The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings were not evaluated in accordance with the levels of evidence for reproductive or developmental criteria established by NTP in March 2009. The findings and conclusions for this study should not be construed to represent the views of NTP or the U.S. Government.
To assess potential reproductive effects over multiple generations, 4-nonylphenol, branched (NP), CAS No. 84852-15-3, was administered in the diet at concentrations of 0, 200, 650, and 2000 ppm to groups (N=30 male and 30 female) of Sprague-Dawley rats over three generations. The F0 generation began exposure as adults and were bred once to produce the F1 generation, the F1 adults were bred once to produce the F 2 generation, and the F 2 adults were bred once to produce the F3 generation. Parameters evaluated over the course of the study included body weights, feed consumption, clinical observations, estrous cyclicity, reproductive performance, anogenital distance, pup survival, sexual development, sperm analysis, gross pathology, organ weights, and limited/selected histopathology.
Reductions in terminal body weights were noted at 650 ppm in F 2 (8%) males and F1 (7%) and PND (post-natal day) 55-58 F3 (10%) females and at 2000 ppm in F1 (9%), F 2 (7%), and PND 55-58 F3 (7%) males and F0 (9%), F1 (12%), F 2 (10%), and PND 55-58 F3 (11%) females. Feed consumption, clinical observations, and mortality were not adversely affected by NP administration.
No treatment-related changes were noted in the litter data from all three mating trials. Estrous cycle length was increased by 14% in the F1 2000 ppm females and by 18% in the F 2 2000 ppm females compared to respective control values. Vaginal opening was accelerated by 1.5-7.3 days at 650 ppm and by 2.9-6.0 days at 2000 ppm in all three generations.
Sperm endpoints were unchanged in the F0 and F1 generations. Epididymal sperm density was decreased by 8-13% in the 650 and 2000 ppm F 2 males, compared to controls. The number of spermatids/mg testis and total spermatids/testis was decreased by 12-13% in the 2000 ppm group vs. to controls. Although the percent abnormal sperm was increased in all treated F 2 male groups, this was due to a low value in the F 2 controls. No changes were noted in computer-assisted sperm analysis parameters for any generation.
Increased relative kidney weights were observed in 650 and/or 2000 ppm adult males from the F0, F1, and F 2 generations and in the F1 2000 ppm adult females. A treatment-related increase in the incidence of renal tubular degeneration/dilatation was seen in the 200, 650, and 2000 ppm males from all generations and in the 2000 ppm females from the F1, F 2, and F3 generations, and in the 200 and 650 females in the F3 generation. Ovarian weights were decreased at 650 ppm in the F 2 generation and at 2000 ppm in the F1, F 2, and F3 generations. No differences in ovarian follicle number were noted between the F 2 controls and 2000 ppm rats. At the PND 55-58 F3 necropsy, while the absolute weight of the right epididymis was decreased by 13 and 9% at 650 and 2000 ppm and the relative right testis weight was increased by 9%, these changes were attributed to the decrease in terminal body weights.
Results of this study show that NP is a male and female reproductive toxicant at concentrations equal to or greater than 650 ppm based on decreased epididymal sperm density and testicular spermatid head counts in males, and increased estrous cycle length and decreased ovarian weights observed in females. A maximum tolerated dose (MTD) was reached based on decreased body weights noted in both sexes and treatment-related renal lesions.
NTIS # PB97-210900