A few days ago, the Municipality of Les Cèdres informed its citizens that THM levels in drinking water had fallen back below the acceptable threshold of 80 micrograms per liter.

Last May, the municipality had issued a statement informing citizens served by the municipal water system that their drinking water contained THMs (trihalomethanes) higher than the average permitted concentration, and that it was implementing an action plan to reduce them.

The municipality of Les Cèdres tripled the number of tests it carried out in order to monitor the situation more closely, as indicated in its July 13 follow-up. While it is required to carry out 4 tests, more than a dozen will be executed in 2023.

Since the implementation of its action plan in June 2023, results have decreased and are below the provincial standard of 80 mcg/L. Precise averages will be communicated in August 2023, when sufficient data has been collected, says the municipality.

It's important to note that no boil-water advisory has been necessitated by this increase in THM concentration.

What are trihalomethanes?

The formation of trihalomethanes (THMs) is a complex process that occurs when chlorine reacts with organic matter naturally present in water. And chlorine is, of course, essential for making water drinkable.

Some citizens were concerned about the rise in THMs in the municipality's drinking water network. Children are considered more sensitive to this exposure.

These compounds can also be absorbed through the skin when in contact with water, or inhaled once they have volatilized. In addition to drinking water, showering, laundry, dishwashing and swimming pools are all sources of THM exposure.

These substances are also detected in food and, to a lesser extent, in outdoor air and certain consumer products.

Long-term exposure in excess of standards can increase the risk of developing various cancers, including bladder, rectum, intestine, brain and pancreas, according to animal tests. Every municipality in Quebec is required to check these levels at least 4 times a year.

City statements are available on the municipality's website and Facebook page.