The report examines water quality monitoring in 2013 for beaches in 30 states on the Atlantic and Pacific oceans, the Gulf of Mexico and the Great Lakes. Ten percent of all monitoring samples exceeded the Environmental Protection Agency's standard for safe swimming, known as the beach action value.
In the three states at the top of the list, only 3 percent of monitoring samples exceeded that value. In Ohio, the figure was 35 percent, in Alaska 24 percent, and Mississippi 21 percent.
Regionally, the tri-state Delmarva area was the cleanest, with only 4 percent of monitoring samples exceeding the EPA standard. That was followed by New York and New Jersey and the Southeast at 7 percent each, the west coast, 9 percent, New England, 11 percent, the Gulf Coast, 12 percent, and the Great Lakes at 13 percent.
The NRDC urged the public to call for stronger policies against storm water runoff and protections for streams and wetlands to prevent pollution that will eventually reach beaches.
"In addition, improving beach water quality depends on policies to incentivize and implement green infrastructure in our cities -- such as green roofs, porous pavement, and street plantings -- which stop rain where it falls," the report said. "Green infrastructure effectively reduces the amount of runoff that makes its way into beach water or triggers harmful sewage overflows, transforming a source of beach pollution into a tremendous local water resource."