Biosolids Experts Downplay Effects of Drugs, Household Chemicals in Land Application

Scare tactic or scientific concern? Wastewater industry experts respond to a recent article that claims biosolids could contaminate groundwater with anti-depressants, hormone-disruptors and more.

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Concerned? Not really.

Interested? Of course

That’s the stance biosolids specialists are taking in response to a May 12 article in Scientific American magazine concerning the fate of household chemicals in land application projects.

The article, headlined “Drugs, Chemicals Seep Deep into Soil from Sewage Sludge,” suggests biosolids applied to farmlands can leave traces of prescription drugs and household chemicals deep in the soil. It was based on a study conducted in eastern Colorado by researchers at the U.S. Geological Survey.

“The findings suggest that widespread use of biosolids could contaminate groundwater near farms with a variety of chemicals, including anti-depressants Prozac and hormone-disrupting compounds (like triclosan) in antibacterial soaps,” the article states.

Scare Tactic?
Sally Brown, associate professor and biosolids specialist at the University of Washington, said articles like this are meant to scare people. “They are written for impact, to get noticed,” she said, and cited this sentence in the article as an example: “Not all the CECs are toxic but some CECs have been linked to effects such as endocrine disruption, and other deleterious effects continue to be identified.”

“The public gets terrified about information like this,” she says.

“Behavior of these compounds in soils is a very different deal than in water. One needs to realize that there’s only enough biosolids produced every year to cover 0.1 percent of the arable land in our country, and only half of that amount is land applied. In fact, there’s a greater quantity of these compounds in wastewater effluent than in biosolids.”

Chris Peot, director of resource recovery and a process engineer with DC Water — which produces about 1,200 tons per day of Class B biosolids and land applies most of it — notes that his agency has been testing for triclosan in biosolids for the past 5 to 6 years.

“Yes, triclosan ends up in soil and breaks down slowly, but we have not seen any migration offsite, nor have we found anything that would lead us to stop land applying our biosolids,” he says. “The concentrations are so incredibly low. Triclosan is a bellwether chemical, ubiquitous in our society. It’s in toothpaste, for example, and ends up going down the drain, through the sewer system, and ends up in biosolids.”

Brown also points out the presence of these compounds in our everyday lives.

“People should realize there are more compounds in everyday household dust than in biosolids — a great deal more,” she says. “Ten pounds of biosolids have less TCC — an antimicrobial compound — than one bar of soap. For these compounds to have any effect on health, one would have to eat a five-gallon pail full of biosolids to get an equivalent dose of one birth control pill. You would need to eat two tons of biosolids to get the same painkiller as the recommended daily dose of Motrin. These are compounds that are critical in our homes. Many have been around for 50 years or more.”

She notes that the USGS study detected no new compounds.

“What’s happened is that analytical methods are now able to detect to very low, low parts per billion levels of compounds that have been around typically for a long time.”

Weighing the Pros and Cons
Both Peot and Brown emphasize the benefits of land application of biosolids far outweigh the risks. Peot emphasized the return of nutrients and organic nitrogen to the soil, the avoidance of commercially manufactured fertilizers, the reduction in the cost of energy and carbon footprint.

 “How much will it cost to remove these compounds at the wastewater treatment plant?” asks Brown. “Is that cost worth it to remove compounds where no toxicity, harm or ill effects in soils have been shown? In fact what we see are benefits of biosolids. What are the energy and environmental impacts of incineration of biosolids? These are much greater, but that gets lost in the discussion.”

Peot described his public presentation on biosolids:

“I bring along a tube of Colgate Total toothpaste. Triclosan (at 0.3 percent by weight) is used to help prevent gingivitis. If you look at the studies, Triclosan was found at levels of 157 parts per billion in the soil.

“While that might sound like a lot to the average person, it’s at much higher concentrations (3,000,000 ppb) in toothpaste that you put in your mouth and that has been approved by the FDA. There’s simply not that much to be concerned about.”

He concluded: “Anything that’s scary needs to be investigated, but at the worst, the risks (of household chemicals showing up in the soil) are undefined.”


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