Hundreds of Chemicals Linked to Increased Breast Cancer Risk, Study Finds

Hundreds of chemicals commonly found in everyday products, including cosmetics and food packaging, may increase the risk of breast cancer, according to a comprehensive study. The research highlights malathion, the active ingredient in the head lice treatment Derbac M, as one such chemical that could pose a risk.

Researchers cautioned that exposure to potentially harmful substances can begin years or even decades before breast cancer develops. "People are exposed to hundreds of chemicals from multiple sources throughout their lives, and these exposures add up," said Dr. Jennifer Kay, the study's lead author. "Breast cancer can take years to develop, so reducing exposure to potentially harmful chemicals early in life is an essential part of cancer prevention."

The study, published in Environmental Health Perspectives, identified other chemicals of concern, including Bisphenol A (BPA), used in drink can linings and till receipts, and methylparaben, a preservative found in moisturizers, shampoos, and deodorants. Benzene, commonly encountered through exhaust fumes and cigarette smoke, and styrene, used in some takeaway coffee cups and food containers, were also flagged.

These findings emerge amidst an increase in breast cancer cases among younger women. Between the ages of 20 and 49, cases rose by nearly 10% over the last decade. To pinpoint major sources of exposure, researchers analyzed over a dozen U.S. government databases related to chemical use, pollution, and human exposure. They focused on more than 900 chemicals previously identified as potentially linked to breast cancer, including those known to disrupt hormones or cause mammary tumors in animals.

The study found that hundreds of these chemicals remain in use in various products, from cosmetics and food packaging to building materials and medical equipment. BPA, for instance, was found in reusable plastic food containers and the lining of drink cans. While banned from baby bottles in Britain in 2011, its use in food-contact materials was further restricted by the European Commission in December 2024, though the UK has not yet followed suit. DEHP, a plasticizer used in some medical equipment, and methylparaben were also highlighted. Parabens can mimic estrogen, a hormone that can fuel the growth of certain breast cancers.

Scientists noted that current safety assessments often examine individual chemicals rather than the combined effects of multiple substances people are exposed to daily, suggesting a potential regulatory oversight. "Tracking and reducing people's exposure to pesticides from multiple sources is an essential part of cancer prevention," Dr. Kay added.

Approximately 59,000 women and 420 men are diagnosed with breast cancer annually in the UK. The study acknowledges that there is no single cause for the disease and does not prove that exposure to any one identified chemical will lead to cancer. Known risk factors include age, family history, alcohol consumption, smoking, obesity, dense breasts, and exposure to certain hormones, such as through hormone replacement therapy.