The Pomperaug's peril is not unique. "Across the nation rivers are stressed," says Katherine Baer, advocacy director for American Rivers, which is based in Washington, D.C. "As drought becomes more common, there is less water in streams for aquatic life. Everywhere we see more development, sprawl, and increased population. So we get higher pollution loads. Pharmaceuticals, which become more concentrated with low water, are only increasing the burden."
At the present time, in a project unrelated to its study of contaminants, the USGS is making hydrologic models of how water enters, moves through, and leaves the Pomperaug watershed. The Pomperaug River Watershed Coalition is studying water quality, the dilution of treated wastewater, and, with the help of Allison MacKay, the environmental fate of compounds left behind after drugs have been metabolized by our bodies, as well as that portion of the drugs that passes through us without being absorbed.
According to the Environmental Protection Agency, which is putting together a database of literature on so-called emerging contaminants, those metabolites are virtually everywhere, from the iconically dirty Chicago River to the iconically pristine headwaters of Boulder Creek in Colorado. They're in the intakes and outflows of water facilities in both urban and rural areas, in groundwater, mountain streams, surface water, and domestic wells. And while levels of pharmaceuticals are sometimes infinitesimally low, their supplies are continually replenished. As a result, organisms that constantly bathe in a chemical broth are beginning to reveal some alarming abnormalities.
In Boulder Creek, David Norris, an environmental endocrinologist at the University of Colorado at Boulder, found that female white suckers, bottom-feeding fish that grow up to a foot long, outnumber males by more than five to one, and that 50 percent of males have female sex tissue. Similar intersex changes have been found in flat-head chubs and smallmouth bass. The cause, Norris suspects, is exposure to estrogen. Like most pharmaceuticals, hormones aren't designed to break down easily. They're supposed to have an effect at low dosages with chronic use, and they only partly dissolve in water.
"I'm worried for fish populations, and I'm worried for human populations," says Norris. "The levels found in Boulder Creek are low in absolute terms, but they aren't low on the biological level. You could have six chemicals below the no-effect level, but all together they are above the no-effect level." In lab tests, frogs and rats have developed infections and deformities after being exposed to multiple pollutants at extremely low levels. Since exposure to only one compound is rare in the modern world, sorting out "mixture effects" is a daunting but critical research area. The estrogenic compounds in drinking water, Norris says, are "adding to the general exposure of the human population to environmental estrogens in our foods, and in containers that hold our foods. They all work through the same mechanisms." In the United Kingdom, hormones in the environment have been linked with lowered sperm counts and gynecomastia -- the development of breasts in men.
A Baylor University researcher found tiny amounts of Prozac in liver and brain tissue of channel catfish and black crappie captured in a creek near Dallas that receives almost all of its flow from a wastewater treatment plant. The creek also connects to a drinking water supply. A University of Georgia scientist found that tadpoles exposed to Prozac morphed into undersize frogs, which are vulnerable to predation and environmental stress. The EPA reports that antidepressants can have a profound effect on spawning and other behaviors in shellfish and that calcium-channel blockers (used to relieve chest pain and hypertension) can dramatically inhibit sperm activity in some aquatic organisms. Even at extremely low levels, ibuprofen, steroids, and antifibrotics -- a class of drugs that helps reduce the development of scar tissue -- block fin regeneration in fish. According to a report by the Scientific Committee on Problems of the Environment, a worldwide network of scientists and scientific institutions, and the International Union of Pure and Applied Chemistry, more than 200 species -- aquatic and terrestrial -- are known or suspected to have experienced adverse reactions to such endocrine disruptors as estrogen and its synthetic mimics. (See "Hundreds of Man-Made Chemicals Are Interfering With Our Hormones and Threatening Our Children's Future" by Gay Daly, OnEarth, Winter 2006.)
Experts say pharmaceuticals have probably been in the environment for as long as we've been using them. We're discovering them now because analytical methods sensitive at the parts-per-trillion level and lower were only recently developed. Surely the technology is a boon to society, but it opens a Pandora's box of questions. We know that low concentrations of some pharmaceuticals are affecting aquatic organisms, but what are they doing to humans? What happens when organisms are exposed to multiple chemicals at the same time? What happens when they bioconcentrate in living creatures or accumulate in sediment?
Traditionally, toxicologists have assessed environmental and health risks one chemical at a time, focusing on such end points as birth defects or cancer. More recently, scientists have begun to examine effects from combinations of chemicals, an approach that more closely mimics the way organisms are exposed to chemicals in the environment. Looking at end points that include immune and reproductive system dysfunctions and neurological, cognitive, and behavioral effects, researchers are finding that mixtures of chemicals can lead to effects at much lower levels than do single chemicals, and that low-level exposure can often induce results not seen at higher levels. Nearly every week, results of new studies on emerging contaminants appear in toxicology and environmental health journals.
"It may seem impossible to figure out what's happening," says Christian Daughton, chief of the environmental chemistry branch of the EPA's National Exposure Research Laboratory in Las Vegas, "but technology has a way of leapfrogging. Less than a decade ago no one thought you could map the human genome. Analytical chemistry progresses at a fast rate. Remember, we're only talking about this now because we developed the technology to find these compounds."
