The Link Between Breast Cancer and Environmental Pollution

Scientists from the National Institutes of Health (NIH) have uncovered a significant connection between breast cancer and pollution — specifically pollution related to fine particulate matter from industrial and wildfire smoke.

In a large study using historical air quality and breast cancer data from nearly 200,000 women from six states across the United States, researchers from the NIH's National Institute of Environmental Health Sciences (NIEHS) and the National Cancer Institute (NCI) found that women living in areas with higher PM2.5 exposure had an 8% increase in breast cancer incidence compared to those residing in regions with lower pollution levels.

Their findings, published on September 11 in the Journal of the National Cancer Institute, add more evidence to the associations between breast cancer and pollution. The study analyzed data from the NIH-AARP Diet and Health Study, which enrolled participants between 1995 to 1996 in California, Florida, New Jersey, Pennsylvania, North Carolina, Louisiana, Atlanta, and Detroit.

Scientists followed the participants for around 20 years, finding that 15,870 women developed breast cancer.

They also estimated the yearly average air pollution concentrations around the participants' residences — particularly 10 to 15 years before the study's onset.

Specifically, the scientists examined PM2.5, which are air particles 2.5 microns in diameter or smaller that can be inhaled deep into the lungs. This type of pollution mainly results from combustion processes, wood smoke, burning vegetation, and industrial emissions.

"The ability to consider historic air pollution levels is an important strength of this research," said senior study author Rena Jones, Ph.D., from the National Cancer Institute, Rockville, MD, in an NIH press release. "It can take many years for breast cancer to develop and, in the past, air pollution levels tended to be higher, which may make previous exposure levels particularly relevant for cancer development."

After the data analysis, the team found that women living in areas with higher PM2.5 concentrations had an increased incidence of breast cancer. However, when the researchers compared ER + and ER – tumors, they found stronger associations between ER + breast cancer and PM2.5 pollution.

The team says these results suggest that PM2.5 pollution may disrupt endocrine pathways, leading to the development of ER + breast cancer — the most common type of breast cancer in the U.S.

Still, the study authors note that state-specific estimates were vague. Therefore, they say future research should examine regional air pollution differences and the impact various types of particulate matter have on breast cancer development. In addition, the participants were primarily white, so it's unclear if the associations between air pollution and breast cancer would be similar for all women.

Notably, the breast cancer and pollution links found in this study are not the only associations observed between air pollution and specific health conditions. For example, reports suggest links between air pollution and infertility and an increased risk of dementia. In addition, a recent study found that polluted air may be associated with antibiotic resistance.