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Abstract for TR-411 - C.I. Pigment Red 23 (CASRN 6471-49-4)


Toxicology and Carcinogenesis Studies of C.I. Pigment Red 23 (CAS No.6471-49-4)in F344 Rats and B6C3F1 Mice (Feed Studies)

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Chemical Formula: C24H17N5O7

C.I. Pigment Red 23 is a bluish red commercial dye used as a coloringagentinpaints, inks, rubber, plastics, lacquers, and paper. Toxicology andcarcinogenicity studies were conducted by feeding groups of rats and micedietscontaining C.I. Pigment Red 23 (greater than 96% pure) for 17 days, 13weeks,and 2 years. Genetic toxicology studies were conducted in Salmonellatyphimurium and in Chinese hamster ovary cells.

17-Day Studies

Groups of five rats and five mice of each sex were feddietscontaining 0, 6,000, 12,500, 25,000, 50,000, or 100,000 ppm C.I. PigmentRed 23for 15 to 17 days. All rats and all female mice lived until the end of thestudies. Two male mice in the 12,500 ppm dose group died accidentally. Noother deaths occurred among male mice. Final mean body weights of ratsandmice receiving C.I. Pigment Red 23 were within 10% of those of the controls.Feed consumption by exposed animals was similar to that of the controls.Hematocrit value, hemoglobin concentration, and erythrocyte count weredecreased in the 50,000 and 100,000 ppm groups of rats. A correspondingdecrease was not seen in mice. Absolute and relative organ weights ofexposedanimals were generally similar to those of the controls. No chemical-relatedgross lesions were seen in rats or mice.

13-Week Studies

Groups of 10 rats and 10 mice of each sex were feddietscontaining 0, 3,000, 6,000, 12,500, 25,000, or 50,000 ppm C.I. Pigment Red23for 13 weeks. All rats and mice lived until the end of the studies. Final meanbody weights of rats and mice receiving C.I. Pigment Red 23 were within 10%ofthose of the controls. Feed consumption by exposed animals was similar tothatof the controls.

In 50,000 ppm male rats, hematocrit and hemoglobin concentrations anderythrocyte counts were significantly less than those of the controls. Infemale rats receiving 3,000, 6,000 and 50,000 ppm C.I. Pigment Red 23,lymphocyte counts were significantly higher than the control values.Leukocytecounts in 3,000 ppm females were also significantly increased. Female mice inthe 6,000 ppm dose group had significantly lower hematocrit and hemoglobinconcentrations than did untreated females. Hematology parameters inexposedmales were similar to those of untreated males.

There were no biologically significant differences in organ weightsamongdosed and control rats. Absolute and relative liver weights of male micereceiving 12,500 ppm C.I. Pigment Red 23 were significantly increasedcomparedto those of the controls. Absolute and relative thymus weights for all but12,500 ppm female mice were significantly lower than those of the controls. Nochemical-related gross or histopathologic lesions occurred in rats or mice.

2-Year Studies

Survival, Body Weights, Feed Consumption, and ClinicalFindings
Because levels of C.I. Pigment Red 23 as high as 50,000 or100,000ppm in the feed did not adversely affect survival and mean body weights in the17-day and 13-week studies, nor cause any chemical- related lesions, dosesof0, 10,000, 25,000, or 50,000 ppm were selected for the 2-year studies. Doseshigher than 50,000 ppm (5%) are not used in 2-year studies because theymaylead to excessive dilution of nutrients in feed which in turn could producenutritional deficiencies.

Survival rates of mid- and high-dose male and of high-dose female ratsweresignificantly greater than those of the controls, due primarily to a chemicalrelated decreased incidence of mononuclear cell leukemia in these groups(survival in male rats: control, 22/50, low-dose, 29/50, mid-dose, 36/50,high-dose, 35/51; female rats: 29/50, 34/50, 33/50, 40/50). Survival of micewas not affected by the administration of C.I. Pigment Red 23, althoughsurvival of low-dose male mice was significantly lower than that of controls(male mice: 29/51, 17/53, 27/52, 30/51; female mice: 35/50, 34/49, 36/50,35/49). The decreased survival in the low- dose males was associated withevidence of body trauma and secondary septicemia caused by fighting.

