National Wastewater Drug Surveillance (NWDS): Understanding the data

About the NWDS

The National Wastewater Drug Surveillance looks at monthly representative wastewater samples from participating regions. The samples give us a picture of the drugs that people are using and shows trends or patterns in drug use.

By monitoring wastewater, Health Canada and NWDS partners can:

• See the differences in drug use by region
• Fill gaps in traditional data sources used to monitor the drug supply
• Get timely data
• Track new psychoactive substances (NPS) and emerging psychoactive substances (EPS)
• Provide information that municipalities, regions and the federal government can use to develop policies, programs and actions

While the NWDS focuses on new and emerging psychoactive substances, we have also included other common drugs like fentanyl, methamphetamine and cocaine. This provides a point of reference to compare trends over different time periods and regions.

Some of the data we collect is incorporated into the Canadian Drug and Substances Watch (CDSW). This data subset highlights new and emerging psychoactive substances.

Definitions

Analogues

Substances that are structurally similar, but have some minor differences.

Cutting agent

Cutting agents are substances deliberately added to increase product bulk, modify or mimic pharmacological effects, or help in drug delivery.

Detection percentage

Number of identifications for a substance divided by the total number of samples analyzed. For example, if we had 12 months of data and 5 sites during that time, the denominator becomes 60.

Emerging psychoactive substances

Emerging psychoactive substances are drugs that have recently appeared or re-appeared on the illegal drug market. These substances are controlled under the Controlled Drugs and Substances Act. An example of an emerging psychoactive substance is protonitazene (from the opioids pharmacological class).

Identification or detection

The identification or detection of a substance in wastewater means that a substance was found via suspect screening by mass spectrometry. Please refer to Methods and Data Limitations for more information.

Metabolites

Metabolites are formed when a drug (parent substance) is broken down by the body. In some cases, metabolites can be used as drugs themselves. There can be more than 1 metabolite associated with each drug. There can also be more than 1 parent substance or drug associated with each metabolite. An example of a metabolite is benzoylecgonine (metabolite of cocaine, from the stimulant pharmacological class).

Monthly representative sample

Equal volumes of all wastewater samples collected in a month are combined to form a single sample (“pooled sample”). The pooled sample represents the month (“monthly representative wastewater sample”).

New psychoactive substances

New psychoactive substances are drugs that have recently appeared on the illegal drug market. They are not controlled under the Controlled Drugs and Substances Act and their sale may be regulated under the Food and Drugs Act. An example of a new psychoactive substances is 5-MeO-DMT (from the hallucinogen pharmacological class).

Parent substance

A parent substance is a drug in its original form that can be detected in wastewater. It may appear either because the body excretes it without metabolizing it, or because the drug was directly disposed of into the wastewater system.

Pharmacological class

Pharmacological classes are a way to group drugs based on their mechanism of action in the body. This results in different observed effects. Examples include opioids, stimulants and hallucinogens.

Drug Analysis Service and Cannabis Laboratory drug classification

Precursor chemicals

Precursors are chemicals that are used to produce other chemicals. The precursors that we screen for in wastewater are used to produce psychoactive substances. In this dataset, precursors are also grouped as parent substances because they are not transformed by the body. An example of a precursor is BMK glycidic acid, which can be used to synthesize methamphetamine.

Psychoactive substances

These are drugs that affect mental processes like perception, consciousness and/or mood. Substances with similar effects are grouped into the same pharmacological class.

Methods

Our approach

Wastewater samples are screened using mass spectrometry. This analytical method can detect substances at very low concentrations.

Data are available in - provinces and - territory, and efforts are being made to expand coverage. The number of wastewater treatment plants sampled varies from year to year (- in 2023; - in 2024; - in 2025).

We screen for over 550 psychoactive drugs and drug metabolites. A full list of substances screened for is available upon request.

We use a qualitative analysis approach to screen these substances (known as suspect screening). This means we analyze wastewater samples for the presence of drugs, their byproducts (metabolites) and precursor chemicals.

