Oct 262004
Authors: Lila Hickey

A CSU study is the first in its kind to demonstrate that

antibiotics fed to livestock are ending up in waterways, according

to an Oct. 19 press release.

Ken Carlson, an associate professor of civil engineering, has

been investigating the presence of antibiotics in Colorado

waterways for two years and has found that antibiotics used only in

animal feed are present in public waterways.

Previous studies demonstrated that antibiotics were present in

public waterways, but there was no way to trace their origins so

Carlson decided to track monensin, an antibiotic used exclusively

in animal feed. When the study revealed the presence of monensin in

public waterways, it showed that livestock antibiotics were somehow

entering the watershed.

“Monesin is only used for feed, for enhancing growth,” he said.

“There aren’t any human uses and it’s not even used


Now Carlson and his co-investigators are trying to track the

antibiotic’s path from livestock grounds to public waterways. Like

many pharmaceuticals, most of the active ingredients in monensin

are not absorbed by animals, so residual antibiotics end up in

manure and in wastewater storage lagoons.

“I think it’s at least 75 percent (of the antibiotics) is

excreted without being changed,” said Jessica Davis, a professor of

soil and crop sciences and co-investigator on the project.

Wastewater treatment plants remove some of the antibiotic

residue, Davis said, but there are still antibiotics that are not


Major concerns related to the drug’s presence in the public

waterway include the potential negative effect on aquatic life and

the possibility that releasing such antibiotics into the

environment will increase antibiotic resistance among dangerous

bacteria, Carlson said.

Antibiotic resistance has been a growing concern in recent

decades, with many scientists and medical groups worrying that a

tendency to overuse antibiotics has allowed many dangerous bacteria

to develop partial or total immunity to the drugs, according the

U.S. Food and Drug Administration’s Web site, www.fda.gov.

While the investigators publish the results of their findings,

research will continue, Carlson said. He and his colleagues are

investigating how antibiotics travel from agricultural areas into

the watershed, as well as searching for ways to degrade the


“We don’t just want to raise the red flag and say, ‘Look,

they’re here,’ and go home,” Carlson said.

He noted that the levels of antibiotics are extremely low, but

warned that they could still affect the environment.

“The ag industry would like it to go away,” Carlson said. “We’re

not willing to do that but we’re also not willing to say the sky is

falling. (The public’s) drinking water’s not at risk.”

Carlson’s colleagues agreed, saying that further research is


“The thing with pharmaceuticals is they’re active at very low

levels,” said co-investigator Amy Pruden, an assistant professor of

civil engineering, citing DDT, a pesticide used in the ’60s and

’70s that was found to disrupt birds’ reproductive cycle.

Pruden is studying animal waste in an effort to reduce

antibiotic presence. Carlson noted that leaving wastewater exposed

to sunlight might help break down antibiotics.

“We feel that the growing and feed operations contributes to

(the antibiotics’ presence),” Carlson said. “We want to know, is

that one of the primary routes for the compounds getting from the

farms to the rivers?”

The researchers hope that determining how the antibiotics get

into waterways will provide insight into stopping the process.

“Maybe there’s just some simple thing you can change,” Pruden

said. Davis and Carlson agreed, noting that they are focused on

working with farmers and ranchers to eliminate the antibiotics in

public water.

Carlson, Pruden and Davis all agreed that while the research is

noteworthy, the public should not be alarmed.

“It’s just a preliminary, ‘hey, these antibiotics are there,'”

Pruden said.

 Posted by at 5:00 pm

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