Feasibility of conducting human studies to address bromate risks

Findings from epidemiologic studies have been important in evaluating risk of exposure to many contaminants in drinking water. In the case of bromate, a byproduct of ozone disinfection of water, it is unlikely that observational studies of populations exposed to bromate in drinking water will be as revealing as studies of other contaminants, unless risks are much higher than predicted from laboratory studies of rodents. Occupational exposure to bromate has occurred in the flour milling and baking industries, as well as in chemical production of potassium bromate, used as a flour additive. The feasibility of a cohort study of bromate-exposed workers should be evaluated by studying the conditions and levels of exposure in these occupational settings. Bromate exposure causes oxidative damage to guanine bases of DNA, producing 8-hydroxy-guanine (8-OH-Gua), which is excised by 8-oxoguanosine glycosylase (OGG1) and excreted in the urine. Polymorphic variants of OGG1 in human populations have been associated with elevated cancer risk. 8-OH-Gua and 8-hydroxy-deoxyguanosine (8-OHdG) have been used as biomarkers of oxidative damage in many human studies, and it would be feasible to employ these indicators in controlled clinical experimental settings to see if exposure to bromate in water at levels close to the maximum contaminant level influences urinary levels of excretion, and if so, to help quantify the level of oxidative damage. Such a study could fill an important data gap by providing human data to help estimate the carcinogenic risk from this exposure.