Assessment of Bioaerosols at a Concentrated Dairy Operation.

Increased bioaerosol loadings in downwind plumes from concentrated animal feeding operations (CAFOs) may increase the risk for allergy and infection in humans. In this study we monitored airborne concentrations of culturable bacteria and fungi at upwind (background) and downwind sites at a 10,000 milking cow dairy over the course of a year. The average bacterial concentrations at the upwind site were 8,400 colony forming units (CFU)/cubic meter and increased to 990,000 CFU/cubic meter at the downwind edge of the cattle pens, decreasing to 63,000 CFU/cubic meter 200 m farther downwind. At the same sites, the average fungal concentrations were 515, 945, and 1010 CFU/cubic meter, respectively. Significant correlations between the ambient weather data and airborne fungal concentrations were identified, but not with bacteria. Sequence analysis of PCR-amplified DNA from bacterial clones and fungal isolates revealed genus and species level differences between upwind and downwind sites. Although we could not cultivate gram-negative bacteria, bacterial clones at downwind sites identified as being gram-negative matched with the following genera: Acinetobacter, Bradyrhizobium, Escherichia, Idiomarina, Methylobacterium, Ralstonia, and Novosphingobium. Fungal isolates from downwind matched with the following genera: Acremonium, Alternaria, Ascomycte, Aspergillus, Basidiomycete, Cladosporium, Davidiella, Doratomyces, Emericella, Lewia, Onygenales, Penicillium, Rhizopus, and Ulocladium. None of the bacterial and fungal sequence matches were affiliated with genera and species known to be pathogenic to humans. Overall, the concentrated dairy operation does not appear to increase the risk of exposure to bioaerosols, especially when an individual increases their downwind distance from the facility