Dr. Buxton and his colleagues note that the compounds they found appeared in concentrations that rarely violated drinking-water or aquatic-life standards.
But, he adds, many of the compounds have no such guidelines. Moreover, samples exhibited chemical stews of up to 38 contaminants, and little is known about how these interact, he says.
"We shouldn't confuse the ability to measure these concentrations with whether or not they're harmful," Buxton cautions, noting that these are two separate issues.
However, he adds, the ability to measure organic waste contaminants in ever weaker concentrations allows researchers to focus on questions of risk early.
Compared with other parts of the world, the United States is a late bloomer on the issue of these emerging organic wastewater contaminants, particularly pharmaceuticals and antibiotics, according to Christian Daughton, who heads the environmental chemistry branch at the Environmental Protection Agency's National Exposures Research Laboratory in Las Vegas, Nev.
The sources for these compounds vary. Hormones and antibiotics in animal feed appear in waste and can leach into local streams and rivers. Drugs and antibiotics designed for humans move through sewage systems.
Tossed into the trash, such leftovers also are often carted off to landfills, where seeping rainwater can dissolve the capsules and carry away the compounds they contain.
EPA chemist Wayne Garrison was the first to identify drugs in sewage, in the mid-1970s. His chemo-sleuthing turned up evidence of caffeine, aspirin, and nicotine. "It was noted, then people shrugged and moved on," Dr. Daughton says.
The issue lay dormant until the 1990s, when the Europeans tested samples from their waterways and found evidence for a range of human and agricultural pharmaceuticals.
"The Europeans have a higher density of urban life around surface waters" than does the US, Daughton says in explaining why European researchers were quicker to focus environmental research on human and animal drugs in their waterways.