Environment and Breast Cancer: Science Review

Evidence From Humans
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Occupation and breast cancer risk among Shanghai women in a population-based cohort study
Ji, B. T., Blair, A., Shu, X. O., Chow, W. H., Hauptmann, M., Dosemeci, M., Yang, G., Lubin, J., Gao, Y. T., Rothman, N., Zheng, W. Am J Ind Med. 2008. 51:2, 100-10.
Topic area
Environmental pollutant - Occupation
Study design
Nested case-control
Study Participants
Number of Cases
586 prevalent cases 438 incident cases
Menopausal Status
The menopausal status of women included in this study is listed here.
No analyses based on menopausal status
Number of Controls
4,688 prevalent control pool 3,504 incident control pool
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
The Shanghai Women's Health Study is a population-based prospective cohort of 74,942 women who were recruited from seven communities of urban Shanghai from 1997-2000, between the ages of 40-70 years. Prevalent breast cancer cases were identified by self-report at study enrollment that the participant had ever received a physician's diagnosis of breast cancer. Incident breast cancer cases were identified through follow-up with cohort members and linkage to the Shanghai Cancer Registry through December 2004. Eight controls were randomly selected for each case (8:1), matched on year of birth (same year) and age at diagnosis (+/- 4 years).
Comment about participation selection
Because the follow-up time for incident case ascertainment was relatively short (about 5-7 years), both prevalent and incident cases were included in the study.
Exposure Investigated
Exposures investigated
Lifetime occupational history questionnaire by in-person interview. >10 major job sectors included.
Exposure assessment comment
99.6% of participants were ever employed, 60% of whom employed in blue collar occupations. The comparison group likely includes both workers and non-workers, so may not be appropriate comparison, though consideration of potential confounders helps.
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, education, age at menarche, age at first birth, number of live births, menopausal status
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
Medical and healthcare OR 1.4 (95% CI 1.0-1.9)
Cotton plantation (4 cases) OR 3.2 (95% CI 1.1-8.8)

Incidence, work started 20+ years before diagnosis
Medical and healthcare OR 1.7 (95% CI 1.2-2.5)

Pickling, canning, and preserved food workers (4 cases) OR 3.5 (95% CI 1.2-10.1)
Rubber and plastic product workers OR 1.3 (95% CI 0.7-2.4)
Work started <10 years before diagnosis:
Tailoring and sewing (3 cases) OR 1.3 (95% CI 0.4-4.2)
Work started 10-19 years before diagnosis:
Pipeline workers, welders, metal installers (7 cases) OR 2.2 (95% CI 1.0-4.8)
Work started >20 years before diagnosis:
Technicians in agriculture, engineering, and forestry OR 1.7 (95% CI 1.0-2.8)
Tailoring and sewing (9 cases) OR 2.3 (95% CI 1.1-4.6)
Results Comments
Results suggested an increased risk of breast cancer among "white-collar" professionals. This study considered many additional job titles. We focus on (1) significant positive associations (2) if a particular job or sector was significantly associated with breast cancer in at least one study, we report results from all other studies that considered that sector, regardless of significance. It is important to note that job coding criteria generally differed across studies.
Author address
National Cancer Institute, NIH, DHHS, Bethesda, Maryland 20852, USA. jib@exchange.nih.gov