The Filthiest Beaches in the US New report card ranks cleanest, dirtiest in the nation By Ruth Brown, Newser Staff Posted Jun 30, 2013 4:50 PM CDT 85 comments Comments The Avalon Harbor and beach on Catalina Island. (AP Photo/Sheri Malone) (Newser) – There's something dangerous lurking in the water at many US beaches, and it isn't a shark. It's bacteria, and it's fouling up many of America's shorelines thanks to runoff from treatment plants and old sewer lines, which can put swimmers at risk of hepatitis, dysentery, and stomach flu, NPR reports. "It's urban slobber flowing untreated into our waterways," says a spokesperson from the Natural Resources Defense Council, which says the EPA needs to reform its national stormwater requirements. The NRDC just released its annual report card on the best and worst beaches in the US. Amongst the findings: Top of the worst offenders list is Avalon Beach in Los Angeles, which is joined by California's Orange Doheny State Beach, Indiana's Lake Jeorse Park Beach, New Jersey's Ocean Beachwood Beach, and many others as the least reliable places for a clean swim; on a state-by-state basis, Ohio was the dirtiest, with more than 500 samples failing national standards. If you want a healthy place to take a dip, try Alabama's Gulf Shores Public Beach, California's San Clemente State Beach, or Delaware's Dewey Beach, which were among those scoring top marks.