Toxicity, Occurrence and Current Status of Bromate in Drinking Waters

7 TOXICITY, OCCURRENCE AND CURRENT STATUS OF BROMATE IN DRINKING WATERS 

The US EPA has subsequently published a comprehensive toxicological review of bromate (US EPA, 2001). Studies with rats based on low-dose linear extrapolation, using the time-to-tumour analysis, and using the Monte Carlo analysis to sum the cancer potency estimates for kidney renal tubule tumoms, mesotheliomas, and thyroid follicular cell tumours, gave an upper-bound cancer potency estimate for bromate ion of 0.70 per mg/kg day. This potency estimate corresponds to a drinking water unit risk of 2 x 10 per pg/L, assuming a daily water consumption of 2 litres/day for a 70-kg adult. Lifetime cancer risks of 10 , 10 , and 10 are associated with bromate concentrations of 5, 0.5, and 0.05 pg/L, respectively. A major source of uncertainty in these estimates is from the interspecies extrapolation of risk from rats to humans. 

The acute toxic dose of bromate (expressed as bromate) for a 70-kg individual is estimated at about 3 g (Dreisbach and Robertson, 1987). As a typical person will consume 2 litres of tap water per day, this would correspond to a bromate concentration of 1500 mg/L acute concentration . This is 150 000 times higher than the statutory EC drinking water limit concentration of 10 pg/L (Council Directive, 1998), which can be regarded as a chronic toxicity safe limit. 

As bromate is stable once generated, attention is being paid to effluents and wastewaters treated by ozonation. Bromide-containing effluents will contribute to the rise of bromate levels in receiving water bodies which are subsequently used as a source for drinking waters. This calls for essential regulation of bromide and bromate in effluents and wastewaters prior to final discharge. 

For bromate analysis, ethylenediamine (EDA) is added to the sample in order to convert any hypobromite present into the corresponding bromamines, thus preventing ongoing conversion to bromate. Bromate has been found to be stable in a range of drinking waters over three months using amber glass bottles either with or without EDA (Thompson, 1999). 

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Toxicity, Occurrence and Current Status of Bromate in Drinking Waters... 

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