Environment and Breast Cancer: Science Review

Evidence From Humans
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Increased standardized incidence ratio of breast cancer in female electronics workers
Sung, T. I., Chen, P. C., Jyuhn-Hsiarn Lee, L., Lin, Y. P., Hsieh, G. Y., Wang, J. D. BMC Public Health. 2007. 7, 102.
Topic area
Environmental pollutant - Trichloroethylene Organic solvents Occupation
Study design
Retrospective cohort
Funding agency
Taiwan Bureau of Health Promotion Taiwan National
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: 63,982
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Female workers from an electronics factory in Taiwan were recruited from the database of the Bureau of Labor Insurance between 1973 and 1997. Breast cancer cases were identified from the National Cancer Registry. Participants who worked less than one day were excluded, but participants employed for >1 day and <1 year were included.
Comment about participation selection
This cohort included women who were first employed at the factory prior to 1974, when high solvent exposures are thought to have been present. Of the cohort participants, 53% worked >1 day and <1 year at the factory accounting for about 53% of the person-time accumulated. Some other occupational studies exclude those who have worked <1 year because it is unclear how short-term exposure may be related to the outcome of interest. However, the authors wanted to account for short-term high exposure experienced by employees prior to 1974.
Exposure Investigated
Exposures investigated
Duration of employment at the factory and calendar year of first employment. Prior to 1974, solvent use was not regulated and employment before regulation is considered "high exposure."
Exposure assessment comment
The exposure metric lacks detailed information on individual workers, for example job task which might address intensity of the exposure. Additionally, environmental sampling or qualitative records of solvent use are not incorporated into the exposure. Information on specific solvents are not available, but TCE was the only organic solvent under regulation that did not appear in industrial records after 1974.
Breast cancer outcome investigated
Primary incident breast cancer
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 and 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 incidence compared to Taiwan population, 15 yr latency:
Overall: SIR 1.09 (95% CI 0.96-1.22)
≥10 years employment: SIR 1.68 (95% CI 1.11-2.42)
Employment before June 20, 1974: SIR 1.38 (95% CI 1.11-1.70)
Employment after June 20, 1974: SIR 0.99 (95% CI 0.85-1.14)
Author address
Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University College of Public Health, Taipei, Taiwan. d91841001@ntu.edu.tw
Reviewers Comments
Because solvent use was regulated in 1974, this study is a natural experiment with exposed and unexposed before and after 1974. After stratifying by duration of employment, both the overall SIR and SIR among those employed before 1974 were significantly elevated only among those with at least 10 years of employment. No significant trend for increased SIR with duration of employment.