Concern Grows Over EPA’s Handling of Sludge

Published April 1, 1998

Regulations frequently have unintended consequences, and EPA’s little-noticed Sludge 503 Rule may soon come back to haunt the agency.

In 1993, EPA with little fanfare reversed course on how it would regulate the disposal of municipal wastes, mostly human sewage. Under the agency’s Sludge 503 Rule, municipal wastes would no longer be disposed of in the ocean, but rather on land in rural areas.

The possible negative consequences of that decision were first brought to the public’s attention by EPA microbiologist David Lewis in an interview published in the December issue of Environment News. In that interview, Lewis pointed out that many EPA scientists opposed the move for a variety of reasons, including the fact that human pathogens from the sludge could make their way into the nation’s food supply. High-level EPA officials overruled those objections, and Sludge 503 Rule went into effect.

At a meeting in Philadelphia last month sponsored by the American Association for the Advancement of Science (AAAS), Lewis pointed out that processed sludge from waste treatment plants that is sold as fertilizer for home gardens may contain disease-causing fecal organisms. As reported in the February 28 issue of Science News, Lewis demonstrated that bacteria such as salmonella can get caught in clumps of gunk in sludge. If the clumps become coated with water-repellant substances like chicken fat, petroleum, or industrial lubricants, standard tests, such as the ones used by EPA, may significantly underestimate the number of bacteria hidden inside them. Clumps sticking to unwashed hands or vegetables could be accidently ingested, Lewis told the AAAS meeting, exposing humans to the bacteria through the churning action and acids in their digestive tracts.

Although EPA regulates the methods used to decontaminate and test sludge, Lewis was quoted in Science News as saying he’s “skeptical as to the whether the regulations protect us or not.”

While EPA continues to vouch for the safety of its testing procedures, Ellen Z. Harrison of the Cornell Waste Management Institute told Science News that the agency should use Lewis’ methods to test sludge certified as free of pathogens to see whether the bacteria indeed escape detection.