FRIDAY, Feb. 8 (HealthDay News) -- When you're at the beach, you may want to stay on dry sand as much as possible, suggests a University of Florida researcher who conducted a two-year study of three Florida beaches to assess possible health effects of beach sand.

"What we found was that there was no increased health risk due to exposure to sand on the upper beach," Tonya D. Bonilla, a doctoral student at the College of Veterinary Medicine's department of infectious diseases and pathology, said in a prepared statement. "However, the longer the period of time people spent in the water and in the wet sand, the higher the probability that they would experience some gastrointestinal illness."

Bonilla had 882 people who spent time at Fort Lauderdale Beach, Hollywood Beach and Hobie Beach fill out a questionnaire four days after their beach visit. The questionnaire asked about the type and duration of beach activity and whether people became ill after their beach visit. The study also included a control group of 609 people who hadn't been to a beach for at least nine days.

The epidemiological data collected in the study was analyzed by Jay. M. Fleisher, an associate professor in the College of Osteopathic Medicine at Nova Southeastern University.

"Our findings suggest that there is an increased risk of acquiring gastroenteritis the longer a bather either sits in the wet sand or stays in the water," Fleisher said in a prepared statement. "The probability that an individual will become sick increases over expected non-exposure rates from six out of 1,000 people for a 10-minute exposure to approximately 12 out of 100 people for a two-hour stay in the wet sand."

"For exposure to water, these rates increase from seven out of 1,000 people affected over expected non-exposure rates for a 10-minute stay to approximately seven out of 100 people exposed for a 70-minute stay," Fleisher said.

"At this point, we don't know whether the increased health risk is due to pathogen exposure. To really understand this, a more comprehensive and targeted epidemiological approach is needed," Bonilla said.

The study was published recently in Marine Pollution Bulletin.

More information

The U.S. Centers for Disease Control and Prevention has more about viral gastroenteritis.