Guiding Risk Reduction for Breast Cancer-Relevant Chemicals (BC-Chems): Chemical Production Volumes, Sources, Intake Levels, Emissions, and Regulations

Abstract

Breast cancer (BC) among women in all age groups continues to increase. Changes in reproductive risk factors cannot explain these trends, and rising rates among women under 40 cannot be explained by cancer screening, suggesting other factors are involved. We recently identified 920 chemicals whose biological activity suggests they can increase BC risk, the breast cancer-relevant chemical (BC-Chem) list, because they induce mammary tumors in rodents or activate estrogen or progesterone signaling in vitro. To develop exposure reduction strategies and inform BC research, we used US government databases to identify production volumes, uses, environmental releases, and predicted exposure levels in the US population. We found that exposure to potential breast carcinogens is ubiquitous. Billions of pounds of BC-Chems were emitted to air in 2020; tens of millions of pounds were released to the environment through industrial activities in 2024; and 143 were produced at 1 million pounds or more in 2019. Further, we found 500 BC-Chems likely present in consumer products, 462 in food, 162 in drinking water, 485 in pesticide formulations, 142 in pharmaceuticals, and 106 in construction materials. High-end predictions for median daily intakes in the US population exceeded 0.1 mg/kg body weight for 84 BC-Chems. Exposure could be reduced by health protective policies such as regulating drinking water contaminants and avoiding use in common products. These findings provide quantitative evidence to guide systematic prioritization of chemicals and mixtures for studying health effects, monitoring exposures, assessing risks, and preventing harm through exposure reduction.