A peer-reviewed study published in the journal Environmental Health Perspectives has identified at least 485 pesticide chemicals linked to breast cancer, raising questions about how the United States regulates the substances found in everyday products. The research was carried out by the Silent Spring Institute, with Jenny Kay among the authors.
The researchers found that 84 of these chemicals are detectable in the general population, based on data from the National Health and Nutrition Examination Survey. They caution that the 485 figure is likely an undercount, since most of the compounds in pesticide products are not tracked at all, which means the true number of exposures may be considerably larger.
Much of the problem, according to the study, lies in how the Environmental Protection Agency evaluates pesticides. The agency reviews each active ingredient on its own rather than the full formula that reaches consumers. Around 4,000 inert ingredients have been approved, and those are rarely subjected to safety review. Only about 145 of the identified chemicals are registered as active ingredients, leaving most of the others outside the agency's main scrutiny.
The authors also point to the agency's handling of a 2023 petition asking for tighter review of inert ingredients, which the EPA rejected. They note that the agency has often dismissed concerns about low-dose hormone effects, even though hormone disruption is one of the mechanisms through which such chemicals are thought to influence breast cancer risk.
The researchers raise concerns about industry influence as well, noting that several of the EPA's top pesticide and chemical officials are former lobbyists, a pattern that critics describe as a revolving door between regulators and the companies they oversee. The chemicals in question turn up in crops, lice treatments, lawn products and flea treatments that people encounter in daily life.
To address the gap, the authors recommend expanding California's Proposition 65, the state law requiring warnings about chemicals linked to cancer and other harms, to cover 16 pesticides. Their findings add pressure on federal regulators to look more closely at the full composition of the products Americans use.
We rewrote this story on 4 November 2026 after an editorial review.
Credit. Based on reporting by Tom Perkins for The Guardian. Is this your work? Write to us.
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