Canada approved neonic pesticides with outdated studies on human health

A growing body of evidence, showing that Canada’s most common insecticides are more dangerous to human health than previously thought, has not been fully assessed by this country’s pesticide regulator, Canada’s National Observer has found. 

Neonicotinoid pesticides (neonics) are a class of commonly used insecticides known to have a devastating impact on bees, birds and biodiversity. They have largely been banned in the European Union and Quebec for that reason. But the pesticides are ubiquitous in waterways around the country, sometimes in levels that exceed federal safety guidelines, and are common in drinking water in agricultural regions like southern Ontario.

A succession of academic papers and government studies from the E.U. and California published in recent years have found that even small amounts of neonics can harm the human reproductive system and fetal brain development, with the impacts potentially only evident after years of exposure.

Canada's National Observer spoke with leading researchers in the nascent field of neonics and health: Jodi Flaws, a reproductive health expert at the University of Illinois and Steeve Thany, a neurobiologist at the  Université d'Orléans in France. Both emphasized that their research shows neonics can harm mammals' physiological functions, and extrapolated that they likely harm human health, but more studies are needed. 

“We find neonics everywhere. It’s hard to find people that haven’t been exposed to some level,” said Darrin Thompson, an environmental health expert at the University of Iowa. “My concern is that, as we learn more, are we going to find out that neonics are not as safe as they’ve been presented?”

These warnings have not prompted an immediate response from Canada's Pest Management Regulatory Agency (PMRA). The agency has so far allowed all pesticides to remain in use and has stuck to its standard 15-year schedule for re-evaluating each individual pesticide. 

Only one has been completed: in 2016, the agency finalized its health review of imidacloprid (the full review was completed in 2021), one of Canada's three most common neonics and the pesticide that prompted health warnings from European and California regulators. That assessment concluded there could be neurodevelopmental problems linked to high doses of imidacloprid, but the regulator had not obtained test results for low- and mid-level doses and said it wasn't concerned about the missing data.  

Re-evaluations for Canada's other two widespread neonics, clothianidin and thiamethoxam, are scheduled to be published in late 2024 or 2025. The agency has also said it will complete its re-evaluation in late 2025 or 2026 for acetamiprid, a neonic that European regulators said in 2013 threatened brain development. 

In a Friday statement, the agency said it "continues to monitor for new information related to neonicotinoids, including regulatory actions taken by other governments, as well as the publication of new scientific literature. The Department will take appropriate action if there are reasonable grounds to believe that approved use of any pest control product is resulting in any risks of concern to human health or to the environment."

The PMRA's silence on emerging research about the health risks of neonics is the latest chapter in its longstanding efforts to keep the pesticides in use. A Canada's National Observer investigation this autumn revealed the agency colluded with pesticide companies to stave off a proposed ban on their use, which was recommended by government scientists to protect biodiversity. 

The problems stretch back even further. In the mid-2000s, Canada and the U.S. collaborated to fast-track approvals for neonics, citing industry claims the chemicals were safe for humans because of their chemical structure. To do so, both agencies waived some of their standard health and environmental safety requirements in what was meant to be a temporary measure to get the pesticides on the market. 

But they never followed up to get that research. This past October, a group of American researchers found out the U.S. Environmental Protection Agency, responsible for pesticide regulation, never obtained key data about the neurodevelopmental toxicity of five neonics at low- and medium doses. Their findings caused concern in light of growing evidence that small amounts of neonics can be harmful. 

A similar situation appears to have played out in Canada. According to the PMRA's 2016 health review for imidacloprid, the agency noted that some of the industry studies it assessed found the pesticide was linked to some developmental neurotoxicity problems. But like its U.S. counterpart, Canadian regulators said in the review they did not obtain the low- and mid-level neurotoxicity data. 

Canada's National Observer asked the PMRA if it had obtained all the developmental neurotoxicity data it typically requests as part of an evaluation, and if the agency had waived any of those requirements. The regulator did not answer directly and instead, pointed to the hard-to-navigate public registry and Pesticide Product Information Database. 

Then, in 2015, Canada's Auditor General published a scathing report about the PMRA's approval process for neonics. The agency's decision to fast-track neonics onto the market, and failure to obtain and review the still-missing safety data risked putting Canadians in danger, the audit concluded. 

But since the pesticides were already being widely used, the Auditor General warned it would be much harder for the PMRA to ban the products, if new research found them to be excessively dangerous to human health or the environment. 

That prediction was prescient. In 2021, after five years of industry pressure, the PMRA backed off a proposed ban on imidacloprid and two other neonics that was meant to protect bees and biodiversity. 

But under the shadow of this debate and similar ones happening in the U.S. and Europe, a constellation of researchers started warning that neonics were harming humans, as well. 

"The field of studying the health effects associated with neonicotinoid exposure is expanding very, very quickly right now," said Alexis Temkin, a toxicologist with the environmental organization Environmental Working Group, specializing in pesticides and toxic chemicals. "And a lot of those studies actually end up showing [dangerous] doses that are a lot lower than what industry-submitted studies show."

She noted that the European Food Safety Agency and the California Environmental Protection Agency have warned that the neonics imidacloprid and acetamiprid might be more dangerous to human health than previously thought.

The European review, published in 2013 before the E.U. banned neonics in 2018, found that imidacloprid and acetamiprid could harm parts of the brain associated with learning and memory.  

The California assessment, completed in 2022, concluded that U.S. groundwater human health guidelines for imidacloprid were dangerously high. Canadian guidelines are lower; however, the report noted that imidacloprid could negatively impact health at doses lower than previously thought. 

But Thany, the French researcher, noted that despite growing warnings about their threat to human health, pesticide companies won't let neonics be more widely banned without a fight. 

"The financial stakes are huge. We are talking about feeding billions of people," he wrote. "But above all, it's about dominating the world market and human agriculture."