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How much pot is Washington smoking, anyway? Sewage tests will find out

How much pot is Washington smoking, anyway? Sewage tests will find out

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It's hard to gather data on how many people are smoking marijuana, but human waste can help public health experts with estimates

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In Spokane, Washington, one of the authors of the state's successful marijuana decriminalization bill has proposed a novel way to track drug use: by monitoring sewage.

It's hard to get reliable data on how exactly how much weed the U.S. is smoking, eating or vaping — law enforcement data is skewed anyway, but now nonexistent in Washington. Monitoring use of marijuana as it's decriminalized may help policymakers track changes in use across the population.

The most surprising finding is that it works

"In some ways, I think my most surprising finding is that it works," Caleb Banta-Green, an epidemiologist at the University of Washington’s Alcohol and Drug Abuse Institute, told the Guardian. "When I first heard about it I was skeptical. I thought, ‘How is this going to be sensitive enough?’"

This isn't the be-all and end-all of studying the effects of drug use in the population, since it tests everyone. But it could help researchers understand how accurate surveys are, since self-reporting of drug use is prone to bias.

This isn't the first time mass drug-testing has been used. Similar monitoring has been performed in several European cities. One of the major benefits is that, unlike surveys, it's cheap: 100 milliliters of sewer water are all that's needed for a lab analysis.