Sewage Epidemiology Not Just a Pipe Dream

Scientists are beginning to analyze sewage to track the use of illegal drugs

Before wastewater is treated, scientists can look for traces of illegal drugs.
Before wastewater is treated, scientists can look for traces of illegal drugs. photo courtesy of flickr user DefMo

Archaeologists often talk about the importance of trash—you can learn a lot about a culture by looking at what it threw away. Chemists may say the same thing about another kind of waste: sewage. Throughout last year, researchers at the Norwegian Institute for Water Research monitored the illegal drug habits of half a million people in Oslo by chemically sifting through the sewers. The work is an example of the emerging field of “sewage epidemiology.”

The research field has developed over the past decade (Popular Science has a good article on the early days). The idea is that screening for drugs that pass through the body and then get flushed down the toilet may be one of the fastest, most accurate ways to assess a community’s drug use. After all, people can lie in surveys, and segments of the population can be overlooked. It’s harder to manipulate what goes into the sewers (although I can imagine that if sewage epidemiology really takes off, paranoid drug users may look for alternative ways to get rid of their personal waste).

In the Norwegian study, published online in the journal Environmental Science & Technology, Christopher Harman, Malcolm Reid and Kevin Thomas placed chemical samplers in a wastewater treatment plant and, over the course of a year, looked for cocaine, amphetamine, methamphetamine, Ecstasy and the chemicals that these drugs break down into during digestion. They found some interesting results. For example, concentrations of cocaine went up on the weekends, and Ecstasy spiked in the month of May. The researchers note that this peak coincided with “russefeiring,” a two-week celebration for recent high school graduates.

Based on the concentrations of each drug—and knowing certain factors like how much of a drug gets excreted by the body—the team calculated backward to figure out drug usage. For cocaine, daily consumption averaged between 0.31 and 2.8 grams per 1,000 inhabitants. The researchers say this is in line with estimates from Spain.

The Norwegian study looked only at one wastewater treatment plant that serves much of Oslo and three neighboring areas, but other studies have tracked drug usage over a much larger area. In 2008, researchers collected samples from 96 municipalities in Oregon, accounting for 65 percent of the state’s population. They found that cocaine use was much higher in urban areas whereas methamphetamine was found everywhere.

The Oregon study was only a one-day snapshot of drug habits. But if such a study were maintained over time, sewage epidemiology could be a powerful drug-tracking tool for law enforcement. As the Popular Science article points out, such analyses could allow officials to evaluate the effectiveness of anti-drug campaigns or follow drug supply lines.

The possibility of constant wastewater monitoring may make some people uncomfortable, but I find it fascinating that scientists can track a range of behaviors—from prescription drug use to preferences in cosmetics—with a test tube of sewer water. I wonder what sewage epidemiologists will be looking for next.