The AIRBAg study was designed to assess the prevalence of chronic obstructive pulmonary disease (COPD) in dairy farmers and to define its associated risk factors. Between March 2012 and February 2017 randomly selected dairy farmers in the French region of Brittany were asked to complete a self-administered questionnaire and undergo an occupational health check-up with electronic mini-spirometry and standard spirometry. Those having one or more of the following features: chronic cough, chronic bronchitis, wheezing, dyspnea and/or a ratio FEV1/FEV6 < 80% were then referred to a pulmonologist for further check-up including spirometry with a reversibility test. Each COPD case was matched with three controls (dairy farmers and non-farm employees), for sex and age ( ± 5 years). Conditional multivariate logistic regression models were used to estimate the odds ratios between COPD occurrence and various risk factors. The 1203 farmers examined included 525 (43.6%) who were "at risk of bronchial obstruction" and 432 (35.9%) of these saw the pulmonologist. This screening identified 16 (1.3%) cases of COPD, including eight non-smokers and five with an FEV1 < 80% of predicted values. Their average age was 54.6 ( ± 7.7) years and 10 of them were men. None complained of illness before the study. Multivariate analyses revealed no significant occupational risk factors for COPD. This unexpected result may be because Breton dairy farms began to modernize early (1950s), giving rise to conditions with much lower exposure to airborne contaminants. •Occupational exposure could be involved in the pathophysiology of COPD.•A total of 1203 dairy farmers (Brittany, France) were screened for COPD.•Risk factors were identified by comparing COPD cases with two control populations.•Multivariate analyses revealed no significant occupational risk factors for COPD.•Farm modernization from 1950 onwards could explain this unexpected result.