Environment and Breast Cancer: Science Review

Evidence From Humans
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Residential exposure to estrogen disrupting hazardous air pollutants and breast cancer risk: the California Teachers Study
Liu, R., Nelson, D. O., Hurley, S., Hertz, A., Reynolds, P. Epidemiology. 2015. 26:3, 365-73.
Topic area
Environmental pollutant - Air pollution
Study design
Prospective cohort
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Analyses stratified by menopausal status (data not shown)
Number in Cohort
Cohort: 112,379
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
The California Teachers Study recruited active and retired females enrolled in the California State Teachers Retirement System from 1995-1996 and followed until 2010 through the California Cancer Registry. Women were not eligible for inclusion if they lived outside California at baseline, had an unknown history of prior cancer, or had prior invasive or in situ breast cancer.
Exposures investigated
Census tract-level modeled ambient concentrations of 11 potential endocrine disrupting air pollutants (inorganic arsenic compounds, biphenyl, cadmium compounds, chlorobenzilate, DEHP, DBP, dimethyl formamide, 4-nitrophenol, styrene, diesel engine emission
How exposure was measured
Environmental sample
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.
Age, race, birthplace, family history of breast cancer, age at menarche, age at first full-term pregnancy, menopausal status and HRT status, alcohol consumption, smoking, physical activity, BMI
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
Diesel engine emissions (ref = Quintile 1)
Q2 HR 1.02 (0.94-1.11)
Q3 HR 1.02 (0.93-1.11)
Q4 HR 1.05 (0.96-1.14)
Q5 HR 1.04 (0.95-1.13)

Nine estrogenic hazardous air pollutants (ref = Quintile 1)
Q2 HR 1.07 (95% CI 0.98-1.16)
Q3 HR 1.05 (95% CI 0.96-1.14)
Q4 HR 1.05 (95% CI 0.96-1.14)
Q5 HR 1.04 (95% CI 0.95-1.13)

ER-/PR- invasive breast cancer risk and exposure to cadmium compounds, among never-smoking, residentially stable participants (ref = Quintile 1):
Q2: HR 1.2 (95% CI 0.8-1.9)
Q3: HR 1.3 (95% CI 0.8-1.9)
Q4: HR 1.6 (95% CI 1.1-2.4)
Q5: HR 1.6 (95% CI 1.1-2.5)

ER-/PR- invasive breast cancer risk and exposure to arsenic compounds, among never-smoking, residentially stable participants (ref = Quintile 1):
Q2: HR 1.5 (95% CI 1.0-2.3)
Q3: HR 1.5 (95% CI 1.0-2.3)
Q4: HR 1.4 (95% CI 0.9-2.2)
Q5: HR 1.7 (95% CI 1.1-2.5)
Results Comments
No significant risks were observed for invasive breast cancer and exposure to the following estrogen disrupting hazard air pollutants: arsenic, DEHP, dibutylphthalate, dimethyl formamide, 4-Nitrophenol, styrene, selenium compounds, diesel engine emissions, exposure potential index of nine estrogenic HAPs. When restricting analyses to non-smoking, residentially-stable participants, no significant risks were observed for overall or ER+/PR+ invasive breast cancer and arsenic or cadmium exposure
Author address
From the aCancer Prevention Institute of California, Berkeley, CA; and bDepartment of Health Research and Policy, School of Medicine, Stanford University, Stanford, CA.