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'Metabolite' is the technical term for what is left over after your body is done turning THC into an enhanced appreciation for The Electric Prunes

The headline finding in the initial paper is that, among the five cities, Halifax’s pee yielded the heaviest point estimate of per-capita cannabis use. This will no doubt be a great help to the Trailer Park Boys-based component of the city’s tourism business. But the whole idea of estimating cannabis usage from metabolites in sewage is in its infancy here, and the bands of uncertainty surrounding the numbers are very wide.

Although there is some existing scientific literature on estimating mass cannabis consumption from sewage samples, it comes from Europe, and in matters like this you have to roll your own science, so to speak. So far Statcan has only six months of data. You can’t get a full picture of seasonal trends and environmental influences without several years of numbers. And if legalization changes the overall quantity of cannabis consumed, that will make it a little harder to correct for seasonal changes: these are measurements Statcan would ideally have been taking for many years before C-Day.

Photo by Andrew Vaughan/CP / The Canadian Press

Still, this kind of measurement has potential, even if it cannot be perfected. It might turn out to be impossible to make city-to-city comparisons of cannabis intensity of the sort that Statcan is highlighting now. Taking the samples will still allow the agency to make intertemporal, within-city comparisons. You may never know if people really smoke more pot in Halifax than in Edmonton, but if the level of cannabis metabolites doubles in one place and does not change in the other, you know something interesting is going on.