If authorities really wanted to determine how common illicit drug use is in a community, what’s the best way they could do it? A recent study suggests that the answer is present in our wastewater.

The study, published in the journal Addiction, indicated that analyzing samples of untreated wastewater for traces of narcotic substances is a viable system for measuring the consumption of illegal drugs in an area. 

Based on Granny’s old saying that “what goes in must come out,” this first-of-its-kind research included researchers at Oregon State University, the University of Washington, and McGill University. The team gathered data from 96 volunteer municipal water treatment facilities across Oregon, concentrating on finding evidence of cocaine, ecstasy and methamphetamine. Researchers compared numerous samples on the same day from an area that included about two-thirds of Oregon’s population.

The distribution of drug use won’t be a surprise to anyone who watches crime shows: Urban areas saw higher traces of cocaine and ecstasy, with ecstasy only turning up in about half of all communities. Both cocaine and ecstasy were almost non-existent in rural regions. Meth was everywhere.

Because these one-day findings proved this methodology to be cheap and viable, authorities could soon be able to track patterns of drug use in multiple regions over time. This would be a smart use of resources to better understand a sizable problem for state, local and even federal governments—illegal drug use often leads to higher police and healthcare costs, not to mention crime.

The real question, can we handle the truth?