"To me, chemicals are chemicals. All chemicals, whether legal or illegal, have the potential to get into the environment, and living organisms have a potential to be exposed," Daughton said.
Daughton, who was interested in environmental ramifications, realized that the data could help law enforcement, sociologists and others trying to gauge trends in drug abuse.
Most of those experts rely on door-to-door annual surveys, which are based on questioning of 70,000 people nationwide. Based on that, they estimate that more than 20 million Americans used illicit drugs in 2006.
Scientists in Italy, led by Roberto Fanelli and Ettore Zuccato, were the first to implement his idea, testing sewage in London; Milan, Italy; and Lugano, Switzerland, in 2005.
Amphetamines, including Ecstasy, were the least prevalent drugs in the three cities, whereas marijuana was widely detected, the Mario Negri Institute for Pharmacological Research reported in the online version of the journal Environmental Health Perspectives on their work, published last month.
For every 1,000 people, about 210 milligrams of heroin were used daily in London, compared with 70 in Milan and 100 in Lugano. Amphetamine use also was higher in London.
The scientists were even able to use sewage to estimate individual use and weekly trends. For instance, they estimated that people in Milan used twice as much cocaine, about 35 grams per person per year, than Italy's government surveys had suggested. Cocaine use peaked on Saturdays, while heroin and marijuana use remained steady weeklong.
In the United States, officials at the Office of National Drug Control Policy looked for cocaine in sewage from Los Angeles County and 23 other regions in 2006.
Untreated sewage at all eight treatment plants tested in Los Angeles County contained cocaine metabolite, according to data obtained from the Los Angeles County Sanitation Districts. Palmdale and Lancaster had the highest concentrations, averaging 3.5 parts per billion. The lowest, averaging 1.4 ppb, were from Long Beach and Valencia.
In all the Los Angeles County locations, the cocaine metabolite was more concentrated than in Omaha and in Italian, Swiss and British cities, which all had less than 1 ppb, according to a comparison of several studies.
Other tests have shown that some U.S. cities have a bigger methamphetamine problem than Europe. Within the U.S., Las Vegas' concentrations were five times higher than Omaha's and twice Oklahoma City's, said Field, who conducted those tests.
