Investigators Find Over 900 Chemicals Can Increase Risk of Breast Cancer

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A study published in Environmental Science & Technology Letters suggests that addressing issues regarding plastic pollution can potentially lower rates of breast cancer while also protecting the environment. According to the investigators, rates of breast cancer have been increasing globally, and these increased rates are notably in younger adults.^1,2

Breast cancer, which is the most common cancer worldwide, has been found to be one of many cancers in recent data to increase in individuals under the age of 50 years. Most of the early-onset diagnoses this research found are breast cancer. While some well-studied risk factors—such as having fewer children—cannot fully explain this trend, researchers have turned to other possible solutions, such as the chemicals in food, water, and consumer products.^1,2

According to the authors, they recently identified that 920 breast cancer-relevant chemicals (BCRCs) based on evidence that they induce mammary tumors in rodents or have specific endocrine-disrupting effects. The authors found that nearly half of these chemicals (n = 414) are found in plastics, signaling a need for changes which can positively impact both the environment and the burden of breast cancer and other health conditions.²

Specifically, the investigators observed that 98 of the 414 chemicals were shown to cause mammary tumors in rodent studies, 188 increase the level of estradiol synthesis, 132 increase the level of progesterone synthesis, and 149 activated the estrogen receptor. Each of these types of biological activities are established pathways to breast cancer. Additionally, the authors found that of the 341 endocrine-active BCRCs in plastics, 166 were shown to have robust responses in vitro whereas 175 have borderline activity that will require additional testing.²

Further, 160 of these endocrine-active chemicals were also found to be genotoxic, another mechanism for carcinogenesis. Overall, the authors prioritized 175 potential breast carcinogens in plastics for regulation and reduction because of evidence that they can cause mammary tumors or have a robust hormonal activity when combined with genotoxicity.²

As evidence of relevance to human health, the investigators noted that epidemiological studies have also shown associations with breast cancer and breast density for several BCRCs, including constituents of air pollution, hair dyes, and dichlorodiphenyltrichloroethane. In experimental studies, chemicals that increase human breast cancer risk were found to also increase the frequency of mammary gland tumors. Additionally, chemicals that cause mammary gland tumors were enriched for endocrine activities that are relevant to breast cancer and its development. The authors note that because methodological barriers to breast cancer epidemiology for universal exposures outside of an occupational setting, inferences from animal and cell studies are an important basis for regulation and are consistent with approaches used by other notable organizations, such as the International Agency for Research on Cancer.²

“Because manufacturers do not always know what chemicals are used in their products, it’s important for leaders to focus on reducing the production and use of specific chemicals, not just the products,” Ruthann Rudel, MS, research director at Silent Spring Institute, said in a news release. “And by prioritizing chemicals that increase breast cancer risk, a global agreement could have a big impact on reducing exposure to substances that are likely contributing to a disease that overwhelmingly impacts women around the world.”¹

The authors urge that new environmental interventions could have a major impact on reducing cancer globally, in particular, breast cancer. Action on limited-data chemicals in addition to those with extensive evidence is crucial in lowering risks. The investigators urge regulators and policymakers to consider the integrated data sources and innovative frameworks or guidelines, which may reduce hazards, rather than allowing possible carcinogens to continue to accumulate within individuals’ bodies, eventually causing harm.^1,2

REFERENCES

1. Silent Spring Institute. Curbing plastics pollution could help reduce global burden of breast cancer. News release. November 29, 2024. Accessed December 20, 2024. https://www.eurekalert.org/news-releases/1066581

2. Shakti R, Kay JE, Franklin ETm et al. Why the UN Treaty on Plastics Can Reduce Early Onset Cancers. Environ Sci Technol Lett. 2024;11(12):1281–1283. doi:10.1021/acs.estlett.4c00942