                                                                   |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/50 (0%)    0/50 (0%)    2/50 (4%)    0/50 (0%)   |1/50 (2%)    0/50 (0%)    0/49 (0%)    0/49 (0%)    |
|POLY-3 ADJUSTED (b)|     0.0%         0.0%         6.4%         0.0%        |2.5%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     1/6 (17%)    0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     ---          ---          701          ---         |552          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.603N     (e)          P=0.214      (e)         |P=0.543N     P=0.519N     P=0.482N     P=0.500N     |
|POLY 3             |     P=0.621N     (e)          P=0.219      (e)         |P=0.546N     P=0.519N     P=0.487N     P=0.507N     |
|POLY 1.5           |     P=0.633N     (e)          P=0.227      (e)         |P=0.546N     P=0.513N     P=0.494N     P=0.507N     |
|POLY 6             |     P=0.608N     (e)          P=0.206      (e)         |P=0.545N     P=0.528N     P=0.480N     P=0.511N     |
|LOGISTIC REGRESSION|     P=0.602N     (e)          P=0.186      (e)         |P=0.540N     P=0.448N     P=0.605N     P=0.468N     |
|COCH-ARM / FISHERS |     P=0.652N     (e)          P=0.247      (e)         |P=0.550N     P=0.500N     P=0.505N     P=0.505N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 7
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Kidney: Renal Tubule                                                                                                             |
|     Carcinoma or Adenoma                                                                                                        |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     2/50 (4%)    1/50 (2%)    2/50 (4%)    2/50 (4%)   |1/50 (2%)    0/50 (0%)    0/49 (0%)    0/49 (0%)    |
|POLY-3 ADJUSTED (b)|     6.0%         3.2%         6.4%         5.5%        |2.5%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     1/6 (17%)    1/8 (13%)   |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     719          684          701          610         |552          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.632      P=0.682N     P=0.578      P=0.691N    |P=0.543N     P=0.519N     P=0.482N     P=0.500N     |
|POLY 3             |     P=0.602      P=0.527N     P=0.668      P=0.669N    |P=0.546N     P=0.519N     P=0.487N     P=0.507N     |
|POLY 1.5           |     P=0.577      P=0.516N     P=0.680      P=0.678N    |P=0.546N     P=0.513N     P=0.494N     P=0.507N     |
|POLY 6             |     P=0.632      P=0.547N     P=0.648      P=0.660N    |P=0.545N     P=0.528N     P=0.480N     P=0.511N     |
|LOGISTIC REGRESSION|     P=0.626      P=0.606N     P=0.622      P=0.668N    |P=0.540N     P=0.448N     P=0.605N     P=0.468N     |
|COCH-ARM / FISHERS |     P=0.542      P=0.500N     P=0.691N     P=0.691N    |P=0.550N     P=0.500N     P=0.505N     P=0.505N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Lung                                                                                                                             |
|     Alveolar/Bronchiolar Adenoma                                                                                                |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     2/50 (4%)    2/50 (4%)    2/50 (4%)    0/50 (0%)   |2/50 (4%)    1/50 (2%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     5.9%         6.3%         6.3%         0.0%        |5.0%         2.7%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |2/23 (9%)    1/19 (5%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     580          579          607          ---         |733 (T)      733 (T)      ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.126N     P=0.604      P=0.592      P=0.234N    |P=0.205N     P=0.567N     P=0.162N     P=0.247N     |
|POLY 3             |     P=0.134N     P=0.669      P=0.669      P=0.225N    |P=0.215N     P=0.529N     P=0.215N     P=0.240N     |
|POLY 1.5           |     P=0.143N     P=0.679      P=0.680      P=0.229N    |P=0.213N     P=0.521N     P=0.224N     P=0.240N     |
|POLY 6             |     P=0.125N     P=0.653      P=0.652      P=0.222N    |P=0.218N     P=0.541N     P=0.206N     P=0.243N     |
|LOGISTIC REGRESSION|     P=0.144N     P=0.679      P=0.674      P=0.230N    |P=0.205N     P=0.567N     (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.157N     P=0.691N     P=0.691N     P=0.247N    |P=0.212N     P=0.500N     P=0.247N     P=0.247N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 8
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Lung                                                                                                                             |
|     Alveolar/Bronchiolar Carcinoma                                                                                              |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/50 (0%)    2/50 (4%)    1/50 (2%)    1/50 (2%)   |0/50 (0%)    0/50 (0%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     0.0%         6.4%         3.2%         2.8%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     1/5 (20%)    0/6 (0%)     1/8 (13%)   |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     ---          692          706          733 (T)     |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.657N     P=0.169      P=0.464      P=0.527     |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.681      P=0.219      P=0.485      P=0.513     |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.670      P=0.227      P=0.492      P=0.508     |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.683N     P=0.206      P=0.474      P=0.518     |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.645N     P=0.162      P=0.458      P=0.527     |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.654      P=0.247      P=0.500      P=0.500     |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Lung                                                                                                                             |
|     Alveolar/Bronchiolar Carcinoma or Alveolar/Bronchiolar                                                                      |
|     Adenoma                                                                                                                     |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     2/50 (4%)    4/50 (8%)    3/50 (6%)    1/50 (2%)   |2/50 (4%)    1/50 (2%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     5.9%         12.6%        9.5%         2.8%        |5.0%         2.7%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     1/5 (20%)    0/6 (0%)     1/8 (13%)   |2/23 (9%)    1/19 (5%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     580          579          607          733 (T)     |733 (T)      733 (T)      ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.175N     P=0.226      P=0.387      P=0.479N    |P=0.205N     P=0.567N     P=0.162N     P=0.247N     |
|POLY 3             |     P=0.196N     P=0.301      P=0.466      P=0.482N    |P=0.215N     P=0.529N     P=0.215N     P=0.240N     |
|POLY 1.5           |     P=0.209N     P=0.316      P=0.482      P=0.488N    |P=0.213N     P=0.521N     P=0.224N     P=0.240N     |
|POLY 6             |     P=0.184N     P=0.277      P=0.444      P=0.481N    |P=0.218N     P=0.541N     P=0.206N     P=0.243N     |
|LOGISTIC REGRESSION|     P=0.179N     P=0.284      P=0.457      P=0.472N    |P=0.205N     P=0.567N     (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.230N     P=0.339      P=0.500      P=0.500N    |P=0.212N     P=0.500N     P=0.247N     P=0.247N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 9
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Mammary Gland                                                                                                                    |
