Bromate: concern for developmental neurotoxicity?

The use of ozonation in the purification of drinking water can lead to the formation of bromate. The current regulatory challenges for bromate contamination of drinking water include the need to assess potential human health risks. One health risk of concern is developmental neurotoxicity. Currently, the need for a developmental neurotoxicity study for bromate, based on the weight of evidence, is uncertain. Bromate induces neurotoxicity in adults at high acute exposures and produces hearing loss and structural damage in the cochlea in humans and rodents. However, there is a wide margin of exposure in these studies compared to environmental levels of bromate in water supplies. Data on the effects of bromate on thyroid hormone levels is not consistent and thyroid endocrine disruption is not likely a causative factor in thyroid tumor formation. There is no evidence that bromate caused central nervous system malformations, brain weight changes in developmental studies, nor are there any known structure-activity relationships to other known neurotoxicants. A prudent approach to reduce the uncertainty in the need for a developmental neurotoxicity study of exposure to bromate in drinking water should include determinations of whether bromate ototoxicity occurs with extended duration, low concentration exposures. These studies would provide invaluable data for the weight-of-evidence approach used to determine the necessity of a developmental neurotoxicity study of bromate.