National Toxicology Program

Reproductive Toxicity of Potassium Dichromate (Hexavalent) (CAS 7778-50-9) Administered in Diet to BALB/c Mice

NTP Report # RACB94014

ABSTRACT

The potential reproductive toxicity of potassium dichromate (hexavalent) [K₂Cr₂O ₇] in BALB/c mice was evaluated using the Reproductive Assessment by Continuous Breeding (RACB) protocol. Based on slightly decreased body weights and increased feed consumption noted at 400 ppm during a previous 9-week dietary study in BALB/c mice, dose levels for the continuous breeding phase for this study were set at 100, 200, and 400 ppm.

Exposure to potassium dichromate in the diet did not affect the reproductive performance of F₀ mice (20 mice/sex/group). Mean body weights of the high-dose F₀ males and females were generally slightly less than controls. Feed consumption was generally unchanged. The mean calculated doses during Task 2 were 19.4, 38.6, and 85.7 mg/kg/day for the F₀ males and females in the 100, 200, and 400 ppm dose groups, respectively. No treatment-related mortality or clinical signs were observed.

At necropsy, the mean absolute liver weights were decreased by 17 and 12% in the 400 ppm males and females compared to controls, respectively. No differences were noted in any other absolute or relative organ weights. No treatment-related gross or microscopic lesions were observed in the F₁ animals. Sperm endpoints were generally comparable among all groups.

In Task 4 (second generation evaluation), the fertility and estrous cyclicity of the F₁ animals were not affected by chromate consumption. Mean body weights of the 400 ppm F₁ animals were slightly less than controls. Mean feed consumption values (g/animal/day) were increased by 35 and 30% for the 100 and 400 ppm males and by 18 and 25% for the 200 and 400 ppm females, respectively, during Task Week 4 compared to control values. The mean calculated doses during Task 4 were 22.4, 45.5, and 104.9 mg/kg/day for the F₁ males and females in the 100, 200, and 400 ppm dose groups, respectively. No treatment-related mortality or clinical signs were observed during Task 4. Treatment-related changes were noted in the hematology data for the F₁ animals. The mean corpuscular volume was decreased by 3% in the 200 and 400 ppm males and by 2, 3, and 4% in the 100, 200, and 400 ppm females, respectively, compared to controls. The mean corpuscular hemoglobin was decreased by 3% in the 400 ppm males and the mean hemoglobin was decreased by 5% in the 400 ppm females compared to controls. The remaining hematology parameters, including erythrocyte morphology, were unchanged. At necropsy, no treatment-related changes were observed in the organ weight or sperm analysis data and no treatment-related gross or microscopic lesions were observed in the F₁ animals.

Results of this study show that potassium dichromate is not a reproductive toxicant at concentrations up to 400 ppm. The no-observable-adverse-effect level (NOAEL) was not established in this study as the 100 ppm F₁ females displayed reduced MCV. A maximum tolerated dose (MTD) was reached for the 400 ppm F₀ and F₁ animals based on slightly decreased body weights, increased feed consumption, and small decreases in MCV, MCH, and HGB ( F₁ animals only).

Report Date: February 25, 1997

NTIS # PB97-144919