Some freshwater streams in Harford, Frederick and Howard counties have high levels of bacteria that indicate the presence of fecal matter, researchers say.
"I think it is concerning that over all three counties, we rarely see a number within the range the EPA considers to be swimmable," said Drew Ferrier, director of the coastal studies program at Hood College in Frederick.
Researchers from the Chesapeake Bay Foundation, Harford Community College, Hood College, and Howard Community College testedabout 18 sites throughout the three counties. They plan to continue testing through August.
They tested for enterococcus bacteria, which indicate the likely presence of human or animal waste, potentially from leaking septic tanks or livestock.
"The higher the level, the greater chance that there is that fecal matter in the water," said Tom Zolper, a spokesman for the Chesapeake Bay Foundation.
Researchers found bacteria levels at Kilgore Falls, a popular swimming hole in Harford County, at nearly 50 times the safety limits set by the Environmental Protection Agency.
Zolper said one cause could be the stream's proximity to agriculture.
"You're basically getting manure in the water," he said.
Exposure to the enterococcus bacteria is not necessarily dangerous in itself, Zolper said, but its presence is a potential indicator of bacteria that can cause gastrointestinal problems like diarrhea.
"It's not life-threatening by any means, but it could be nasty," he said. "If you think back in the Middle Ages when sewage was dumped in the street, that was the thing that made people commonly sick — the mixing of fecal of matter where people are living."
Many of the sites the researchers tested are not intended for swimming, Ferrier said, but people, and particularly children, could still be exposed to unsafe water.
"What I oftentimes see in these public places is not swimming as much as kids wading, or rolling over rocks or simply cooling off a bit," he said. "It would be too bad if there aren't places where kids can have access to water just to play."
Barry Glotfelty, director of environmental health services at the Frederick County Health Department, said officials oversee bacteria levels at two swimming beaches, but not other water sources.
"We would recommend you swim in a lake that we regulate," he said.
The county Health Department has not received reports of illness after contact with freshwater, Glotfelty said. He suggested people "exercise reasonable caution" in unknown waters: Don't drink it, avoid contact with cuts and wash after exposure.
There are no approved bathing beaches in Harford County. County Health Department spokesman William D. Wiseman said it's up to residents' discretion to spend time in local water.
"Warning signs in these areas indicating that visitors 'Swim at their own risk' apply not only to safe behavior in the water but also to decisions to use these areas in the first place where the risk of exposure to poor water quality/contamination may exist," he said in a statement.
Zolper said those who visit public water sources should limit their exposure, especially within 48 hours of a rainstorm.
"If you're going to swim, you might want to rinse off afterwards, not open your mouth," said Zolper. "That's the highest risk, when you're ingesting this water."