Objective Specific farming types and tasks have never been studied in relation to colorectal cancer (CRC). We evaluated associations between 5 types of livestock and 13 types of crops in relation to CRC and its subsites within the Agriculture and Cancer (AGRICAN) study.

Methods AGRICAN cohort includes 181 842 agricultural workers living in 11 French geographical areas. Data on farming types and tasks was collected by self-administered questionnaires. We identified 2 609 CRC, 972 right colon, 689 left colon and 898 rectal incident cancer cases during follow-up from 2005 to 2015. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI).

Results Significantly increased CRC risk was observed for farmers producing horses (HR=1.18, 95% CI 1.06–1.31), sunflower (HR=1.23, 95% CI 1.03–1.45) and field vegetables (HR=1.18, 95% CI 1.02–1.36). Positive associations were also observed for pig, poultry and wheat/barley. Some associations were observed only for specific subsites: left colon cancer was associated with fruit growing (HR=1.36, 95% CI 1.09–1.70) and potato (HR=1.28, 95% CI 1.05–1.57). Tasks related to livestock (animal care, insecticide treatment, disinfection of milking equipment and building) or to crop (haymaking, sowing, pesticide treatment, seed treatment, harvesting) were also associated with CRC. Duration and size of farming types/tasks increased the risk for some of the associations. Analysis stratified by gender suggested an interaction with several farming types/tasks.

Conclusion The current study showed original and positive findings for several farming types and tasks and CRC risk, overall and by subsites.