For years, farmers across South Carolina have used sludge from factories and sewage plants to fertilize the fields where crops grow and cattle graze.

Applied to thousands of acres since the 1990s, the sludge is billed as a cheap way to enrich the soil.

But increasingly, chemicals suspected of causing cancer, high cholesterol and other health problems are being found in the mucky waste.

Scientists, environmentalists and some farmers worry that the pollutants in sludge, called PFAS or forever chemicals, are contaminating drinking water, poisoning crops and sickening people.

“We’re talking about cancer-causing chemicals that can get into surface water and, therefore, into drinking water systems or in fish people eat,’’ said environmental lawyer Ben Cunningham, who has pushed the S.C. Department of Health and Environmental Control to tighten state oversight of sewer sludge.

Statewide, DHEC has approved at least 80,000 acres of agricultural land to be sprayed with sludge, a mushy byproduct from wastewater plants, textile factories and other industrial facilities, according to a first-of-its-kind analysis by The State Media Co. and McClatchy, the Columbia newspaper’s parent company.

That’s more than 3,500 agricultural fields that have been approved for sludge disposal, the news organizations found.