Cancer Risks In A Population-Based Cohort Of 70,000 Canadian Agricultural Workers
Linda KACHURI, Cancer Care Ontario; Dalla Lana School of Public Health at the University of Toronto, Canada
HARRIS A. 2,3,4
, HARDT J. 2
, TJEPKEMA M. 5
, PETERS P. 6
, DEMERS P. 1,2,3
1 Prevention and Cancer Control, Cancer Care Ontario, Toronto, Canada
2 Occupational Cancer Research Centre, Cancer Care Ontario, Toronto, Canada
3 Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
4 School of Occupational and Public Health, Ryerson University, Toronto, Canada
5 Health Analysis Division, Statistics Canada, Ottawa, Canada
6 Departments of Sociology and Economics, University of New Brunswick, Fredericton, Canada
Purpose: Agricultural workers may be exposed to potential carcinogens including pesticides, sensitizing agents and solar radiation. Previous studies indicate increased risks of hematopoietic cancers and decreased risks at other sites, possibly due to differences in lifestyle or risk behaviours. We present findings from the Canadian Census Cohort, the largest national population-based cohort of agricultural workers.
Methods: Statistics Canada created the cohort using deterministic and probabilistic linkage of the 1991 Canadian Long Form Census to National Cancer Registry records for 1992-2010. Self-reported occupations were coded using the Standard Occupational Classification (1991) system. Analyses were restricted to employed persons aged 25-74 years at baseline (N=2,050,300), with follow-up until December 31, 2010. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards for all workers in agricultural occupations (n=70570; 49965 male), stratified by sex and adjusted for age at cohort entry, province of residence, and level of education.
Results: A total of 9800 incident cancer cases (7775 in males) occurred in agricultural workers. Among men, increased risks were observed for Non-Hodgkin lymphoma (HR=1.10, 95% CI=1.00-1.21), prostate (HR=1.11, 95% CI=1.06-1.16), melanoma (HR=1.15, 95% CI=1.02-1.31), and lip cancer (HR=2.14, 95% CI=1.70-2.70). Decreased risks in males were observed for lung, larynx, and liver cancers. Among female agricultural workers there was an increased risk of pancreatic cancer (HR=1.36, 95% CI=1.07-1.72). Increased risks of melanoma (HR=1.79, 95% CI=1.17-2.73), leukemia (HR=2.01, 95% CI=1.24-3.25) and multiple myeloma (HR=2.25, 95% CI=1.16-4.37) were observed in a subset of female crop farmers.
Conclusions: Exposure to pesticides may have contributed to increased risks of hematopoietic cancers, while increased risks of lip cancer and melanoma may be attributed to sun exposure. The array of decreased risks suggests reduced smoking and alcohol consumption in this occupational group compared to the general population.
Funding Source: Work Safety Insurance Board of Ontario (Grant #11024)