Excess haloacetic acids detected in Thames Centre drinking water

The Middlesex-London Health Unit (MLHU) and the Municipality of Thames Centre have announced levels of haloacetic acids (HAA) in the town's water supply that exceed the province's maximum acceptable concentration.

HAAs are a group of byproducts that can form in drinking water systems when chlorine compounds used as disinfectants react with organic materials in the water. There is no immediate health risk to people using the water for showering, drinking, and other purposes, officials say.

"Theoretically if you drink it for a long, long time, your risk of cancer can go up ever so slightly by a very, very small amount," said Dr. Alex Summers, the region's medical officer of health. "The key thing we want people to know is that these findings do not resemble and do not reflect an immediate health risk to those who are using the water."

The level of HAAs currently found in the Thames Centre water supply are just barely above acceptable levels. The province mandates that levels must not exceed 80 micrograms per litre, or 80 parts per billion. Based on testing that's done four times per year, the municipality's concentration was pegged at 82.6 micrograms per litre, or 82.6 parts per billion.

Although the health unit typically assists municipalities with plans to reduce HAA levels, most of the decision making happens at the municipal level.

"Some of those options might include finding alternative sources of water. Sometimes it means modifying the disinfection process and the filtering process to try and lower the amount of organic material that's in the water to start," he said.

Thames Centre is trying to reduce the number of the acids through chemical processes while water is being treated, said Jarrod Craven, director of public works for the municipality. 

There is no reason to believe the high HAA concentration in Thames Centre is indicative of potential issues in the water supplies of other municipalities, Summers said. 

A statement by the MLHU says the benefits of chlorination to disinfect and treat water has led to the virtual elimination of waterborne disease, and far outweighs potential risks associated with slightly elevated HAA concentrations.