Food Safety Awareness Note 1

Food Safety Awareness Note 1

Health Risks of Bromate in Drinking Water

Occurrence in Drinking water

Bromate (BrO3-) is an anion composed of Bromine and Oxygen atoms. It exists in a number of salts, the most common of which are potassium bromate and sodium bromate. Potassium bromate is soluble in water (7.5 g/100 mL) at 25°C and is highly stable in water at room temperature. Bromate is not a natural component of water but may be formed during the disinfection of water through ozonation or hypochlorination which ultimately results in oxidation of bromide ions present in water and their conversion to Bromate ions. Under certain conditions, bromate may also be formed in concentrated hypochlorite solutions used to disinfect drinking-water , due to the presence of bromide in the raw materials. Bromide (Br-) itself is naturally found in sea water (65 – 85 mg/L) and ground water.

Health Risks of Bromate

Acute Exposure

Bromate is a highly toxic substance that may cause irreversible renal failure and deafness resulting from neural damage in the ear. Deaths have also been reported from single oral doses of Bromate in the range of 200 to 500 mg/kg body weight. Toxic effects of Bromate include nausea, vomiting, abdominal pain, anuria and diarrhoea, peripheral neuropathy, haemolytic anaemia, hypotension, central nervous system dysfunction and pulmonary oedema.

Chronic Exposure

Bromate is associated with the following health risks when ingested in small doses (exceeding maximum permissible limits) over long periods of time:

1- Kidney failure (non-carcenogenic)

2- Increased Cancer risk and Genotoxicity:

Carcinogenic risks of long-term exposure to Bromate in drinking water include renal tumours and thyroid cancers believed to be caused by oxidative stress and DNA damage leading to chromosomal mutations.

The life time cancer risk is associated with Bromate levels in drinking water, consumption rates and duration of exposure. Scientific studies indicate that long-term consumption of drinking water with Bromate levels in the range 46 – 65 μg/L are associated with the risk of cancer in one individual out of a population of ten thousand. Cancer risks increase with increased Bromate levels (See table 1).

Table 1

Bromate Concentration range in drinking water (μg/L)	Life time cancer risk per population consuming Bromate contaminated water
46 – 65 μg/L	1 in a population of 10 thousand
4.6 – 6.5 μg/L	1 in a population of 100 thousand
0.46 – 0.65 μg/L	1 in a population of 1 million

Source : Kurokawa et al., 1986

Maximum Permissible Limits

The UN World Health Organisation (WHO) regulated an interim maximum permissible level of 10 μg/L of Bromate in drinking water, which is a figure that is subject to review in light of developments in analytical and treatment technology and additional data on health risks associated with exposure to bromate in drinking water. Other international organizations such as the USEPA set a target value of zero bromate in drinking water.

References:

1. Bromate in Drinking Water, Background document for WHO Guidelines for Drinking Water Quality, WHO/SDE/WSH/03.04/78, 2004.

2. Guidelines for Carcinogen Risk Assessment, USEPA, Risk Assessment Forum, EPA/630/P-03/001B, March 2005.

3. Bromate-Induced Ototoxicity, proceedings of the workshop to evaluate the State-of-the-Science in All Aspects of Bromate Toxicity including the Mechanisms of Cancer Induction, Campbell, C.M., February 2005.

4. Kurokawa, Y., Takayama, S., Konishi, Y., Hiasa, Y., Asahina, S.,Takahashi, M., Maekawa, A. and Hayashi, Y. Long-term in vivo carcinogenicity test of potassium bromate, sodium hypochlorite and sodium chlorite conducted in Japan. Environ. Health Perspect., 69:221–235 (1986).