Environment and Breast Cancer: Science Review

Evidence From Humans
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Breast cancer among women in Michigan following exposure to brominated flame retardants
Terrell, M. L., Rosenblatt, K. A., Wirth, J., Cameron, L. L., Marcus, M. Occupational and environmental medicine. 2016. .
Topic area
Environmental pollutant - Consumer product chemicals
Study design
Prospective cohort; Nested case-control
Funding agency
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Number of Controls
Controls: 202
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Members of the Michigan long-term polybrominated biphenyl (PBB) study were Michigan residents, including 1,930 women, recruited by the Michigan Department of Community Health (MDCH) in 1976 if they lived on or received food from a farm that was quarantined after having fed accidentally PBB-contaminated feed to livestock. For this study, 1,749 were eligible based on having completed a baseline interview and provided a blood sample. Breast cancer cases were identified by study follow-up (with physician confirmation) from 1974 until 1985 and from the Michigan Cancer Registry from 1985-2004. Controls were selected by incidence density sampling from among alive and under follow-up at the time the matched case was diagnosed, who did not have a previous breast cancer diagnosis or current cancer conditions other than non-melanoma skin cancer or carcinoma in situ (excluding in situ bladder). Four eligible controls were selected for each case matched on age during the exposure incident using 5-year strata. One remaining case was matched to two controls.
Comment about participation selection
Authors note they were unable to ascertain cases among women who moved out of the state of Michigan before they were diagnosed. This could bias results if those who moved were different from those who did not with regard to both PBB exposure and case-control status.
Exposure Investigated
Exposures investigated
Serum concentration of polybrominated biphenyls (PBBs) in samples collected 1976-1978
Exposure assessment comment
The PBB-contamination of livestock feed was the result of an industrial accident, when the wrong product (FireMaster flame retardant rather than NutriMaster livestock feed) was accidentally sent to the Michigan Farm Bureau Services. The make-up of the PBB mixture is thus known to have been mostly PBB–153 or 2,2'4,4'5,5'–hexabromobiphenyl. Blood was collected in 1976-1978 but cases were identified starting in 1974 so the temporal relationship of exposure and outcome assessment was not consistent across all participants.
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, family history, age at first live birth, history of alcohol consumption, smoking history, and BMI at enrollment.
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
PBB levels at enrollment, compared to levels at or below LOD:
< 75th percentile (>1 to ≤ 9 ng/mL): aOR 1.17 (95% CI 0.59-2.33)
≥75th percentile (≥10 ng/mL) (9 cases): aOR 2.60 (95% CI 0.93-7.27)

Ever vs. never drank milk or ate meat or eggs from quarantined farm during 1973-1974: aOR 1.94 (95% CI 0.65-5.78)

Ever vs. never lived on a quarantined farm: aOR 1.27 (95% CI 0.68-2.37)
Results Comments
The OR for PBB levels ≥75th percentile vs at or below LOD was marginally significant (p = 0.07)
Author address
Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA. Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA. Departments of Epidemiology and Bio