A 5-year follow-up study on respiratory disorders and lung function in workers exposed to organic dust from composting plants

Objectives: To evaluate acute and chronic effects of long-term exposure to organic dust on respiratory disorders and lung function among employees at 41 composting facilities in Germany. Methods: A total of 218 compost workers and 66 control subjects were enrolled in the cohort. They were evaluated using a standardized questionnaire, a clinical examination, and spirometric measurements. Changes of symptoms, respiratory disorders, and lung function were determined in a first survey after 5 years of exposure in 123 compost workers and 48 controls. Exposure measurements were performed at six composting facilities for respirable dust, cultivable microorganisms, and endotoxins. Results: Exposure measurements revealed high concentrations of thermo- tolerant/thermophilic actinomycetes and filamentous fungi in the bioaerosols at the composting sites. A significantly higher job fluctuation was observed among the compost workers compared to control subjects (95 vs. 18; p < 0.05). Compost workers reported a significantly higher prevalence of mucosal membrane irritation (MMI) of the eyes and upper airways than control subjects. Conjunctivitis was diagnosed significantly more often in compost workers. Forced vital capacity in percent of predicted (FVC%) of the non-smoking compost workers declined significantly (-5.4%) during the observation period compared to control subjects. The decline of FVC% in 16 compost workers exceeded 10% of initial values. A significant increase was observed in the number of compost workers suffering from chronic bronchitis (RR = 1.41; 95% CI = 1.28-1.55). Allergic alveolitis was diagnosed clinically in two compost workers. Conclusions: The exposure to organic dust at workplaces of composting facilities is associated with adverse acute and chronic respiratory health effects, including MMI, chronic bronchitis, and an accelerated decline of FVC%. The pattern of health effects differs from those at other workplaces with exposures to organic dust possibly due to high concentrations of thermo-tolerant/thermophilic actinomycetes and filamentous fungi at composting plants.