National Geographic News
Building sand castles and playing beach volleyball may be grittier vacation pastimes than you think, according to a new report.
Sand at many U.S. beaches contains bacteria that indicate potentially unhealthy levels of fecal material, the report states. The Clean Beaches Council, a Washington, D.C.-based advocacy group, issued the report earlier this month.
The so-called indicator bacteria, including a benign form of E. coli, pose little health risk to humans. But such microbes serve as warning signs that harmful fecal microorganisms may also be present, according to Walter McLeod, president of the Clean Beaches Council.
"It's sort of like the canary-in-the-coal-mine situation," he said. "If the canary dies, it's not the canary we're concerned about, it's what the canary was exposed to."
Scientists have only recently become aware of indicator bacteria in beach sand, said Elizabeth Alm, a microbiologist at Central Michigan University at Mount Pleasant and author of one of the studies included in the report.
The consequences for human health are uncertain.
"We know [that in] water, if fecal indicators exceed specific levels, then the risk of intestinal illness in swimmers increases," Alm said. "The same kinds of studies have not been done for the sand. We don't know what levels are safe or dangerous."
She added that lots of people play in the sand, but few seem to get sick from it.
Nevertheless, McLeod said it's important "to err on the side of safety." He encourages people to wash themselves thoroughly after a day at the beach.
"We can't say conclusively one way or another that there is a risk," he said. "It would be wrong to say, Don't touch the sand, or, There's a high risk for playing in contaminated sand. But it's also wrong to say there's no risk."
The tell-tale bacteria often occur at higher levels in the sand than in the water, according to the report. Studies also show that the microbes survive in sand longer than they do in water.
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