Beaches from Crystal River, Florida, to Ogunquit, Maine, have been under advisories warning about water quality this week because of elevated levels of bacteria associated with fecal waste. The advisories typically discourage beachgoers from going in the water because the bacteria can cause gastrointestinal illness, rashes and nausea.

There have been closures this week at some of the country’s most popular beach destinations, including Keyes Memorial Beach in the Cape Cod village of Hyannis in Barnstable, Massachusetts; Benjamin’s Beach on Long Island in Bay Shore, New York; and a portion of the Imperial Beach shoreline near San Diego. Even on the pristine, white sand beaches of Hawaii, the Hawaii State Department of Health is warning of a high bacteria count at Kahaluu Beach Park on the Big Island.

It’s a longstanding and widespread problem. Nearly two-thirds of beaches tested nationwide in 2024 experienced at least one day in which indicators of fecal contamination reached potentially unsafe levels, conservation group Environment America said in a report issued this summer.

The group reviewed beaches on the coasts and Great Lakes and found that 84% of Gulf Coast beaches exceeded the standard at least once. The number was 79% for West Coast beaches, 54% for East Coast beaches and 71% for Great Lakes beaches.

The report also said more than 450 beaches were potentially unsafe for swimming on at least 25 percent of the days tested. A key reason is outdated water and sewer systems that allows contamination from sewage to reach the places where people swim, said John Rumpler, clean water director and senior attorney with Environment America.

“These beaches are a treasure for families across New England and across the country. They are a shared resource,” said Rumpler, who is based in Boston. “We need to make the investment to make sure that literally our own human waste doesn’t wind up in the places where we are swimming.”

Other factors have also played a role in contaminating beaches, including increasingly severe weather that overwhelms sewage systems, and suburban sprawl that paves over natural areas and reduces the ecosystem’s ability to absorb stormwater, Rumpler said.

But many people plan to jump in the ocean anyway. Despite a two-day warning of elevated fecal indicator bacteria last month at Rehoboth Beach, Delaware, beachgoer Yaromyr Oryshkevych was not concerned.

“I really don’t expect to be in any kind of danger of fecal contamination,” said Oryshkevych, a retired dentist. He said he didn’t think Rehoboth was close enough to notable pollution to be concerned, and he expected the ocean’s natural currents to take care of any problems with contamination in the area.

Dana West, a federal worker visiting Rehoboth Beach, recalled an instance earlier this year where a dozen members of his vacationing party experienced gastrointestinal issues. The symptoms occurred after they went on a snorkeling excursion, an activity that increases the likelihood of swallowing seawater, off the coast of Isla Mujeres, Mexico.

It was an unpleasant experience, but he doesn’t expect a repeat this weekend in Delaware.

“But generally, I have no concerns about the level of fecal and bacterial matter,” said West while admiring Rehoboth’s shore. ”I assume the local authorities will tell us if there are higher levels than normal.”

Despite West’s confidence, some beaches in the area of Rehoboth, including nearby Rehoboth Bay and Dewey Beach bayside, were indeed under water advisories this week. Such advisories are not always posted on public signs.

Environment America assessed beach safety in its report by examining whether fecal bacteria levels exceeded standards set by the U.S. Environmental Protection Agency that trigger an alert to avoid the water. Fecal bacteria at those levels can cause illness in 32 out of every 1,000 swimmers.

In North Carolina, five beaches were under advisories in late August because of elevated levels of fecal bacteria. The beaches are open, but swimmers are advised that going in the water could be risky, said Erin Bryan-Millush, environmental program supervisor with the North Carolina Department of Environmental Quality.

Hurricane Erin caused extensive erosion and storm surge in some coastal areas, according to the Department of Environmental Quality. Heavy rain events this summer also exacerbated the contamination problem in some areas, Bryan-Millush said.

“Those storm drains carry everything,” Bryan-Millush said. “It could be really bad for someone who is immune compromised.”