Introduction Exposure to organic dust may lead to decrease in lung function among healthy subjects or development of respiratory symptoms. Studies done among coffee workers reported significant exposure to endotoxins with no evidence of decrease in lung function. The current study aimed at determining seasonal variation of lung function among coffee workers due to endotoxin exposure.

Methods The study was done in coffee factory where 30 workers were monitored for one season of coffee processing that is from June 2016 to February 2017. Lung function tests were performed once in the morning on any day before the season, then on Monday morning and Friday evening at mid-season and end of the season. A portable spirometer WinspiroLIGHT was used. ATS/ERS guidelines were followed. All measurements were taken in standing position. Data was analysed by paired-sample T-test. Smoking and age used to adjust lung function change in linear regression.

Results The mean age of participants was 38 (8.4) and mean time of working in coffee factories was 10 (6.8) years. There was a significant decrease of 24 and 20 mls for FEV₁ and FVC, the change being high in the mid-season compared to end season. Improved in FEV₁ (3.29 l/s – 3.65 l/s) at the beginning of season to mid-season was observed.

Discussion Lung function decrease is observed along the season with higher decrease at the end of season. The slight increase in FEV₁ between beginning of season and mid-season could be due to cessation of exposure.