|     Carcinoma                                                                                                                   |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    1/50 (2%)    0/50 (0%)    0/50 (0%)   |2/50 (4%)    2/50 (4%)    4/50 (8%)    4/50 (8%)    |
|POLY-3 ADJUSTED (b)|     3.0%         3.2%         0.0%         0.0%        |4.9%         5.5%         9.1%         10.0%        |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |1/23 (4%)    2/19 (11%)   3/33 (9%)    2/22 (9%)    |
|FIRST INCIDENCE    |     681          614          ---          ---         |488          733 (T)      701          597          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.322N     P=0.703      P=0.576N     P=0.500N    |P=0.258      P=0.636      P=0.470      P=0.332      |
|POLY 3             |     P=0.331N     P=0.746      P=0.517N     P=0.488N    |P=0.284      P=0.658      P=0.377      P=0.331      |
|POLY 1.5           |     P=0.339N     P=0.752      P=0.509N     P=0.492N    |P=0.280      P=0.669      P=0.361      P=0.331      |
|POLY 6             |     P=0.321N     P=0.735      P=0.531N     P=0.485N    |P=0.285      P=0.643      P=0.395      P=0.327      |
|LOGISTIC REGRESSION|     P=0.333N     P=0.749      P=0.531N     P=0.484N    |P=0.272      P=0.681      P=0.345      P=0.340      |
|COCH-ARM / FISHERS |     P=0.348N     P=0.753N     P=0.500N     P=0.500N    |P=0.272      P=0.691N     P=0.339      P=0.339      |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Mammary Gland                                                                                                                    |
|     Carcinoma or Adenoma                                                                                                        |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    1/50 (2%)    0/50 (0%)    0/50 (0%)   |3/50 (6%)    3/50 (6%)    5/50 (10%)   4/50 (8%)    |
|POLY-3 ADJUSTED (b)|     3.0%         3.2%         0.0%         0.0%        |7.4%         8.2%         11.3%        10.0%        |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |2/23 (9%)    3/19 (16%)   4/33 (12%)   2/22 (9%)    |
|FIRST INCIDENCE    |     681          614          ---          ---         |488          733 (T)      701          597          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.322N     P=0.703      P=0.576N     P=0.500N    |P=0.449      P=0.583      P=0.527      P=0.488      |
|POLY 3             |     P=0.331N     P=0.746      P=0.517N     P=0.488N    |P=0.478      P=0.616      P=0.403      P=0.494      |
|POLY 1.5           |     P=0.339N     P=0.752      P=0.509N     P=0.492N    |P=0.472      P=0.630      P=0.385      P=0.494      |
|POLY 6             |     P=0.321N     P=0.735      P=0.531N     P=0.485N    |P=0.480      P=0.597      P=0.426      P=0.490      |
|LOGISTIC REGRESSION|     P=0.333N     P=0.749      P=0.531N     P=0.484N    |P=0.464      P=0.627      P=0.393      P=0.499      |
|COCH-ARM / FISHERS |     P=0.348N     P=0.753N     P=0.500N     P=0.500N    |P=0.462      P=0.661N     P=0.357      P=0.500      |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 10
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Mammary Gland                                                                                                                    |
|     Fibroadenoma                                                                                                                |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    0/50 (0%)    1/50 (2%)    1/50 (2%)   |22/50 (44%)  19/50 (38%)  30/50 (60%)  27/50 (54%)  |
|POLY-3 ADJUSTED (b)|     3.0%         0.0%         3.2%         2.8%        |52.9%        46.6%        65.6%        62.9%        |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     1/6 (17%)    0/8 (0%)    |14/23 (61%)  8/19 (42%)   23/33 (70%)  16/22 (73%)  |
|FIRST INCIDENCE    |     719          ---          733 (T)      664         |581          440          560          511          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.626      P=0.638N     P=0.686      P=0.754N    |P=0.118      P=0.542      P=0.563      P=0.170      |
|POLY 3             |     P=0.607      P=0.516N     P=0.744      P=0.746N    |P=0.144      P=0.357N     P=0.152      P=0.230      |
|POLY 1.5           |     P=0.589      P=0.509N     P=0.752      P=0.751N    |P=0.136      P=0.367N     P=0.117      P=0.214      |
|POLY 6             |     P=0.630      P=0.529N     P=0.731      P=0.741N    |P=0.138      P=0.353N     P=0.199      P=0.230      |
|LOGISTIC REGRESSION|     P=0.616      P=0.576N     P=0.723      P=0.745N    |P=0.129      P=0.456N     P=0.211      P=0.179      |
|COCH-ARM / FISHERS |     P=0.563      P=0.500N     P=0.753N     P=0.753N    |P=0.131      P=0.342N     P=0.080      P=0.212      |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Mammary Gland                                                                                                                    |
|     Fibroma, Fibroadenoma or Adenoma                                                                                            |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    0/50 (0%)    1/50 (2%)    1/50 (2%)   |22/50 (44%)  20/50 (40%)  31/50 (62%)  27/50 (54%)  |
|POLY-3 ADJUSTED (b)|     3.0%         0.0%         3.2%         2.8%        |52.9%        49.1%        67.8%        62.9%        |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     1/6 (17%)    0/8 (0%)    |14/23 (61%)  9/19 (47%)   24/33 (73%)  16/22 (73%)  |
|FIRST INCIDENCE    |     719          ---          733 (T)      664         |581          440          560          511          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.626      P=0.638N     P=0.686      P=0.754N    |P=0.140      P=0.462      P=0.500      P=0.170      |
|POLY 3             |     P=0.607      P=0.516N     P=0.744      P=0.746N    |P=0.178      P=0.446N     P=0.104      P=0.230      |
|POLY 1.5           |     P=0.589      P=0.509N     P=0.752      P=0.751N    |P=0.168      P=0.453N     P=0.079      P=0.214      |
|POLY 6             |     P=0.630      P=0.529N     P=0.731      P=0.741N    |P=0.172      P=0.446N     P=0.140      P=0.230      |
|LOGISTIC REGRESSION|     P=0.616      P=0.576N     P=0.723      P=0.745N    |P=0.158      P=0.547N     P=0.156      P=0.179      |
|COCH-ARM / FISHERS |     P=0.563      P=0.500N     P=0.753N     P=0.753N    |P=0.159      P=0.420N     P=0.054      P=0.212      |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 11
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Mammary Gland                                                                                                                    |
|     Fibroma, Fibroadenoma, Carcinoma, or Adenoma                                                                                |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     2/50 (4%)    1/50 (2%)    1/50 (2%)    1/50 (2%)   |23/50 (46%)  21/50 (42%)  32/50 (64%)  30/50 (60%)  |
|POLY-3 ADJUSTED (b)|     5.9%         3.2%         3.2%         2.8%        |54.4%        51.5%        69.8%        68.5%        |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     1/6 (17%)    0/8 (0%)    |14/23 (61%)  10/19 (53%)  24/33 (73%)  17/22 (77%)  |
|FIRST INCIDENCE    |     681          614          733 (T)      664         |488          440          560          511          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.442N     P=0.636N     P=0.619N     P=0.493N    |P=0.068      P=0.453      P=0.508      P=0.102      |
|POLY 3             |     P=0.478N     P=0.526N     P=0.531N     P=0.477N    |P=0.081      P=0.481N     P=0.092      P=0.117      |
|POLY 1.5           |     P=0.496N     P=0.515N     P=0.516N     P=0.485N    |P=0.072      P=0.474N     P=0.072      P=0.108      |
|POLY 6             |     P=0.455N     P=0.546N     P=0.556N     P=0.470N    |P=0.085      P=0.497N     P=0.120      P=0.121      |
|LOGISTIC REGRESSION|     P=0.456N     P=0.548N     P=0.576N     P=0.470N    |P=0.067      P=0.541N     P=0.143      P=0.094      |
