Toxin Talks: What’s new about toxin oversight in the amended Act

On this page

Introduction

Prior to the 2026 Human Pathogens and Toxins Act amendments, a toxin was exhaustively listed in Schedule 1 or Schedule 5 to the Human Pathogens and Toxins Act so that only those human toxins were regulated in Canada. In order to be on one of those schedules, the Minister of Health needed to be of the opinion that it was a substance produced by, or derived from a microorganism and able to cause disease in a human.

The amended Human Pathogens and Toxins Act better reflects the evergreen nature of human pathogens and toxins with the removal of outdated “Schedules 1 to 4” and the introduction of the Registry of Human Pathogens and Toxins (Registry), which is now a subset of the existing ePATHogen database. The human pathogens and toxins formerly in Schedule 5 are still prohibited and remain listed exhaustively in a single schedule to the Human Pathogens and Toxins Act.

A new toxin definition was introduced in the amended Human Pathogens and Toxins Act. Explained in detail below, this definition:

  • formalizes the definition of a toxin with some added precision;
  • introduces a new class of toxins known as bioweapon toxins; and
  • further indicates that toxins - with the exception of bioweapon toxins - are now listed non-exhaustively, similar to human pathogens.

Toxins in the schedule (formerly Schedule 5) continue to be listed exhaustively, though none are included there currently.

This amendment means that the Centre for Biosecurity can respond more nimbly to add, remove, or vary the status of a toxin to keep pace with evolving science (for example, nomenclature can be more easily updated).

Schedule 1 is gone! How is a toxin defined in the amended Human Pathogens and Toxins Act?

In the amended Human Pathogens and Toxins Act, a toxin is defined as a substance that is produced by, or derived from, a micro-organism that:

  1. poses a moderate-to-high risk to the health of individuals; or
  2. poses a moderate-to-high risk to the health, safety or security of the public due to a reasonable risk of intentional use as a bioweapon (“bioweapon toxin”); or
  3. is listed in Part 1 of the schedule (formerly Schedule 5) – toxins where all activity is prohibited.

Additional precision in part (a) of the definition indicates that toxins posing a moderate to high risk to the health of individuals will be listed non-exhaustively in the new Registry, and the listing may also specify the minimum quantity (trigger quantity) at which they pose such a risk. This amendment brings toxin regulation in-line with human pathogen regulation and reflects the evergreen nature of human pathogens and toxins.

By contrast, bioweapon toxins (part (b) of the definition) must be identified exhaustively in the Registry and must include the minimum quantity (trigger quantity) at which they pose such a risk. In most cases, toxins that pose a bioweapon risk will also pose an individual health risk; however, a toxin that poses an individual health risk may not necessarily pose a bioweapon risk.

Simply speaking, if it’s a substance produced by or derived from a microorganism, a toxin could fall into one of four categories, as shown in Table 1.

Table 1: Human Pathogens and Toxins Act-defined toxin categories with associated Registry and trigger quantity requirements

Category

Toxin Category Description

Registry and Trigger Quantity

(a) 

Toxin that poses a moderate to high risk to the health of individuals

Toxin may or may not be in the Registry and may or may not have an associated trigger quantity at which it poses that risk (non-exhaustive listing)

(b)

Toxin that poses a moderate to high risk to the health, safety or security of the public due to a reasonable risk of intentional use as a biological weapon (“bioweapon toxin”)

Toxin will always be clearly identified in the Registry and with the specific quantity at which it poses that risk (exhaustive listing)

(a) + (b)

Toxin that poses both

a moderate to high risk to individual health and a bioweapon risk

Toxin will always be identified in the Registry and will always have a bioweapon risk trigger quantity (exhaustive listing) but may or may not have an individual health risk trigger quantity

(c)

Toxin in respect of which all activity is prohibited

Toxin will be listed in Part 1 of the schedule (exhaustive listing) and will not be listed in the Registry

The amended Human Pathogens and Toxins Act is talking about minimum quantities or “trigger” quantities. What’s that about?

Minimum (also known as “trigger”) quantities have been introduced into the amended Human Pathogens and Toxins Act because in some cases, toxins only present a meaningful risk when present at or above a certain quantity. Unlike human pathogens, toxins do not reproduce or “amplify” following exposure and person-to-person transmission does not occur. Commonly referred to as the dose-response relationship, in general, the severity and prevalence of specific toxic effects will increase with increasing exposure to a toxin, as determined by exposure route, dose, duration, and frequency. Toxic effects, including acute toxicity following a single exposure, are considered to have a threshold, meaning it is assumed that there is a dose below which the toxin will not elicit a response or will not elicit a defined moderate to severe response.

