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.
Acrylamide (ACRL), known to cause reproductive toxicity, neurotoxicity, and induce dominant lethal mutations, was tested in a modified Reproductive Assessment by Continuous Breeding (RACB) Protocol in Swiss CD-l mice. The goal was to attempt to define the chronology of onset of these toxicities during exposure to low doses of ACRL, and separate the neurotoxicity from the reproductive toxicity. Dose levels were 3, 10, and 30 ppm in water. Clinical signs of toxicity were minimal at these low doses of ACRL and consisted only of increased water consumption for males at Weeks 1 and 16 and decreased water consumption for high-dose females at Week 1. Non dose-related decreases in water consumption were observed at Week 27. Feed consumption was normal. as were male and female body weights throughout the study. Overall, forelimb and hind limb grip strength tests administered at various times to detect neurotoxicity in the Fo males and females were all normal. Exposure to ACRL at doses ranging from 0.72±0.05 mg/kg/day in the low-dose group (3 ppm) to 9.16±0.23 mg/kg/day in the high-dose group (30 ppm), for 27 weeks did not significantly affect measures of reproductive competence, including initial fertility, mean number of litters per pair, the proportion of pups born alive, or adjusted live pup weight. However, overall live litter size was reduced by slightly more than one pup/litter at 30 ppm.
A dominant lethal test was performed using the F0 males after approximately 20 weeks of ACRL treatment, resulting in increased postimplantation (early resorption) loss of one pup/litter at 30 ppm. A crossover mating trial was not sensitive enough to determine which sex was responsible for the reduced number of pups/litter. The number of live pups per litter tended to be lower when sires were treated with 30 ppm ACRL (control x control; 11.4 ± 0.6 vs. ACRL male x control females: 9.4 ± 1.3), but this was not significant.
At necropsy of F0 adults no dose-related trends in reproductive or somatic organ or body weights were noted. Testicular spermatid numbers were decreased (11%) in mid- and high-dose mice. No treatment-related neural (sural and gastrocnemius nerves) or somatic organ histopathology was observed.
ACRL at dose levels of less than or equal to 30 ppm in water did not adversely affect pre-weaning growth or survival of the F1 generation, nor was there an effect on feed consumption before 82±10 days of age. Calculated exposure averaged 6.7±0.3 and 8.8±0.3 mg/kg/day for adult 82-day-old F1 males and females, respectively. Water consumption was increased at 30 ppm by 110 days of age for both sexes. No treatment-related clinical signs were noted. ACRL at 30 ppm had significant effects on the reproductive competence of the F1 generation, causing a 47% reduction in the number of F2 pups per litter. Some evidence of neurotoxicity was noted in the F1 generation at 10 and 30 ppm, as forelimb and hind limb grip strength was reduced in males at 10 and 16 weeks of age, respectively. Grip strength was not affected in females.
There was no evidence of treatment effect on F1 body or organ weights, sperm parameters, or histopathology in males, except for smaller absolute prostate weights at 30 ppm. In females, terminal body weight was not reduced, and ACRL had no affect on reproductive organ weight, vaginal cytology, or histopathology. An indication of general toxicity occurred in F1 females: absolute kidney/adrenal weight was decreased. and relative liver weight was increased at greater than or equal to 10 ppm.
In summary, exposure to ACRL in water at dose levels of 30 ppm (9.2 mg/kg) resulted in slight reproductive toxicity (decreased pups/litter and spermatid head counts) and increased postimplantation loss (dominant lethal effect) in the absence of demonstrable neurotoxicity for the F0 animals. F1 animals dosed with 30 ppm ACRL were more severely affected than the F0 animals, exhibiting a more profound effect on fertility in the presence of slight neurotoxicity (decreased grip strength in males).
NTIS # PB93-158285