|COCH-ARM / FISHERS |     P=0.521N     P=0.500N     P=0.500N     P=0.500N    |P=0.070      P=0.420N     P=0.054      P=0.115      |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Pancreas                                                                                                                         |
|     Adenoma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     2/50 (4%)    1/50 (2%)    0/50 (0%)    0/50 (0%)   |0/50 (0%)    0/50 (0%)    0/49 (0%)    0/49 (0%)    |
|POLY-3 ADJUSTED (b)|     5.9%         3.2%         0.0%         0.0%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     1/7 (14%)    0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     691          684          ---          ---         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.182N     P=0.608N     P=0.273N     P=0.232N    |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.190N     P=0.528N     P=0.255N     P=0.222N    |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.200N     P=0.516N     P=0.246N     P=0.228N    |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.177N     P=0.548N     P=0.269N     P=0.218N    |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.182N     P=0.596N     P=0.282N     P=0.222N    |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.212N     P=0.500N     P=0.247N     P=0.247N    |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 12
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Pituitary Gland: Pars Distalis or Unspecified Site                                                                               |
|     Adenoma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     43/50 (86%)  40/49 (82%)  40/50 (80%)  41/49 (84%) |39/50 (78%)  33/49 (67%)  37/50 (74%)  36/49 (73%)  |
|POLY-3 ADJUSTED (b)|     93.0%        89.2%        87.1%        86.9%       |87.8%        77.1%        76.5%        83.7%        |
|TERMINAL (d)       |     6/7 (86%)    3/5 (60%)    5/6 (83%)    6/8 (75%)   |21/23 (91%)  13/18 (72%)  25/33 (76%)  21/22 (96%)  |
|FIRST INCIDENCE    |     476          460          453          490         |496          455          399          469          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.155N     P=0.289      P=0.355      P=0.297N    |P=0.543N     P=0.509      P=0.030N*    P=0.484N     |
|POLY 3             |     P=0.280N     P=0.377N     P=0.240N     P=0.233N    |P=0.492      P=0.126N     P=0.111N     P=0.391N     |
|POLY 1.5           |     P=0.385N     P=0.386N     P=0.260N     P=0.321N    |P=0.525      P=0.160N     P=0.200N     P=0.399N     |
|POLY 6             |     P=0.210N     P=0.378N     P=0.244N     P=0.179N    |P=0.401      P=0.104N     P=0.060N     P=0.462N     |
|LOGISTIC REGRESSION|     P=0.442N     P=0.467N     P=0.374N     P=0.404N    |P=0.495N     P=0.308N     P=0.201N     P=0.299N     |
|COCH-ARM / FISHERS |     P=0.566      P=0.376N     P=0.298N     P=0.483N    |P=0.555      P=0.168N     P=0.408N     P=0.385N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Basal Cell Adenoma                                                                                                          |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/50 (0%)    0/50 (0%)    0/50 (0%)    2/50 (4%)   |0/50 (0%)    0/50 (0%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     0.0%         0.0%         0.0%         5.5%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     ---          ---          ---          688         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.074      (e)          (e)          P=0.266     |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.048 *    (e)          (e)          P=0.253     |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.045 *    (e)          (e)          P=0.247     |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.052      (e)          (e)          P=0.260     |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.061      (e)          (e)          P=0.255     |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.042 *    (e)          (e)          P=0.247     |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 13
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Basal Cell Carcinoma                                                                                                        |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/50 (0%)    2/50 (4%)    0/50 (0%)    0/50 (0%)   |0/50 (0%)    0/50 (0%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     0.0%         6.4%         0.0%         0.0%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     1/5 (20%)    0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     ---          607          ---          ---         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.341N     P=0.193      (e)          (e)         |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.382N     P=0.221      (e)          (e)         |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.386N     P=0.228      (e)          (e)         |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.380N     P=0.210      (e)          (e)         |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.362N     P=0.207      (e)          (e)         |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.390N     P=0.247      (e)          (e)         |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Basal Cell Carcinoma, Basal Cell Adenoma, Basosquamous                                                                      |
|     Tumor (benign, malignant or NOS), or Trichoepithelioma                                                                      |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/50 (0%)    2/50 (4%)    0/50 (0%)    2/50 (4%)   |0/50 (0%)    0/50 (0%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     0.0%         6.4%         0.0%         5.5%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     1/5 (20%)    0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     ---          607          ---          688         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.385      P=0.193      (e)          P=0.266     |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.314      P=0.221      (e)          P=0.253     |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.303      P=0.228      (e)          P=0.247     |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.326      P=0.210      (e)          P=0.260     |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.347      P=0.207      (e)          P=0.255     |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.290      P=0.247      (e)          P=0.247     |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 14
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Basal or Sq. Cell Carcinoma, Carcinoma, Basosq. Tumor                                                                       |
|     (M or B), Basal Cell Adenoma, Adenoma, Papilloma, Sq Papilloma, Keratoacanthoma, Trichoepitheliom                           |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     3/50 (6%)    7/50 (14%)   3/50 (6%)    7/50 (14%)  |1/50 (2%)    0/50 (0%)    2/50 (4%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     8.8%         21.5%        9.5%         19.2%       |2.5%         0.0%         4.5%         0.0%         |
|TERMINAL (d)       |     1/7 (14%)    2/5 (40%)    1/6 (17%)    3/8 (38%)   |1/23 (4%)    0/19 (0%)    1/33 (3%)    0/22 (0%)    |
|FIRST INCIDENCE    |     621          552          574          688         |733 (T)      ---          651          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.402      P=0.092      P=0.560      P=0.187     |P=0.437N     P=0.538N     P=0.601      P=0.509N     |
|POLY 3             |     P=0.275      P=0.128      P=0.631      P=0.176     |P=0.423N     P=0.517N     P=0.537      P=0.503N     |
|POLY 1.5           |     P=0.257      P=0.140      P=0.646      P=0.170     |P=0.427N     P=0.512N     P=0.522      P=0.502N     |
