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On The Pot: Sewage Water Reveals Our Marijuana Habits

Dan Burgard
A freezer packed with sewage water at the University of Puget Sound


Sewage reveals a lot about our daily habits. With that in mind, the federal government is paying for a study to test sewage water in Washington State to determine how much marijuana people are consuming.


Dan Burgard, an associate chemistry professor at the University of Puget Sound in Tacoma, has been collecting waste water samples since December 2013, about eight months before the first legal pot stores opened.


“We have two freezers full of frozen waste water and we are excited to finally start processing them,” says Burgard.


The wastewater is being collected from two cities in Washington State but Burgard will not reveal the locations until after the study is completed.


Burgard is measuring the level of THC -- the psychoactive ingredient in marijuana -- in local wastewater. Comparing the results from the sewage to sales reported by the liquor control board, Burgard will be able to determine if legal marijuana is replacing the black and medicinal markets.


“If we see an increase in sales, but we don’t seen an increase in use according to the sewers,” explains Burgard, “then possibly the legal market is replacing some of the other ways of getting marijuana.”


Samples are being taken over the course of multiple, consecutive days. This will reveal any patterns of marijuana use, such as whether there is an increase of THC in sewage water collected on weekends. Another goal of the research is to answer the question: Does access to legal marijuana lead to people consuming more of the drug?


Sewage samples will be collected for the next few years. A $120,000 grant from the National Institutes of Health is funding the project. Burgard is collaborating with Caleb Banta-Green from the University of Washington’s Alcohol and Drug Abuse Institute.


Jennifer Wing is a former KNKX reporter and producer who worked on the show Sound Effect and Transmission podcast.