Environment and Breast Cancer: Science Review

Evidence From Humans
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Mortality among 24,865 workers exposed to polychlorinated biphenyls (PCBs) in three electrical capacitor manufacturing plants: A ten-year update
Ruder, A. M., Hein, M. J., Hopf, N. B., Waters, M. A. Int J Hyg Environ Health. 2014. .
Topic area
Environmental pollutant - PCBs
Study design
Follow-up of retrospective cohort
Funding agency
National Institute for Occupational Safety and Hea
Study Participants
Number of Cases
Total: 239 Among those employed β‰₯ 3 months: 165
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Number in Cohort
Cohort: 13,077 women, 11,788 men
Cohort participation rate
Not applicable. This study was records-based.
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
The National Institute for Occupational Safety and Health (NIOSH) Capacitor Cohort combined 26,588 male and female workers from three plants that manufactured electrical capacitors in Indiana (1957-1977), Massachusetts (1938-1976), and New York (1946-1977). Mortality was followed through 2008 through NDI with cause of death identified from NDI-Plus. Previous follow-up data from cohort had been obtained using records from SSA, IRS, NDI, US postal service and credit bureaus. NDI does not include deaths before 1979, so workers lost to follow-up before that year were censored at date last observed. Those not employed during the years of PCB use or employed for less than one day, and those missing employment dates, birth dates, or dates of death were excluded.
Comment about participation selection
One-third of the cohort was employed for less than 3 months, and the median length of work was less than one year for the cohort.
Exposure Investigated
Exposures investigated
PCB exposure for each worker was determined using a plant-specific job exposure matrix based on detailed work histories and modified to reflect changes in PCB usage during distinct "eras". Potential exposures from inhalation and dermal pathways were consi
How exposure was measured
Job history Other: Job exposure matrix (JEM)
Exposure assessment comment
Plant-specific job exposure matrices are a strength. A greater percentage of workers at the Massachusetts and New York plants fell into the highest quartile of estimated cumulative exposure, compared to workers at the Indiana plant.
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.
Gender, race, age, birth year, manufacturing plant
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
Female breast cancer mortality in the capacitor cohort compared to 1960-2007 US female breast cancer mortality rates:
Overall: SMR 0.96 (95% CI 0.82-1.12)
Indiana plant: SMR 0.64 (95% CI 0.28-1.26)
Massachusetts plant: SMR 0.91 (95% CI 0.74-1.11)
New York plant: SMR 0.86 (95% CI 0.65-1.11)

Cumulative exposure, among workers employed β‰₯ 3 months (ref = 0 -<40,000 unit-days):
Quartile 2 (40,000-<150,000): SRR 1.24 (95% CI 0.80–1.94)
Quartile 3 (150,000-<600,000): SRR 0.87 (95% CI 0.53–1.41)
Quartile 4 (β‰₯600,000): SRR 0.90 (95% CI 0.57–1.42)

Male breast cancer mortality in the capacitor cohort compared to 1960-2007 US ale breast cancer mortality rates:
SMR (2 cases): 1.68 (95% CI 0.20-6.07)
Results Comments
Information on race/ethnicity was not available for most workers (46% of women and 81% of men). Based on demographic information of each study area, those with unknown race were assumed to be Caucasian, which could bias the analyses given that race-specific rates were considered.
Author address
Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, OH, USA. Electronic address: aruder@cdc.gov.
Reviewers Comments
Breast cancer mortality is not a sensitive measure of breast cancer risk. Because the general population was chosen as the comparison population, the SMR estimates may be biased downward due to a healthy worker effect.