Dust and bioaerosols at a biosolids composting facility

Workers at composting facilities are exposed to organic dusts and bioaerosols. The bioaerosols of major concern are Aspergillus fumigatus (A. fumigatus) and endotoxin. An evaluation of employee exposure to dust, endotoxin, and A. fumigatus spores was conducted in a totally enclosed biosolids composting facility that composts biosolids with sawdust. Total and respirable dust, endotoxin, and A. fumigatus were measured during several of the major composting activities. Periodic total dust levels exceeded the OSHA PEL standard for nonspecific dust. Endotoxin levels as high as 640 ng/m(3) were recorded when piles were tom down. During mixing of biosolids and sawdust, A. fumigatus counts exceeded 6,000 CFU/m(3). Based on the data obtained, several mitigation measures were implemented. Evaluation of the facility after the changes were made found that levels of total dust, endotoxin, and A. fumigatus were reduced by 90 percent.