"That tells us we're not doing our job of reducing storm water pollution," said Mark Gold, the executive director for the group. "California's efforts to protect public health at the beach have been woefully inadequate."

Storm drain run-off polluted the most, followed by sewage spills, said the report, which recommended that swimmers wait at least three days before taking to the waters after storms.

Beach lovers can take solace in the fact that months can pass between rains in the summer months on many parts of the California coastline.

During dry weather beaches from Oregon to Mexico scored better than ever before, with 415 of the 463 monitored beaches earning grades of A or B. Just 27 beaches flunked, meaning they were polluted to the point of being unhealthy for humans.

The study used data gathered by county health departments, local clean water groups and state testing at 346 locations to grade beaches. The 10 worst beaches include four in Los Angeles County, two in San Diego county and two in Orange County -- all in the southern part of the state which promotes an image of sun, surf and fun.

Several are well-known tourist spots, including beaches in Malibu and Redondo Beach, Catalina Island and Paradise Cove in Los Angeles. One of the two worst is a beach just north of the Mexican border, in Imperial Beach, which is polluted by Mexican sewage and run-off from the Tijuana slough.

"There's more urban development, more coastal development and more storm drains discharging into the ocean in southern California," Gold said. "And there's not enough funding to educate people and control pollution despite the region's reliance on the beaches to draw tourism."

About 100 million people visit California's beaches each year. Those who are exposed to pollutants such as fertilizer, motor oil, human and animal waste and plant matter, risk skin and sinus infections, stomach problems and a host of bacterial infections.