Abstract
BackgroundAgricultural 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 CanCHEC (Canadian Census Health and Environment Cohort), the largest national population-based cohort of agricultural workers.MethodsStatistics 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 = 2,051,315), with follow-up until December 31, 2010. Hazard ratios (HR) and 95% confidence intervals (CI) were modeled using Cox proportional hazards for all workers in agricultural occupations (n = 70,570; 70.8% male), stratified by sex, and adjusted for age at cohort entry, province of residence, and highest level of education.ResultsA total of 9515 incident cancer cases (7295 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.ConclusionsExposure 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.
Highlights
Agricultural workers may be exposed to potential carcinogens including pesticides, sensitizing agents and solar radiation
The same inclusion criteria were maintained for Canadian Census Health and Environment Cohort (CanCHEC), which was created by expanding the linkage of the 1991 Canadian Census to the Canadian Cancer Database (CCDB), in addition to updating the Canadian Mortality Database (CMDB) (1991–2011) and Historic Tax Summary Files (HTSF) (1984–2011) data to 2011
Farmers and managers constituted 61.4% of the main exposure group with 43,365 individuals, while the remaining 27,205 subjects (38.6%) were classified as manual laborers. Examining this distribution by gender revealed that most male agricultural workers (68.0%, 33,980 subjects) were farmers and managers, whereas the majority of women (54.5%, 11,220 subjects) worked in occupations associated with manual labour
Summary
Agricultural workers may be exposed to potential carcinogens including pesticides, sensitizing agents and solar radiation. Studies of agricultural workers point to a number of elevated cancer risks in this population, Kachuri et al BMC Cancer (2017) 17:343 especially for lymphatic and hematopoietic cancers, melanoma, lip cancer, prostate cancer and brain tumors [2, 3, 5, 7]. This pattern is consistent with hazards associated with occupational exposure to pesticides, solvents, sunlight, dusts, and biological agents, such as zoonotic viruses, fungi and bacteria. Similar comprehensive studies were lacking in Canada, despite the fact that agriculture has historically been one of the largest sectors of the Canadian economy
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