Question: The statement about injecting human waste into the soil [in the TIME article “What If the World’s Soil Runs Out?”] concerns me. How does Rodale [Institute] feel about this issue? -Lisa

Treated human waste (otherwise known as sewage sludge or biosolids) has been floated as the “solution” to everything from the topsoil loss to dwindling supplies of mined phosphorus. But it has also been indicated as a risk to human and environmental health for a multitude of reasons. Heavy metals, although declining in recent years, are still a concern. Other concerns include antibiotics, hormones, steroids and other pharmaceuticals, or things like triclosan, flame retardants, and solvents that end up poured down drains.

Photo by Brad Folkens/Flickr

Researchers at Virginia Tech, for example, recently warned that excreted antibiotics spread on farm fields are contributing to antibiotic-resistant bacteria and are a serious environmental problem.

And sewage sludge is already sprayed on conventional farm fields across the U.S. The only sector of agricultural land restricted from using biosolids is that of certified organic farms. While nutrient cycling and a closed-loop system are key principles of organic agriculture, lifting the restrictions on sewage sludge for these farms could open the gate for a whole host of new problems.

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