Washington pot law's author suggests testing sewage to gauge weed use
Woman using toilet (Shutterstock)

The main author of a Washington state law that legalized recreational marijuana said on Wednesday that testing sewage for the active ingredient in pot could give municipalities a broader and more reliable picture of drug use than traditional surveys.

Alison Holcomb, who is also an American Civil Liberties Union attorney, said wastewater analysis for psychoactive THC could provide policymakers crucial data at a time of sweeping shifts in marijuana policy in U.S. states and cities.

"Using wastewater data to actually get a baseline of what drug use looks like in various communities over time can help us develop more sound drug policies," Holcomb told Reuters. "It's too easy for surveys to be skewed."

Holcomb's suggestion came at the Spokane City Council's marijuana policy committee meeting on Tuesday, she said.

The panel of educators, law enforcement and lawmaking officials were seeking input on how to measure cannabis use, including by minors, and the growth of marijuana tourism, among other data, Holcomb said.

She said the analysis could be similarly applied to test other harder drugs and how isolated population segments react to policy shifts, but it should not target individuals or replace traditional surveys, which can provide more granular demographic data.

The United States has become a patchwork of local cannabis laws as voters in two states have sanctioned its recreational use and other states and cities increasingly allow medicinal use, while marijuana remains illegal under federal law.

Policymakers may find themselves walking a fine line between seeking to maximize pot tax revenue and ensuring public safety and compliance nearly three months after cannabis retail shops opened in Washington. They opened in Colorado earlier this year.

Holcomb said Oregon, Alaska and the District of Columbia could use the testing methods, including freezing feces for later analysis, as they weigh legalizing recreational marijuana in upcoming votes.

She cited research that found deviations between self-reported levels of drug use and the measured amounts in sewage, and University of Puget Sound researchers who used such analysis to confirm reported increases of amphetamine use by students during times of high academic stress.

Spokane's sewage has not been tested for THC, but wastewater director Dale Arnold said he would check with a lab on the proposal's viability, The Spokesman-Review newspaper reported.

"A large portion of that wastewater doesn't come out of human beings," he said, according to the Spokesman-Review.

(Reporting by Eric M. Johnson; Editing by Cynthia Johnston, Cynthia Osterman and Ken Wills)