Environment and Breast Cancer: Science Review

 

Occupational exposures and breast cancer among women textile workers in Shanghai

Ray, R. M., Gao, D. L., Li, W., Wernli, K. J., Astrakianakis, G., Seixas, N. S., Camp, J. E., Fitzgibbons, E. D., Feng, Z., Thomas, D. B., Checkoway, H. Epidemiology. 2007. 18:3, 383-92.

Topic area
Environmental pollutant - Occupation

Study design
Case-cohort

Funding agency
US National Cancer Institute National Institutes o

Link to Abstract

Number of Cases
1,709

Menopausal Status
Stratified analysis based on menopausal status (for some agents)

Number of Controls
Controls: 3,155

Country where study was conducted
China

Cohort participation rate
Not reported

Participant selection: Inclusion and exclusion criteria
Cases and controls were selected from a cohort of 267,400 female textile workers from 526 Shanghai factories who enrolled from 1989 to 1991 in a randomized trial of breast self-examination. The cohort included active and retired employees of the Shanghai Textile Industry Bureau (STIB) born between 1925-1958 and permanent residents of Shanghai at baseline. 1,763 cases were identified through 2000 from the STIB cancer and death registry (which in turn is compiled from reports from factory clinics). The cohort was also followed in the Shanghai Cancer Registry through 1998 (manual checks and computerized matching) to identify cases who left the STIB before the end of the study period. A 3,199 person subcohort was randomly selected from the entire cohort at baseline, with matching (to all cancer cases, not just breast cancer cases) on birth year intervals. Fifty-four cases and 11 controls were excluded from analysis because of missing work history information from factory records or in-person interview (done for 6% of cases and 4% of subcohort controls). An additional nineteen controls were excluded due to a history of breast cancer or mastectomy at baseline.

Comment about participation selection
The subcohort is selected from the entire cohort at baseline and so can include individuals who ultimately develop the outcome during follow-up. Indeed, 16 members of the subcohort were diagnosed with breast cancer during follow-up; they contributed person-time to the subcohort until their dates of diagnosis.

Exposures investigated
Work histories combined with Job Exposure Matrices (JEMs) to estimate exposures to cotton, wool, silk, and synthetic fiber dust, endotoxin (bacterial component that contaminates cotton dust), solvents, metals, dyes, inks, lubricants, bleaches, acids, base

How exposure was measured
Job history

Exposure assessment comment
For most agents, it was not possible to classify based on intensity of exposure. Cotton dust exposure was estimated based on 1975-1999 measurements made by industry hygienists across 56 factories.

Early life exposures considered
No

Breast cancer outcome investigated
Primary incident breast cancer

Confounders considered
Age at baseline, age at menarche, total number of live births, age at first live birth, duration of breast-feeding, contraceptive use, cigarette smoking, alcohol use, history of prior breast lumps, menopausal status at baseline, and history of breast canc

Genetic characterization included
No

Strength of associations reported
Duration of employment in job process involving....(Ref = 0 years):

Dyeing
<10 years: aHR 1.42 (95% CI 0.72-2.80)
10-<20 years: aHR 1.28 (95% CI 0.61-2.70)
20+ years: aHR 0.73 (95% CI 0.31-1.75)

Wool fibers
<10 years: aHR 1.97 (95% CI 1.04–3.76)
10-<20 years (6 cases): aHR 0.46 (95% CI 0.18–1.16)
20+ years: aHR 0.98 (95% CI 0.57–1.68)

Mixed fibers
<10 years: aHR 1.10 (95% CI 0.79–1.52)
10-<20 years: aHR 1.43 (95% CI 1.05–1.96)
20+ years: aHR 0.90 (95% CI 0.68–1.19)

Printing
<10 years (2 cases, 8 controls): aHR 0.36 (95% CI 0.07–1.73)
10-<20 years (7 cases, 9 controls): aHR 1.09 (95% CI 0.37–3.27)
20+ years (10 cases, 7 controls): aHR 2.07 (95% CI 0.75–5.72)

Cutting/sewing
<10 years (2 cases, 8 controls): aHR 0.83 (95% CI 0.56–1.22)
10-<20 years (7 cases, 9 controls): aHR 1.61 (95% CI 1.16–2.25)
20+ years (10 cases, 7 controls): aHR 0.80 (95% CI 0.56–1.16)

Duration of occupational exposure to....(Ref = 0 years):

Solvents
<5 years: 1.05 (95% CI 0.73–1.53)
5 -<10 years: aHR 0.94 (95% CI 0.64–1.36)
10-<20 years: aHR 1.27 (95% CI 0.96–1.68)
20+ years: aHR 1.04 (95% CI 0.79–1.39)

Benzene
<10 years (2 cases, 7 controls): aHR 0.52 (95% CI 0.10–2.58)
10+ years (4 cases, 8 controls): aHR 0.80 (95% CI 0.23–2.83)

Pesticides
<10 years: aHR 0.77 (95% CI 0.34–1.77)
10+ years: aHR 0.70 (95% CI 0.33–1.47)

Cumulative compared to never exposure (mg/m3 x yr) with 20 year lag time:

Cotton dust
>0-54.94: aHR 0.81 (95% CI 0.69-0.96)
54.95-95.81: aHR 0.70 (95% CI 0.57-0.85)
95.82-142.00: aHR 0.62 (95% CI 0.49-0.77)
>142.00: aHR 0.49 (95% CI 0.39-0.62)

Endotoxin
>0-1509.19: aHR 0.80 (95% CI 0.68-0.95)
1509.20-2418.29: aHR 0.68 (95% CI 0.55-0.83)
2418.30-3516.98: aHR 0.52 (95% CI 0.41-0.66)
>3516.98: aHR 0.62 (95% CI 0.49-0.77)

Results Comments
No associations for EMFs or nonionizing radiation. Authors state that analyses of cotton dust and endotoxin stratified by menopausal status at baseline did not yield appreciably different results, but do not show data.

Author address
Program in Epidemiology, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA. rray@fhcrc.org