Bromate
(endorsed 1996)
Guideline
Based on health considerations, the concentration of bromate in drinking water should not exceed 0.02 mg/L.
General description
Bromate is not a normal component of water but may be formed from bromide during ozonation. Concentrations up to 0.09 mg/L have been reported in ozonated drinking water. Bromate is a strong oxidant and will probably react with organic matter in water, forming bromide as a by-product.
Bromate is used in home hair permanent-wave neutralising solutions. Although it is used in some foods overseas, Australian Food Standards do not allow bromate to be used in food in Australia.
Typical values in Australian drinking water
It is unlikely that bromate would be present in Australian reticulated drinking water supplies unless ozonation is used for disinfection.
Treatment of drinking water
There are no published methods for the removal of bromate from drinking water supplies.
Measurement
The concentration of bromate in drinking water can be determined using ion chromatography with conductivity detection. The limit of determination is about 0.005 mg/L.
Health considerations
Bromate is rapidly absorbed from the gastrointestinal tract of rats. Although bromate was not subsequently detected in tissue, bromide concentrations were significantly increased in plasma, red blood cells, pancreas, kidney, stomach and small intestine.
Most cases of human poisoning from bromate are due to accidental or intentional ingestion of home permanent-wave solutions, which can contain 2–10% bromate. Toxic effects include nausea, abdominal pain and diarrhoea, central nervous system depression and pulmonary oedema, most of which are reversible. Irreversible effects include kidney failure and deafness.
In rats exposed to bromate in drinking water for 15 months, adverse effects included inhibited body-weight gain, marked kidney damage, and renal adenocarcinoma. Kidney tumours have been reported in other long-term studies using male and female rats, but not with female mice; male rats also exhibited peritoneal mesotheliomas. There is evidence that tumours occur only after a minimum total cumulative dose has been exceeded.
Bromate exhibited mutagenic activity in tests using bacteria, and caused chromosomal aberrations in cultured mammalian cells. Some evidence of DNA damage has also been reported in rats given potassium bromate.
The International Agency for Research on Cancer has concluded that bromate is possibly carcinogenic to humans (Group 2B, no data in humans but sufficient evidence in animals) (IARC 1986).
Derivation of guideline
The guideline value for bromate in drinking water was derived as follows:
where:
30 mg/kg body weight per day is a lowest effect level from a 15-month drinking water study using rats (Nakano et al. 1989).
70 kg is the average weight of an adult.
0.2 is the proportion of total daily intake attributable to the consumption of water.
2 L/day is the average amount of water consumed by an adult.
10,000 is the safety factor in using the results of an animal study as a basis for human exposure (10 for interspecies variations, 10 for intraspecies variations, 10 because a lowest effect level was used instead of a no-effect level and 10 for carcinogenic and mutagenic effects).
The World Health Organization (WHO) guideline value of 0.025 mg/L was based on a calculation that estimated an additional lifetime risk of seven fatal cancers per 100,000 people. It was recognised that this approach may not be appropriate if, as reported, tumours only occur above a dose threshold. The two different approaches, however, result in essentially the same guideline value.
This guideline should be reviewed when new data are available.
References
IARC (International Agency for Research on Cancer) (1986). IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans: some naturally occurring and synthetic food components, furocoumarins, ultraviolet radiation and potassium bromate. World Health Organization, IARC, 40.
Nakano K, Okada S, Toyokuni S, Midorikawa O (1989). Renal changes induced by chronic oral administration of potassium bromate or ferric nitrilotriacetate in Wistar rats. (In Japanese). Japanese Archives of Internal Medicine, 36:41–47.
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