A recent Quebec study shows that a multitude of pesticides can be found in tap water, even after being treated in a water treatment plant.
Sébastien Sauvé, professor of Environmental Chemistry at the University of Montréal, supervised the study that was published in the June edition of the scientific magazine Water Research.
For more than two years, from 2021 to 2023, the researchers collected water samples twice a week of the Châteauguay River in the Quebec Montérégie region.
The samples were collected from the river as the water was pumped to a water treatment plant and compared with treated water samples that left the plant for distribution as drinking water.
The river was chosen because it crosses areas of intensive agricultural activity, where the pesticides used by farmers eventually make their way from the fields to the river roads.
The objective, said Sauvé, was to observe how the concentrations of pesticides in the water varied over time, as well as before and after processing in a water treatment plant.
The highest pesticide concentrations occurred in June and July at the beginning of the growth season, and although none of the samples collected exceeded Quebec guidelines for safe drinking water, the researchers discovered that the treatment process did not effectively filter pesticide.
Scientists warn that they have found traces of pesticides in the drinking water of the municipalities along the Châteauguay River. Although the levels found complied with the Quebec regulations, the study authors recommend that the authorities make changes.
Trace of at least 50 different types of pesticides and metabolites in tap water were found, in some cases in higher concentrations than the source water. Metabolites are molecules that result from the degradation or decomposition of pesticides.
“There is enough,” said Sauvé, adding that some pesticides were found in almost all samples, while others were not detected so often.
“One of the main ones, or the highest concentration, was for glyphosate,” said Sauvé, which is the main active ingredient used in many herbicide formulations.
It is used to kill weeds and is commonly sold under the brand summary.
In Quebec, many municipalities, including Montreal, have banned their sale and use for domestic purposes about concerns for the environment and the possible impact on human health.
In 2015, the International Research Agency of the World Health Organization on Cancer (IARC) concluded that glyphosate was probably carcinogenic for humans.
Health Canada, however, says it does not cause any harmful effect if used correctly.
Cocktail effect a concern
However, more than the impact of any specific pesticide, Sauvé said it is concerned about its combined effect.
“We are receiving a cocktail from different pesticides and all together, they join,” he said.
The way in which compounds react together can affect toxicity, he said, explaining that they can add, partially neutralize or even multiply.
“In a situation like this, with approximately 50 different pesticides and metabolites that we have measured, we cannot know what is the real combined effect of the toxicity of all these compounds, so there are many strangers,” said Sauvé.
Maryse Bouchard, a professor of Environmental Health at the Institut National de la Recherche Scientifique, He told Radio-Canada that the study highlights the need to better evaluate the risks of the “cocktail effect.”
“It is disturbing to see the amount of different pesticide molecules, many with proven toxicity,” he said.
Possible solutions
While Sauvé said there was no reason for tap water consumers to scare, the findings raise some concerns.
“It is definitely not a case for panic. It is a case to ask questions, ask local authorities, ‘Can we improve our system?'” He said.
What you would like to see are stricter guidelines similar to those used in Europe. Specifically, he would like to see an upper limit in the total concentration of combined pesticides allowed in tap water.
“And then, the cities that are exposed to those levels would simply have to improve their water treatment,” said Sauvé, adding that he should be on attention.
Sarah Dorner is a professor in the Department of Civil, Geological and Minera Engineering in Polytechnique Montreal and Industrial Co -President about Drinking Water in Polytechnique.
He said that having stricter standards for drinking water could help, but said it is important to keep in mind that 20 percent of exposure to pesticides is supposed to come from drinking water, and 80 percent through other sources such as food.
In his opinion, the improvement of water treatment plants can be expensive and would only solve part of the problem.
“It will solve the problem to drink water,” he said, but not other problems related to biodiversity and ecosystem health.
A better approach, he said, could be to reduce the application of pesticides at the source and work with agricultural communities that use them to better understand how they are used and what can be done.
Look | Prohibited glyphosate for domestic use in Montreal:
In a written statement to CBC News, Mélina Jalbert, spokesman for the Quebec Ministry of Environment, said he collaborates with several government partners, including Health Canada and the Institut National de Santé Publique du Québecto guarantee the quality of drinking water in Quebec.
In addition, Jalbert said the Ministry verifies pesticide levels in water around agricultural lands every year.
“It should be noted that the last pesticide evaluation shows a decrease in the agricultural sector and that we continue our efforts to reduce its use,” he wrote.
Sauvé acknowledged that the government does annual controls, but said they could not be taking measures when pesticide levels reach their maximum point.
