Evidence From Humans
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Breast Cancer Risk in Relation to Ambient Air Pollution Exposure at Residences in the Sister Study Cohort
Reding, K. W., Young, M. T., Szpiro, A. A., Han, C. J., DeRoo, L. A., Weinberg, C., Kaufman, J. D., Sandler, D. P. Cancer Epidemiol Biomarkers Prev. 2015. .
Topic area
Environmental pollutant - Air pollution
Study design
Prospective cohort
Funding agency
NIEHS U.S. EPA STAR National Institute of Nursing
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analyses based on menopausal status
Number in Cohort
Cohort: 49,340
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Participants in the Sister Study were 50,884 initially breast cancer-free women aged 35-74 who had a sister diagnosed with breast cancer. Women were enrolled 2003-2009, followed through self-report until January, 2013. Women without residential air pollution estimates available (1,234 women, including 24 invasive and 6 in situ breast cancer cases) were excluded from this analysis.
Comment about participation selection
The main reason given for missing air pollution data was residence outside conterminous US. As the authors note, because the Sister Study consists of women who had a sister with breast cancer, the results may not be generalizable to women without a family history of breast cancer.
Exposure Investigated
Exposures investigated
Annual average PM2.5, PM10, and NO2 concentrations estimated at baseline home address.
How exposure was measured
Air pollution concentrations were modeled at each participant's home, using geographic features and monitoring data from 2006 for PM2.5 and NO2, and data from 2000 for PM10.
Exposure assessment comment
The timing of exposure is in adult women in this study, which may or may not reflect the etiologic period of breast cancer development. The air measurements were taken near the time of enrollment in the study, and the participants were followed for an average of 5 years after enrollment, which means that the air measurements may have been taken near the time of breast cancer diagnosis.
Breast cancer outcome investigated
Primary incident breast cancer
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
Based on causal diagram: Age at diagnosis, race, educational attainment, smoking status, menopausal hormone therapy.
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked Yes. No, if not.
Strength of associations reported
NO2 (per 5.8 ppb increase in average annual concentration):
overall: aHR 1.02 (0.97-1.07)
ER+/PR+ tumors: aHR 1.10 (1.02-1.19)
ER-/PR- tumors: aHR 0.92 (0.77-1.09)

PM10 (per 5.8 μg/m3 increase in average annual concentration):
overall: aHR 0.99 (0.98-1.00)
ER+/PR+ tumors: aHR 1.02 (0.96-1.09)
ER-/PR- tumors: aHR 0.96 (0.83-1.10)

PM2.5 (per 3.6 μg/m3 increase in average annual concentration):
overall: aHR 1.03 (0.96-1.11)
ER+/PR+ tumors: aHR 1.00 (0.91-1.09)
ER-/PR- tumors: aHR 0.99 (0.81-1.20)
Results Comments
Authors note that NO2 serves as a marker for pollution from traffic, which contains PAHs; some PAHs have estrogenic properties, perhaps explaining the association with ER+/PR+ breast cancers. p-value for test of interaction between NO2 exposure and tumor subtype was 0.04. Authors also report that results were unchanged for analyses restricted to participants who had lived at current residence long-term (data not shown).
Author address
University of Washington School of Nursing, Seattle, Washington. Fred Hutchinson Cancer Research Center Public Health Sciences, Seattle, Washington. kreding@uw.edu. University of Washington School of Public Health, Seattle, Washington. University of Washi
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