In an analysis of how regulators review pesticides for their potential to cause cancer, researchers at Silent Spring Institute identified more than two dozen registered pesticides that were linked with mammary gland tumors in animal studies. The new findings raise concerns about how the US Environmental Protection Agency (EPA) approves pesticides for use and the role of certain pesticides in the development of breast cancer.
New research from scientists at Silent Spring Institute publishes an extensive list of registered pesticides (approved by the US Environmental Protection Agency) that is demonstrated to be linked to mammary gland tumors in animal studies. The toxicology report highlight the need for more informed regulation on pesticides that are supposedly “safe”.
Reported in the journal Molecular and Cellular Endocrinology, the investigation began when Silent Spring scientists found that exposure to a common herbicide called triclopyr caused rodents to develop mammary gland tumors.
Ruthann Rudel, an environmental toxicologist and director of research at Silent Spring, commented that this initial finding sparked suspicion. "We know pesticides like DDT increase breast cancer risk, so we decided to look into it," says co-author Rudel. "After examining pesticide registration documents from EPA, we found two separate studies in which rodents developed mammary gland tumors after being exposed to triclopyr, yet for some reason regulators dismissed the information in their decision not to treat it as a carcinogen." Was the same oversight happening with other pesticides?
Rudel and colleague scientist Bethsaida Cardona reviewed more than 400 EPA pesticide documents in order to categorize the health effects of each pesticide. In their analysis, they identified 28 pesticides that are linked with mammary gland tumors. Only nine were flagged by the EPA.
Of the 28 registered pesticides identified with a link to mammary gland tumors, many are endocrine disruptors, meaning they alter steroid synthesis in H295R cells, activate nuclear receptors, or affect xenobiotic-metabolizing enzymes.
The team urges the EPA to re-evaluate five key pesticides that are widely used: malathion, triclopyr, atrazine, propylene oxide, and 3-iodo-2-propynyl butylcarbamate (IPBC). As Eureka Alert reports, “IPBC is a preservative in cosmetics; triclopyr is an agricultural herbicide that is also used to control vegetation growth along rights-of-way; malathion is a common residential and agricultural pesticide and is used in some lice treatments; atrazine is one of the most commonly used herbicides in agriculture; and propylene oxide is used to preserve food, cosmetics, and pharmaceuticals, and has many similarities with ethylene oxide, a known human carcinogen.”
"In light of our findings, we hope EPA updates its guidelines for assessing mammary gland tumors by considering evidence that more completely captures the biology of breast cancer, such as the effects of endocrine disruptors," says Cardona.