Farming, pesticide exposure and respiratory health: a cross-sectional study in Thailand

Objective To assess the association of lung function and respiratory symptoms with farming, particularly pesticide use, in an agricultural province in Thailand. Methods We undertook a cross-sectional survey of adults aged 40-65 in Nan province, Thailand, between May and August 2019. We randomly recruited 345 villagers and enriched the sample with 82 government employees. All participants performed post-bronchodilator spirometry and completed a questionnaire covering information on respiratory symptoms, farming activities, pesticide use and known risk factors for respiratory disease. Associations of respiratory outcomes with farming and pesticide exposures were examined by multivariable regression analysis. Results The response rate was 94%. The prevalence of chronic airflow obstruction among villagers was 5.5%. Villagers had, on average, a lower percent predicted post-bronchodilator forced expiratory volume in one second/forced vital capacity (FEV1/FVC) than government employees (98.3% vs 100.3%; p=0.04). There was no evidence of association of lung function with farming activities, the use of specific herbicides (glyphosate and paraquat), insecticides (organophosphates and pyrethroids) or fungicides. The exceptions were poultry farming, associated with chronic cough and an increase of FEV1/FVC, and atrazine, for which duration (p-trend <0.01), intensity (p-trend <0.01) and cumulative hours (p-trend=0.01) of use were all associated with higher FEV1/FVC in an exposure-response manner. Cumulative hours (-280 mL/hour), low duration (-270 mL/year) and intensity (-270 mL/hour/year) of atrazine use were associated with lower FVC. Conclusions Chronic airflow obstruction is uncommon among villagers of an agricultural province in Nan, Thailand. Farming and pesticide use are unlikely to be major causes of respiratory problems there.