Study Flags 90% of Commonly Used Chemicals as Potential Breast Cancer Risks

The increasing number of synthetic chemicals in use poses a significant challenge in identifying potential risks and harm associated with exposure. Scientists, in a recent study led by Dr. Jennifer Kay from the Silent Spring Institute, have developed a rapid method to predict whether a chemical is likely to cause breast cancer based on specific traits exhibited by the chemical. 

Breast cancer remains the most commonly diagnosed cancer in the United States, with recent data indicating an increase in rates among young women that cannot be solely explained by genetic factors. The study aims to provide a roadmap for regulators and manufacturers to swiftly identify chemicals that may contribute to breast cancer, enabling preventive measures and the exploration of safer alternatives. 

The researchers conducted an extensive search through international and U.S. government databases, including the International Agency for Cancer Research (IARC), the National Toxicology Program, the U.S. Environmental Protection Agency (EPA), and the National Cancer Institute. They identified chemicals that had been linked to causing mammary tumors in animals.

Additionally, the team analyzed data from the EPA’s ToxCast program to identify chemicals acting as endocrine disruptors, specifically those activating the estrogen receptor in breast cells or inducing the production of estrogen or progesterone, established risk factors for breast cancer. 

The study identified a total of 921 chemicals with potential links to the development of breast cancer. Importantly, 90% of these chemicals are commonly found in consumer products, food and drink, pesticides, medications, and workplaces. The breakdown revealed 278 chemicals causing mammary tumors in animals, more than half of which induce the production of estrogen or progesterone, while about a third activate the estrogen receptor. 

Considering breast cancer as a hormonal disease, the researchers expressed concern about the high number of chemicals capable of altering estrogen and progesterone levels. To assess the potential risk further, the team examined databases for evidence of DNA damage, identifying 420 chemicals on their list exhibiting both DNA-damaging and hormone-altering characteristics. 

The study highlighted that chemicals causing mammary tumors in animals were more likely to possess these DNA-damaging and hormone-disrupting traits. Traditionally, chemicals causing mammary tumors in animals have been considered indicative of potential breast cancer risks in humans.

However, conducting such animal studies is resource-intensive and time-consuming, leading the researchers to propose that screening chemicals for hormonal traits could be an effective strategy for identifying potential breast carcinogens. 

Environmental factors, including exposure to various chemicals, have been increasingly recognized as significant contributors to cancer development. Some studies have already established links between breast cancer and pesticides, hair dyes, and air pollution. Moreover, exposure to hormone-disrupting chemicals during crucial developmental periods, such as in the womb or during puberty, has been associated with alterations in breast development that may increase the risk of cancer later in life. 

The study conducted by the Silent Spring Institute may influence how the EPA assesses chemicals for safety. Notably, more than 30 pesticides identified in the study had previously been approved by the EPA despite evidence linking them to mammary tumors.

The authors hope that their comprehensive list of breast cancer-relevant chemicals, including numerous endocrine disruptors, will inform the EPA’s strategic plan to evaluate pesticides for their hormonal effects, thereby enhancing public protection from harmful exposures. 

The study provides a valuable tool for identifying potential breast cancer-related risks associated with synthetic chemicals. By focusing on hormonal traits and the potential to cause mammary tumors, this approach offers a faster and more efficient means of screening chemicals, aiding regulators and manufacturers in making informed decisions to protect public health. 

Journal Reference 

Application of the Key Characteristics framework to identify potential breast carcinogens using publicly available in vivo, in vitro, and in silico data, Environmental Health Perspectives (2024). DOI: 10.1289/EHP13233. ehp.niehs.nih.gov/ehp13233.