Enlarge ImageBiopharming? Treated sewage sludge, here about to be spread on fields, commonly contains antibiotics and other pharmaceuticals.Credit: U.S. Geological Survey What's the downside to clean water? Dirty sludge. A nationwide survey of sewage treatment plants shows that the sludge they produce--the residue from cleaning up wastewater--contains a wide variety of toxic metals, pharmaceuticals, flame retardants, and other compounds, including some antibiotics in surprisingly high concentrations. That's significant because every year more than half of the roughly 7 million metric tons of these so-called biosolids produced in the United States are applied as fertilizer to farm fields. Whether the...
