MOUNT PLEASANT — People swimming and paddling in waters like Shem Creek are likely being joined by loads of fecal waste.

And, until recently, the state was OK with that. Certain saltwater bodies could contain about five times more fecal waste than similar ones, creating a health hazard for those who used the areas for recreation.

A change, which went into effect earlier this year, would require the same bacteria standards for two classes of recreational saltwater bodies.

DHEC changed the regulation after more than a yearlong push from environmental groups, including Charleston Waterkeeper and South Carolina Environmental Law Project.

Andrew Wunderley, Charleston Waterkeeper’s executive director, said the group began testing bacteria in swimming and paddling hot spots in 2013 and compared the findings with state standards. They quickly discovered there were two different standards to regulate the quality of recreational saltwater bodies in the state.

One standard allowed for 80 percent more bacteria than the other. But both were supposed to be protective of public health, Wunderley said.

Waters that exceed the maximum bacterial standard are considered unsafe for recreational use. Enterococci, the targeted bacteria, lives in the intestinal tracts of humans and animals and can indicate that bodies of water are contaminated by fecal waste. The U.S. Environmental Protection Agency said the bacteria can sicken swimmers and people who eat raw fish from the waters.

Much of the contamination comes from stormwater runoff containing pollutants such as gasoline and pet waste.

The state of South Carolina classifies tidal saltwater bodies in multiple ways. Class SA includes areas like the Ashley River. Shem Creek, Wappoo Creek and the entire Charleston Harbor are in Class SB.

Class SB was allowed to have more bacteria than the Class SA waters.

Leslie Lenhardt, staff attorney for the South Carolina Environmental Law Project, said the different standards masked the pollution problems. For example, Shem Creek’s high bacteria levels didn’t violate the low standards that were in place.

“So (Shem Creek) is basically more polluted, but it wasn’t triggering a violation,” Lenhardt said.

Public health officials and scientists measure bacteria levels by the estimated number of cell colonies in 100 milliliters of water. That’s about a half a cup. With the new DHEC regulation, both classes of recreational saltwater bodies cannot exceed a daily maximum of 104 colony-forming units of bacteria per 100 milliliters. In the past, Class SB waters could allow a daily maximum of 501 colony-forming units.

“It’s a little tweak that has a big impact for water quality,” Wunderley said.

He said he believes this change will highlight polluted areas that are unsafe for swimming. If a waterway is not meeting its water-quality standard — which is the case for Shem Creek and James Island Creek — the state is obligated to set cleanup targets, Wunderley said.

“And then the local cities and towns that are in the creek’s watershed have to work together to limit the amount of bacteria being discharged to help the creek meet its water- quality standard in the future,” Wunderley said.

The James Island Creek Task Force is working on a watershed management plan that will allow it to seek funding for water-quality projects to improve the creek’s health.

The state does not close waterways to prevent people from using them, so it is the public’s responsibility to make sure they have the most updated information for local water quality. Charleston Waterkeeper shares results from its water-quality tests at charlestonwaterkeeper.org.

Wunderley said the new regulation is a big win for clean water and anyone who likes to swim, paddle or jump in the water.

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