Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2010
Publication Date: 2/28/2011
Citation: Dungan, R.S., Leytem, A.B. 2011. Ambient Endotoxin Concentrations and Assessment of Offsite Transport at Open-Lot and Open-Freestall Dairies.. Journal of Environmental Quality. 40(2):462-467.
Interpretive Summary: Endotoxins are derived from bacteria and are a potential respiratory health risk if inhaled. Acute exposures can cause lung disfunction and flue-like symptoms. In this study we monitored airborne endotoxin concentrations at the downwind edge of a 10,000 milking cow open-lot and open freestall dairy over an 8-hour period to assess daily fluctuations. Compared to background environments, the downwind concentrations were statistically higher and increased with wind speed, animal activity, and lot management practices. A model was then used to predicted ground-level endotoxin concentrations up to 2,000 m from the dairies. Predicted endotoxin concentrations decreased with distance and reached background levels within 500 to 2,000 m depending on source concentration and climatic conditions. Individuals in the downwind environment will have a lower risk of exposure to airborne endotoxin as distance from the production facilities is increased.
Technical Abstract: Endotoxins are derived from gram-negative bacteria and are a potent inducer of inflammatory reactions in the respiratory tract when inhaled. To assess daily fluctuations of airborne endotoxin and their potential for transport from dairies, endotoxin concentrations were monitored over an 8-h period at upwind (background) and downwind (5 m from edge of dairy) locations on three separate days at two dairies. The dairies consisted of an open-lot or an open-freestall production system, both of which were stocked with 10,000 milking cows. Upwind concentrations were stable throughout the sampling period, averaging between 1.2 and 36.8 endotoxin units (EU) m-3, whereas downwind concentration averages ranged from 179 to 989 EU-3. Downwind endotoxin concentrations increased with wind speed, animal activity, and lot management practices, resulting in concentrations up to 136-fold higher than upwind concentrations. An area-source model was used to predict downwind ground-level endotoxin concentrations at distances up to 2000 m from the production facilities. Predicted concentrations decreased with distance and reached background levels within 500 to 2000 m, depending on the source emission rate and meteorological conditions.