Most counties with shorelines post online updates on any beaches that have been closed or where bacteria levels have tested high.

Baltimore County tests water every other week at a dozen beaches, according to Health Department spokeswoman Monique Lyle. When bacteria levels are too high, the county closes the beach, posts signs and puts the information on the county website.

The state coordinates efforts in the various counties to ensure they use the same standards. The state helps with publicity, too, distributing signs and fliers to the counties.

But it can be a challenge to get people thinking about safety when they're at the beach, said Kathy Brohawn, an environmental program manager with the state Department of the Environment.

"There's always a group that is on the websites all the time, and some that, no matter what kind of outreach you do, you'll never get to them," she said. "We're always looking for new ways to get information out."

Behind the bacteria

Multiple culprits are behind high bacteria counts.

Stormwater is the top reason for bacterial contamination. When it rains, water rushes along pavement, picking up animal waste, trash and other contaminants that get flushed into creeks, rivers and the bay.

Other potential sources include animal waste — especially from geese and ducks — as well as sewage spills or leaks.

Stormwater runoff is the likely cause of high readings in Anne Arundel recently, Zitnik said.

"This time of year, particularly with these monsoon-like rains we've been having over the last two or three weeks, the high bacteria results could be a result of stormwater rushing into the waterways," he said.

Stormwater is such a concern that the county and state have a standing advisory warning people not to swim within 48 hours of a rainstorm. The county Health Department doesn't even take water samples after rainfalls because they know counts will be off the charts.

Private groups, however, test even after rains. "I want to give people the real data," Trumbauer said. "I know people go out the day after it rains and want to go swimming."

Trumbauer said people should be outraged that stormwater is such a problem that simple rain makes it unsafe to swim.

"We're OK with that? No, we shouldn't be," he said.

Baltimore Sun reporter Alison Knezevich contributed to this article.


For those who swim in rivers and the Chesapeake Bay, officials offer the following tips:

•Cover any cuts or wounds with waterproof bandages.