Scientists analyzing the chemical composition of raw sewage in cities in the U.S. and Europe have made some surprising discoveries about drug-use patterns, the Los Angeles Times reported June 23.

Likened to a citywide drug test, the studies estimate drug use based on the chemicals excreted in feces and urine by community residents. Researchers have found, for example, that Los Angeles has more cocaine in its sewage than many European cities, and that London's heroin usage may be higher than in cities in Italy and Switzerland. More methamphetamine apparently is used in Las Vegas than in Omaha, Neb., or Oklahoma City, Okla., the studies suggest.

"Every sample has one illicit drug or another, regardless of location," said researcher Jennifer Field of Oregon State University. "You may see differences from place to place, but there's always something."

"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," said Christian Daughton, chief of environmental chemistry at the Environmental Protection Agency's National Exposure Research Laboratory.

The sewage testing is seen as an adjunct to other types of drug-use assessments, such as surveys. Sewage research has shown that cocaine use seems to peak on Saturdays, for example, while heroin and marijuana use appears to be steady throughout the week.

However, there are complications to measuring drug use with sewage: concentration of chemicals can vary based on sewage flow, time of day, and how long it takes waste to flow through the pipes. "This has caught on only recently, and people are still trying to understand the uncertainties," said Field.

Some communities also are resistant to the studies, wary that the results could put them in a bad light. San Diego, for examples, has barred researchers from studying the drug contents of its sewage.

Researchers also have begun checking the environment for traces of illicit drugs.