Environmentalists concerned about air and water pollution have alleged air and water pollution from dairy dust in western dairy operations and poultry house fan discharges on the East Coast. However, a recent study by USDA's Agricultural Research Service study counters those claims.
The study investigated dust stirred up by wind and restless cattle at dairies. They do contain bacteria, fungi and small bacterial remnants such as endotoxins, acknowledges Rob Dungan, ARS microbiologist at the ARS Northwest Irrigation and Soils Research Laboratory in Kimberly, Ida. But the potentially problematic particles aren't found at high levels far beyond the barnyard.
In one study, Dungan and his colleagues set up three sampling sites at a 10,000-cow, open freestall dairy to measure airborne endotoxins and culturable microorganisms like bacteria and fungi during the fall, spring and summer. The overall average inhalable airborne endotoxin concentrations were five endotoxin units (EU) per cubic meter of air 655 ft. upwind of the barn — their "background" levels" — and 426 and 56 EU/cubic meter of air 165 ft. and 655 ft. downwind of the barn, respectively.
Close to the barn, endotoxin concentrations at night were significantly higher than morning concentrations, and were similar to afternoon concentrations. The scientists attributed the higher levels to increased animal activity and lower wind speeds during these times. However, at two sites, endotoxin concentrations didn't vary significantly over 24 hours.
Samples of bacterial concentrations showed a similar pattern, with the highest counts — 84,000 colonies per cubic meter of air — measured near the barn. The other two sites had fewer than 8,000 colonies per cubic meter of air.
The bottom line: Aerial concentrations fall off quickly in all cases as the distance from the cattle or barns increased.
Information courtesy of Feedstuffs FoodLink.