More than 900 chemicals, many of which are present in common consumer products, have the potential to increase breast cancer risks, a new study has concluded.

Researchers at the Silent Spring Institute examined chemicals listed in major reference databases, including those from the International Agency for Research on Cancer and the US Environmental Protection Agency. They then classified chemicals based on their toxicity and ability to interfere with key human hormones associated with breast cancer.

Based on that analysis, the researchers identified 921 chemicals that can promote breast cancer, including pesticides and those used in food, drinks and medications. Chemicals on the list include permethrin, which is used to control mosquitoes; profenofos, which is used to kill bugs on cotton crops; and trifluralin, which is used to control weeds.

About a third of the chemicals on the list have been linked to mammary tumours in rodents, according to the study, which was published on 10 January 2024 in Environmental Health Perspectives.

Chemicals associated with mammary tumours included 30 pesticides and herbicides approved by the US Environmental Protection Agency, such as malathion. Public Health Watch reports that in August 2023, the EPA limited application of malathion — used as an insecticide in both food agriculture and residential gardening — to protect birds, fish and other wildlife from harm.

[This entry is based on a news update from The Watch, published by the US non-profit Public Health Watch].

• Jones R, White A. Invited Perspective: New Motivations and Future Directions for Investigating Environmental Risk Factors for Breast Cancer, Environmental Health Perspectives, 10.1289/EHP13777, 132, 1, (2024).