Unintended Consequences of Wastewater Treatment
Some pharmaceuticals that find their way into sewage may emerge from wastewater treatment with intensified potency because of unexpected chemical interactions between the drugs and the agents intended to purify the water.
Scientists have found two common methods of purification may have the unintended consequence of strengthening prescription medication residues in water instead of removing them. In one instance, researchers performed tests on wastewater before and after treatment with microbes often used to decompose organic matter at the South Shore Water Reclamation Facility in Oak Creek, Wisconsin, which serves the greater Milwaukee area. They found carbamazephine, an anti-seizure and mood stabilizing drug sold under brand names that include Tegretol, Carbarol and Epitol, was 80 percent stronger than when it went into the sewage. The same researchers found ofloxacin, an antibiotic sold under many brand names, was 120 percent stronger. The findings are described in Scientific American and Environmental Health stories by Brian Bienkowski.
Similar findings were reported elsewhere, though the strengthen effect was not discovered in most testing. Canadian researchers found that carbamazephine more than doubled its medicinal strength after passing through treatment in a plant in Peterborough, Ontario, Bienkowski writes. Blair and colleagues found 48 pharmaceuticals in the wastewater they tested, and carbamazephine and ofloxacin were the only two that increased in strength.
It’s not surprising that sewage contains pharmaceuticals, because people who take prescription drugs excrete whatever passes through their systems, unused drugs are often flushed down toilets, and some pharmaceutical manufacturing plants emit waste products into the environment. But how do the drugs get stronger? Dr. Benjamin Blair, now a postdoctoral fellow at the University of Colorado, began the research when he was a PhD student at the University of Wisconsin. He thinks when people take medications, their bodies break them down into different metabolites, and that the microbes used in water treatment take those different parts of the drug and put them back together, recombining them in new ways that intensity potency.
Dr. Oyla Keen from the University of North Carolina and colleagues found that when the common antibiotic doxycycline was exposed in laboratory tests to the chlorine used to treat wastewater, the resulting product was even stronger than the doxycycline that had been the parent compound. A ScienceDaily story reports that chlorine treatment may even encourage the formation of new previously unknown antibiotics that could contribute to antibiotic resistance when they enter the environment. Research is underway to identify the new products.
“Treated wastewater is one of the major sources of pharmaceuticals and antibiotics in the environment,” Keen told ScienceDaily. “Wastewater treatment facilities were not designed to remove these drugs. These molecules are typically very stable and do not easily get biodegraded. Instead, most just pass through the treatment facility and into the aquatic environment,” and into streams, rivers, lakes, reservoirs and eventually drinking water. Environmental groups have asked drug companies to design medicines that are more efficiently metabolized by the body.
The World Health Organization reports that the very low concentration of pharmaceuticals that get into drinking water pose a very low human health risk. But WHO calls drugs in the water an emerging issue that needs continuing review. The effects of long term exposure and the possible combined effects of pharmaceutical mixtures are unknown. Keen says pharmaceuticals can harm aquatic creatures, slowing their reaction time in the wild and disrupting their hormone systems. The Harvard Health newsletter says estrogen and similar chemicals have had feminizing effects on male fish and have altered male-to-female ratios among fish. The newsletter also reports fish downstream of wastewater treatment plants have been found with antidepressant medications concentrated in their brain tissue.
Read an Associated Press report on pharmaceutical chemicals found in drinking water in American cities.