Why Not Drug Test Everyone via Sewage?

By
 Ryme Windham smokes marijuana at 4:20 pm outside at Hempfest on April 20, 2014 in Seattle, Washington. Seattle Hempfest is an annual event for the purpose of educating the public about the benefits of marijuana and advocating for its decriminalization.
Photo: Meg Roussos/Getty Images

If you’re a city in a state that’s recently legalized recreational marijuana, how do you monitor drug levels without relying on self-reported surveys? Spokane, Washington, thinks it may have found the answer: drug testing en masse by monitoring levels of the drug in the city’s sewage. Though it’s tempting to dismiss the plan as overly ambitious — not to mention gross — similar projects have already been implemented for harder drugs in several European cities. And until a pot test is perfect, “sewage can be frozen and tested later.”

Why Not Drug Test Everyone via Sewage?