Marijuana use study targets sewage

The US government is chipping in money for a three-year pilot study using sewage samples to determine levels of marijuana use in two Washington cities — research that could help answer some key questions about pot legalisation, the University of Puget Sound announced.

The National Institutes of Health has agreed to pay $120,000 (107,000) so Dan Burgard, an associate chemistry professor, can conduct a three-year study that will look at how per-capita pot use changed after Washington’s first legal pot shops opened last July.

The research, based on methods first developed by scientists in Italy in 2005, involves analysing wastewater samples for levels of metabolites produced when the body processes drugs.

Burgard began collecting marijuana data in December 2013 — after voters passed legalisation in 2012 but eight months before legal pot shops began opening.

The upcoming study is aimed at helping determine whether the opening of pot shops increase a community’s marijuana use, whether data from the wastewater correlate to what people answer in surveys about their marijuana use, and whether weekday or weekend use has increased.

The data could also show how much of the illicit black market for marijuana the state’s legal stores are capturing, by comparing the wastewater data with the state’s close tracking of marijuana sales.