In a sophisticated laboratory in Denver, researchers are creating water quality tests so sensitive, they can catch caffeine on the breath of the person who dipped the sampling bottle into a river.
U.S. Geological Survey chemist Mark Burkhardt has had to ask his field workers not to breathe directly onto samples.
"That's how low we can go," he said. "We're counting molecules."
That precision has made the $450,000 "National Reconnaissance of Emerging Contaminants" project, now nearing completion, possible.
With the new instruments in the agency's National Water Quality Laboratory, scientists have discovered tiny amounts of chemicals that no one knew were present in the country's natural waterways.
There's caffeine, for example, excreted by millions of Americans or poured down sinks; antibiotics that slip through waste water treatment plants; and human hormones, both synthetic and natural.
Concerned that traces of pharmaceuticals and other chemicals may be affecting waterways and aquatic creatures, the survey's researchers are taking the first step: Finding them.
"It's like glasses: I can't see if he's a good guy or a bad guy without my glasses," chemist Ed Furlong said, pointing to Burkhardt. "Until recently, we didn't have the glasses to find these things."
But for a handful of the chemicals, science already suggests reasons for concern: At very low concentrations, chemicals common in household cleaners can wreak havoc on the reproductive biology of fish, said researcher Larry Barber.
For the emerging contaminants project, scientists pulled water samples from 142 streams and 55 wells around the country and sent them to Denver.
New machines here, liquid and gas chromatography mass spectrometers that once took up whole rooms and now take up half a lab bench, crunch through dozens of samples a day.
Researchers are probing for 95 different chemicals, said Herb Buxton, coordinator of the Toxic Substances Hydrology Program.
"Some are pharmaceuticals, they're hormones, they're things that have a potential mode of action to affect living organisms," he said.
Furlong declined to talk in detail about results until March, but said that many of the compounds are showing up at low concentrations.
He's quick to explain that such results shouldn't make people reluctant to drink coffee or use antibiotics.
"There's thousands of new compounds introduced every year, and I wouldn't be alive today without them," Furlong said. "But we haven't closed the loop."
It's time to do that, said Barber. Scientists have spent a lot of time and money looking for a small handful of "historical contaminants" in streams, chemicals such as cancer-causing PCBs and dioxins.
"We may not find dioxin in a sample," he said, "but there may be hundreds of other compounds that may, or may not, have implications for streams."
In particular, he has worried about endocrine disrupters, chemicals that can affect animals' growth and reproductive systems.
Various forms of estrogen, including those in birth control pills and hormone replacement therapy, may act as endocrine disrupters. So can nonylphenols, found in car wash soap and commercial kitchen sprays.
Research shows that even at extremely low levels, endocrine disrupters can affect wildlife.
"(They) can turn boy fish into girl fish," Barber said. Male fish exposed to levels of such chemicals may start developing female features; females may start forming sperm.
And then there's caffeine. The chemical isn't necessarily harmful to fish or people, but the fact that it comes almost exclusively from the bladders of coffee-drinking people and their kitchen sinks could make it useful for research.
"When you measure caffeine, you can say that water has been impacted by municipal waste discharges," Barber said.
So if ocean water at a popular beach is laced with caffeine, it may be laced, too, with disease-causing bacteria sometimes found in sewage.
The researchers are also looking for triclosan, an antibiotic used widely in antibacterial soaps, gels, creams and even socks.
In natural waterways, bacteria can form an important part of the ecosystem, Buxton said. Antibiotics might kill some, and might allow others, including disease-causing strains, to develop resistance.
"It's not clear yet if they can develop resistance in exposure to low levels of antibiotics in environment," Buxton said. "Our lack of understanding is based in part on the fact that we don't have good understanding of the concentration and distribution."
Chris Rudkin, water quality coordinator for the city of Boulder, Colo., said that although Boulder Creek is not one of the survey's target rivers, a local study, called the Millennium Baseline, should be able to identify whether a handful of pharmaceuticals or hormone-mimics are present at significant levels.
He, too, expects results in the next month or so.
If chemicals turn up at surprising levels, the city's wastewater treatment managers will have some thinking to do, Rudkin said: It's one thing to ask an industry to clean up its polluted water before sending it down the sewer; it's quite another if the pollutants are in minute quantities and come from thousands or tens of thousands of households.
Barber said that's one of the challenges of emerging contaminants: Keeping some of them out of waterways would require a Herculean effort to not only change industry, but people's expectations.
Endocrine disrupters, for example, are ubiquitous, Barber said. They're used in car washes, breweries and everyday cleaning products.
"People love them," he said. "You can take a bottle, squirt it and wipe. Your counters don't foam and the grease is gone. You could do the same thing with hot water and scrubbing ... but consumers want performance."