Polluted water isn't the only health threat for Southern California beachgoers: The sand at some of the region's most popular beaches can be laced with bacteria even when the water is clean.
A UCLA study to be released today of Santa Monica Bay beaches from Malibu to Redondo shows that, although water bacteria levels may meet state health standards, sand acts as an incubator in which microbes can flourish and contaminate water used by swimmers and surfers.
"It can actually grow in the sand," said Jennifer Jay, UCLA professor of environmental engineering who headed the study. "Even on days when the water is very clean, bacteria is still in the sand for a week. We feel it can be an important exposure route" for contamination.
Researchers found the worst offenders were the sheltered side of Cabrillo Beach in San Pedro, Mother's Beach in Marina del Rey, Santa Monica Beach near the pier and Topanga Beach in Malibu. Sheltered or enclosed beaches showed persistent elevated levels of bacteria.
Health standards for beach sediment have not been developed, however, so it is difficult to evaluate how much of a health risk these bacteria pose, Jay said.
Health officials have long known that microbes, mainly \o7E. coli \f7and enterococci bacteria found in fecal material, can reach harmful levels in ocean water. Urban runoff from city streets, farms and industries carries a witches' brew of pollutants that are concentrated to unhealthful levels around storm drains and river mouths. The new study, to be published in the forthcoming issue of the journal Water Research, adds to a growing body of evidence that health risks extend to the shore.
"People haven't looked at the sand until recently," said Alexis Strauss, director of the water division for the U.S. Environmental Protection Agency. "Our urban existence yields bacteria year-round."
Of greatest concern is that scientists discovered the highest sand bacteria concentrations at beaches favored by parents with toddlers. Mothers take children to sheltered sites because they are protected from high surf and dangerous undercurrents. But Jay said those conditions may contribute to more bacteria because the still waters do not agitate sand and flush it clean.
"This is particularly relevant when we're talking about sheltered beaches such as Mother's Beach and the enclosed part of Cabrillo Beach, for example, which appear to be more conducive to the persistence of these bacteria," Jay said. "The levels of enterococci were approximately 1,000 times higher than the levels observed at the beaches open to the ocean."
Mark Gold, executive director of the Santa Monica-based advocacy group Heal the Bay, said the study adds urgency to beach cleanup efforts and could lead to additional warnings posted along the shore. He said the problem underscores how difficult it will be for beaches to meet new water quality standards set to take effect July 15. Heal the Bay plans to release a list of the most polluted California beaches at a news conference Wednesday.
Jay and graduate researcher Christine Lee tested three beaches -- Surfrider Beach in Malibu; Santa Monica Beach; and Mother's Beach in Marina del Rey -- during a storm in February 2003. They also took samples of water and sand to test in the lab. And they surveyed sand at 13 beaches in Santa Monica Bay during summer.
Researchers focused on wet sand near the water's edge; the bleached, dry sand farther inland does not show significant levels of bacteria. Also, the sand pollution is more pronounced during and after storms. Beachgoers can reduce their risk by not ingesting polluted water or sand, exposing open wounds or cuts, and washing with soap and water after contact with sand or water.
Jay, a mother of twins, said her children enjoy splashing in the ocean, though she avoids the placid, enclosed beaches that are popular with youngsters and their parents.
"My kids play in the sand at the open beaches all the time. I wouldn't worry much about that," she said.
Jay said the presence of fecal bacteria is not definitive proof that dangerous pathogens are present.
She said the next phase of the study would examine whether viruses are present in the sand.
Jay will discuss the findings at 7 p.m. Wednesday at UCLA. For details, visit www.engineer.ucla.edu/events/jay.html.