Cannabis use highest in Halifax, while Edmonton had highest use of meth, wastewater samples show

Wastewater samples collected from across the country have given the federal governmenta better indication of what drugs are being used in Canadian cities, suggesting the highestconsumption of cannabis is in Halifax while the highest useof methamphetamine wasin Edmonton.

Statistics Canada has reported its findings from a 12-month pilot project beginning in March 2018 that involved collecting municipal wastewater from sewagetreatment plants infive large urban centres. Samples from Halifax, Montreal, Toronto, Edmonton and Vancouver were tested for traces of cannabis, methamphetamine and cocaine, and the results show varied use depending on the city and the time of year.

Cannabis consumption across the country was varied. A compound called 11-nor-9-carboxy-tetrahydrocannabinol(THC-COOH) is produced by the body when cannabis is consumed. The average for THC-COOH for all sites was 450 grams per million people per week.

Halifax residents were the highest consumers of weed at 936 grams.Montreal andToronto are second and third at 833 grams and 327 grams, respectively. Vancouver, often considered a marijuanahub, didn't break the top three. Vancouver pot partakers averaged313 gramsand in Edmonton, the average was 244 grams.

According to TimWerschler, who designed and implemented the study, the research not only provides information about cannabis use in Canada, it also helpsthe federal government estimate how much cannabis is still being bought on the black market despite being legalized in October 2018.

Meth and morphine

The research shows cannabis use was lower in western cities, but according to Werschler, these cities have higher use ofmethamphetamine.

"Vancouver and Edmonton were definitely higher," Werschler told CBC's The Early Edition in a phone interview. The average levels in these two cities Edmonton, 534 grams, and Vancouver, 490 gramswere almost four times higher than in Montreal and Toronto. Halifax, which had the highest levels of cannabis consumption, had the lowest meth use.

Meth use in Halifax was over six times lower than Toronto, the next-lowest city.

Thetesting also looked for evidence of opiates, which break down quickly in wastewater and leave morphine traces behind. Werschler said Vancouver and Edmonton were considerably higher for morphine than the other three cities.

"Itis evidence that these [morphine] levelsreflect higher illicit use of some compounds," said Werschler, who suggested that could be heroin or prescriptionopiates.

In contrast to cannabis and meth, there were no significant differences between cities when it came to cocaine use. Cocaine use averaged 340 grams per million people per week across the country.

Seasonal variations

Cocaine consumption did have seasonal variations though. The wastewaterdata suggested cocaine consumption goes up in the summer, drops during the fall and then increases again in the winter.

Cannabis also showed seasonal spikes in May, June and December 2018.There were no seasonal variations in meth.

Statistics Canada explains in the report that because this is the pilot year,more data is required to determine if the seasonal variations repeat themselves every year.

The agency notes there are other limitations to the data.

Data was collected from 14 treatment plants that serve over eightmillion people, approximately20 per cent of the country's population, but not all citieswere sampled equally. For example,the entire metropolitan population of Vancouver was included in the study, whereas in Halifax only 50 per cent of the metropolitan population's sewage was sampled.

The findings could also be influenced by differing factors in city sewage systems, such as chemicals that are introduced from industrial activities. The human body also processes and excretes different drugs differently.