Just in time for swimsuit season, federal researchers are touting a faster, more accurate water-quality test to keep beaches open and people healthy.
But it’s expensive, and most of the nation’s cash-strapped cities and counties can afford it.
Local officials traditionally check for bacteria in ocean and lake water with tests that take about 24 hours to complete. Now the U.S. Environmental Protection Agency is recommending testing at the molecular level – tagging DNA and counting bacteria – which provides results within hours.
“Water quality can change significantly in 24 hours. This way we’re identifying threats to human health almost immediately,” said Meredith Nevers, a research ecologist with the U.S. Geological Survey who is studying the EPA’s new DNA test.
An estimated 3.5 million people get sick every year after a trip to the beach because of E. coli or other pathogens from sewage overflows, spills and polluted runoff, according to the EPA. Exposure can cause gastrointestinal illness, skin rashes and infections.
About 43 percent of beaches along the East and West coasts and the Great Lakes had at least one water-quality advisory in 2011, according to EPA data.
Counties and cities test beaches routinely – often weekly but depending on the location and season. Beaches also are tested after spills to determine when they can be reopened.
Traditional tests involve waiting 24 hours to allow E. coli, coliform or enterococci to grow in a water sample, then counting the colonies. That means decisions to close down beaches are based on samples collected the day before.
The new method speeds up DNA replication. Researchers then use fluorescent probes to see how many bacteria are present in a water sample by counting the DNA copies that fragmented. Other same-day tests are in various stages of research, but all generally use two steps: capturing microbes and tagging them so they can be counted.
Comparing the new method to the culture-based tests at Lake Michigan beaches, Nevers and colleagues concluded that beach closures and illness rates “could be minimized.” They couldn’t predict how many unnecessary closings or illnesses it would prevent, but it would be “significant,” Nevers said.
“Rapid testing is great – the faster the results, the better,” said Shannon Briggs, a toxicologist at the Michigan Department of Environmental Quality, which works with communities throughout the state on beach testing. “The goal is to keep beaches open all the time and keep people safe and this will help.”
But it’s not cheap.
DNA testing requires new labs and newly trained staff – a significant hurdle for cities and counties. Nevers estimated the new tests would cost about twice as much as the old ones.
Universities throughout Michigan are partnering with some coastal communities to help get the ball rolling.
The only community using the method right now to make beach safety decisions is Racine, Wis. The city received clearance last year from the EPA to use the DNA test on its two beaches that frequently exceed safe bacteria counts after years of testing it, said Julie Kinzelman, a research scientist at the Racine Health Department.
“We used to have to say, ‘well, you swam yesterday and now we know the water wasn’t clean. Sorry we couldn’t tell you in time,’” Kinzelman said.
Racine still uses culture tests to check the reliability of the DNA testing. Kinzelman said over the years the two different tests have been at about 90 percent agreement.