Skip to main content
An official website of the United States government

Outdoor Air Pollution and Terminal Duct Lobular Involution of the Normal Breast


Previous studies have established an association between outdoor air pollution and an increased risk of breast cancer, particularly with regard to traffic-derived air pollutants, and more recently, fine particulate matter (PM2.5). Despite these discoveries, the effect of outdoor air pollution on underlying mechanisms associated with breast cancer risk, like terminal duct lobular unit (TDLU) involution, remain unaddressed. Notably, decreased TDLU involution is associated with increased breast cancer risk.

Study Team

DCEG researchers are working closely with investigators from National Institute of Environmental Health Sciences, including Drs. Alexandra White and Nicole Niehoff.

Lead Investigators

Gretchen Gierach, Ph.D., Chief and senior investigator
Integrative Tumor Epidemiology Branch

Rena Jones, Ph.D., investigator
Occupational and Environmental Epidemiology Branch

Background and Purpose

Researchers in DCEG initiated this study to investigate the association between exposure to PM2.5 and TDLU involution. Utilizing breast tissue donated to the Susan G. Komen Tissue Bank, they assessed pathologist-enumerated TDLU counts in 1904 women between the ages of 18 and 75 with respect to the 2009 annual PM2.5 total mass (µg/m3) at each woman’s residential address.

Heat map of the United States, with a concentrated cluster in Indiana.

Map of the residential addresses of women who donated breast tissue to the Susan G. Komen Tissue Bank, according to PM2.5 component cluster.

Study Results and Select Findings

In both premenopausal and postmenopausal women, more corresponded with higher TDLU counts, suggesting that exposure to air pollution may be associated with reduced TDLU involution, and thus increased breast cancer risk.