This approach allows us to:

• screen for many drugs
• obtain real-time data more quickly and at a lower cost
• identify possible emerging psychoactive substances of concern
• identify and further analyze possible new psychoactive substances of interest

The screening list was compiled using:

• substances of public health concern
• scientific literature and data from the following national surveys:
  • Canadian Substance Use Survey
  • Canadian Student Alcohol and Drugs Survey

The screening list is regularly updated. It:

• includes stimulants, hallucinogens, opioids, dissociatives, sedatives and hypnotics, synthetic cannabinoids, precursor chemicals and antipsychotics
• excludes most pharmaceuticals, with some exceptions (like xylazine, fentanyl, morphine)
  • a pharmaceutical that's detected in wastewater is not necessarily a case of illicit use

The methodology involves these steps:

• Influent wastewater (sewage) samples are collected from wastewater treatment plants.
• Samples are preprocessed at the Public Health Agency of Canada's (PHAC) National Microbiology Laboratory in Winnipeg or at a regional laboratory to prepare them for mass spectrometry analysis.
• UPLC-QToF mass spectrometry analysis takes place at Health Canada's Drug Analysis Service. The analytical method identifies substances using a curated mass spectrometry library.
• Health Canada's Office of Drug Research and Surveillance (ODRS) analyzes the data.

Metabolites and parent substances

On the Overview page, metabolites are grouped with their parent substance. In some cases, a substance may be a metabolite or a parent substance. Metabolites are only grouped with their parent substance if they are exclusively a metabolite.

All metabolites of a given parent substance are only counted once per monthly representative sample and are referred to as their parent substance. For example:

• Cocaine and multiple metabolites of cocaine (such as benzoylecgonine, ecgonine methyl ester) that are identified in a sample are listed once as cocaine.
• A metabolite of MDMA (such as HMMA) that's identified in the absence of MDMA in a sample is listed once as MDMA.

Some substances are both active metabolites and parent substances. For example:

• Amphetamine is a metabolite of methamphetamine. Therefore, amphetamine in wastewater could indicate methamphetamine and/or amphetamine use.

Any metabolites found in the wastewater, along with their associated parent substances, are shown on the metabolites page.

Not all drugs detected in wastewater samples are consumed by people. Some may have been flushed.

By analyzing and reporting on both, we can determine if a drug detected in wastewater likely indicates consumption at the community level. This approach gives us more reliable data and a more accurate picture of drug use.

Data limitations

Understanding wastewater drug testing

• We can only detect drugs that are on our screening list, which we update regularly. However, it is impossible to include every possible substance.
• When a new drug is added to the list, it might appear in our data for the first time. This does not necessarily mean it was absent  in the wastewater before.
• Weather and environmental conditions (like heavy rain, flooding, or snowmelt) can dilute or change wastewater samples and sometimes interrupt testing. This can affect how accurate or comparable the results are between locations or over time.
• Some substances are both active metabolites and parent substances. For example, amphetamine is a metabolite of methamphetamine. Therefore, amphetamine in wastewater could indicate methamphetamine and/or amphetamine use.
• Our testing only covers a limited number of municipalities, which can change from month to month. Because of this, the results do not represent all of Canada, and trends should be viewed with caution.

Mass spectrometry analysis

• Samples are analysed using a UPLC-QToF mass spectrometry instrument. A majority of substance identifications are made using a forensic toxicology library provided by the manufacturer.
• No second technique or instrument is used to confirm results.
• The instrument has a detection limit. If a substance is present in wastewater but below this limit, it will not be detected.
• Some substances that have very similar chemical structures (called isomers) may be identified under the same general name because mass spectrometry cannot differentiate between them. For example, different chemical structures closely related to fluorofentanyl (called isomers) are all reported simply as “fluorofentanyl.”

The type of wastewater testing that Health Canada is conducting here is known as “suspect screening”. The results should be interpreted as a list of likely drug candidates in wastewater.

Acknowledgements

Health Canada's Office of Drug Research and Surveillance thanks all collaborators who contributed to the National Wastewater Drug Surveillance initiative, including:

• Our project partners from the participating provinces and territories
• Environment and Climate Change Canada
• Statistics Canada's Canadian Wastewater Survey

We also thank PHAC's National Microbiology Laboratory for their continuous support with wastewater monitoring. This support includes bringing on participating sites and helping to pre-process samples for analysis by our partner laboratory at Health Canada's Drug Analysis Service.

Related links

• Chemicals Management Plan Wastewater Monitoring Program - Open Government Portal
• Canadian Wastewater Survey (CWS)
• Wastewater dashboard (for infectious disease monitoring)
• Food and Drugs Act
• Controlled Drugs and Substances Act