Breast cancer incidence linked to high particulate air pollution

Recent findings by scientists at the National Institutes of Health (NIH) have raised concerns about the potential impacts of particulate air pollution on breast cancer rates. 

This research, published in the Journal of the National Cancer Institute, is one of the most extensive examinations to date on how outdoor air pollution, specifically fine particulate matter, might influence breast cancer incidence.

The study was led by a team of researchers from the National Institute of Environmental Health Sciences (NIEHS) and the National Cancer Institute (NCI), both prominent divisions of NIH. 

Focus of the study

The focus of the research was on particulate matter of 2.5 microns in diameter or smaller (PM2.5). 

These minute particles are known to originate from several sources, including vehicle emissions, combustion of materials like oil and coal, industrial releases, and even the burning of wood and vegetation. 

Given their size, these particles can easily penetrate the deeper parts of our respiratory system when inhaled.

Significant findings

“We observed an 8% increase in breast cancer incidence for living in areas with higher PM2.5 exposure. Although this is a relatively modest increase, these findings are significant given that air pollution is a ubiquitous exposure that impacts almost everyone,” said Alexandra White, Ph.D., lead author and head of the Environment and Cancer Epidemiology Group at NIEHS. 

“These findings add to a growing body of literature suggesting that air pollution is related to breast cancer.”  

How the research was conducted 

To obtain a comprehensive dataset, the team used information from the NIH-AARP Diet and Health Study. This exhaustive research had enrolled over half a million men and women from six states and two metropolitan areas between 1995 and 1996. 

The primary demographic in focus was women, with an average age of 62, predominantly non-Hispanic white. Over a span of two decades, a total of 15,870 breast cancer cases emerged within this cohort.

Historic pollution levels 

A unique aspect of this study was the researchers’ method to estimate PM2.5 exposure. Instead of just considering the pollution levels at the time of enrollment, they also factored in historical pollution levels from the past 10-15 years. 

“The ability to consider historic air pollution levels is an important strength of this research,” said Rena Jones, Ph.D., senior author and principal investigator of the study at NCI. “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.”

What the researchers learned 

Furthermore, the experts delved deeper into the connection between air pollution and specific types of breast cancer. They found a higher incidence of estrogen receptor-positive (ER+) breast cancer linked with PM2.5 exposure. 

However, no such correlation was observed with estrogen receptor-negative (ER-) tumors. This intriguing discovery points towards the possibility that PM2.5 might be influencing breast cancer through endocrine disruption pathways. Notably, ER+ tumors are the predominant type diagnosed in U.S. women.

Study limitations

The researchers acknowledged that the study did not account for regional variances in the relationship between breast cancer and air pollution. 

They recommend that future research should factor in regional pollution differences, especially the various PM2.5 types women encounter, to fully understand their potential risk.

For those curious about the air quality in their region, the Environmental Protection Agency has a handy tool: the Air Now website. This platform allows residents to quickly gauge air quality by simply entering their zip code, providing real-time data, including PM2.5 levels.

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