Just like you can test a person’s urine for drugs, scientists have tested entire cities’ worth of urine to see just how much cannabis those cities consume. These test results show that one American city is, ‘ahem’, hitting the bong and then hitting the john like no one else.
Published in the journal Addiction, this is one of the first studies of cannabis users to use hard data instead of survey-based results. It’s part of a larger international study of cannabis use in 60-80 other cities around the world, including that hallowed cannabis city, Amsterdam.
In the study, Dr. Dan Burgard and a team of researchers at the University of Puget Sound and the University of Washington analyzed the public wastewater of Puget Sound that comes from the Seattle-Tacoma area to test how much cannabis the city consumed over the years. They collected it straight from two sewage treatment plants.
“We set out to perform a wastewater-based analysis that explored the impact of newly legalized retail cannabis sales on its use, and to determine if this approach could estimate the size of the legal market place,” said Burgard, who chairs the chemistry department at Puget Sound, in a news release put out by that university.
“You can ask somebody with a survey, how much of this illicit drug do you use and you may or may not get the right answer,” Dr. Burgard told KING 5 News.
The team took samples from Seattle’s sewers between the years of 2013 and 2016, evaluating how usage has fluctuated before and after Washington State’s 2014 legalization. To do this, they used new methods sensitive enough to detect trace amounts of THC metabolites in the waste stream. Dr. Burgard explained to KING 5, “One dose would be diluted into hundreds of millions of gallons of wastewater. So trying to find those really low levels in a sample that’s pretty messy is a sophisticated technique. But in the end, it is measuring some stuff in sewage.” Burgard told Greenstate the study also took into account other factors that could influence the results, like longer showers, and all that rain Seattle is famous for.
The results showed that cannabis usage had, unsurprisingly, increased. In fact, it steadily increased at nine percent per quarter, amounting to a doubling in consumption over the breadth of the study. They also saw a particularly large spike at the end of 2016. However, when that growth is compared to the fact that legal cannabis sales shot up a whopping 70 percent per quarter from legalization in 2014 to the end of 2016, the study’s authors realized it indicated most users were merely switching from illegal sources to legal ones, like dispensaries.
“Given that wastewater represents a total population measure, these findings suggest that many established users switched very quickly from the illegal to the legal market,” says Burgard. “This is the strongest statement possible regarding displacement of the illegal market.”
And guess what? When compared to other cities around the world, Seattlites used more cannabis than any of them. Yes, Western Washington ‘flopped’ that epic global drug test even more than Amsterdam. “We are part of an international study” Burgard told KING 5, “with 60-80 other cities around the world. And according to wastewater, the Puget Sound area has the highest cannabis use per capita, even over Amsterdam.”
Brian Smith of the Washington State Liquor and Cannabis Board told KING 5, “There’s been a lack of research on marijuana use because it’s illegal federally, and that has an impact on what people can really know … things like this are a step in the right direction.”
“I hope the whole regulatory community recognizes its potential," Dr. Jonathan Caulkins, a Professor at Carnegie Mellon’s Heinz College said. "The U.S. used to lead in innovative data collection on drug use, and we’ve lost that edge, but this is promising.”