Department of Water Resources
A daily compilation of significant news articles and comment
September 4, 2007
4. Water Quality
Researchers study bacteria at beaches
TESTS OF SAND SHOW MICROBES PRESENT AT MANY STATE SITES
By Suzanne Bohan
MediaNews
Here's a term you may start to hear more often: "Sand pollution."
No one knows exactly what's causing it, but scientists do know that beaches often contain high levels of bacteria linked to the presence of harmful pathogens.
And along the
While the particular strains of these microbes aren't usually harmful to humans, they do signal the possible presence of more harmful microbes such as viruses or other bacteria that cause illnesses.
The study, published in the July 1 issue of Environmental Science & Technology, is the most extensive one yet assessing sand pollution along the
It also provides evidence that bacteria permeating wet sands are carried away by waves, increasing bacteria levels in the adjacent waters. Dry sands above the tide line have low levels of bacteria, researchers noted.
"We know that (bacteria) can leave the sand and enter water," said Alexandria Boehm, assistant professor of civil and environmental engineering at Stanford, who led the study team.
Along the nearby coastline,
County beaches tested, Boehm said. In
The Bean Hollow figures didn't surprise Gary Strachan, supervising ranger for Año Nuevo State Reserve because dogs are permitted at the beach. "People don't always pick up after" their pets, he said.
Ray Stearns, a spokesman for the California Department of Parks and Recreation, which manages Bean Hollow, added that beaches are the last terrestrial repository for pollution from urban runoff, creeks and storm drains. "We're the last stop for it on our beaches," he said.
But before you retire the beach volleyball set and scratch plans to build a sand castle with the kids, keep in mind that scientists are still investigating the meaning of this growing body of data.
"I wouldn't want to discourage people from doing what they do, because the risk is really unknown," said Jenny Jay, a professor of environmental engineering at UC-
The health effects of exposure to pathogens in water are well known. Between 2003 and 2004, 2,698 people were sickened by microbes found in recreational waters, according to the U.S. Centers for Disease Control and Prevention. But nothing is yet known about the health effects of exposure to bacterial-laced sands. Jay, however, said she's participating in the first study to assess this health risk. The research is being conducted on
Awareness of sand pollution hit the radar in 1994, when researchers found that levels of these "indicator bacteria" were far higher in wet sand, compared with the adjacent water, according to the Clean Beaches Council. A 2003 study from the U.S. Geological Survey found the levels were five to 10 times higher along the shore than in water.
But the question for scientists is whether these bacteria just grow more vigorously in the hospitable environment of moist sediment, compared with open water, or do they signal that sandy beaches harbor high levels of the pathogens that come from human and animal waste.
"It could be these harmless guys are replicating," said Jay. "Or it could indicate that pathogens also exist."
For more information, read the "2005 State of the Beach Report: Bacteria and Sand" from the Clean Beaches Council. You can find the report at www.cleanbeaches.org/mediacenter.
http://www.mercurynews.com/politics/ci_6796132
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