In the latest attempt to crack down on illegal drug use, scientists say they can determine the extent and pattern of illicit drug use—from marijuana to heroin to cocaine—by sampling sewage and extracting the telltale by-products.

For example, cocaine is snorted, does its brain-altering business and then passes through the liver and the kidneys on its way out of the body. It emerges in urine as benzoylecgonine and, as that urine travels from toilet to treatment plant, it mixes with a host of other by-products of human activity.

Environmental analytical chemist Jennifer Field of Oregon State University and her colleagues, using an automated system they developed, test small samples automatically collected at wastewater treatment plants over a 24-hour period. Solids are centrifuged out and the sewage sample then travels at high pressure through a machine that chemically separates the various compounds of interest chemically, such as benzoylecgonine. By measuring the relative mass of the various residual chemicals, the chemists can then identify what specific drugs have been recently used in that community.

"Here's a new tool for taking snapshots of communities over space and in time and getting a less biased view of drug use," Field says. Current methods, she notes, rely on either self-reporting in surveys or actual overdoses. "Certainly compared to the statistics approach, which is waiting for people to die," she adds, "this is more real-time."

The technique has been tried in at least 10 U.S. cities, ranging from towns with populations hovering around 17,000 people to medium-size cities of 600,000, according to Fields, though she declined to specify the municipalities by name. One trend: use of methadone and methamphetamine (a prescription opiate withdrawal aid and speed) remained constant over 24 days in these cities, but cocaine consumption routinely spiked on the weekends. "You can see this upswing in the recreational use of cocaine as evidenced by increases in some cases starting as early as Thursday," of each week studied, Field says.

The researchers presented the new drug testing technique at the biannual American Chemical Society conference in Boston today and hope to form partnerships in the future with interested communities. The work is part of a growing trend to monitor drug use via sewage pioneered in the Po River valley by toxicologist Roberto Fanelli of the Mario Negri Institute for Pharmacological Research in Milan. The U.S. government has undertaken such drug-testing experiments since 2006 in more than 30 municipalities, ranging from San Diego to Fairfax County, Va. (just outside of Washington, D.C.).

The technique might help communities determine where to apply law enforcement or track the success of targeted drug-use prevention efforts, the researchers say—for example, helping to get a handle on methamphetamine-related deaths in Oregon, which have tripled over the past decade. But the strategy also raises privacy concerns, Field says. She notes it would be extremely difficult to track individual drug use with this method, both because it is hard to reliably estimate from a community-wide measure how many individuals are actually using the drug and sampling would have to take place almost all the way back in the individual toilet to trace it to a particular household. "It's not getting back to the individual," she emphasizes.

The next step, Fields says, will be to trace the unique by-products of extremely common drugs, such as caffeine and nicotine, to enable even more precise readings of local use. "We will be exploring are there ways to use human urinary biomarkers to try and assess the population?" she says. "Can you follow worker populations? Students moving in and out? And then answer questions about trends in drug use."