|POLY 6             |     P=0.292      P=0.111      P=0.608      P=0.177     |P=0.423N     P=0.523N     P=0.554      P=0.506N     |
|LOGISTIC REGRESSION|     P=0.350      P=0.109      P=0.614      P=0.180     |P=0.436N     (e)          P=0.534      (e)          |
|COCH-ARM / FISHERS |     P=0.230      P=0.159      P=0.661N     P=0.159     |P=0.437N     P=0.500N     P=0.500      P=0.500N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Fibroma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    0/50 (0%)    2/50 (4%)    0/50 (0%)   |1/50 (2%)    0/50 (0%)    1/50 (2%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     3.0%         0.0%         6.4%         0.0%        |2.5%         0.0%         2.3%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |1/23 (4%)    0/19 (0%)    1/33 (3%)    0/22 (0%)    |
|FIRST INCIDENCE    |     648          ---          678          ---         |733 (T)      ---          733 (T)      ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.404N     P=0.535N     P=0.421      P=0.464N    |P=0.483N     P=0.538N     P=0.679N     P=0.509N     |
|POLY 3             |     P=0.396N     P=0.518N     P=0.472      P=0.488N    |P=0.469N     P=0.517N     P=0.738N     P=0.503N     |
|POLY 1.5           |     P=0.412N     P=0.510N     P=0.485      P=0.493N    |P=0.472N     P=0.512N     P=0.747N     P=0.502N     |
|POLY 6             |     P=0.377N     P=0.532N     P=0.452      P=0.487N    |P=0.469N     P=0.523N     P=0.728N     P=0.506N     |
|LOGISTIC REGRESSION|     P=0.393N     P=0.514N     P=0.449      P=0.495N    |P=0.483N     (e)          P=0.679N     (e)          |
|COCH-ARM / FISHERS |     P=0.437N     P=0.500N     P=0.500      P=0.500N    |P=0.478N     P=0.500N     P=0.753N     P=0.500N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 15
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Fibroma, Fibrosarcoma, Sarcoma, Myxoma, Myxosarcoma,                                                                        |
|     or Fibrous Histiocytoma                                                                                                     |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     2/50 (4%)    0/50 (0%)    2/50 (4%)    0/50 (0%)   |3/50 (6%)    3/50 (6%)    1/50 (2%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     5.9%         0.0%         6.4%         0.0%        |7.4%         8.0%         2.3%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |2/23 (9%)    1/19 (5%)    1/33 (3%)    0/22 (0%)    |
|FIRST INCIDENCE    |     639          ---          678          ---         |488          548          733 (T)      ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.257N     P=0.277N     P=0.601      P=0.205N    |P=0.074N     P=0.594      P=0.212N     P=0.128N     |
|POLY 3             |     P=0.248N     P=0.258N     P=0.664      P=0.225N    |P=0.079N     P=0.625      P=0.276N     P=0.123N     |
|POLY 1.5           |     P=0.265N     P=0.249N     P=0.678      P=0.229N    |P=0.078N     P=0.635      P=0.288N     P=0.122N     |
|POLY 6             |     P=0.228N     P=0.277N     P=0.640      P=0.224N    |P=0.082N     P=0.612      P=0.263N     P=0.127N     |
|LOGISTIC REGRESSION|     P=0.257N     P=0.249N     P=0.653      P=0.233N    |P=0.076N     P=0.658      P=0.315N     P=0.119N     |
|COCH-ARM / FISHERS |     P=0.290N     P=0.247N     P=0.691N     P=0.247N    |P=0.076N     P=0.661N     P=0.309N     P=0.121N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Fibrosarcoma, Sarcoma, Myxosarcoma, or Fibrous Histiocytoma                                                                 |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    0/50 (0%)    0/50 (0%)    0/50 (0%)   |2/50 (4%)    3/50 (6%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     3.0%         0.0%         0.0%         0.0%        |4.9%         8.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |1/23 (4%)    1/19 (5%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     639          ---          ---          ---         |488          548          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.504N     P=0.532N     P=0.560N     P=0.472N    |P=0.110N     P=0.440      P=0.196N     P=0.245N     |
|POLY 3             |     P=0.524N     P=0.518N     P=0.518N     P=0.489N    |P=0.117N     P=0.462      P=0.219N     P=0.244N     |
|POLY 1.5           |     P=0.535N     P=0.510N     P=0.509N     P=0.493N    |P=0.114N     P=0.473      P=0.226N     P=0.242N     |
|POLY 6             |     P=0.505N     P=0.532N     P=0.532N     P=0.487N    |P=0.122N     P=0.449      P=0.211N     P=0.249N     |
|LOGISTIC REGRESSION|     P=0.538N     P=0.509N     P=0.509N     P=0.500N    |P=0.111N     P=0.509      P=0.293N     P=0.221N     |
|COCH-ARM / FISHERS |     P=0.547N     P=0.500N     P=0.500N     P=0.500N    |P=0.110N     P=0.500      P=0.247N     P=0.247N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 16
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Keratoacanthoma                                                                                                             |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     3/50 (6%)    4/50 (8%)    2/50 (4%)    4/50 (8%)   |1/50 (2%)    0/50 (0%)    1/50 (2%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     8.8%         12.5%        6.4%         11.1%       |2.5%         0.0%         2.3%         0.0%         |
|TERMINAL (d)       |     1/7 (14%)    1/5 (20%)    1/6 (17%)    2/8 (25%)   |1/23 (4%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     621          552          574          700         |733 (T)      ---          651          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.598      P=0.390      P=0.593N     P=0.522     |P=0.477N     P=0.538N     P=0.702N     P=0.509N     |
|POLY 3             |     P=0.523      P=0.463      P=0.538N     P=0.530     |P=0.470N     P=0.517N     P=0.737N     P=0.503N     |
|POLY 1.5           |     P=0.502      P=0.478      P=0.520N     P=0.520     |P=0.472N     P=0.512N     P=0.746N     P=0.502N     |
|POLY 6             |     P=0.544      P=0.436      P=0.569N     P=0.536     |P=0.470N     P=0.523N     P=0.725N     P=0.506N     |
|LOGISTIC REGRESSION|     P=0.573      P=0.438      P=0.552N     P=0.544     |P=0.477N     (e)          P=0.756N     (e)          |
|COCH-ARM / FISHERS |     P=0.469      P=0.500      P=0.500N     P=0.500     |P=0.478N     P=0.500N     P=0.753N     P=0.500N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Sarcoma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    0/50 (0%)    0/50 (0%)    0/50 (0%)   |1/50 (2%)    2/50 (4%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     3.0%         0.0%         0.0%         0.0%        |2.5%         5.4%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |1/23 (4%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     639          ---          ---          ---         |733 (T)      548          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.504N     P=0.532N     P=0.560N     P=0.472N    |P=0.243N     P=0.453      P=0.428N     P=0.509N     |
|POLY 3             |     P=0.524N     P=0.518N     P=0.518N     P=0.489N    |P=0.252N     P=0.477      P=0.480N     P=0.503N     |
|POLY 1.5           |     P=0.535N     P=0.510N     P=0.509N     P=0.493N    |P=0.248N     P=0.483      P=0.488N     P=0.502N     |
|POLY 6             |     P=0.505N     P=0.532N     P=0.532N     P=0.487N    |P=0.259N     P=0.470      P=0.471N     P=0.506N     |
|LOGISTIC REGRESSION|     P=0.538N     P=0.509N     P=0.509N     P=0.500N    |P=0.240N     P=0.491      (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.547N     P=0.500N     P=0.500N     P=0.500N    |P=0.240N     P=0.500      P=0.500N     P=0.500N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 17
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Squamous Cell Papilloma                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/50 (0%)    1/50 (2%)    2/50 (4%)    1/50 (2%)   |0/50 (0%)    0/50 (0%)    1/50 (2%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     0.0%         3.2%         6.4%         2.8%        |0.0%         0.0%         2.3%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     1/6 (17%)    1/8 (13%)   |0/23 (0%)    0/19 (0%)    1/33 (3%)    0/22 (0%)    |
