Germs Living in Your Sandcastles

Bacteria and microbes developed for health department reference

(RxWiki News) Going to the beach means digging in the sand, building sandcastles, being buried in sand… But most health departments have no way of determining how "clean" that sand is.

A new research article by two scientists attempts to come up with a marker of what a clean enough beach would be.

It would mean low enough levels of microbes and germs that the sand's risk to a person's health is no greater than the water when the water is deemed appropriately safe.

"Check with local health departments about safe beaches."

Authors Tomoyuki Shibata and Helena Solo-Gabriele sought to come up with references guidelines for determining what level of bacteria and other microorganisms in sand was safe before a beach's sand should be considered too contaminated.

Shibata is from the Institute for the Study of the Environment, Sustainability & Energy and the School of Nursing and Health Studies at Northern Illinois University. Solo-Gabriele is from the Department of Civil, Architectural & Environmental Engineering at the University of Miami.

Sewage runoff can contaminate both water and sand at beaches and lead to skin infections or gastrointestinal disorders if a person is exposed to certain kinds of bacteria.

One study mentioned in the article describes an association found between those who dug or buried themselves in the sand and a higher rate of gastrointestinal illness and diarrhea.

Although the Environmental Protection Agency in the U.S. has guidelines for sea water and freshwater regarding when the bacteria levels are too high for the water to be safe for swimming, a similar guideline does not currently exist for sand.

The scientists describe one study that found a single fingertip's worth of sand had enough bacteria to cause intestinal problems if a person put the finger in his or her mouth.

Having a reference point for health departments to determine when sand becomes too contaminated for digging, playing, building sandcastles, burying or other activities would help parents keep their children safe.

"The focus of children at the beach environment is especially important, due to play behavior at beach sites that would increase a child's exposure," the authors wrote.

The researchers followed a standard four-step process to develop the guidelines, which involves identifying what pathogens might pose a health risk to people and how much of a risk they pose. This calculation allows them to determine how much exposure someone could or should safely have to that risk.

Shibata and Solo-Gabriele looked at the full range of microbes, including bacteria, protozoa, viruses, fungi and yeasts.

They studied microbe concentrations on beaches in California and Florida to figure out how many microorganisms would need to exist in beach sand before it reached the safe limits of what the EPA allows in swimming water.

Therefore, their final calculations equated the benchmarks for water contamination measurements to the safe level benchmarks in sand.

The guideline is defined as a 1.9 x 10-2 infection risk, a computation that most people would not find useful but which health departments can use to determine a beach's safety in terms of human health risks.

The two researchers also recommended that additional studies be done to determine the levels of certain groups of microbes present in sand, including nematodes and norovirus, which causes the stomach flu.

The study appeared in the April issue of Environmental Science & Technology. The research was funded by the National Science Foundation and the National Institute of Environmental Health Sciences.

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Review Date: 
May 2, 2012