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Traces of dairy antibiotics found in groundwater, UC Davis report says

August 27, 2010 |  7:46 pm

Core sampling at dairy A recent report by UC Davis scientists found that antibiotics administered to dairy cattle do end up in manure lagoons and on the ground, but that only a small amount enters the groundwater -- and that the majority of the drugs break down before then.

The study was done on two large dairy farms in the San Joaquin Valley between 2006 and 2008. It was funded by the CALFED Bay-Delta Authority Drinking Water Program and with monies from dairy farmers collected by state Department of Food and Agriculture.

"What we found is that antibiotics can frequently be found at the manure-affected surfaces of the dairy operation (such as corrals and manure flush lanes) but generally degrade in the top 12 inches of soil," Thomas Harter, an expert on the effects of agriculture on groundwater quality and the Robert M. Hagan Chair for Water Management and Policy at UC Davis, said in a statement.

"A very small amount of certain antibiotics do travel into shallow groundwater,” he added. “Our next task is to determine whether these particular antibiotics are further degraded before reaching domestic and public water wells."

An abstract of the study -- published in the online version of the American Chemical Society's Environmental Science & Technology -- can be found here.

-- P.J.Huffstutter

Photo: Researchers Mike Mata of UC Davis, left, and Brian Bergamaschi of the U.S. Geological Survey drill core samples from the ground under a dairy freestall. Credit: Thomas Harter / UC Davis