Pharmaceuticals degrade in top 12 inches of soil

By WES SANDER

Capital Press

A study by university researchers in California has determined that most of the antibiotics administered to dairy cows never reach ground water.

Researchers at the University of California-Davis call it the first large study tracking the "wide range" of antibiotics given to dairy cows.

The researchers found that, while the antibiotics are routinely flushed from dairy floors and into manure lagoons, they mostly break down in upper layers of soil.

UC-Davis ground water researcher Thomas Harter said most antibiotics degrade in the first 12 inches of soil, although small amounts do enter ground water.

"Our next task is to determine whether these particular antibiotics are further degraded before reaching domestic and public water wells," Harter said in a statement.

The study was conducted on two San Joaquin Valley dairies that sit above shallow water tables in sandy soil, which is easily permeated. Michael Marsh, CEO of Western United Dairymen, said it serves to counter critics who argue for reduced antibiotics.

"It gives us a scientific basis for some kind of perspective," Marsh said.

In Sacramento, a bill by Sen. Dean Florez, D-Shafter, to discourage antibiotic use in animal agriculture died early this year. Florez and other critics cited fears that routine use could increase resistance among disease-causing bacteria, putting animals as well as consumers at risk.

While no further regulatory proposals have since surfaced, the study can help inform future debates by addressing the extent to which local residents may be drinking tainted water, Marsh said.

The study could also provoke thought among producers on how to tighten further their own operations, with the goal of keeping antibiotics out of ground water entirely, he said.

"You do want to know, as a producer, what you can do to better operate your farm," Marsh said.

The study was published in August in the journal Environmental Science and Technology. It was funded by the CALFED Bay-Delta Authority, the U.S. Geological Survey and California Department of Food and Agriculture, which assesses producers for industry-specific programs and studies.