Bioaerosol exposure in waste collection: A comparative study on the significance of collection equipment, type of waste and seasonal variation

Recent Danish studies on waste collectors' bioaerosol exposure are summarized. Generally the median exposure levels ranged from 105 to 106 cells m−3 (total microorganisms), 104 to 105 cfu m−3 (culturable fungi) and 103 to 104 cfu m−3 (culturable bacteria). The type of waste was a governing factor for exposure. Garden waste collectors frequently experienced concentrations exceeding 105 cfu m−3 for mesophilic fungi and 104 cfu m−3 for the thermophilic fungus Aspergillus fumigatus. Workers collecting compostable, mixed and sorted waste occasionally experienced similar concentrations of the fungal groups while workers collecting ‘bulky waste’ and paper had low exposure. Type of collection vehicle was identified as another governing factor for exposure. Vehicles loaded from the top (approximately 3 m above the ground) caused lower exposure (by a factor of 25) to fungi than vehicles loaded at the level or the breathing zone of the workers. Exposure was also affected by season of the year—the concentration of total microorganisms, culturable fungi, Aspergillus fumigatus and endotoxin was low in winter. Exposure to total microorganisms counted by microscopy was found to have a fairly high validity (Va) as an indicator of exposure to culturable fungi (Va = 1.45) or culturable bacteria (Va = 1.25). Likewise, dust may also be used as an indicator of exposure to total microorganisms (Va= 1.36), culturable fungi (Va= 1.31) and culturable bacteria (Va = 1.35).