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Data lacking on safety of treated sludge applied to US land, report says

Biosolids contain hundreds of contaminants that haven’t been assessed for risk, EPA watchdog says

by Cheryl Hogue
December 2, 2018 | A version of this story appeared in Volume 96, Issue 48


Photo shows transfer of biosolids from a dump truck to a tractor.
Credit: US Geological Survey
EPA estimates that some 7 million metric tons of treated sewage, called biosolids, are applied to US lands each year.

Each year, farmers across the US spread tons of treated sewage sludge, called biosolids, on their fields to fertilize and boost the carbon content of soil. But the US Environmental Protection Agency (EPA) can’t assure that land application of biosolids is actually safe, the EPA’s internal watchdog says.

That’s because the agency lacks data to determine the safety of hundreds of pollutants found in biosolids, the EPA’s Office of Inspector General says in a report.

As required by a 1993 Clean Water Act regulation, the EPA consistently monitors biosolids for nine metals: arsenic, cadmium, copper, lead, mercury, molybdenum, nickel, selenium, and zinc, the report finds.

But the agency has yet to address 352 other identified contaminants found in treated sludge, including organic compounds such as polychlorinated biphenyls, dioxins, pharmaceuticals, and surfactants as well as pathogens including bacteria, viruses, and parasites, the report says. Of these contaminants, 35 are regulated as pollutants under the Clean Water Act, 32 are classified as hazardous waste, and 16 are listed as hazardous drugs.

The inspector general’s office recommends the agency collect data, conduct risk assessments, and regulate these 352 contaminants as needed. EPA has agreed to do so, the report indicates. But the agency has not agreed to another recommendation: to change a web page on biosolids to say that the EPA does not yet have the data to determine whether this material is safe.


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