Assessment of Bioaerosols At a Large Open-Freestall Dairy Operation.

High bioaerosol loadings in the downwind plumes from large dairy operations may increase the risk for allergy and infection in humans. Information will be presented with respect to the concentration and behavior of airborne bacteria, fungi, and endotoxin in the downwind environment of a 10,000 cow open-freestall dairy in southern Idaho.  Compared to background locations, the general trend is that bioaerosol concentrations are higher immediately downwind, then decrease with distance from the production facility.  While bioaerosol concentrations did not follow a seasonal trend, they did significantly correlate with meteorological factors such as temperature and solar radiation.  Concentrations immediately downwind from the dairy were also found to be greatest at night, which can be attributed to changes in animal activity and wind speed and reduced exposure of the airborne microorganisms to UV radiation.  An analysis of clones generated from air samples revealed that none of sequence matches were affiliated with bacteria known to be pathogenic to otherwise healthy humans.