Levels of Drugs in the Wastewater of Participating Canadian Cities

Additional information

Purpose

The purpose of this dashboard is to provide insight into consumption patterns of select drugs of concern in select cities in Canada using data from the Canadian Wastewater Survey (CWS).

The CWS drug component measures the levels of drug residues from controlled substances in the wastewater of several municipalities across Canada: Halifax, Moncton, Montréal, Toronto, Prince Albert, Saskatoon, Edmonton, and Metro Vancouver. Combined, the catchment areas of participating wastewater treatment plants serve a population of approximately 9.2 million people.

Data from the CWS provide information that complements and enhances other Statistics Canada programs related to economic and social statistics that include health and lifestyle conditions. This dashboard displays data from January 2024 to the most recent available.

Wastewater-based epidemiology

Measuring drug levels in wastewater can complement other sources of data on drug use (e.g. deaths, drug seizure data) by providing information on geographical and temporal trends. After a drug is used, the body breaks it down, producing drug metabolites that are excreted in feces and urine and enter the wastewater system. Some amount of the consumed drug (parent drug) can be excreted intact alongside its metabolites. The measurement of specific metabolites in the wastewater can reflect the use of their parent drugs by the population serviced by the wastewater plant. By considering the number of people served by the wastewater treatment plant, a daily excreted amount of drug per capita can be calculated (daily load per capita).

Importantly, the values presented are estimates of the excreted amount of drug metabolites in the wastewater and do not correspond directly to consumption levels of the parent drugs. Another source of the parent drug in wastewater could be unconsumed drug dumped into the sewer system.

Wastewater samples are collected for seven consecutive days starting the second Wednesday of every other month starting in January of each year. Each sample is a composite of 24 hours of influent arriving at the wastewater treatment plant. The samples are shipped to the Centre de Toxicologie du Québec laboratory and analyzed by mass spectrometry to measure drug metabolites concentrations.

The daily loads per capita are calculated by considering the total volume of influent arriving to the treatment plant on the day of sampling and the estimated population in the sewershed. The population estimates are based on the 2021 StatCan Census of Population and are projected forward using growth estimates for the census subdivisions including each treatment plant catchment.

Missing samples were excluded from the calculation of bi-monthly averages. From the population-weighted average daily results, the CWS produces bi-monthly estimates of levels (mass loads per capita) of drug metabolites in the wastewater of each municipality. Bi-monthly averages are suppressed when there are less than 5 days of data from all participating sites in a given municipality.

The number of wastewater treatment plants from which samples were collected in each municipality is as follows: Halifax (3), Moncton (1), Montreal (2), Toronto (3), Prince Albert (1), Saskatoon (1), Edmonton (1), Vancouver (2).

Measured substances

The CWS currently includes estimates for ten substances. Among them are excreted products of controlled and illegal drugs.

• Amphetamine: a widely used stimulant.
• Cannabis (THC-COOH): a derivative of tetrahydrocannabinol which is the primary psychoactive compound in cannabis.
• Cocaine (Benzoylecgonine): the primary and an exclusive metabolite of cocaine, a stimulant drug.
• Codeine: a prescription painkiller medication and also available in some places as an over-the-counter medication. Codeine is metabolized to morphine and excreted as unchanged codeine.
• Fentanyl (Norfentanyl): the primary metabolite of fentanyl, a potent prescription painkiller medication that is often obtained from illicit sources and misused.
• Ecstasy (MDMA): 3,4-methylenedioxymethamphetamine (MDMA) is ecstasy also known as "molly", a psychoactive drug used for recreational purposes.
• Methadone: a synthetic drug used to treat opioid dependence and chronic pain.
• Methamphetamine: a potent stimulant drug.
• Morphine: a potent painkiller medication. Many opiates produce morphine when metabolized. For example, morphine is the most abundant metabolite of heroin and of its main metabolite, 6-monoacetylmophine. Morphine is also an excretory product of morphine itself and its derivatives, and of codeine. Thus, consumption of codeine and of other drugs that contain codeine derivatives will also contribute to morphine levels in the wastewater.
• Oxycodone: a prescription painkiller medication that is often obtained illegally and misused.

Some drug metabolites are exclusive to their parent drug, such as benzoylecgonine to cocaine, i.e. they are not excretory products of any other drug's metabolism. Because they clearly point to a particular drug, these metabolites are ideal targets for wastewater-based drug epidemiology. Unfortunately, not every drug of interest has such suitable specific metabolites.

Limitations and other considerations

Wastewater-based epidemiology is an inexpensive and powerful tool for estimating city-level drug consumption. However, there are some limitations in the analysis and interpretation of the wastewater data:

• The results from this data do not provide insights about those who uses drugs, such as their demographics, drug co-consumption, or specific location. They can only provide information about the overall drug consumption trends in the region.
• The CWS is not designed to produce data that is representative of the entire Canadian population.
• The population coverage by the area served by the wastewater treatment plant varies for each municipality.
• Population estimates for municipalities may not fully represent the population contributing wastewater due to factors such as commuting patterns, tourism, travel, and temporary population changes due to special events.
• Moderate and small differences between cities must be interpreted carefully since each city's wastewater sewershed is different and that can be in part the source of the differences in results between cities.
• Drug residues degrade in the wastewater and may be converted into other compounds. It is important to note that the absence of detection of a drug residue in the wastewater does not necessarily mean the parent drug was not consumed. For example, this could be due to high chemical instability of the drug metabolite in wastewater. This loss of residue can occur at different stages: in wastewater, in transport after collection, and in storage (at decreased intensity due to the frozen storage of the samples, which may affect comparability of the results between two different time frames).

Uncertainty in estimates of drug loads in wastewater is introduced from many sources: including the wastewater collection process, the measurement and analysis of biomarkers, the stability of biomarkers in the wastewater, and the calculations of per-capita consumption from excretion profiles and population estimates. The data collected do not allow this uncertainty to be quantified. These uncertainties also exist in other wastewater measurement programs and have been further explored in Castiglioni et al. (2013).

References

• Castiglioni, S., Bijlsma, L., Covaci, A., Emke, E., Hernandez, F., Reid, M., et al. (2013). Evaluation of uncertainties associated with the determination of community drug use through the measurement of sewage drug biomarkers, Environmental Science & Technology 47, pp. 1452–1460.
• Subedi, B. & Burgard, D. (2019). Wastewater-Based Epidemiology as a Complementary Approach to the Conventional Survey-Based Approach for the Estimation of Community Consumption of Drugs. Wastewater-Based Epidemiology: Estimation of Community Consumption of Drugs and Diets. Ed(s) Subedi, B., Burgard, D., & Loganathan, B. ACS Symposium Series; American Chemical Society. Washington, DC.https://pubs.acs.org/doi/pdf/10.1021/bk-2019-1319.ch001
• Other international programs
• Wastewater analysis and drugs, a program of the European Union Drugs Agency
• National Wastewater Drug Monitoring Program reports of the Australian Criminal Intelligence Commission