Canadian Government Tests Urban Wastewater for Cannabis Metabolites
According to initial results from wastewater analysis in major Canadian cities, the government estimates that the population may be consuming between 400 and 1,600 tons of cannabis per year.
Last Thursday, Canadian authorities released the results of the first in a series of epidemiological studies aimed at measuring the level of legal cannabis consumption among the population by analyzing the concentration of cannabinoid metabolites in the wastewater of large cities. The first measurements were conducted at 15 water treatment plants located in the country’s five largest cities, from Toronto to Vancouver.
Researchers measured the average concentration of THC metabolites—the main psychoactive cannabinoid in cannabis—over the period from March to August of this year. The research team hopes to repeat the analysis in more cities in the future to assess the impact of full cannabis legalization on national consumption levels.
According to the available results, Montreal residents consume the most cannabis, with approximately 1,992 grams used per week based on cannabinoid metabolite concentrations in wastewater. Toronto ranks second with about 1,257 grams per week, while Vancouver is third with 721 grams per week.
Scientists claim that this method of analyzing consumption levels provides the government with more accurate information about public interest in cannabis than social surveys, in which some citizens may hide their use due to the lingering stigma of cannabis as a “drug.”
“The results of cannabis consumption before legalization allow us to estimate the size of the gray and black markets for cannabis in different cities, which should help law enforcement in their ongoing fight against illegal operations,” the report on the analysis states.
“Of course, these data only allow us to estimate the overall level of cannabis consumption. To distinguish between users of legal and illegally grown cannabis, we will still need to work on feedback from those interested in using the plant,” the report also notes.
Additionally, researchers point out that the analysis does not account for the type and concentration of cannabinoids in the products consumed, so it is possible that people are using smaller amounts of cannabis with higher THC concentrations.
“It’s possible that popular methods of cannabis consumption also affect the level of cannabinoid metabolites in wastewater, since different cannabis products have varying psychoactive strengths and rates of metabolism in human tissues,” the researchers suggest.
The second round of this analysis is expected to begin in the spring of next year. Water sample collection in various cities will continue through the end of 2019.