This is both wonderfully practical and totally hilarious: A couple of Oregon scientists developed a technique that lets you take a teaspoon of water from a city’s sewer plant and detect which drugs the population is currently using. It’s based on a simple point: Every drug you take eventually comes out in your urine, and a community’s urine all goes in one direction — down the toilet.

They’ve only tested a few different cities, but the regional differences are intriguing:

One of the early results of the new study showed big differences in methamphetamine use city to city. One urban area with a gambling industry had meth levels more than five times higher than other cities. Yet methamphetamine levels were virtually non-existent in some smaller Midwestern locales, said Jennifer Field, the lead researcher and a professor of environmental toxicology at Oregon State.

The ingredient Americans consume and excrete the most was caffeine, Field said. [snip]

She said that one fairly affluent community scored low for illicit drugs except for cocaine. Cocaine and ecstasy tended to peak on weekends and drop on weekdays, she said, while methamphetamine and prescription drugs were steady throughout the week.

This is, of course, largely being viewed as a technique for urban-health analysis and crime prevention: By knowing which drugs are on the rise in a particular city, doctors and police can help prepare for the health implications, and try to combat them. But just imagine the more sordid uses of the information! Like the bragging rights these tests could give to urban decadents, or even travel guides. “New York City — highest per-capital use of injectable heroin in the nation!!”

(Thanks to Top 10 Sources for this one!)