What Is Bromate?
Bromate may be formed in water during ozonation when the bromide ion is present. Under certain conditions, bromate may also be formed in concentrated hypochlorite solutions used to disinfect drinking-water. This reaction is due to the presence of bromide in the raw materials (chlorine and sodium hydroxide) used in the manufacture of sodium hypochlorite. Bromide is not oxidized by chlorine dioxide, so the use of chlorine dioxide will not generate hypobromous acid, hypobromite ion or bromate. Bromate can also be formed in electrolytically generated hypochlorous acid solutions when bromide is present in the brine.
How Does Bromate Get In Drinking Water?
Bromate is usually found in drinking water as a result of water treatment, rather than through source water contamination. The presence of bromate in treated drinking water is primarily related to the reaction between ozone and naturally occurring bromide in source water and to its formation during the generation of hypochlorite solutions used to disinfect water.
What Are The Health Effects Of Bromate?
The U.S. Environmental Protection Agency developed a level that it considers protective of non-cancer health effects from long-term exposure, including individuals who may be more susceptible including women of childbearing age and children. Assuming an adult drinks about two quarts of water a day at the drinking water standard of 10 micrograms per liter, their exposure is about a sixth of that level. The increased lifetime cancer risk from drinking this water everyday poses a moderate risk level of about two in ten thousand. These exposure and risk estimates are likely to be overestimates since most people would not consume two quarts of water containing bromate at the standard for their lifetime.
The information on the toxicity of bromate comes from accidental or intentional poisonings in people and from studies on laboratory animals. Some people who ingested large amounts of bromate had gastrointestinal symptoms such as nausea, vomiting, diarrhea and abdominal pain. Some individuals who ingested high concentrations of bromate also experienced kidney effects, nervous system effects and hearing loss. However, these people were exposed to bromate levels many thousand of times the amount that would come from drinking water at its standard.
Exposure to large amounts of bromate for a long period of time caused kidney effects in laboratory animals. Long-term exposure to high levels of bromate has also caused cancer in rats. Whether bromate can cause cancer in people is not known.
Some people may be at greater risk for developing health effects from bromate exposure or have concerns for their pregnancy or nursing infant. Because bromate can cause health effects in kidneys, it is possible that those with pre-existing kidney conditions could be at greater risk. The information on the effects of bromate on reproductive health is limited, but does not indicate a concern at levels near the drinking water standard.