Health risks for Southern California swimmers and surfers have increased due to a decrease in beach-water testing, the result of recession-related budget cuts, according to a report by an environmental organization yesterday.

“Less testing may lead to fewer pollution warnings, but it doesn’t make our beaches any cleaner,’’ said Noah Garrison, attorney for the National Resources Defense Council’s Water Program. “In order to keep our beaches safe for swimmers and surfers, it’s critical that we test for pollution and also stop it at its source.’’

The NRDC’s 20th annual beach water report indicated that 4,500 fewer samples in Los Angeles and Orange counties were collected in 2009 than the previous year. And during that time span, only one-third as many samples were taken at Santa Monica Beach at the pier, Surfrider and Cabrillo, which were cited as three of the dirties beaches, each exceeding bacteria standards at least 45% of the time.

Southern California beach testing dropped by nearly one-quarter overall between 2008 and 2009, the report found. The NRDC found that there were 2,904 closure and advisory days in the state last year, and 18,682 nationwide. Of note was the fact that Northern California beaches saw a dramatic increase in closure and advisory days, whereas Southern California had a dramatic drop — due largely to the lack of testing and unusually dry weather.

L.A. County had the highest percentage of days exceeding state bacteria-level standards, at 16%, followed by Orange and Santa Barbara counties with 8%, San Diego with 6% and San Luis Obispo and Ventura counties at 5%.

The beach with the highest percentage of days exceeding bacteria standards was Avalon Beach north of GP Pier at 82%, followed by Orange County’s Poche County Beach with 63%.