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SUBCHRONIC SODIUM CHLORATE EXPOSURE IN DRINKING WATER RESULTS IN A CONCENTRATION-DEPENDENT INCREASE IN RAT THYROID FOLLICULAR CELL HYPERPLASIA
Citation:
Hooth, M J., A B. DeAngelo, M H. George, E. T. Gaillard, G. S. Travlos, G. A. Boorman, AND D C. Wolf. SUBCHRONIC SODIUM CHLORATE EXPOSURE IN DRINKING WATER RESULTS IN A CONCENTRATION-DEPENDENT INCREASE IN RAT THYROID FOLLICULAR CELL HYPERPLASIA. TOXICOLOGIC PATHOLOGY 29(2):250-259, (2000).
Description:
Chlorine dioxide (C102) is an effective water disinfectant but sodium chlorate (NaC103) has been identified as a potentially harmful disinfection by-product. Studies were performed to describe the development of thyroid lesions in animals exposed to NaC103 in drinking water. Male and female F344 rats and B6C3F1 mice were exposed to 0, 0.125, 0.250, 0.500, 1.0 or 2.0 g/L NaC103 for 21 days. Additional male F344 rats were exposed to 0, 001, 0.010, 0.100, 1.0, or 2.0 g/L NaC103 for 90 days. Female F344 rats were exposed to 0, 0.500, 1.0, 2.0, 4.0 or 6.0 g/L of NaC103 for 105 days. Thyroid tissues were processed by routine methods for light microscopic examination and follicular cell hyperplasia was diagnosed using a novel method. Thyroid hormone levels were altered after 4 and 21 days. NaC103 treatment induced a concentration-dependent increase in the incidence and severity of thyroid follicular cell hyperplasia. Male rats are more sensitive to the effects of NaC103 treatment than females. Follicular cell hyperplasia was not present in male or female B6C3F1 mice. These data can be used to estimate the human health risk that would be associated with using C102, rather than chlorine, to disinfect drinking water.