Quebec study finds 'cocktail of different pesticides' in treated tap water

CBC News

· Posted: May 13, 2025 4:00 AM EDT | Last Updated: 10 minutes ago

A caller Quebec survey shows that a multitude of pesticides can beryllium recovered successful pat water, adjacent aft being treated astatine a h2o attraction plant.

Sébastien Sauvé, an biology chemistry prof astatine Université de Montréal, supervised the survey that was published successful the June contented of the technological diary Water Research. 

For much than 2 years, from 2021 to 2023, researchers collected h2o samples doubly a week from the Châteauguay River successful Quebec's Montérégie region. 

The samples were collected from the stream arsenic h2o was being pumped into a h2o attraction works and were compared to treated h2o samples leaving the works for organisation arsenic drinking water.

The stream was chosen due to the fact that it runs done areas of intensive agriculture activity, wherever pesticides utilized by farmers yet marque their mode from the fields into waterways. 

The objective, Sauvé said, was to look astatine however pesticide concentrations successful the h2o varied implicit time, arsenic good as before and aft processing astatine a h2o attraction plant. 

Highest concentrations of pesticides occurred successful June and July astatine the opening of increasing season, and portion nary of the samples collected exceeded Quebec guidelines for harmless drinking water, researchers discovered that the treatment process did not efficaciously filter retired pesticides.

WATCH | What's successful the water? 

Traces of at slightest 50 antithetic kinds of pesticides and metabolites were recovered successful pat water, in immoderate cases successful higher concentrations than the root water. Metabolites are molecules that effect from the degradation oregon breakdown of pesticides.

"There is rather a bit," Sauvé said, adding immoderate pesticides were recovered successful astir each the samples, portion others weren't detected arsenic often.

"One of the main ones, oregon the highest concentration, was for glyphosate," Sauvé said, which is the main progressive constituent utilized successful galore herbicide formulations. 

It is utilized to termination weeds and is commonly sold nether the marque sanction Roundup.

In Quebec, galore municipalities, including Montreal, person banned its merchantability and usage for home purposes implicit concerns for the situation and imaginable interaction connected quality health.

In 2015, the World Health Organization's International Agency for Research connected Cancer (IARC) concluded that glyphosate was astir apt carcinogenic to humans. 

Health Canada, however, says it does not origin immoderate harmful effects if utilized properly. 

Cocktail effect a concern

More than the interaction of immoderate specific pesticide, however, Sauvé said he's disquieted astir their combined effect.

"We're getting a cocktail of antithetic pesticides and each together, they adhd up," helium said.

How the compounds respond unneurotic tin impact toxicity, helium said, explaining they tin adhd up, partially neutralize each different oregon adjacent multiply.

"In a concern similar this, with astir 50 antithetic pesticides and metabolites that we've measured, we cannot cognize what the actual combination effect of the toxicity of each these compounds are, truthful there's a batch of unknown," Sauvé said. 

Maryse Bouchard, a prof of biology wellness astatine the Institut nationalist de la recherche scientifique, told Radio-Canada that the survey highlights the request to amended measure the risks of the "cocktail effect." 

"It's disturbing to spot the quantity of antithetic pesticide molecules, galore with proven toxicity," she said.

Possible solutions

While Sauvé said determination was nary crushed for consumers of pat h2o to panic, the findings bash rise immoderate concerns. 

"It's decidedly not a lawsuit for panic. It's a lawsuit for asking questions, asking the section authorities, 'can we amended our system?'" helium said. 

What he'd similar to spot are stricter guidelines akin to those utilized successful Europe. Specifically, he'd similar to spot an precocious bounds connected the full attraction of combined pesticides allowed successful pat water.

"And then, the cities that are exposed to those levels would simply person to amended their h2o treatment," Sauvé said, adding it should beryllium connected a case-by-case basis.

Sarah Dorner is simply a prof successful the section of civil, geological and mining engineering astatine Polytechnique Montréal and concern co-chair connected drinking h2o astatine Polytechnique.

She said having stricter standards for drinking h2o could help, but said it's important to enactment that 20 per cent of   vulnerability to pesticides is assumed to travel from drinking water, and 80 per cent through different sources specified arsenic food.

In her view, upgrading h2o attraction plants tin beryllium costly and would lone lick portion of the problem.

"It'll lick the occupation for drinking water," she said, but not different problems linked to biodiversity and ecosystem health. 

A amended approach, she said, might be to reduce the exertion of pesticides astatine the root and enactment with cultivation communities who usage them to get a amended knowing of however they are utilized and what tin beryllium done.

WATCH | Glyphosate banned for home usage successful Montreal: 

In a written connection to CBC, Mélina Jalbert, a spokesperson for Quebec's Environment Ministry, said it collaborates with respective authorities partners, including Health Canada and the Institut nationalist de santé publique du Québec, to guarantee the prime of drinking h2o successful Quebec.

Furthermore, Jalbert said the ministry checks pesticide levels successful the h2o astir cultivation lands each year.

"It should beryllium noted that the latest pesticide appraisal shows a alteration successful the cultivation assemblage and that we are continuing our efforts to trim their use," she wrote. 

Sauvé acknowledged the authorities does yearly checks, but said they mightiness not beryllium taking measurements erstwhile levels of pesticides peak.