After five years studying the application of sewage sludge as a fertilizing agent, the Environmental Protection Agency has found virtually no adverse health effects and has declined to impose regulations on the practice.
EPA had conducted the study in response to claims of adverse health effects and demands for regulatory action issued by environmental activist groups. The activist groups contended that using the sludge—which contains dioxins as a byproduct of water treatment plants—was resulting in such unintended health effects as increased cancer rates.
EPA conducted its study by modeling a “most at-risk” scenario: Farm families spending a lifetime applying sewage sludge to fertilize their crops and animal feed, and then consuming a disproportionate amount of their own crops and farm animals over their lifetimes. The agency concluded such families would develop only 0.003 new cases of cancer each year as a result of the practice.
“The risk of new cancer cases from this source is small, substantially smaller than other chemicals we regulate,” said Geoffrey Grubbs, EPA’s director of water science and technology programs. “We just do not see a basis or justification for further regulation of this particular set of contaminants in sludge.”
Grubbs emphasized that EPA’s five-year study was peer-reviewed and examined all aspects of sludge fertilizer, including the practice’s effect on wildlife. Under all scenarios, EPA did not find “any significant impacts,” said Grubbs.
Activist groups nevertheless expressed anger at EPA’s announcement.
“This is not about a farm product,” said Nancy Stoner, director of the Natural Resources Defense Council’s clean water project. “This is about sewage sludge that comes out of large urban environments.”
The fact that the sludge is imported into farm environments from urban settings does not make the practice any less safe, according to the EPA research. “We’re closing the books on dioxins in sewage sludge,” said Grubbs. “There is not a high enough risk for this route of exposure.”
EPA emphasized very few persons will ever be subjected to even the minuscule 0.003 increased cancer rate voluntarily assumed by the most at-risk farm families. “The risk to people in the general population of new cancer cases resulting from sewage sludge containing dioxin is even smaller due to lower exposures to dioxin in land-applied sewage sludge than the highly exposed farm family which EPA modeled,” said an agency statement.
The study additionally noted that dioxin levels in the environment generally have declined steadily since EPA’s last formal survey in 1988. The downward trend is the result of regulatory controls on dioxin sources from combustion and manufacturing processes. According to EPA, dioxin releases have fallen by 90 percent since the 1988 survey.
James M. Taylor is managing editor of Environment & Climate News. His email address is [email protected].