Exposure to environmentally-relevant concentrations of hexavalent chromium does not induce ovarian toxicity in mice

Exposure to high concentrations of hexavalent chromium [Cr(VI)] in drinking water (≥250 ppm) is reported to decrease ovarian follicle counts and increase follicular atresia in mice. To assess effects at lower concentrations, herein we exposed B6C3F1 mice to 0.1–150 ppm Cr(VI) in drinking water for 90 days in a GLP-compliant study. Ovarian follicular counts, differentiation, and degeneration were assessed from every 10th serial section (up to 14 sections per ovary). Ovarian follicular counts, differentiation, and rate of atresia were not altered in any exposure group. Gross and microscopic changes were not apparent in any of the evaluated reproductive or glandular organs. The no observable adverse effect level (NOAEL) for follicular effects was 150 ppm. In addition to these findings, published Cr(VI) studies examining follicles were scored using two methods for assessing study quality for use in risk assessment—including the Toxic Substance Control Act (TSCA) scoring method. Both methods revealed that studies reporting adverse effects on follicles generally received low scores. Overall, the current study indicates no/low potential for Cr(VI) to induce follicular toxicity in mice below 150 ppm Cr(VI) in drinking water (17.7 mg/kg bodyweight).