Although water quality at Los Angeles County beaches is generally improving, the county still has seven of the 10 most polluted beaches in the state, according to a report released today by the environmental group Heal the Bay.

Avalon Harbor Beach on Catalina Island tops the list of "Beach Bummers" named in the group's 22nd annual Beach Report Card. The Malibu area has four beaches on the list: Puerco Beach near the Marie Canyon storm drain, Surfrider, Dan Blocker County Beach and Escondido State Beach. Also making the list were Cabrillo and Topanga beaches.

Two Orange County beaches made the "Bummer" list -- Doheny State Beach at the San Juan Creek outlet and Poche Beach.

Cowell Beach in Santa Cruz County ranked second.

Despite the prevalence of Los Angeles County beaches on the "Bummers" list, Heal the Bay reported that the county was generally showing improvement in ocean-water quality.

"We are heartened by numerous individual beach success stories, but this year highlighted that there is still a long way to go in addressing stormwater pollution," said Kirsten James, Heal the Bay's director of water quality. "Locally, Heal the Bay will be focusing efforts on advocating for a strong municipal stormwater permit to address this critical beach water quality issue."

Heal the Bay's report card assigns A-to-F letter grades to beaches up and down the coast, based on water pollution levels during the dry-weather period from April to October 2011. In Los Angeles County, 82 percent of the sites tested earned A or B grades, compared to 75 percent last year, according to the report.

The report specifically hails efforts to improve water quality in Long Beach, where a number of sewer-repair and storm-drain-diversion projects have been undertaken. The result was a drastic improvement, with 93 percent of Long Beach sites earning A or B grades, compared to 27 percent in the last report.

Long Beach Mayor Bob Foster hailed the report's findings.

"I'm proud to see our efforts to clean our coastal waters are paying off," Foster said. "We created partnerships and implemented innovative technologies to tackle one of Southern California's biggest environmental challenges. We're not done yet, but our efforts have yielded some of our best scores ever. Long Beach should be proud of that."

Statewide, 92 percent of beaches earned either A or B grades. Despite improvements, Los Angeles County still has the highest number of beaches with poor water quality of any county in the state, according to the report.

Eleven beaches in Los Angeles County received F grades, up from nine last year.