The Covert Threat: The Association Between Air Pollution and Increased Breast Cancer Risk

Researchers from the National Institutes of Health (NIH) have established a link between elevated levels of particulate air pollution and a heightened risk for breast cancer.

NIH scientists collated historical data on air quality with breast cancer statistics from a comprehensive U.S. study.

Scientists at the National Institutes of Health (NIH), particularly those affiliated with the National Institute of Environmental Health Sciences (NIEHS) and the National Cancer Institute (NCI), revealed that residing in areas with high concentrations of particulate air pollution correlates with an elevated occurrence of breast cancer. This research, unveiled on September 11 in the Journal of the National Cancer Institute, is among the most extensive studies thus far, examining the nexus between outdoor air pollution—specifically fine particulate matter—and breast cancer prevalence.

Significant Findings and Observations

The team found that the most significant upticks in breast cancer cases were among women who, on average, were exposed to higher levels of fine particulate matter (PM2.5) near their homes prior to participating in the study, as opposed to those residing in areas with lower PM2.5 levels. Particulate matter consists of a blend of microscopic solid particles and liquid droplets in the air and originates from multiple sources such as vehicular exhaust, combustion of fossil fuels like oil and coal, burning of wood and vegetation, and industrial emissions. The particulate matter evaluated in this study had a diameter of 2.5 microns or less, making it small enough to be inhaled deep into the respiratory system. The Environmental Protection Agency offers a resource known as Air Now, where individuals can input their zip codes to access localized air quality data, including levels of PM2.5.

The study’s lead author, Alexandra White, Ph.D., who heads the Environment and Cancer Epidemiology Group at NIEHS, stated, “We recorded an 8% increment in breast cancer cases among those residing in regions with elevated PM2.5 exposure. Although this represents a relatively modest rise, the implication is profound given that air pollution is a pervasive issue affecting a broad swath of the population.” She further commented that these findings contribute to an expanding body of research indicating that air pollution is connected to breast cancer.

Research Approach

The study relied on information from the NIH-AARP Diet and Health Study, which enrolled over half a million men and women between 1995 and 1996 across six states—California, Florida, Pennsylvania, New Jersey, North Carolina, and Louisiana—and two metropolitan regions, Atlanta and Detroit. The average age of the women in the cohort was around 62, and most identified as non-Hispanic white. They were monitored for roughly 20 years, during which 15,870 cases of breast cancer were diagnosed.

Annual average PM2.5 concentrations at each participant’s residence were calculated by the researchers. They were especially focused on pollution levels a decade or a decade and a half prior to the study enrollment, given the lengthy period required for certain cancers to manifest. Previous research largely concentrated on the risk of breast cancer concerning pollution levels at or near the time of study enrollment, often neglecting historical exposure levels.

Rena Jones, Ph.D., the senior author and principal investigator of the study at NCI, emphasized, “The capacity to account for historical levels of air pollution is a notable advantage of this research. As the development of breast cancer can span many years, and given that past air pollution levels were generally higher, evaluating historical exposure becomes highly relevant for cancer development.”

Additional Insights and Constraints

The research team also examined the differential impact of air pollution on various types of breast cancer tumors, specifically estrogen receptor-positive (ER+) and estrogen receptor-negative (ER-) tumors. Their observation indicated that PM2.5 was linked to a greater occurrence of ER+ breast cancer, but not ER-, suggesting a biological mechanism involving endocrine disruption. ER+ tumors constitute the majority of breast cancer diagnoses in the United States.

Nevertheless, the study had certain limitations regarding its ability to distinguish variations in the connection between air pollution and breast cancer across distinct geographical regions. Future research is recommended to probe deeper into how regional variances in air pollution, including diverse sources of PM2.5, may influence the risk of developing breast cancer.

Citations

The research article, titled “Ambient fine particulate matter and breast cancer incidence in a large prospective US cohort,” was authored by Alexandra J. White, Ph.D., Jared A. Fisher, Ph.D., Marina R. Sweeney, Ph.D., Neal D. Freedman, Ph.D., Joel D. Kaufman, M.D., Debra T. Silverman, Sc.D., and Rena R. Jones, Ph.D., and was published on September 11, 2023, in the Journal of the National Cancer Institute. DOI: 10.1093/jnci/djad170.

Funding for this research was provided by the NIEHS and NCI Intramural Program, under grant numbers 1ZIAES103332 and 1Z01CP010125.

Frequently Asked Questions (FAQs) about Air Pollution and Breast Cancer Risk

More about Air Pollution and Breast Cancer Risk

• Journal of the National Cancer Institute – Research Article
• NIH-AARP Diet and Health Study
• National Institute of Environmental Health Sciences (NIEHS)
• National Cancer Institute (NCI)
• Environmental Protection Agency – Air Now
• PM2.5 – Particulate Matter
• Estrogen Receptor-Positive (ER+) Breast Cancer
• Breast Cancer Statistics in the United States