Colorado is famous for clear-running streams, but a recent study from the U.S. Geological Survey shows that even the state’s most calendar-worthy creeks aren’t as pure as they appear.

In January, researchers at the agency’s Colorado office announced the results of a study that tested the state’s streams and groundwater for dozens of chemical compounds, including caffeine, steroids and pesticides. Researchers took samples from 15 urban streams and one forested stream, along with nearly 90 domestic and municipal wells.

Urban streams carried the greatest number and concentration of substances: Fifty-seven chemicals were detected, with concentrations of non-prescription drugs, flame retardants and detergent breakdown products exceeding 10 parts per billion. But researchers were surprised to find that samples from the forested stream also contained low levels of 11 chemicals, including disinfectants, artificial fragrances, and insect repellents.

"Most of these chemicals originate with people, so we weren’t expecting so many in forested areas," says Lori Sprague, the study’s lead author. She speculates that campers, recreational boaters or nearby septic systems are responsible for the traces of pollution.

Though few of these substances are regulated by federal agencies, especially at such low levels, even infinitesimally small amounts may have a big impact on wildlife and plants — and possibly on human health. Water-quality researchers and regulators usually focus on better-known pollutants like perchlorate and arsenic, but a growing number of scientists are turning their attention to this more subtle set of aquatic contaminants.

Streams flow with hormones and chemicals

Until the 1990s, studies of low levels of pharmaceuticals and personal care products, or PPCPs, in streams and groundwater were almost unknown: Lab equipment just wasn’t sensitive enough to pick up tiny concentrations of the substances. Researchers in Europe carried out the first large-scale PPCP studies, and the U.S. Geological Survey (USGS) followed suit in the late 1990s.

The agency’s first "nationwide reconnaissance," published in 2002, measured concentrations of 95 compounds — ranging from hormones to acetaminophen to codeine to caffeine — in 139 streams throughout the United States, most of which were downstream of cities or intensive agricultural operations. Low levels of PPCPs showed up in about 80 percent of the streams sampled.

The next step — understanding the effects of these small concentrations of PPCPs on the environment, and on human health — is a very tricky business. Environmental Protection Agency researcher Christian Daughton emphasizes that each type of compound behaves differently in nature. "Every single class has a mechanism that’s unique," he says. "There are a wide array of possibilities, and aquatic toxicologists are just starting to develop a body of work."

The Department of Energy’s Pacific Northwest National Laboratory in Washington state found that captive male trout exposed to low levels of synthetic estrogen (such as that used in birth-control pills) were half as fertile as trout kept in estrogen-free water. At Baylor University in Texas, Professor Bryan Brooks discovered that fish exposed to concentrations of the active ingredient in Prozac approximating those found in streams showed significant differences in levels of certain brain chemicals — chemicals known to affect basic functions such as eating and reproduction.

And in Colorado, University of Colorado physiologist David Norris and his colleagues have been studying sex ratios of white suckers in Boulder Creek and the South Platte River. Unlike the fish upstream of wastewater treatment plants, he says, the fish downstream are overwhelmingly female. Norris has also observed high numbers of "intersex" fish, with both ovarian and testicular tissue, below treatment plants. For most fish, says Norris, "intersexes are unusual — they’ve been described in nature, but at very, very low frequencies. So when we find two out of 10, or three out of 10, we think it’s of major concern."

Worries about the environmental effects of PPCPs are particularly acute in the Southwest, where some streams are 100 percent treated wastewater. In Tucson, USGS researcher Gail Cordy and her colleagues have been collecting baseline information on the persistence of pharmaceuticals, detergents, fire retardants and other substances in the Santa Cruz River. "The thing with effluent-dependent streams," she says, "is that you’re going to see more compound, and no dilution."

A growing awareness

Regulation of low concentrations of PPCPs in the environment isn’t likely to happen soon. But the mounting evidence of environmental impacts could eventually spur action by the Environmental Protection Agency or the federal Food and Drug Administration. For its part, the USGS plans to continue studying the presence and persistence of these substances in streams and other water sources. "We’re hoping to understand what’s in the environment, so that we can help toxicologists and other researchers focus their studies," says Colorado USGS researcher Sprague.

Current wastewater treatment processes allow most, if not all, PPCPs to slip through, and even state-of-the-art systems are not believed to be entirely effective. And improvements to treatment facilities may soon become more difficult. The Bush administration’s proposed 2006 budget cuts funding for the Clean Water State Revolving Fund — which provides states with loans for sewage-treatment plant improvements — by one-third, according to Democratic staff on the House Budget Committee.

Chris Rudkin, water quality coordinator for the City of Boulder, says new scientific findings, or federal rules, could drive the search for solutions. "There might be a new treatment process, or there might be a way to go back to the source," he says. "For instance, can we improve (pharmaceutical) use so that we don’t have to put as much material down the drain?"

Awareness of the problem is increasing in the scientific community, but it’s just starting to trickle into the wider world. "Most people figure that when they flush the toilet, the water goes into a treatment plant, and that it comes out at the other end and everything’s fine," says Tucson researcher Cordy. "This is (the) breaking edge of understanding some of these compounds in the environment."

The author is contributing editor of HCN.



CONTACT:

The USGS study can be found at http://water.usgs.gov/pubs/fs/2004/3127

Useful background on PPCPs is available at www.epa.gov/nerlesd1/chemistry/pharma/index.htm.