Occupational exposures and risks of liver cancer among Shanghai female textile workers--a case-cohort study.
BACKGROUND
Liver cancer is the fifth most frequent malignancy worldwide. Viral hepatitis B and C, alcohol, and aflatoxin are the major established risk factors. Little is known about the aetiological contributions of occupational exposures, as previous occupational epidemiological studies of liver cancer suggest few agent-specific associations. We investigated associations of occupational exposures to dusts and chemicals in a cohort of female textile workers.


METHODS
Cancer incidence was determined among 267,400 female textile workers in Shanghai, China, who had been enrolled in an intervention trial of breast self-exam efficacy during 1989-98. Subjects were interviewed at baseline regarding basic demographics, smoking habits, alcohol consumption, and contraceptive practices. A case-cohort study of 360 liver cancer cases and 3,186 age-stratified randomly chosen subcohort subjects was conducted within this cohort. Exposures to workplace dusts and chemicals were reconstructed from complete work history data, historical exposure monitoring data for selected agents, and a specially designed job-exposure matrix for the textile industry. Relative risks and dose-response trends were estimated by Cox proportional hazards modelling, adapted for the case-cohort design. Latency analyses with different lag years were also applied.


RESULTS
2,095,904 person-years were contributed by this female cohort. The results of the case-cohort analysis revealed a protective effect of cotton fibre exposure years [adjusted hazards ratio (HR) = 0.64; 95% confidence interval (95% CI) 0.44-0.92] or endotoxin exposure (adjusted HR = 0.60; 95% CI 0.41-0.88) for the fourth quartile with significant trends for 20 year exposure lags.


CONCLUSIONS
This study suggests that chronic exposure to endotoxin or some other component of cotton dust exposure may have reduced liver cancer risk in this population.
Chang
Chin-Kuo
CK
Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA. ckchang@cuhk.edu.hk
Astrakianakis
George
G
Thomas
David B
DB
Seixas
Noah S
NS
Ray
Roberta M
RM
Gao
Dao Li
DL
Wernli
Karen J
KJ
Fitzgibbons
E Dawn
ED
Vaughan
Thomas L
TL
Checkoway
Harvey
H
D000328:Adult; D002681:China / Q000453:epidemiology; D004391:Dust / Q000032:analysis; D004731:Endotoxins / Q000009:adverse effects / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D004812:Epidemiologic Methods; D062665:Epidemiological Monitoring; D005260:Female; D015386:Hazardous Substances / Q000009:adverse effects / Q000032:analysis; D006801:Humans; D008113:Liver Neoplasms / Q000453:epidemiology / Q000209:etiology*; D008875:Middle Aged; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology*; D016273:Occupational Exposure / Q000009:adverse effects / Q000032:analysis; D013783:Textile Industry / Q000706:statistics & numerical data*
D004391:Dust; D004731:Endotoxins; D015386:Hazardous Substances