|FIRST INCIDENCE    |     ---          684          654          733 (T)     |---          ---          733 (T)      ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.645      P=0.459      P=0.197      P=0.527     |P=0.786N     (e)          P=0.572      (e)          |
|POLY 3             |     P=0.601      P=0.485      P=0.220      P=0.513     |P=0.768N     (e)          P=0.520      (e)          |
|POLY 1.5           |     P=0.587      P=0.491      P=0.228      P=0.508     |P=0.769N     (e)          P=0.512      (e)          |
|POLY 6             |     P=0.615      P=0.475      P=0.208      P=0.518     |P=0.769N     (e)          P=0.529      (e)          |
|LOGISTIC REGRESSION|     P=0.624      P=0.463      P=0.195      P=0.527     |(e)          (e)          P=0.572      (e)          |
|COCH-ARM / FISHERS |     P=0.563      P=0.500      P=0.247      P=0.500     |P=0.772N     (e)          P=0.500      (e)          |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Squamous Cell Papilloma, Papilloma, Squamous Cell                                                                           |
|     Carcinoma or Keratoacanthoma                                                                                                |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     3/50 (6%)    5/50 (10%)   3/50 (6%)    5/50 (10%)  |1/50 (2%)    0/50 (0%)    2/50 (4%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     8.8%         15.6%        9.5%         13.9%       |2.5%         0.0%         4.5%         0.0%         |
|TERMINAL (d)       |     1/7 (14%)    1/5 (20%)    1/6 (17%)    3/8 (38%)   |1/23 (4%)    0/19 (0%)    1/33 (3%)    0/22 (0%)    |
|FIRST INCIDENCE    |     621          552          574          700         |733 (T)      ---          651          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.543      P=0.254      P=0.560      P=0.383     |P=0.437N     P=0.538N     P=0.601      P=0.509N     |
|POLY 3             |     P=0.442      P=0.318      P=0.631      P=0.384     |P=0.423N     P=0.517N     P=0.537      P=0.503N     |
|POLY 1.5           |     P=0.422      P=0.334      P=0.646      P=0.375     |P=0.427N     P=0.512N     P=0.522      P=0.502N     |
|POLY 6             |     P=0.459      P=0.293      P=0.608      P=0.385     |P=0.423N     P=0.523N     P=0.554      P=0.506N     |
|LOGISTIC REGRESSION|     P=0.509      P=0.289      P=0.614      P=0.392     |P=0.436N     (e)          P=0.534      (e)          |
|COCH-ARM / FISHERS |     P=0.387      P=0.357      P=0.661N     P=0.357     |P=0.437N     P=0.500N     P=0.500      P=0.500N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 18
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin                                                                                                                             |
|     Squamous Cell Papilloma, Papilloma, or Keratoacanthoma                                                                      |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     3/50 (6%)    5/50 (10%)   3/50 (6%)    5/50 (10%)  |1/50 (2%)    0/50 (0%)    2/50 (4%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     8.8%         15.6%        9.5%         13.9%       |2.5%         0.0%         4.5%         0.0%         |
|TERMINAL (d)       |     1/7 (14%)    1/5 (20%)    1/6 (17%)    3/8 (38%)   |1/23 (4%)    0/19 (0%)    1/33 (3%)    0/22 (0%)    |
|FIRST INCIDENCE    |     621          552          574          700         |733 (T)      ---          651          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.543      P=0.254      P=0.560      P=0.383     |P=0.437N     P=0.538N     P=0.601      P=0.509N     |
|POLY 3             |     P=0.442      P=0.318      P=0.631      P=0.384     |P=0.423N     P=0.517N     P=0.537      P=0.503N     |
|POLY 1.5           |     P=0.422      P=0.334      P=0.646      P=0.375     |P=0.427N     P=0.512N     P=0.522      P=0.502N     |
|POLY 6             |     P=0.459      P=0.293      P=0.608      P=0.385     |P=0.423N     P=0.523N     P=0.554      P=0.506N     |
|LOGISTIC REGRESSION|     P=0.509      P=0.289      P=0.614      P=0.392     |P=0.436N     (e)          P=0.534      (e)          |
|COCH-ARM / FISHERS |     P=0.387      P=0.357      P=0.661N     P=0.357     |P=0.437N     P=0.500N     P=0.500      P=0.500N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Skin: Sebaceous Gland                                                                                                            |
|     Adenoma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/50 (0%)    2/50 (4%)    1/50 (2%)    0/50 (0%)   |0/50 (0%)    0/50 (0%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     0.0%         6.4%         3.2%         0.0%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     ---          664          700          ---         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.311N     P=0.202      P=0.500      (e)         |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.347N     P=0.221      P=0.485      (e)         |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.355N     P=0.228      P=0.492      (e)         |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.340N     P=0.211      P=0.474      (e)         |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.325N     P=0.204      P=0.460      (e)         |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.366N     P=0.247      P=0.500      (e)         |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 19
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Testes                                                                                                                           |
|     Adenoma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     23/50 (46%)  28/50 (56%)  29/50 (58%)  25/50 (50%) |                                                    |
|POLY-3 ADJUSTED (b)|     59.1%        70.4%        74.2%        61.1%       |                                                    |
|TERMINAL (d)       |     5/7 (71%)    3/5 (60%)    6/6 (100%)   6/8 (75%)   |                                                    |
|FIRST INCIDENCE    |     379          460          496          583         |                                                    |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.183N     P=0.065      P=0.066      P=0.553N    |                                                    |
|POLY 3             |     P=0.343N     P=0.180      P=0.087      P=0.522     |                                                    |
|POLY 1.5           |     P=0.400N     P=0.181      P=0.116      P=0.476     |                                                    |
|POLY 6             |     P=0.288N     P=0.208      P=0.057      P=0.584     |                                                    |
|LOGISTIC REGRESSION|     P=0.214N     P=0.117      P=0.061      P=0.585N    |                                                    |
|COCH-ARM / FISHERS |     P=0.489N     P=0.212      P=0.158      P=0.421     |                                                    |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Thyroid Gland: C-Cell                                                                                                            |
|     Adenoma                                                                                                                     |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     5/48 (10%)   4/48 (8%)    5/48 (10%)   7/50 (14%)  |7/50 (14%)   6/50 (12%)   3/49 (6%)    5/49 (10%)   |
|POLY-3 ADJUSTED (b)|     14.8%        12.8%        16.5%        18.3%       |17.6%        16.4%        6.8%         12.7%        |
|TERMINAL (d)       |     2/7 (29%)    0/5 (0%)     1/6 (17%)    0/8 (0%)    |7/23 (30%)   6/19 (32%)   1/33 (3%)    3/22 (14%)   |
