Is bacteria test buggy?

Biofilms, which can result in beach closures, may occur naturally, new research suggests.

October 06, 2006|By Alicia Robinson

Testing methods could be leading water-quality experts to post bacteria warnings at clean beaches, new research from Orange County's Newport Beach water-quality lab shows.

The research describes how "biofilms" can foster the growth of the bacteria that water-quality testers look for. The bacteria are supposed to indicate the presence of sewage, but scientists found they may also grow naturally in the environment.

Donna Ferguson, who supervises the Orange County Health Care Agency's water-quality lab on Shellmaker Island, will present the lab's findings next week at a national Environmental Protection Agency conference in New York.


Scientists now test for three kinds of "indicator bacteria" — bacteria that don't make people sick but are usually found in water contaminated by sewage or other human waste.

The Shellmaker lab's research has shown that the bacteria may give a "false positive," or indicate that water is contaminated when in fact there's no sewage in it, said Dr. Douglas Moore, the lab director.

Biofilms, of which one example is "the slimy substance that coats your teeth," can also play a role in bacteria growth, Moore said. The indicator bacteria can grow in a biofilm — say, in a storm-drain pipe — and then recontaminate water that's already been cleaned.

So the bacteria that indicate poor water quality can grow even when there's no accompanying contamination.

"This calls in question the reliability of indicator that we use and that's used across the nation," Newport Beach Assistant City Manager Dave Kiff said.

Water quality tests are important in Newport Beach, where thousands of visitors flock to the surf and sand each summer.

Moore said Ferguson and other scientists will do further research on indicator bacteria, and they hope to tweak the testing methods or find new ones that don't pick up bacteria that occurs in the environment.

"We always want to be protective of public health, that's priority No. 1, but we don't want beaches to get a black eye when they're not dangerous, and we think that's probably happening now," Moore said.

For Kiff, the bottom line is that more research is needed before anything will change. There are too many obstacles to expect a sudden shift in the way water is tested and when it's considered a risk, he said.

"The difficulty that we have in taking Donna's work and going forward with it is it's taken years and years to get the water quality standards that we have," Kiff said. "I'm not optimistic that the law is going to change any time soon."

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