Environment and Breast Cancer: Science Review

Evidence From Humans
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Metalworking fluid exposure and cancer risk in a retrospective cohort of female autoworkers
Friesen, M. C., Betenia, N., Costello, S., Eisen, E. A. Cancer Causes Control. 2012. 23:7, 1075-82.
Topic area
Environmental pollutant - Occupation
Study design
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 analyses based on menopausal status
Number in Cohort
Cohort: 4,787
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
The female autoworkers mortality cohort includes women hired between January 1st, 1938 and January 1st, 1982 at one of three Michigan United Auto Workers-GM plants. Mortality data for the period January 1st, 1941 through December 31st, 1994 were obtained from the National Death Index. Women from the general population in Michigan were used for external comparisons and were followed from 1980 to 2004. Women from an incident hire population were used for internal comparisons and were followed for the years 1941 to 2004, excluding those with greater than 50 percent missing work history.
Exposure Investigated
Exposures investigated
Detailed industrial hygiene analysis linked to work history from company records to determine exposure to straight, soluble and synthetic metalworking fluid (MWFs).
Exposure assessment comment
Authors note average MWF exposures to soluble and straight MWFs for women in this cohort were much lower than for men.
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.
Race, hire date, calendar year
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
Breast cancer mortality among female autoworkers for the years 1980 to 2004: SMR 1.03 (95% CI 0.75-1.39)

Exposure to straight MWFs and breast cancer mortality among female autoworkers for the years 1941 to 2004:
>0 to < median exposure: aHR 0.5 (95% CI 0.1-1.2)
>/= median exposure: aHR 1.4 (95% CI 0.7-2.5)
Results Comments
No significant risks were observed for oil-based, water-based, soluble, or synthetic MWFs
Author address
Occupational and Environmental Epidemiology Branch, National Cancer Institute, North Bethesda, MD 20892, USA. friesenmc@mail.nih.gov
Reviewers Comments
Mortality is not a sensitive measure of breast cancer risk. Overall low death rates in this cohort compared to the general female population suggest the SMR may be underestimated due to the healthy worker effect.