To Gauge Pot Use, Canada Turns to Its Sewers

Canadian officials are developing a peculiar plan to measure the country’s cannabis use. In an effort to figure out just how much pot Canadians are consuming every year, they’ll turn to the country’s human waste

Six cities have agreed to contribute samples from the place where all drains congregate — their wastewater treatment plants. Toronto, Montreal, Edmonton, Alberta; Vancouver and Surrey in British Columbia; and Halifax, Nova Scotia, will participate. All told, the network would capture data on drug use from about a quarter of Canada's total 36 million inhabitants.

The idea is not unheard of. Italy appears to have been the first to experiment with the idea when it began testing wastewater for cocaine in 2004. Several European countries, as well as Australia, now test wastewater to measure illicit drug use.

Experts say it’s fairly easy to detect trace amounts of THC even in diluted water. The problems arise after that -- namely, in figuring out the precise amount consumed and where consumption took place.

"The suburban users, are they peeing in the city but consuming in the suburbs?,” Canada’s head researcher asks.

Canada’s sewer testing expedition comes as the country prepares to legalize recreational marijuana. Prime Minister Justin Trudeau has said he hopes to have a law in place by July, but draft legislation passed by the Canadian Senate on March 22 is already headed for changes.