What Are Genetically Engineered Drugs Doing to Our Water Supply?
Glen Boyd's students didn't know what they might find as they dipped containers into the water and took them back for tests. What turned up? Medicine.
There was cholesterol medication. There was the hormone estrone, a form of the estrogen prescribed to help menopausal women. And there was a strong pain reliever called naproxin. Low levels of these medications have also shown up in surface waters in other parts of the world.
While no one claims this mildly revved-up water hurts humans—it is further diluted before it reaches home faucets—some scientists are concerned about negative effects on the environment. And with a flood of new drugs as findings from the Human Genome Project are released, researchers wonder: How many more medications will end up in rivers and lakes?
After all, drug companies now target about 500 known biochemical receptors in the human body. That number is soon expected to jump as much as 20-fold—to 10,000 targets, says Environmental Protection Agency scientist Christian Daughton.
“The enormous array of pharmaceuticals will continue to diversify and grow as the human genome is mapped,” says Daughton, whose research on the topic appeared in the peer-reviewed journal Environmental Health Perspectives. He says the large number of drugs being introduced “is adding exponentially to the already large array of chemical classes, each with distinct modes of biochemical action, many of which are poorly understood.”
Researchers say drugs reach rivers and streams the old-fashioned way: With each flush of the toilet, body wastes containing traces of pharmaceuticals leave for septic tanks, which too often leak. Or they flow through wastewater treatment facilities that don't scrub pharmaceuticals from water. From there, the water that once sat in toilets and bathtubs eventually rejoins rivers and lakes, especially when storms rush in, overwhelming storm and sanitary sewers.
What does this mean for the environment? Many chemicals are designed to profoundly affect humans' physiology. Therefore, Daughton says, it wouldn't be surprising if they affected fish, birds, frogs and insects, as well. Yet, unlike pesticides, these drugs—as well as shampoos, sunscreens and other personal care products rushing down the drain—aren't examined for their effect on the environment before they're placed on the market. “This is surprising,” Daughton says, “especially since certain pharmaceuticals are designed to modulate endocrine and immune systems.” Hence, they “have obvious potential as endocrine disruptors in the environment.”
Some products, meanwhile, have “very high acute aquatic toxicity,” Daughton reports. It's impossible to predict how many of the pharmaceuticals would affect nature. After all, scientists don't even understand the process by which some drugs affect humans. After Canada's federal environmental agency, Environment Canada, found high levels of estrogen and birth control compounds in the effluent of sewage treatment plants in 1998, a Trent University researcher replicated these conditions in a laboratory, reports Rachel's Environment & Health Weekly. Some fish developed characteristics of both sexes.
Lots of water sources are apparently affected. Field studies conducted at wastewater treatment plants in California, Arizona and Texas found in their recycled sewer water a substance called organic iodine—a chemical used in medicinal
X-ray examinations, says Joerg E. Drewes, associate director of Arizona State University's National Center for Sustainable Water Supply. These seem to be slow to break down in the environment; they were still found at high concentrations in groundwater six to 12 months later.
Drewes has found plenty of chemicals in treated wastewater—an antibiotic, a chemical used in perfume production, the muscle relaxant drug carisoprodol, and its metabolite meprobamate, among others. Meanwhile, in metropolitan Kansas City, more than 40 percent of stream samples analyzed by U.S. Geological Survey scientist Donald Wilkison had detectable concentrations of common over-the-counter drugs—notably ibuprofen and acetaminophen—as well as prescription medicines for high-blood pressure (diltiazem) and antibiotics (trimethiprim-sulfamethoxazole). Even more stream samples—60 percent—had detectable levels of an anti-bacterial agent found in newfangled soaps (triclosan). “Deleterious environmental impacts are likely, either as agents of endocrine disruption, or through direct harm to bacterial and aquatic health,” Wilkison reports.
While this rash of new drugs portends bad news for the environment, there could just as easily be good news, some scientists say.
The genomics revolution may make it possible for doctors to more finely target drugs to particular types of people. How many times have you tried a variety of medications to knock out a cold before finally landing on one that works? “It seems to me that we are entering a phase where we will understand more about individual's drug metabolism,” says Dr. Paul R. Billings, co-founder of GeneSage, an Internet-based health company that provides genetic information, services and products. “That might reduce overall drug use. It will also allow us to subtype humans and ask if environmental influences affect all the same or differ.”
“I think it's a pretty far stretch to draw a conclusion one way or another,” says Taylor Crouch, CEO of Variagenics, a leading Boston-area company that applies genetic-variance information to the drug development process. “You could argue that if we get patients on more appropriate medications, they'll metabolize them better, more efficiently and, therefore, we would see less drug waste. But that's not necessarily provable.” Yet, he adds, “to the extent that we can get less trial-and-error medications into patients,” he does predict “a slight decrease in the overall excreted medications.”
So, what does the future hold? It depends. If manufacturers are aware that some personal-care products “survive and potentially accumulate in the environment, they might design more biodegradable agents,” says Drewes, adding, “We have to change something, that's for sure.”