TACOMA, Washington -- Promoted as a great way to dispose of treated waste, the sewage sludge sold to homeowners to spray on their lawns and gardens may also be adding drugs, flame retardants and other chemicals to the landscape, according to a study.
Chad Kinney, an assistant professor of chemistry and biochemistry at Eastern Washington University, found dozens of medicinal, industrial and household compounds in treated sewage sludge, also known as biosolids, that government agencies sell as lawn-and-garden enhancements.
"No matter what biosolid we looked at, there were some of these compounds in it," said Kinney, whose research on the subject was published in online editions of the journal Environmental Science & Technology. The U.S. Geological Survey's Toxic Substance Hydrology Program supported his work, which began while he was a postdoctoral fellow at the U.S. Geological Survey.
Kinney and his team studied nine biosolid products from seven states: Washington, Arizona, Wisconsin, Kansas, Colorado, Texas and Iowa.
The scientists found that it didn't matter what wastewater treatment method was used, 25 compounds were found in each of the samples. They were looking for 87 different compounds and found 55 in one or more of the biosolids and at least 30 in each of the samples. The product with the most compounds had 45.
Although government regulators and health officials said there is no immediate risk to public health, the study's authors called for more research on the long-term impact on the environment.
"We've been using biosolids for over 30 years safety," said Peggy Leonard, biosolids program manager for King County's waste treatment division, which produces GroCo. "As far as I know, there is no risk."
Thomas Burke, a professor of public health policy at Johns Hopkins University in Baltimore, said Kinney's research and other studies should be a wake up call for the U.S. Environmental Protection Agency.
"I don't think people understood before this that they might be applying pharmaceuticals and disinfectants to their front lawns," Burke said.
The EPA has promoted the benefits of biosolids for decades because they contain the same nutrients - nitrogen and phosphorus - found in fertilizers.
Rick Stevens, national biosolids coordinator for the EPA, said in an e-mail to The News Tribune of Tacoma that the agency stands by its existing biosolids regulations. State officials also said they do not think people should worry about exposure to chemicals in biosolids.
In King County, Leonard called Kinney's research a "good start," but said it fails to answer whether the chemicals break down in soils and whether they pose danger.
Dan Thomas, Tacoma's wastewater operations manager, said the issues raised by Kinney's report are not new.
"It's something we need to keep our eye on but we're not super-concerned at this time. We know these constituents are here. There's no reason to believe there's a health threat," Thomas said.
Soil scientists at Cornell University's Waste Management Institute have been asking for more regulatory scrutiny of biosolids.
"I certainly would not use this material on my garden" said Ellen Harrison, director of the Waste Management Institute.
Burke of Johns Hopkins called the EPA regulations out of date, adding that some of the chemicals identified in the study have been shown to disrupt fish reproduction.
"These are things that have biological implications and we have to understand them better," Burke said.
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