When news gath­er­ing goes down the crap­per

Sackville Tribune - - OPINION - Rus­sell Wanger­sky Rus­sell Wanger­sky’s col­umn ap­pears in 36 Saltwire news­pa­pers and web­sites in At­lantic Canada. He can be reached at rus­sell. wanger­[email protected]­gram.com — Twit­ter: @wanger­sky.

As stud­ies go, it’s a head­line beauty.

Or a night­mare. Or a de­vi­ous way to find some­thing close to the truth.

Or just plain click­bait.

Stay with me now.

The prob­lem was sim­ple: Statis­tics Canada wanted to find out if peo­ple were telling the truth about their cannabis use, but the agency was afraid the facts of the mat­ter were, well, hid­den un­der­ground.

So, know­ing a few vari­ables about the size of var­i­ous mu­nic­i­pal pop­u­la­tions, the rate at which cannabis me­tab­o­lites are ex­creted by peo­ple who used mar­i­juana, and sewage tech­nol­ogy, Stats Can fol­lowed the lead of Euro­pean science and went sam­ple-gath­er­ing at 15 sewage treat­ment plants.

The idea was sim­ple: sam­ple the sewage, and back­wards-cal­cu­late how much weed was be­ing con­sumed. (The sam­ples were taken be­tween March and Au­gust of this year, but also will con­tinue postle­gal­iza­tion on into March 2019.)

The re­sult gave Hal­i­fax the “high” five: that city tested high­est for cannabis me­tab­o­lites in sewage ahead of Ed­mon­ton, Mon­treal, Toronto and Van­cou­ver.

And that’s pretty much the way the study was cast in the me­dia — com­plete with some out­lets get­ting com­ments like, “should match up that study with unem­ploy­ment stats — lazy ston­ers.”

But if you go back to the study it­self, you’ll find it’s very clear on how it doesn’t prove any­thing of the kind, at least not at this point.

Among the caveats? “For ex­am­ple, the wastew­a­ter treat­ment plant in Hal­i­fax was si­t­u­ated in the core area of the city and as a re­sult, the con­sump­tion of cannabis mea­sured there may not rep­re­sent the city’s en­tire metropoli­tan pop­u­la­tion.”

So, not ap­ples to ap­ples. OK — so that’s a sim­ple one.

But there are more warn­ings: “Re­sults for al­most every site var­ied sub­stan­tially from month to month. 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.”

And there’s more: “In ad­di­tion, dif­fer­ences in tem­per­a­ture, acid­ity and the pres­ence of in­dus­trial chem­i­cals or bac­te­ria in the sewer sys­tem of each city could have an im­pact on the amount of cannabis de­tected in wastew­a­ter and af­fect the com­pa­ra­bil­ity of data from dif­fer­ent cities.”

And more: “Fur­ther­more, the month- to- month vari­a­tion in loads is large. For ex­am­ple, be­cause of the amount of monthly vari­a­tion in Hal­i­fax, it can only be ex­pected that the true an­nual us­age is con­tained within the bounds of 603 mcg/per­son­week and 2,018 mcg/per­son-week two-thirds of the time. Given this large range of uncer­tainty, it is all the more dif­fi­cult to make com­par­isons be­tween cities with very much con­fi­dence.”

Fi­nally: “Statis­tics Canada will con­tinue to col­lect more data from each par­tic­i­pat­ing wastew­a­ter treat­ment plant to as­sess whether the rates dif­fer as a re­sult of true dif­fer­ences in con­sump­tion rates, or as a re­sult of method­ol­ogy.”

Think about that sen­tence. Hal­i­fax’s weed win might be noth­ing more than a sam­pling gl­itch.

It’s a bit like sam­pling gro­cery store dump­sters in St. John’s, count­ing the spoiled heads of let­tuce, and ar­gu­ing (with­out con- sider­ing spoilage dur­ing long ship­ping, the amount of let­tuce com­ing into the stores, and a host of other vari­ables) that St. John’s res­i­dents eat fewer greens than peo­ple in other prov­inces.

The sewer/cannabis study is a piece of the puz­zle, a tool in the tool­box for try­ing to put a real num­ber on cannabis use.

It makes for a quick head­line, but it’s far from com­plete science, and even Statis­tics Canada ad­mits that.

It shows two things.

One is that con­sum­ing news is not as sim­ple as read­ing one story. The other thing?

A day will come when we will have no se­crets. They’re sam­pling your sewage.

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