With the implementation of Initiative 502, which legalized recreational retail marijuana in Washington, there was a unique opportunity to estimate marijuana consumption before and after legal dispensaries opened. Marijuana consumption is typically based on survey data, however recently sewage-based drug epidemiology has emerged as a complimentary technique to estimate drug use. This study focused largely on method development to quantify the main metabolite of marijuana, 11-nor-delta-9-carboxy-tetrahydrocannabinol (THC-COOH) in raw wastewater influent to a Wastewater Treatment Plant (WWTP). A method was developed that employs Solid Phase Extraction (SPE) and LC-MS/MS for analyte extraction and quantification. Raw influent 24-hour composite samples were obtained from a city Central WWTP (Treatment Plant #1) before and after legal retail stores opened. The optimized method quantifies both THC-COOH and an anthropogenic population biomarker (PB). The PB chosen for this study is the metabolite of serotonin, 5-hydroxyinoleacidic acid (5-HIAA). The PB allows for better consumption estimates by allowing for the normalization of the contributing population. This paper will specifically focus on method development for THC-COOH, and the optimized method, as well as preliminary concentration results of THC-COOH, will be presented.

Method development towards quantifying marijuana consumption using sewage based drug epidemiology: Preliminary results for Treatment Plant #1

249th National Meeting (2015)

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