Charlotte’s export of sewage sludge to rural South Carolina has made it a target of neighbors who say the stuff is making them sick.

A University of North Carolina study published last week supported their claims. It found evidence that sludge used to fertilize farm fields can be unhealthy for people who live up to a mile away.

The study’s release followed a packed public hearing last month in Richburg, S.C., on renewal of the Charlotte-Mecklenburg Utility Department’s permit to spread sludge on 6,600 acres in Chester, York, Lancaster and Fairfield counties.

Many speakers in the crowd of 300 complained of nauseating odor and health problems after sludge was spread on nearby fields. Farmers, who get free fertilizer, spoke up for sludge.

Charlotte-Mecklenburg says its sludge is not to blame. The department says no formal complaints have been filed about its product in the past five years, an assertion the S.C. Department of Health and Environmental Control confirms.

Public records, however, do refer to at least one odor complaint about Charlotte’s sludge, in 2011, and some residents remain convinced Charlotte is part of the problem. But DHEC said most such complaints in the area involve sludge from Rock Hill.

Rock Hill utilities director Scott Motsinger acknowledged odor complaints from the area. The city stopped land application in early February, he said, and now incinerates its sludge in Concord.

Because no public notice is required when sludge is spread on farm pastures, it’s often hard for neighbors to know where it comes from or to whom to complain. Charlotte-Mecklenburg uses a contractor, Synagro Technologies, to haul and spread its sludge.

It’s just as hard, some residents say, to get DHEC to investigate complaints.

“It’s regulated but not policed,” said Dave Cole, a Chester County data analyst whose review of public records since 2007 found no sludge citations by DHEC.

Cole started researching sludge after a January day in 2010, soon after he and his wife Melinda, who has asthma, bought a small farm in northern Chester County.

“I went out and noticed an odor,” he said. “She went out and I turned around and she’s got her hand on her chest and her eyes were as big as saucers and she was gasping for breath. I threw her in our car and we evacuated our home to get away from it.”

DHEC, he said, later told him he couldn’t prove that sludge triggered the episode.

“There has been very little research on the human health impacts of spreading sewage sludge on farmland,” said Amy Lowman, the epidemiology researcher leading the UNC study.

The study, published Monday in the journal Environmental Health Perspectives, was based on interviews with 34 people who live within a mile of sludge fields. Twenty live in North Carolina and the others in South Carolina and Virginia.

More than half reported burning eyes, nausea, vomiting or diarrhea, symptoms similar to those reported by people who live near industrial hog farms. Family members with sensitivities because of chronic illnesses seemed to be most affected, Lowman said.

A 2007 University of Toledo survey of more than 400 people who live within a mile of Ohio sludge fields also found evidence of increased risk for respiratory, gastrointestinal and other diseases.

Safe or toxic?

The Environmental Protection Agency set standards for land application of sewage sludge in 1993, regulating nine metals that can be toxic in high doses.

Since then, science has learned more about what’s in sludge but unregulated, including pharmaceuticals, flame retardants and steroids. While regulations are aimed at keeping sludge contaminants out of water, some chemicals can also disperse into the air and be carried by wind.

The Catawba Riverkeeper Foundation, a water watchdog group, cited concerns about nutrient overload, pharmaceuticals, bacteria and metals in urging DHEC to deny Charlotte-Mecklenburg a renewed sludge permit. The foundation noted that alternatives are available, including incinerating or landfilling the material. The utility could also be required to treat sludge to a higher standard, known as Class A, it said.

Charlotte-Mecklenburg says it is proud of its product. The sludge meets EPA standards, which include testing for metals and pathogens. Its sludge program also has an international certification for environmental safety and is audited by outside reviewers.

The sludge “cake” at the Irwin Creek treatment plant in southwest Charlotte is black and crumbly in the hand of Jean Creech, the department’s residuals technical services manager.

It’s been processed for 30 days at 95 to 105 degrees as specialized microbes munch bacteria in an oxygen-free environment. Once water is squeezed out, it’s ready to be spread on farmland.

The sludge smells lightly of ammonia, a form of nitrogen. Once on the land, it breaks down into another form, nitrate, that fertilizes plants.

“There can be some kind of odor, but it’s not going to be any stronger than you smell now,” Creech said.

Serving as ‘Charlotte’s toilet’

Charlotte-Mecklenburg produces 81,000 wet tons of sludge a year. Nearly two-thirds of it has been shipped to South Carolina, chiefly Chester and York counties, over the past five years.

Creech said the availability of open land might explain the spread of sludge on 2,579 acres in South Carolina last year compared to 1,088 acres in North Carolina. More farmers want sludge than the utility can generate, she said.

Nancy Holt, a longtime anti-sludge activist in Orange County, said Charlotte-Mecklenburg’s distribution fits a familiar pattern.

“Municipalities get rid of the toxic waste in rural areas without the permission of the people they’re impacting,” she said of farm neighbors. “The counties get nothing for it but polluted water and devalued real estate.”

South Carolina requires testing to make sure farmland-bound sludge meets environmental standards. Sludge can’t be spread on wet fields, on steep slopes, within 50 feet of property boundaries or within 100 feet of water.

DHEC says it is too soon to tell whether new conditions might be added to Charlotte-Mecklenburg’s permit.

“We are looking at all concerns that have been raised, including health and odor concerns, and will be taking all factors into account while making our final decision,” DHEC spokeswoman Lindsey Evans said by email.

The packed hearing last month, Dave Cole said, shows the South Carolina communities “got tired of serving as Charlotte’s toilet.”

In rural Chester County, Alfonzo Wherry, 55, said the odor alone has ruined July Fourth cookouts. He also recounts his wife’s headaches, his niece’s stomachaches and a neighboring boy’s allergy-like attacks when sludge is sprayed.

“It seems like it kind of gets in my throat and just lingers, like a cold that won’t move,” Wherry said. “It made me nauseated enough that it made me want to get away from it. You go in the house, and it still comes in the air-conditioning vents and stuff. It’s frustrating, because you can’t even enjoy your own house.

“If I lived in a gated community,” he said, “this wouldn’t happen.”