Beaches are mostly clean in Delaware, Maryland and Virginia, but there are many that can make you sick. (Bigstock)

Headed for the beach this summer? The Natural Resources Defense Council suggests you check out the condition of the water you might be swimming in.

“The water at your local beach might be contaminated by human or animal waste, putting your health at risk: bacteria, viruses, and other pathogens in that waste can make exposed swimmers sick,” the NRDC says in the introduction to its annual Testing the Waters survey. For this year’s report, the environmental group’s scientists tested samples from 3,458 beaches along the U.S. shores of the Atlantic and Pacific oceans, the Gulf of Mexico and the Great Lakes.

The bad news is that 10 percent of the samples had levels of pathogens exceeding the Environmental Protection Agency’s safety standard, known as the Beach Action Value, or BAV. The agency places most blame on storm-water runoff, which can also trigger sewage overflows.

The good news — at least for Washington-area vacationers — is that in general, the region’s beaches do pretty well on this survey, with the coasts of Delaware coming in first, Maryland fourth and Virginia sixth on the NRDC’s list of cleanest water.

These states include six of the NRDC’s 35 “superstar beaches” — those that not only had no samples exceeding BAV limits in 2013, but none in the four preceding years (when national standards were lower). They are: in Delaware, Dewey Beach, Swedes; in Maryland, Point Lookout State Park and Assateague State Park; and in Virginia, Back Bay Beach and Virginia Beach at 28th and 45th streets.

The report also points to some of the nation’s worst beaches. Lake Erie, shallow and surrounded by industry, has long had a reputation for polluted water, so it may not be surprising that seven of the report’s 17 “repeat offenders” — beaches where more than 25 percent of samples exceed pollution standards for each of the last five years — are in Ohio.

But that list also includes a stretch of sand famous in California beach lore: the beach at Malibu, 50 yards east of the famous pier.