How much pot do Canadians use? Stats Can studied wastewater to find out

Ever wondered how much cannabis people truly consume in this country?

Statistics Canada has studied wastewater, to learn once and for all just how much marijuana Canadians use.

Preliminary data released on Nov. 29 suggests Canadians consume anywhere from 400 to 1,600 tonnes of pot per year.

The wastewater study, which took place from March to August of this year, tested for traces of THC, the main psycho-active constituent of cannabis.

It’s believed to be one of the world’s largest studies of its kind, which examined catchment areas served by 15 wastewater treatment plants in five large urban centres across the country (Metro Vancouver, Edmonton City, Toronto City, Montreal Island and Central Halifax) representing nearly 8.4 million Canadians.

See also: Canada to study social media to learn about perception of pot

While Stats Can has been collecting data to track the role of cannabis in Canada, there have been concerns that people “may under-report” their use, due to stigma.

According to Stats Can, the data could also be used to estimate the size of the illegal cannabis market in this new world of legal cannabis – by comparing retail sales with total consumption.

Not surprisingly, the preliminary data revealed bigger cities (Montreal, Toronto and Vancouver) tended to use more cannabis. Halifax and Edmonton had the least consumption overall. Results for almost every site varied substantially from month to month, noted Stats Can.

“However, at this point, it is difficult to determine whether the variations were due to real changes in behaviour or to statistical phenomena related to sampling and flow rates,” Statistics Canada reported.

According to Stats Can, the “wastewater-based epidemiology,” aka WBE, is a method that’s been used in Europe for the last decade. They also say studying waste water is cost effective and yields “relatively rapid results.”

In December of 2017, Statistics Canada released its first estimate of cannabis consumption (which was, of course, not based on the WBE). It suggested Canadians consumed 773 tonnes of cannabis in 2017, recognizing that was likely lower than the reality.

Click here to read more about the new study, and its methodology.