Background Lung cancer is the most common and deadliest worldwide. Studies have shown a lower risk among farmers compared to the general population, partly due to lower smoking prevalence and possibly to exposure to certain substances in cattle farming, possibly endotoxins. While several lung carcinogens were identified in farms such as diesel engine exhaust, welding fumes, asbestos and creosote, very few studies have documented the role of these exposures in farming.
Objective The aim of this study was to estimate the risk of lung cancer in farming associated with exposure to these carcinogens, by histological subtype.
Methods Analyses included 83,543 participants in the Agriculture and Cancer cohort (AGRICAN) who completed the 10-year follow-up questionnaire (2015-2017), which collected these exposure data. Incident cases of lung cancer (n=366 including 98 squamous cell carcinoma (SCC)) were identified through population-based cancer registries from enrolment (2005-2007) to 2017. We used a Cox model with attained age at the end of follow-up as the time scale (in days), adjusted for pack-years of cigarette consumption to calculate hazard ratios (HR) and 95% confidence intervals (95%CI).
Results Increased risks of SCC were found in men for (i) treating or installing creosote-treated poles (HR=1.92; 95%CI: 0.93, 3.97), (ii) certain tasks involving exposure to asbestos (HR=1.87; 95%CI: 0.87, 4.02), particularly for exposure ≥60 days during occupational life, (iii) welding work ≥730 days during occupational life (HR=1.83; 95%CI: 0.83, 4.03). Risks were particularly increased among those not exposed to potentially protective substances in livestock farming.
Conclusion Our study provides new findings on specific tasks performed in agricultural settings that increase lung cancer risk and identified at-risk subpopulation. These results are of great relevance to occupational risk prevention in agriculture.