Dust from dairies does contain bacteria, fungi and small bacterial remnants such as endotoxins, USDA noted. But the particles are not found in high levels far beyond the facilities. USDA said the findings have important implications for residents who are concerned that living near a dairy facility could increase the potential risk of exposure to bacteria and endotoxins.
Rob Dungan, a microbiologist with the Agricultural Research Service (ARS), is investigating dispersal patterns and transport of these particles, also called bio-aerosols. In one study, Dungan and his colleagues established three sampling sites at a 10,000-cow open-freestall dairy to measure airborne endotoxins, bacteria and fungi during fall, spring and summer.
"The researchers found that overall average inhalable airborne endotoxin concentrations were 5 endotoxin units (EU) per cubic meter of air 655 feet upwind of the barn—their "background" levels"—and 426 and 56 EU per cubic meter of air 165 and 655 feet downwind of the barn, respectively," USDA noted.
Close to the barn, researchers found endotoxin concentrations were significantly higher at night compared to morning concentrations and similar to afternoon concentrations, USDA said. Researchers attributed the higher levels to increased animal activity and lower wind speeds during these times. But at the other two sites, endotoxin concentrations did not vary significantly over a 24 hour period.
Samples of bacterial concentrations showed a similar pattern, with the highest counts — 84,000 colonies per cubic meter of air — measured near the barn.