|FIRST INCIDENCE    |     540          583          678          534         |733 (T)      733 (T)      552          663          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.395      P=0.630      P=0.518      P=0.441     |P=0.422N     P=0.600      P=0.062N     P=0.410N     |
|POLY 3             |     P=0.360      P=0.549N     P=0.563      P=0.468     |P=0.416N     P=0.565N     P=0.117N     P=0.384N     |
|POLY 1.5           |     P=0.319      P=0.529N     P=0.594      P=0.443     |P=0.419N     P=0.546N     P=0.136N     P=0.392N     |
|POLY 6             |     P=0.419      P=0.578N     P=0.518      P=0.502     |P=0.420N     P=0.593N     P=0.097N     P=0.381N     |
|LOGISTIC REGRESSION|     P=0.346      P=0.568N     P=0.500      P=0.421     |P=0.413N     P=0.600      P=0.131N     P=0.420N     |
|COCH-ARM / FISHERS |     P=0.266      P=0.500N     P=0.630N     P=0.409     |P=0.425N     P=0.500N     P=0.167N     P=0.394N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 20
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Thyroid Gland: C-Cell                                                                                                            |
|     Carcinoma                                                                                                                   |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/48 (0%)    0/48 (0%)    2/48 (4%)    1/50 (2%)   |2/50 (4%)    3/50 (6%)    6/49 (12%)   2/49 (4%)    |
|POLY-3 ADJUSTED (b)|     0.0%         0.0%         6.6%         2.8%        |5.0%         8.0%         13.7%        5.1%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     1/6 (17%)    0/8 (0%)    |0/23 (0%)    0/19 (0%)    4/33 (12%)   1/22 (5%)    |
|FIRST INCIDENCE    |     ---          ---          520          607         |720          603          534          729          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.482      (e)          P=0.218      P=0.533     |P=0.452N     P=0.422      P=0.247      P=0.673      |
|POLY 3             |     P=0.472      (e)          P=0.219      P=0.520     |P=0.444N     P=0.473      P=0.164      P=0.686      |
|POLY 1.5           |     P=0.456      (e)          P=0.227      P=0.516     |P=0.447N     P=0.479      P=0.148      P=0.685      |
|POLY 6             |     P=0.491      (e)          P=0.207      P=0.525     |P=0.452N     P=0.467      P=0.183      P=0.682      |
|LOGISTIC REGRESSION|     P=0.422      (e)          P=0.234      P=0.484     |P=0.445N     P=0.480      P=0.151      P=0.670      |
|COCH-ARM / FISHERS |     P=0.431      (e)          P=0.247      P=0.510     |P=0.453N     P=0.500      P=0.128      P=0.684      |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Thyroid Gland: C-Cell                                                                                                            |
|     Carcinoma or Adenoma                                                                                                        |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     5/48 (10%)   4/48 (8%)    7/48 (15%)   8/50 (16%)  |9/50 (18%)   9/50 (18%)   9/49 (18%)   7/49 (14%)   |
|POLY-3 ADJUSTED (b)|     14.8%        12.8%        22.7%        20.7%       |22.5%        23.9%        20.1%        17.7%        |
|TERMINAL (d)       |     2/7 (29%)    0/5 (0%)     2/6 (33%)    0/8 (0%)    |7/23 (30%)   6/19 (32%)   5/33 (15%)   4/22 (18%)   |
|FIRST INCIDENCE    |     540          583          520          534         |720          603          534          663          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.325      P=0.630      P=0.277      P=0.345     |P=0.339N     P=0.428      P=0.336N     P=0.434N     |
|POLY 3             |     P=0.290      P=0.549N     P=0.310      P=0.365     |P=0.326N     P=0.550      P=0.495N     P=0.400N     |
|POLY 1.5           |     P=0.248      P=0.529N     P=0.341      P=0.338     |P=0.332N     P=0.561      P=0.547N     P=0.408N     |
|POLY 6             |     P=0.356      P=0.578N     P=0.266      P=0.403     |P=0.332N     P=0.538      P=0.433N     P=0.398N     |
|LOGISTIC REGRESSION|     P=0.261      P=0.568N     P=0.256      P=0.309     |P=0.321N     P=0.480      P=0.548N     P=0.444N     |
|COCH-ARM / FISHERS |     P=0.195      P=0.500N     P=0.379      P=0.304     |P=0.341N     P=0.602N     P=0.584      P=0.410N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 21
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Thyroid Gland: Follicular Cell                                                                                                   |
|     Carcinoma                                                                                                                   |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |                                                        |                                                    |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/48 (2%)    0/48 (0%)    0/48 (0%)    5/50 (10%)  |1/50 (2%)    0/50 (0%)    0/49 (0%)    0/49 (0%)    |
|POLY-3 ADJUSTED (b)|     3.0%         0.0%         0.0%         13.5%       |2.5%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |1/23 (4%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     661          ---          ---          618         |733 (T)      ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.010 *    P=0.528N     P=0.572N     P=0.134     |P=0.553N     P=0.538N     P=0.428N     P=0.509N     |
|POLY 3             |     P=0.004 **   P=0.519N     P=0.521N     P=0.125     |P=0.549N     P=0.517N     P=0.484N     P=0.505N     |
|POLY 1.5           |     P=0.004 **   P=0.511N     P=0.511N     P=0.120     |P=0.548N     P=0.512N     P=0.492N     P=0.505N     |
|POLY 6             |     P=0.005 **   P=0.534N     P=0.536N     P=0.130     |P=0.550N     P=0.523N     P=0.475N     P=0.507N     |
|LOGISTIC REGRESSION|     P=0.006 **   P=0.521N     P=0.523N     P=0.124     |P=0.553N     (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.004 **   P=0.500N     P=0.500N     P=0.112     |P=0.550N     P=0.500N     P=0.505N     P=0.505N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Uterus                                                                                                                           |
|     Polyp Stromal                                                                                                               |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |                                                        |8/50 (16%)   9/50 (18%)   8/50 (16%)   5/50 (10%)   |
|POLY-3 ADJUSTED (b)|                                                        |18.9%        23.0%        18.0%        12.1%        |
|TERMINAL (d)       |                                                        |1/23 (4%)    4/19 (21%)   7/33 (21%)   2/22 (9%)    |
|FIRST INCIDENCE    |                                                        |529          420          626          407          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |                                                        |P=0.178N     P=0.381      P=0.396N     P=0.297N     |
|POLY 3             |                                                        |P=0.169N     P=0.429      P=0.567N     P=0.287N     |
|POLY 1.5           |                                                        |P=0.169N     P=0.451      P=0.581N     P=0.283N     |
|POLY 6             |                                                        |P=0.181N     P=0.396      P=0.557N     P=0.307N     |
|LOGISTIC REGRESSION|                                                        |P=0.172N     P=0.521      P=0.605      P=0.248N     |
|COCH-ARM / FISHERS |                                                        |P=0.172N     P=0.500      P=0.607N     P=0.277N     |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 22
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|Zymbal's Gland                                                                                                                   |
