Environment and Breast Cancer: Science Review

Evidence From Humans
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Mortality of aircraft maintenance workers exposed to trichloroethylene and other hydrocarbons and chemicals: extended follow-up
Radican, L., Blair, A., Stewart, P., Wartenberg, D. J Occup Environ Med. 2008. 50:11, 1306-19.
Topic area
Environmental pollutant - Solvents
Study design
Follow-up of retrospective cohort
Funding agency
NIH Merck & Co. Inc.
Study Participants
Number of Cases
26 exposed cases. Number of unexposed cases not reported.
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Number in Cohort
Cohort: 3,725 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.
The Hill Air Force Base cohort was established in the early 1980s by the National Cancer Institute (NCI). This records-based cohort includes 14,455 civilians employed at a Utah aircraft maintenance facility for at least one year between 1952 and 1956. The cohort was followed in the National Death Index (NDI) through 2000.
Exposures investigated
Estimated exposures (yes/no) for 21 solvents and chemicals derived for each job-organization combination, collected from worker files, office records, facility history files, position descriptions, walk through surveys and some interviews. TCE exposure wa
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, race, calendar period. Those of unknown race (10% of entire cohort -- including men and women) were classified as white. The remainder of the cohort was 87% white and 3% non-white.
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
Compared to female workers with no chemical exposure:

Ever TCE exposure: HR 1.23 (95% CI 0.73-2.06)
0-5 unit-yrs exposure: HR 1.57 (95% CI 0.81-3.04)
5-25 unit-yrs exposure (3 exposed cases): HR 1.01 (95% CI 0.31-3.30)
>25 unit-yrs exposure: HR 1.05 (95% CI 0.53-2.07)

Low, intermittent TCE exposure: HR 1.92 (95% CI 1.08-3.43)
Low, continuous TCE exposure (8 exposed cases): HR 1.71 (95% CI 0.79-3.71)
Peak, infrequent TCE exposure (3 exposed cases): HR 1.18 (95% CI 0.36-3.86)
Peak, frequent TCE exposure: HR 1.08 (95% CI 0.57-2.02)

Ever methylene chloride exposure: HR 2.35 (95% CI 0.98-5.65)
Ever freon exposure: HR 2.71 (95% CI 1.33-5.50)
Ever solder flux exposure (9 exposed cases): HR 2.76 (95% CI 1.32-5.76)
Ever isopropyl alcohol exposure (9 exposed cases): HR 2.64 (95% CI 1.30-5.35)
Results Comments
Non-significant positive associations for any solvent exposure, 1,1,1-trichloroethane, metal fumes/dust, methylethyl ketone, other alcohols, styrene, toluene, and zinc chromate. No associations for carbon tetrachloride, JP4 gasoline, 0-dichlorobenzene, perchloroethylene, stoddard solvent.
Author address
Global Outcomes Research Department, Merck and Co, Inc, NJ 08889, USA. larry_radican@merck.com
Reviewers Comments
Mortality is not a sensitive measure of breast cancer risk. The reference group of civilian employees at Hill Air Force not ever exposed to chemical of interest may be more appropriate than the general population. However, comparability of exposed vs non-exposed with regard to job titles and other socioeconomic variables was not discussed.