From Science:

Pharmaceuticals in drinking water: it’s a made-for-TV topic that can stir up public outcry faster than you can say “barely detectable residues.”

With little data on how much excreted and dumped medicines are in the environment, and even less showing a cause-effect relationship between an active ingredient and an adverse effect, researchers, health and environmental agencies, and water-quality regulators have been playing hot potato with the question for decades. But now it’s getting serious attention from the European Commission and some pharmaceutical companies. A conference convened with the University of Verona met at the Royal Society of Medicine here on Monday to discuss whether increased monitoring of medicines’ effects on the environment, or “ecopharmacovigilance,” warrants more intense scrutiny, and what, if anything, can be done to green an increasingly drug-dependent world.

“Pharmaceuticals are new pollutants,” said Yves Levi of the University of Paris-Sud. What makes them different, he said, is that the whole point of a drug is to have a very targeted effect from the lowest dose possible. Doctors and pharmacists should keep in mind the potential for unintended exposure, said Christian Daughton of the U.S. Environmental Protection Agency, comparing drug waste in water to doctors prescribing a cocktail of unknown medications to healthy people at random.

Weighing the benefit of expensive water cleanup procedures is tough to do when you don’t know much about the risk of environmental exposure. Only a few studies have shown cause-effect relationships. For instance, wide use of the animal growth promoter avoparcin, which chemically resembles vancomycin, is believed to have enabled the evolution of vancomycin-resistant enterococci, which can cause intestinal infections. And in several rivers around the world, endocrine disruptors such as ethinyl estradiol (EE2), the main component in most oral birth control pills, have been linked to the feminization of male fish. (Some research questions whether this has any effect on the fishes’ ability to reproduce, however.) No studies have shown any effects on human health or on developing fetuses, potentially the biggest causes for concern.

While some governments have been concerned, E.U. leaders have not seen pharmaceutical pollution as a priority in the past. Right now, the European Commission requires an environmental risk assessment to be performed prior to drug approval. For veterinary products, approval can be denied based on environmental hazard (although this has never happened). Human medicinal product approval cannot be denied for this reason.

But Sweden, for one, is taking the issue seriously. Over the past decade, Sweden has begun monitoring the environment for approved pharmaceuticals and instituted a national classification system that ranks drugs based on their possible toxic effects and potential to build up, or bioaccumulate, in the tissues of organisms. The government disseminates this information to doctors and pharmacies (state-owned in Sweden) to encourage environmentally sound decisions. At the conference, Åke Wennmalm of the consulting agency Sustainpharma in Stockholm presented part of a new, expanded classification system that analyzes the environmental impacts of a drug—where data are available—as it travels through manufacturing, disposal, and human waste. But Sweden does not set threshold limits for any drug.