ScienceDaily (June 25, 2008) — Scientists in Wisconsin are reporting that typical wastewater treatment processes do not degrade prions.

Prions, rogue proteins that cause incurable brain infections such as Mad Cow disease and its human equivalent, variant Creutzfeldt-Jakob Disease, are difficult to inactivate, resisting extreme heat, chemical disinfectants, and irradiation. Until now, scientists did not know whether prions entering sewers and septic tanks from slaughterhouses, meatpacking facilities, or private game dressing, could survive and pass through conventional sewage treatment plants.

Joel Pedersen and colleagues used laboratory experiments with simulated wastewater treatment to show that prions can be recovered from wastewater sludge after 20 days, remaining in the "biosolids," a byproduct of sewage treatment sometimes used to fertilize farm fields.

Although emphasizing that prions have never been reported in wastewater treatment plant water or biosolids, the researchers note that existing tests are not sufficiently sensitive to detect the extremely low levels of prions possible in those materials. Their report appears in a paper scheduled for the July 1 issue of the American Chemical Society's Environmental Science & Technology.

Journal reference:

1. Hinckley, Glen T., Johnson, Christopher J., Jacobson, Kurt H., Bartholomay, Christian, McMahon, Katherine D., McKenzie, Debbie, Aiken, Judd M., and Pedersen, Joel A. Persistence of Pathogenic Prion Protein during Simulated Wastewater Treatment Processes. Environ. Sci. Technol., Web Release Date: June 10, 2008 DOI: 10.1021/es703186e

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Wastewater treatment plants do not reduce harmful proteins called prions that cause incurable brain infections, such as Mad Cow disease, scientists report. (Credit: Courtesy of Katherine McMahon)

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