Environment and Breast Cancer: Science Review

Evidence From Humans
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Mortality and cancer incidence of aircraft maintenance workers exposed to trichloroethylene and other organic solvents and chemicals: extended follow up
Blair, A., Hartge, P., Stewart, P. A., McAdams, M., Lubin, J. Occupational and Environmental Medicine. 1998. 55:3, 161-71.
Topic area
Environmental pollutant - Occupation, trichloroethylene, organic solvents
Study design
Nested case-control Other: Cohort
Funding agency
NCI Other: US Air Force
Study Participants
Number in Cohort
Cohort: 14457 males and females; 3138 white women, 122 non-white women, 467 women of unknown race (classified as white)
Cohort participation rate
97% of cohort successfully traced to 1982; later d
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Civilians employed greater than one year between 1952-1956 in aircraft maintenance at Hill Air Force Base, Utah. Mortality compared to general population of Utah; and mortality, morbidity of exposed vs. unexposed workers.
Exposures investigated
Job title, department codes and dates; semiquantitative assessment of trichloroethylene based on intensity, frequency, and duration of peak exposures and low level exposures, based on work practices
Breast cancer outcome investigated
Mortality from breast cancer 1952-1990
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
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.
A deficit in breast cancer in the cohort weighs against confounding by a social factor associated with working at the base as an explanation for elevated risks.
Description of major analysis
Standardized mortality ratios; rate ratios for mortality and incidence from comparison of exposed an unexposed cohort members by Poisson regression, adjusting for age, calendar year of death, and sex
Strength of associations reported
No male breast cancer deaths. Results are for females only.
SMR 82 (95% CI 62-109) (49 cases)
Mortality rate ratio 1.8 (0.9-3.3) 20 exposed cases, 20 unexposed cases
Mortality rate ratios are higher for exposed workers who were NOT exposed to trichloroethylene
Mortality rate ratios for trichloroethylene vs. no chemical exposure: low intermittent exposure RR 3.1 (1.5-6.2); low continuous exposure RR 3.4 (1.4-8.0); frequent peaks RR 1.4 (0.7-3.2)
No excess incidence for women exposed to trichloroethylene.
Mortality rate ratio for exposure to any solvent 1.6 (0.9-2.8) 28 cases; freon RR 3.8 (1.7-8.8); solder flux RR 3.7 (1.6-8.4); Isopropyl alcohol 3.7 (1.6-8.4); trichloroethane 3.3 (1.0-11.2); toluene RR 2.0 (0.9-4.2); methyl ethyl ketone RR 2.1 (0.9-4.7); methylene chloride 3.0 (1.0-8.8). No elevated risk for jet fuel. Some other compounds show slightly and nonsignificantly elevated risk.
Results Comments
Non-significantly elevated risk associated with working with solvents does not appear to be specific to trichloroethylene. Significantly elevated mortality was observed for freon, solder flux, isopropyl alcohol, trichloroethane, methylene chloride; and low exposure to trichlorethylene.
Author address
Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892-7364, USA.