Environment and Breast Cancer: Science Review

Evidence From Humans
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Mortality among workers exposed to polychlorinated biphenyls (PCBs) in an electrical capacitor manufacturing plant in Indiana: an update
Ruder, A. M., Hein, M. J., Nilsen, N., Waters, M. A., Laber, P., Davis-King, K., Prince, M. M., Whelan, E. Environ Health Perspect. 2006. 114:1, 18-23.
Topic area
Environmental pollutant - PCBs
Study design
Follow-up of retrospective cohort
Funding agency
National Institute for Occupational Safety and Hea
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Number in Cohort
Cohort: 852 women
Cohort participation rate
Not applicable. This study was records-based.
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Cohort members were 3,569 male and female workers ever employed at an Indiana plant that manufactured capacitors where PCBs were used from 1957-1977. Exposure was calculated beginning from 1960 (or relevant employment date), and vital status was followed until 1998 in the National Death Index (NDI). Cause of death determined from death certificates coded by nosologist or NDI-Plus. NDI does not include deaths before 1979, so workers lost to follow-up before that year were censored at date last observed.
Comment about participation selection
Seventy-one of the total 3,643 workers ever employed at the facility were described as "ineligible" with no further explanation.
Exposure Investigated
Exposures investigated
PCB exposure for each worker was determined using a 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 considered separatel
How exposure was measured
Job history Other: Job exposure matrix (JEM)
Exposure assessment comment
The authors acknowledge differences in PCB commercial mixtures in different time periods captured in this study. Estimated cumulative exposure and serum PCB levels among 221 workers who gave blood samples in 1977 were somewhat correlated (r = 0.37, p < 0.00001)
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, calendar year, latency
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 compared to Indiana rates 19860-1986:
Overall: SMR 0.83 (95% CI 0.4-1.6)
Cumulative exposure:
Quartile 2 (<11,000 unit-days, 4 cases): SMR 1.04 (95% CI 0.3-2.7)
Quartile 3 (11,000 > and <90,000 unit-days, 3 cases): SMR 0.92 (95% CI 0.2-2.7)
Results Comments
No breast cancer cases occurred among those with highest cumulative exposure tertile (≥ 90,000 unit-days). However there were few women (1.2%) in highest exposed jobs.
An Indiana capacitor-manufacturing cohort (n=3,569) was exposed to polychlorinated biphenyls (PCBs) from 1957 to 1977. The original study of mortality through 1984 found excess melanoma and brain cancer; other studies of PCB-exposed individuals have found excess non-Hodgkin lymphoma and rectal, liver, biliary tract, and gallbladder cancer. Mortality was updated through 1998. Analyses have included standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) using rates for Indiana and the United States, standardized rate ratios (SRRs), and Poisson regression rate ratios (RRs). Estimated cumulative exposure calculations used a new job-exposure matrix. Mortality overall was reduced (547 deaths; SMR, 0.81; 95% CI, 0.7-0.9). Non-Hodgkin lymphoma mortality was elevated (9 deaths; SMR, 1.23; 95% CI, 0.6-2.3). Melanoma remained in excess (9 deaths; SMR, 2.43; 95% CI, 1.1-4.6), especially in the lowest tertile of estimated cumulative exposure (5 deaths; SMR, 3.72; 95% CI, 1.2-8.7). Seven of the 12 brain cancer deaths (SMR, 1.91; 95% CI, 1.0-3.3) occurred after the original study. Brain cancer mortality increased with exposure (in the highest tertile, 5 deaths; SMR, 2.71; 95% CI, 0.9-6.3); the SRR dose-response trend was significant (p=0.016). Among those working >or= 90 days, both melanoma (8 deaths; SMR, 2.66; 95% CI, 1.1-5.2) and brain cancer (11 deaths; SMR, 2.12; 95% CI, 1.1-3.8) were elevated, especially for women: melanoma, 3 deaths (SMR, 5.99; 95% CI, 1.2-17.5); brain cancer, 3 deaths (SMR, 2.87; 95% CI, 0.6-8.4). These findings of excess melanoma and brain cancer mortality confirm results of the original study. Melanoma mortality was not associated with estimated cumulative exposure. Brain cancer mortality did not demonstrate a clear dose-response relationship with estimated cumulative exposure.
Author address
National Institute for Occupational Safety and Health, Cincinnati, Ohio 45226, USA. amr2@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, these estimates may be biased downward due to a healthy worker effect.