From approximately week 20 of the study, the group mean body weightsofexposed female rats were consistently lower than those of controls; at week101, mean body weights of mid- dose (25,000 ppm) and high-dose (50,000ppm)females were 6% and 8% less, respectively. The final mean body weights ofexposed male rats and male and female mice were similar to those ofcontrols.

Feed consumption values for exposed male and female rats and miceweresimilarto those of the controls and there were no clinical signs associated with theadministration of C.I. Pigment Red 23.

Pathology Findings
Renal tubule adenomas occurred in two high- dosemalerats. Renal tubule carcinomas occurred in one high-dose male and onemid-dosemale rat. No renal tubule neoplasms were seen in the controls. Renal tubuleneoplasms are uncommon and have occurred in 8/499 (1.6%) untreatedhistoricalcontrols with a range of 0% to 6%. The residual halves of kidneys from controland high-dose males were step sectioned and examined; renal tubuleadenomaswere observed in a control male and in two additional high- dose males.Because of the low numbers of renal neoplasms, it is uncertain if they wererelated to chemical administration. The incidence of renal tubule hyperplasia(3/50, 6/48, 5/50, 8/50) and the mean severity of nephropathy were alsoslightly increased in high-dose male rats. The incidence of mononuclear cellleukemia occurred with a significant negative trend in exposed male andfemalerats.

No chemical-related increases in the incidence of neoplasms wereobserved inmice of either sex. There was a chemical-related increase in the incidence ofhyperplasia (male mice: 0/49, 1/48, 1/50, 7/48; female mice: 6/49, 14/49,43/50, 47/49) and hyperkeratosis of the forestomach epithelium attributed tochemical administration.

Genetic Toxicology

C.I. Pigment Red 23 was mutagenic in Salmonella typhimurium strains TA100, TA1537, and TA98 with and without exogenousmetabolic activation (S9), but it was not mutagenic in strain TA1535. C.I.Pigment Red 23 induced sister chromatid exchanges in Chinese hamsterovarycells in the absence of S9, but not with S9 activation. The pigment wasnegative for the induction of chromosomal aberrations in Chinese hamsterovarycells both in the presence and absence of S9.


Under the conditions of these 2-year feed studies, therewasequivocal evidence of carcinogenic activity of C.I. Pigment Red 23 in maleF344 rats as evidenced by a marginally increased incidence of renal tubulecellneoplasms. There was no evidence of carcinogenic activity of C.I. PigmentRed23 in female F344 rats fed diets containing 10,000, 25,000, or 50,000 ppm. Mononuclear cell leukemia occurred with a decreased incidence in male andfemale rats receiving C.I. Pigment Red 23. There was no evidence ofcarcinogenic activity of C.I. Pigment Red 23 in male and female B6C3F1 micefeddiets containing 10,000, 25,000 or 50,000 ppm.

The severity of kidney nephropathy was increased in exposed male rats. Inmice, C.I. Pigment Red 23 caused an increase in hyperkeratosis and epithelialhyperplasia of the fore- stomach.

Synonyms: 2-Naphthalenecarboxamide; 3-hydroxy-4-((2-methoxy-5-nitrophenyl)azo)-N-(3- nitrophenyl); 3-hydroxy-4-((2-methoxy-5-nitrophenyl)azo)-3 -2-naphthanilide; Alkali Resistant Red Dark; Calcotone Red3B; Carnation Red Toner B; CI 12355; Congo Red R- 138; Fenalac Red FKBExtra;Malta Red X2284; Naphthol Red B; Naphthol Red T Toner 35- 6001; NaphtholRedDeep 10459; Pigment Red BH; Rubescence Red MT-21; Sanyo Fast Red 10B;SaponaRed Lake RL-6280; Sengale Light Rubin RG; Textile Red WD-263

Report Date: December 1992

Pathology Tables, Survival and Growth Curves from NTP 2-year Studies

Target Organs & Incidences from 2-year Studies

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