Workplace-related chronic cough on a mushroom farm

Background: Mushroom spores have frequently been associated with respiratory allergy. The aims of this study were to elucidate the incidence and causes of chronic cough in a mushroom farm. Methods: Participants were 69 mushroom workers who produce Hypsizigus marmoreus (Bunashimeji) and 35 control subjects. We excluded six workers because they had had asthma or allergic rhinitis before working. Participants completed a cross-sectional health survey 2 years after starting work at the mushroom farm. Results: The mean airborne endotoxin levels in the harvesting and packing rooms were approximately 60-fold higher than those in the offices. Of 63 workers, 42 workers (67%) reported chronic cough after working on this farm, 19 workers had no cough, while 2 workers had hypersensitivity pneumonitis develop to the spore, which has been previously reported by us. Of the 42 workers with cough, 6 workers had organic dust toxic syndrome (ODTS), 18 workers had postnasal drip syndrome, 15 workers had cough variant asthma, and 3 workers had eosinophilic bronchitis. Seventy-one percent of the workers noticed the cough in the first 3 months, and the mean latent period in ODTS workers was the shortest. The cough had a trend to improve or disappear after weekend holidays. Bronchial hyperresponsiveness but not FEV₁/FVC% in the 42 workers with cough was significantly (p < 0.001) increased as compared with the control subjects. Conclusions: Working on a mushroom farm carries a significant risk for chronic cough from inhalation of mushroom spores, and we suggest that elevated airborne endotoxin on this farm is the cause.