|     Carcinoma                                                                                                                   |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     0/50 (0%)    2/50 (4%)    1/50 (2%)    0/50 (0%)   |0/50 (0%)    0/50 (0%)    1/50 (2%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     0.0%         6.3%         3.2%         0.0%        |0.0%         0.0%         2.3%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     ---          607          714          ---         |---          ---          680          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.322N     P=0.216      P=0.455      (e)         |P=0.793N     (e)          P=0.545      (e)          |
|POLY 3             |     P=0.346N     P=0.223      P=0.484      (e)         |P=0.768N     (e)          P=0.521      (e)          |
|POLY 1.5           |     P=0.354N     P=0.229      P=0.492      (e)         |P=0.769N     (e)          P=0.512      (e)          |
|POLY 6             |     P=0.339N     P=0.215      P=0.473      (e)         |P=0.769N     (e)          P=0.530      (e)          |
|LOGISTIC REGRESSION|     P=0.342N     P=0.234      P=0.457      (e)         |P=0.773N     (e)          P=0.499      (e)          |
|COCH-ARM / FISHERS |     P=0.366N     P=0.247      P=0.500      (e)         |P=0.772N     (e)          P=0.500      (e)          |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|All Organs                                                                                                                       |
|     Histiocytic Sarcoma                                                                                                         |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    0/50 (0%)    2/50 (4%)    0/50 (0%)   |0/50 (0%)    0/50 (0%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     3.0%         0.0%         6.3%         0.0%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     1/6 (17%)    0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     705          ---          496          ---         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.416N     P=0.623N     P=0.468      P=0.573N    |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.395N     P=0.517N     P=0.478      P=0.487N    |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.412N     P=0.509N     P=0.489      P=0.492N    |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.375N     P=0.530N     P=0.462      P=0.484N    |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.417N     P=0.557N     P=0.480      P=0.487N    |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.437N     P=0.500N     P=0.500      P=0.500N    |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 23
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|All Organs                                                                                                                       |
|     Leukemia: Lymphocytic, Monocytic, Mononuclear, or                                                                           |
|     Undifferentiated                                                                                                            |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     21/50 (42%)  21/50 (42%)  20/50 (40%)  31/50 (62%) |18/50 (36%)  16/50 (32%)  22/50 (44%)  17/50 (34%)  |
|POLY-3 ADJUSTED (b)|     54.9%        55.5%        52.4%        71.1%       |41.6%        39.9%        46.8%        37.3%        |
|TERMINAL (d)       |     6/7 (86%)    4/5 (80%)    2/6 (33%)    7/8 (88%)   |7/23 (30%)   7/19 (37%)   13/33 (39%)  3/22 (14%)   |
|FIRST INCIDENCE    |     467          514          497          505         |421          420          534          407          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.188      P=0.255      P=0.380      P=0.137     |P=0.504N     P=0.523      P=0.494N     P=0.535N     |
|POLY 3             |     P=0.028 *    P=0.575      P=0.504N     P=0.075     |P=0.349N     P=0.525N     P=0.386      P=0.421N     |
|POLY 1.5           |     P=0.019 *    P=0.569      P=0.506N     P=0.053     |P=0.402N     P=0.494N     P=0.338      P=0.457N     |
|POLY 6             |     P=0.047 *    P=0.586      P=0.484N     P=0.115     |P=0.313N     P=0.568N     P=0.443      P=0.398N     |
|LOGISTIC REGRESSION|     P=0.030 *    P=0.468      P=0.571      P=0.063     |P=0.489N     P=0.466N     P=0.284      P=0.482N     |
|COCH-ARM / FISHERS |     P=0.011 *    P=0.580N     P=0.500N     P=0.036 *   |P=0.489N     P=0.417N     P=0.270      P=0.500N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|All Organs                                                                                                                       |
|     Malignant Lymphoma And Histiocytic Sarcoma                                                                                  |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     1/50 (2%)    0/50 (0%)    2/50 (4%)    0/50 (0%)   |0/50 (0%)    0/50 (0%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     3.0%         0.0%         6.3%         0.0%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     1/6 (17%)    0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     705          ---          496          ---         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.416N     P=0.623N     P=0.468      P=0.573N    |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.395N     P=0.517N     P=0.478      P=0.487N    |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.412N     P=0.509N     P=0.489      P=0.492N    |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.375N     P=0.530N     P=0.462      P=0.484N    |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.417N     P=0.557N     P=0.480      P=0.487N    |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.437N     P=0.500N     P=0.500      P=0.500N    |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 24
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|All Organs                                                                                                                       |
|     Mesothelioma: Benign, Malignant, NOS                                                                                        |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     3/50 (6%)    2/50 (4%)    0/50 (0%)    0/50 (0%)   |0/50 (0%)    0/50 (0%)    0/50 (0%)    0/50 (0%)    |
|POLY-3 ADJUSTED (b)|     8.7%         6.3%         0.0%         0.0%        |0.0%         0.0%         0.0%         0.0%         |
|TERMINAL (d)       |     0/7 (0%)     0/5 (0%)     0/6 (0%)     0/8 (0%)    |0/23 (0%)    0/19 (0%)    0/33 (0%)    0/22 (0%)    |
|FIRST INCIDENCE    |     544          547          ---          ---         |---          ---          ---          ---          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.082N     P=0.570N     P=0.160N     P=0.110N    |(e)          (e)          (e)          (e)          |
|POLY 3             |     P=0.081N     P=0.540N     P=0.138N     P=0.110N    |(e)          (e)          (e)          (e)          |
|POLY 1.5           |     P=0.087N     P=0.522N     P=0.128N     P=0.113N    |(e)          (e)          (e)          (e)          |
|POLY 6             |     P=0.073N     P=0.570N     P=0.155N     P=0.110N    |(e)          (e)          (e)          (e)          |
|LOGISTIC REGRESSION|     P=0.099N     P=0.495N     P=0.120N     P=0.128N    |(e)          (e)          (e)          (e)          |
|COCH-ARM / FISHERS |     P=0.098N     P=0.500N     P=0.121N     P=0.121N    |(e)          (e)          (e)          (e)          |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|All Organs                                                                                                                       |
|     Benign Tumors                                                                                                               |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     48/50 (96%)  46/50 (92%)  49/50 (98%)  49/50 (98%) |42/50 (84%)  45/50 (90%)  48/50 (96%)  46/50 (92%)  |
