Maryse Bouchard: the health risks associated with pesticides

The series “Tour d’horizon en trois questions” highlights research in all its forms and takes an informed look at current events.

Maryse Bouchard, professeure chercheuse spécialisée en santé environnementale à l’INRS

Glyphosates and neonicotinoids have created quite a bit of buzz in the media. These pesticides were—and still are—used not only in agriculture to protect crops from pests and diseases, but also in parks and public spaces to fight weeds.

Pesticide residues are also found in produce and even in drinking water, which is raising growing public health concerns.

The risks associated with pesticides are known the world over. Yet Professor Maryse Bouchard of the Institut national de la recherche scientifique (INRS) deplores the glaring lack of research and funding in this area. She believes that there are not enough studies to assess the true risks of pesticides for human health in Quebec and the rest of Canada.

The environmental health researcher sheds light on this public health issue.

Traces of pesticides are everywhere: in our fields, on our plates, in our water, in our parks and public spaces. Do we know the actual risks to human health from these repeated and multiple exposures?

A lot of people ask me about the risks of pesticides, but it’s a difficult question to answer because there are hundreds of different pesticide chemicals being released into the environment in Canada. Numerous studies have shown how many pesticides are harmful to the health of agricultural workers, with effects like reduced male fertility, Parkinson’s disease, respiratory problems, multiple myeloma, and cancer of the lung, prostate, and colon. Even for those who are not exposed at work, epidemiological studies suggest that many pesticides may be endocrine disruptors; research has reported associations between exposure and changes in sex hormone concentrations. Some pesticides have even been found to interfere with the intestinal microbiome, inducing metabolic disorders in animals.

Personally, I’ve been particularly interested in documenting the risks of pesticides for children. I began working on the subject as a postdoctoral fellow at the Harvard School of Public Health (now the Harvard T.H. Chan School of Public Health) in 2009, where I was fortunate enough to have access to invaluable data from an American national survey by the National Institutes of Health (NIH). The results of that study showed that the urinary concentration of certain insecticides (namely organophosphates) was associated with an increased risk of attention deficit disorder with or without hyperactivity (ADD/ADHD). From there, I continued my research to better understand how prenatal exposure to pesticides can affect child development. This led me to join Professor Brenda Eskenazi’s team at the University of California, Berkeley, in 2010 to work on a cohort of pregnant women as part of her study. This experience was particularly enlightening, as the project focused on women from Latin America who worked, or whose spouses worked, in agriculture. This meant that the women were vulnerable on several levels: they had high pesticide exposure, low socioeconomic status, and precarious immigration status. What’s more, Professor Eskenazi’s community-based, participatory approach was particularly exciting for me as a young researcher. At the end of this second post-doctorate, I published a study showing that prenatal exposure to organophosphate pesticides was associated with significant IQ deficits in children at age 7.

So yes, there are more and more clear links between pesticide exposure and certain diseases, but we need to redouble our efforts and carry out more research to grasp the real impact on public health, particularly in at-risk populations such as those in agricultural areas.

A number of controversies have arisen concerning the Canadian government’s management of pesticides. There has been criticism of the transparency and reliance on data provided by pesticide manufacturers such as Bayer-Monsanto, particularly when it comes to glyphosate residue limits on certain foods. Do you think scientists should be more involved in the government’s management of chemicals?

It’s essential to get involved. I was particularly concerned when I learned in 2021 that the Pest Management Regulatory Agency (PMRA) was considering making the regulations more permissive for glyphosate, rather than strengthening those regulations, even as more and more scientific data shows the dangers of pesticides for both ecosystems and human health. It’s very clear that the pesticide lobby has an enormous influence on government decisions.

This controversy was widely reported in the media, and the Canadian government decided to set up a science advisory committee to reinforce the independence and transparency of the PMRA’s pesticide assessments. I’ve been involved in this committee since 2023, along with my colleague, Professor Valérie Langlois, an expert in chemical and environmental toxicology. Our committee provides independent advice on the scientific assessment of pesticides, examining the processes used to estimate their risks. We are already seeing many benefits emerge thanks to our committee’s recommendations, but much remains to be done, in particular to tighten pesticide regulations in Canada.

Closer to home, Quebec has also had its fair share of controversies. A former Minister of Agriculture even said that “Monsanto is more powerful than the Quebec government.” And then there is Louis Robert, an agronomist who lost his job at MAPAQ (Quebec’s ministry of agriculture) after blowing the whistle on the influence of pesticide industry lobbies. The government subsequently organized a major consultation, in which I took part by presenting my brief on the effects on public health to a parliamentary committee. One of the outcomes of this parliamentary committee was the creation of a fund to carry out more research into reducing the use of pesticides. To that end, in 2021, the team I am on received a $2.5 million grant over 5 years from the Fonds de recherche du Québec to create the Quebec Sustainable Agriculture Research Network (RQRAD). As part of the RQRAD’s activities, I am currently conducting a study to assess the contamination of produce grown using different agronomic methods.

Pesticide use is closely related to intensive agriculture, yet you are the first researcher to look into the exposure of people living in farming areas in Quebec. Can you tell us more about your research project and how it’s innovative?

This project stems from my long-standing interest in the issues surrounding the risks of pesticides for the public. At this point, I think it’s fair to say that in Quebec, we have more information on pesticide exposure in fish, insects, and amphibians than in humans!

This lack of data is especially marked given Canadians’ growing concern about the issue. What’s more, the Montérégie region is the place in Canada where the most people are potentially overexposed to pesticides due to the population density and the intensity of pesticide spraying.

Our EPURA study on pesticide exposure in agricultural regions, which is funded by the Canadian Institutes of Health Research (CIHR), will allow us to document in detail the ways in which people are exposed to pesticides in farming areas. As a public health researcher, I think it’s important to work with vulnerable subsets of the population. People who live near areas where pesticides are sprayed are undoubtedly vulnerable in this context.

We have just completed the first year of data collection from almost 200 men, women, and children. By the end of the study, we will have collected data from 600 people in several farming communities in the Montérégie region. For each of them, we will estimate the exposure dose based on urinary concentrations and analyze their relationship to the different sources of pesticide exposure: residues from food and water, indoor and outdoor environments, and spraying in nearby fields. The analyses will measure over 50 different pesticides in our samples.

Based on the EPURA data, we will be able to determine the respective significance of the different sources of pesticide exposure. The data will also be used to identify the groups in the community who are most at risk, and the factors that determine their level of exposure. This information is crucial for estimating the risks of toxic effects, and for prioritizing the actions to take to mitigate those risks.

Maryse Bouchard: the health risks associated with pesticides

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