Ambient air levels of Aspergillus fumigatus and thermophilic actinomycetes in a residential neighborhood near a yard-waste composting facility

Composting is a biological process that has thepotential to emit large quantities ofbioaerosols and, therefore, could adverselyaffect public health. Numerous previousstudies have demonstrated bioaerosol levelselevated above background adjacent tocomposting waste materials, but effects onoffsite bioaerosol levels due tocomposting-facility bioaerosol emissions havenot been extensively investigated. Of the fewsuch studies published, most have not foundelevated compost-related bioaerosols downwindfrom the composting operation. We investigatedviable Aspergillus fumigatus andthermophilic actinomycete levels upwind anddownwind of a large yard-waste compostingfacility and sought to determine whether levelsin a residential neighborhood near the facilitywere elevated above background levels due tofacility bioaerosol emissions. Mean bioaerosollevels at the composting facility weresignificantly higher than the mean backgroundlevels, exceeding the background means byroughly 20-fold. When a neighborhood samplingsite about 500 m from the facility was in thedownwind direction mean levels weresignificantly higher than for other winddirections, and excursions well abovebackground levels were significantly morefrequent than at background sites. There was asignificant temporal correlation betweenbioaerosol levels at the composting facilityand the downwind sampling site. The resultsindicate that bioaerosol emissions from a largeyard-waste composting facility cansignificantly increase bioaerosol exposurelevels at least 500 m downwind from thefacility.