Six municipalities have already signed on to have their wastewater surveyed for drug traces, but Saskatoon and Regina have yet to be contacted by the federal government or Statistics Canada.

The national data collector is attempting to measure the production, consumption and distribution of non-medicinal cannabis, which will be made legal later this year.

The sewage testing is part of a five-month pilot project.

"As soon as we develop some confidence in the estimates and reliability, we're hoping to roll it out to all the provinces and, to the extent possible, the territories. It all depends on the waste treatment plant infrastructure," said Tony Peluso, assistant director of Statistics Canada.

The survey tests for 19 different drugs, including THC, cocaine, opioids, and methamphetamines.

While this type of data collection is new for Canada, it has been in practice for almost a decade in Europe, where the SCORE network (sewage analysis CORE group – Europe) has become the worldwide authority on the measurement of a population's consumption of illicit drugs.

Bids are now open to SCORE-accredited labs to apply to do the work for the Canadian federal government.

Accurate in identifying trends

'It is an exact science in the sense you can get reliable evidence,' says Robert LaPrairie. (University of Saskatchewan) The survey will not be invasive and will not be able to pinpoint individual marijuana users.

First, samples will be collected at sewage treatment plants, the flow at the time of collection will be recorded, and samples will be refrigerated, documented and analyzed. The results will eventually be fed into a model to determine the overall consumption per person in a given area.

"When doing a test for THC, what you're really looking for is the presence or the absence of the drug," said Robert LaPrairie, an associate professor at the University of Saskatchewan and the research chair in drug discovery and development.

"This is a feasible way at getting at overall cannabis use in Canada, because it gives you this broad tool to look at overall use in an area without having to ask individual people what might be a personal question."

Similar surveys have been performed in the Netherlands, where wastewater was tested in four different cities and an airport to track drug levels on a quarterly basis.

"It is an exact science in the sense you can get reliable evidence. The techniques used are quite sensitive and impressive for what they are," said LaPrairie.