Determinants of microbial exposure in grain farming

Exposure to dust and endotoxin of employees in cucumber and tomato nurseries

Exposure to bioaerosols in occupational settings is associated with a range of adverse health effects. The aim of this study was to investigate the exposure levels to dust and endotoxin of people working in two cucumber nurseries and two tomato nurseries. Exposure was measured for greenhouse workers (n = 70) mainly working on harvesting cucumbers and tomatoes and clearing the plants after the harvest season. The people were exposed to between 0.2 and 15 mg inhalable dust m(-3) (median = 1.6 mg m(-3)) and between 0.5 and 400 ng inhalable endotoxin m(-3) (median = 32 ng m(-3)). The exposure to 'total dust' and endotoxin measured by stationary samplers (n = 30) in the greenhouses was low. Endotoxin was present in relatively high concentrations on cucumber leaves compared with leaves on pot plants. The Danish occupational exposure limit (OEL) for total organic dust is 3 mg m(-3) and 36% and 17% of the cucumber and tomato workers, respectively, were exposed to >3.0 mg inhalable dust m(-3). There is no OEL for endotoxin, but 'no effect levels' at approximately 15 ng m(-3) have been found. The majority of subjects (65%) were exposed to >15 ng m(-3). Significantly higher exposure was found for employees in cucumber nurseries than for employees in tomato nurseries. Clearing tomato plants after the harvest season caused a higher exposure to endotoxin than tomato harvesting. In conclusion, people working in cucumber and tomato nurseries were often exposed to high levels of inhalable dust and endotoxin. Cucumber harvest workers were exposed to significantly more dust and endotoxin than tomato harvest workers. The dust and endotoxin aerosolized during the working processes were only transported to other areas in the greenhouses to a very low degree. Cucumber and tomato leaves were identified as endotoxin reservoirs.