Environment and Breast Cancer: Science Review

Evidence From Humans
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A proportionate cancer morbidity ratio study of workers exposed to chlorinated organic solvents in Taiwan
Chang, Y. M., Tai, C. F., Lin, R. S., Yang, S. C., Chen, C. J., Shih, T. S., Liou, S. H. Industrial Health. 2003. 41:2, 77-87.
Topic area
Environmental pollutant - Occupation, chlorinated organic solvent, PCE, TCE
Funding agency
Republic of China
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number in Cohort
52,835 index cohort compared with 25,596 textile and 17,960 electronics workers.
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Workers at an electronics factory with a history of improper solvent disposal and comparison workers in textile or electronics industries. Identified from the Bureau of Labor Insurance 1978-1997 database. Comparison cohort selected from female-predominant textile and electronics industries in the same county.
Comment about participation selection
By choosing workers as a comparison, confounding is reduced; but the comparison group is likely chemical-exposed.
Exposures investigated
Years of employment in electronics factory with a history of improper disposal of chlorinated organic solvent wastes. The factory operated from 1968-1992. PCE, TCE, vinyl chloride were reported in groundwater, with PCE and TCE at 10 times the groundwate
Statistical Analysis
Breast cancer outcome investigated
Primary breast cancer
Mortality from breast cancer
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.
Not controlled
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
Proportionate cancer morbidity ratio (PCMR)
Strength of associations reported
135 breast cancers observed.
Among all workers PCMR 1.2 (1.0-1.4)
Workers with more than 3 months employment at factory and latent period < 5 years PCMR 1.5 (1.2-1.9)
Workers with more than 3 months employment at factory and latent period < 10 years PCMR 1.6 (1.2-2.0)

Results Comments
Age of women in the cohort is not reported. 87% started work in the factory before 30 years of age. Follow-up time may be too short. Comparison to other industrial workers with some likely exposure may reduce observed relative risk, while mitigating confounding. Analyses by duration of employment are reported and do not show consistent dose-response (PCMR 1.3 for more than 5 years employment; 3.9 for 1-5 years), but this may be a healthy worker effect.
Author address
Graduate Institute of Life Sciences, National Defense Medical Center, 161 Ming-Chun East Road, Sec. 6, Nei-Hu, Taipei, Taiwan, 114, ROC.