Great Lakes Article:

E. coli levels unpredictable, study says

Researcher stresses complexity of measuring beach waters' safety

By JO SANDIN
Article courtesy of the Milwaukee Journal Sentinel

Oct. 12, 2001

The safest days to swim in Lake Michigan are those when the beaches are closed, a top researcher said Thursday to illustrate that conditions making it unsafe to swim are complex and difficult to predict.

Richard Whitman, chief of the U.S. Geological Survey's Lake Michigan Ecological Research Station in Porter, Ind., outlined his findings in during the annual meeting of the Great Lakes Commission, a citizen body established in 1955 to advises the federal and state governments on policies to preserve Great Lakes water and fish resources.

Whitman said he had recently completed a six-month examination of 5,000 water samples from the 63rd St. Beach in Chicago. E. coli concentrations from the Thursdays when the water was tested were compared to concentrations on the following days whenever the beach was closed because of high E. coli counts from the water samples.

"The beach is safer when it's closed than when it's open," Whitman said.

His study proved that "we cannot predict the E. coli level from one day to the next, or from morning to evening," Whitman said.

Although the most important public health threat at Great Lakes beaches still is domestic pollution, he said, his research had shown that contaminated swimming waters are a far more complex phenomena than he had previously imagined.

In addition to the 63rd St. Beach study, Whitman said he had analyzed data from a Toronto beach, where closings were considered to be the result of sanitary sewer overflows after heavy rainfalls, and from Sleeping Bear National Lakeshore in Michigan, where there are no sewers, during a period of dry weather.

"Closures are not always due to rainfall and not always associated with a (sewage treatment plant) bypass," he said. "There are places where we have no sewage and we still have closures."

While the study did not examine Wisconsin beaches, closings have been a concern in the Milwaukee area. This summer, for example, South Shore Beach in Milwaukee was closed at least 25 days since it opened in mid-June because of high bacteria counts. North Shore beaches - Klode Park in Whitefish Bay and Atwater Park in Shorewood - also closed more than 10 times each this year.

At Sleeping Bear National Lakeshore, he said, Canada geese congregate on a popular swimming bay. When the wind blows toward the bay, he said, E. coli concentrations spike until the water is at least waist deep.

"When the wind is from the shore, E. coli drops to zero," he said.

Whitman said analysis of 12 years of beach closing data had produced these certainties: Sunlight kills E. coli. Deep water disperses it. Offshore winds blow pollution away from the beach.

Also, experiments proved that to reach even a 70% level of confidence that tests accurately reflected water quality, at least eight samples at a beach were necessary, he said.

"That is well beyond the pocketbooks of most beach managers," said Whitman.

However, the complete mechanism that results in health-threatening levels of E. coli on beaches used by thousands of people remains a mystery, he said.

"Whatever's happening is happening on a system-wide basis," he said.

Therefore, it is inadequate to monitor beach pollution by merely looking at the water or the sand.

Nevertheless, said another speaker, Cameron Davis, executive director of the private, non-profit conservation group the Lake Michigan Federation: "If we are going to solve this problem, we are going to have to solve it on a community-by-community basis."