Immunotoxicity of sodium bromate in female B6C3F1 mice: A 28-day drinking water study

Bromate is one of the water disinfection by-products (DBPs) produced during the process of ozonation. The purpose of this study was to evaluate the im munotoxic potential of sodium bromate (SB) in female B6C3F1 mice. SE was ad ministered in the drinking water for 28 days at doses of 80-800 mg/l. There was no difference in drinking water consumption between the animals expose d to SE and the tap water controls. Exposure to SE did not produce any sign s of overt toxicity. Furthermore, no significant differences were observed in body weight, body weight gain, or the weights of thymus, liver, kidneys or lungs. No gross pathological lesions were observed in SE-treated animals . However, animals exposed to SE had a significant increase in absolute (28 %) and relative (26%) spleen weights. The erythrocyte count, hemoglobin, he matocrit, mean corpuscular volume (MCV), platelet count, total leukocyte co unt, and counts of differential leukocytes were unaffected by SE. A dose-re lated increase in reticulocytes was observed following exposure to SE with the greatest increase (78%) observed at the highest dose level. Overall, th ere were no changes in the absolute number of total T cells, CD4(+)CD8(-) T cells, CD4(-)CD8(+) T cells, natural killer (NK) cells and macrophages. Ex posure to SE did not affect the percentage of B cells, although a slight in crease in absolute number of B cells at the dose of 600 mg/l was observed. There was no alteration in IgM antibody-forming cell (AFC) response. mixed leukocyte reaction (MLR) and NK cell activity after exposure to SE. When th e activity of peritoneal macrophages, unstimulated or stimulated with IFN-g amma and LPS, was evaluated using the cytotoxic/cytostatic assay of B16F10 tumor cells, the suppressive effect of macrophages on the proliferation of B16F10 tumor cells was decreased after exposure to SE. In conclusion, SE, w hen administered in the drinking water at doses from 80 mg/l to 800mg/l, pr oduced minimal toxicological and immunotoxic effects in female B6C3F1 mice.