|POLY-3 ADJUSTED (b)|     98.3%        98.3%        99.8%        98.4%       |92.7%        94.8%        96.1%        95.7%        |
|TERMINAL (d)       |     7/7 (100%)   5/5 (100%)   6/6 (100%)   8/8 (100%)  |22/23 (96%)  17/19 (90%)  32/33 (97%)  21/22 (96%)  |
|FIRST INCIDENCE    |     379          460          453          490         |496          420          399          407          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.192N     P=0.230      P=0.191      P=0.403N    |P=0.342      P=0.105      P=0.192N     P=0.241      |
|POLY 3             |     P=0.793N     P=0.898      P=0.659      P=0.821     |P=0.444      P=0.507      P=0.375      P=0.417      |
|POLY 1.5           |     P=0.536      P=0.666N     P=0.510      P=0.671     |P=0.342      P=0.316      P=0.170      P=0.248      |
|POLY 6             |     P=0.701N     P=0.998      P=0.993      P=0.864N    |P=0.508      P=0.698N     P=0.642      P=0.611      |
|LOGISTIC REGRESSION|     P=0.612      P=0.528N     P=0.418      P=0.571     |P=0.262      P=0.086      P=0.145      P=0.135      |
|COCH-ARM / FISHERS |     P=0.249      P=0.339N     P=0.500      P=0.500     |P=0.263      P=0.277      P=0.046 *    P=0.178      |
|=================================================================================================================================|
       Date:  06/19/97                           EXPERIMENT: 88070 TEST: 03                                            Page 25
                     Statistical Analysis of Primary Tumors in Rats(FISCHER344)       -                ISOBUTENE
                                         Terminal Sacrifice at 104 weeks 
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|All Organs                                                                                                                       |
|     Malignant Tumors                                                                                                            |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     31/50 (62%)  33/50 (66%)  28/50 (56%)  40/50 (80%) |30/50 (60%)  24/50 (48%)  30/50 (60%)  25/50 (50%)  |
|POLY-3 ADJUSTED (b)|     72.1%        78.4%        68.5%        87.1%       |63.6%        56.1%        63.6%        54.3%        |
|TERMINAL (d)       |     7/7 (100%)   5/5 (100%)   5/6 (83%)    7/8 (88%)   |12/23 (52%)  9/19 (47%)   20/33 (61%)  9/22 (41%)   |
|FIRST INCIDENCE    |     379          469          453          505         |390          216          534          407          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.413      P=0.147      P=0.443      P=0.263     |P=0.368N     P=0.440N     P=0.151N     P=0.317N     |
|POLY 3             |     P=0.030 *    P=0.314      P=0.445N     P=0.040 *   |P=0.257N     P=0.303N     P=0.585      P=0.237N     |
|POLY 1.5           |     P=0.025 *    P=0.343      P=0.398N     P=0.038 *   |P=0.280N     P=0.252N     P=0.578      P=0.236N     |
|POLY 6             |     P=0.042 *    P=0.290      P=0.521N     P=0.052     |P=0.254N     P=0.361N     P=0.573N     P=0.251N     |
|LOGISTIC REGRESSION|     P=0.050      P=0.339      P=0.385N     P=0.062     |P=0.310N     P=0.149N     P=0.537      P=0.197N     |
|COCH-ARM / FISHERS |     P=0.022 *    P=0.418      P=0.342N     P=0.038 *   |P=0.310N     P=0.158N     P=0.581N     P=0.211N     |
|=================================================================================================================================|
|                   |                                                        |                                                    |
|                   |                              Males                     |                       Females                      |
|Dose               |     CONTROL      500 PPM      2000 PPM     8000 PPM    |CONTROL      500 PPM      2000 PPM     8000 PPM     |
|                   |                                                        |                                                    |
|=================================================================================================================================|
|                                                                                                                                 |
|All Organs                                                                                                                       |
|     Malignant and Benign Tumors                                                                                                 |
|                                                                                                                                 |
|                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------|
|TUMOR RATES        |     #            #            #            #           |#            #            #            #            |
|-----------        |                                                        |                                                    |
|OVERALL (a)        |     50/50 (100%) 48/50 (96%)  49/50 (98%)  50/50 (100%)|50/50 (100%) 48/50 (96%)  49/50 (98%)  48/50 (96%)  |
|POLY-3 ADJUSTED (b)|     100.0%       99.6%        99.8%        100.0%      |100.0%       98.0%        98.0%        98.0%        |
|TERMINAL (d)       |     7/7 (100%)   5/5 (100%)   6/6 (100%)   8/8 (100%)  |23/23 (100%) 18/19 (95%)  32/33 (97%)  21/22 (96%)  |
|FIRST INCIDENCE    |     379          460          453          490         |390          216          399          407          |
|-------------------|                                                        |                                                    |
|STATISTICAL TESTS  |                                                        |                                                    |
|-------------------|                                                        |                                                    |
|LIFE TABLE         |     P=0.166N     P=0.231      P=0.258      (e)         |P=0.510N     P=0.283      P=0.027N*    P=0.544N     |
|POLY 3             |     P=1.000      P=1.000N     P=1.000N     (e)         |P=0.521N     P=0.496N     P=0.500N     P=0.496N     |
|POLY 1.5           |     P=0.816      P=0.830N     P=0.976N     (e)         |P=0.521N     P=0.495N     P=0.500N     P=0.496N     |
|POLY 6             |     P=1.000      P=1.000N     P=1.000N     (e)         |P=0.521N     P=0.496N     P=0.500N     P=0.496N     |
|LOGISTIC REGRESSION|     (e)          P=0.431N     (e)          (e)         |P=0.387N     P=0.422N     (e)          P=0.365N     |
|COCH-ARM / FISHERS |     P=0.366      P=0.247N     P=0.500N     (e)         |P=0.342N     P=0.247N     P=0.500N     P=0.247N     |
|=================================================================================================================================|

(a)  Number of tumor-bearing animals /  number of animals examined at site.
(b)  Poly-3 adjusted lifetime tumor incidence.
(d)  Observed incidence at terminal kill.
(f)  Beneath the control incidence are the P-values associated with the trend 
test.  Beneath the dosed group incidence are the P-values corresponding to 
pairwise comparisons between the controls and that dosed group.  The life
table analysis regards tumors in animals dying prior to  terminal kill as
 being (directly or indirectly) the cause of death.
Logistic regression is an alternative
 method for analyzing the incidence of non-fatal tumors. The Cochran-Armitage
and Fishers exact tests compare directly the overall incidence rates
For all tests a negative trend is indicated by N
(e)  Value of Statistic cannot be computed.
(I)  Interim sacrifice
(T)  Terminal sacrifice
#   Tumor rates based on number of animals necropsied.
*   To the right of any statistical result, indicates significance at (P<=0.05).
**  To the right of any statistical result, indicates significance at (P<=0.01).