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Sludge Sloughs Off Perfluorinated Chemicals

For related articles and more information, please visit OCA's Environment and Climate Resource Center page, Farm Issues page, and our Toxic Sludge & Organic Compost page.

Farmers often add nutrients to their fields in the form of treated sewage sludge, also called biosolids. Environmental scientists worry that chemical contaminants-in particular perfluorochemicals-in these biosolids could leach into the soil and eventually enter groundwater. In the first rigorous field study of how perfluorochemicals could leach from biosolids, researchers have found relatively low levels of the chemicals in soils treated with urban sewage sludge (Environ. Sci. Technol., DOI: 10.1021/es103903d).

Many consumer products, such as clothing and food wrappers, use perfluorochemicals as stain- or grease-resistant coatings. These chemicals get into household wastewater and eventually reach sewage systems. The contaminants are persistent and studies have linked them to reproductive and developmental problems in animals.

In 2008, scientists from the Environmental Protection Agency studying fields in Decatur, Ala., measured some of the highest concentrations of perfluorochemicals ever recorded in U.S. soils. They also found perfluorochemicals in groundwater, grass, and cattle that grazed nearby. The Decatur findings raised the possibility that sludge applied to farm soils could contaminate groundwater, says chemist George O'Connor of the University of Florida.

But Decatur's municipal sludge contained industrial waste, so its levels of perfluorochemicals were greater than most biosolids' levels, O'Connor adds.