The new toxin definition and Registry provisions in the Human Pathogens and Toxins Act allow for publication of two (2) separate minimum or “trigger” quantities related to toxins as follows:

  • Human Pathogens and Toxins Act Toxin Exclusion Quantity: Pursuant to subsection 9(3), the Human Pathogens and Toxins Act toxin exclusion quantity is the minimum quantity at which, in the opinion of the Minister, a toxin presents a moderate to high risk to the health of individuals (for toxins fitting part (a) of the new toxin definition). It can be thought of as the quantity below which “a toxin is not toxic”. This “Human Pathogens and Toxins Act exclusion quantity” is not mandatory to publish in the Registry. If no exclusion quantity is displayed for this type of toxin, then any quantity of that toxin (no matter how small the volume) is regulated.
  • Bioweapon Toxin Trigger Quantity: Pursuant to subsection 3(1) (part (b) of the “toxin” definition) and subparagraph 9(2)(a)(ii), the bioweapon trigger quantity is the minimum quantity at which, in the opinion of the Minister, a toxin is a bioweapon toxin. All bioweapon toxins will be identified clearly in the Registry along with the minimum quantity at which they are considered to be a bioweapon toxin, even where that quantity is any quantity greater than zero.

As a result, two (2) separate trigger quantities may be published in the Registry for any given regulated toxin depending on its category. Note that it is also conceivable that the minimum quantities for both types could be the same, including the possibility that any quantity greater than zero is the minimum quantity for both. Table 2 below captures the category of regulated toxin and what to expect in the Registry.

Table 2: Registry and trigger quantity requirements for different Human Pathogens and Toxins Act-defined toxin categories

Toxin Category

Toxin that poses a moderate to high risk to the health of individuals [(category (a)]

Toxin that poses a bioweapon risk [category (b)]

Toxin that poses both a moderate to high risk to individual health and a bioweapon risk [category (a)+(b)]

Toxin published in Registry?

Generally, yes*

Yes

Yes

Human Pathogens and Toxins Act Exclusion quantity published in Registry?

Dependent on assessment

Not applicable

Dependent on assessment

Bioweapon trigger quantity published in Registry?

Not applicable

Yes

Yes

*Note: the Registry does not provide an exhaustive listing of all regulated human pathogens and toxins (apart from bioweapon toxins, which will always be listed).

What happened to Security Sensitive Biological Agent toxins and the trigger quantity table in the Human Pathogens and Toxins Regulations? Are bioweapon toxins just a new way of saying Security Sensitive Biological Agent toxins?

Prior to the Human Pathogens and Toxins Act amendments, a toxin was “prescribed” (also known as Security Sensitive Biological Agent), if it was:

  • included on both Schedule 1 and the List of Human and Animal Pathogens and Toxins for Export Control as published by the Australia Group; and
  • (if listed in the table in subsection 10(2) of the Human Pathogens and Toxins Regulations, was present in a part of a facility in a quantity greater than the quantity specified in that table.

Consequential amendments to the Human Pathogens and Toxins Regulations made by the amended Act include changes to the definition of prescribed toxins in section 10 of the Human Pathogens and Toxins Regulations. In the amended Human Pathogens and Toxins Regulations, prescribed (or Security Sensitive Biological Agent) toxins are those that are:

  • listed both in the Registry and on the List of Human and Animal Pathogens and Toxins for Export Control; and
  • present in a part of a facility in a quantity equal to or greater than the bioweapon trigger quantity for that toxin indicated in the registry.

Accordingly, prescribed (or Security Sensitive Biological Agent) toxin trigger quantities are considered the same as those published in the Registry as “bioweapon toxin trigger quantities”. As a consequential amendment to the Human Pathogens and Toxins Regulations (made by the amended Human Pathogens and Toxins Act), the Human Pathogens and Toxins Regulations subsection 10(2) Security Sensitive Biological Agent toxin trigger quantity table has been removed.

Currently, all bioweapon toxins listed in the Registry, along with their trigger quantities, are also included on the List of Human and Animal Pathogens and Toxins for Export Control and considered Security Sensitive Biological Agent toxins for which additional security conditions apply when present at or above the listed bioweapon trigger quantity. Should a situation arise where a bioweapon toxin identified in the Registry is not prescribed (for example, not included on the List of Human and Animal Pathogens and Toxins for Export Control or otherwise excluded from being prescribed in regulations), then clear differentiation will be made in the Registry.

Where exactly do I find all these toxin trigger quantities?

Toxin trigger quantities can be found published in the Registry within the “considerations for containment and/or regulatory oversights” field that is available when a toxin listed in the registry is selected to view additional information.

If the toxin is identified as a bioweapon toxin, the quantity at which it poses this risk will always be published. However, for toxins posing a moderate to high risk to the health of individuals, the Human Pathogens and Toxins Act exclusion quantity, or the minimum regulatory quantity, may or may not be published. If no exclusion quantity is displayed, then any quantity of toxin (no matter how small the volume) is considered regulated. See Table 2 above.

Who determines when a toxin is regulated and what the trigger quantities are?

Pursuant to section 9 of the amended Human Pathogens and Toxins Act, the Minister of Health is the sole authority to determine whether to list a toxin in the registry and assign trigger quantities. This is with the exception of toxins in Part 1 of the schedule, in respect of which all activity is prohibited, which is under the authority of the Governor in Council (none are currently listed there). However, as noted above, toxins meeting part (a) of the toxin definition (for example, an individual health risk) do not necessarily need to be listed in the registry in order to be considered regulated.

Toxins will continue to be assessed in the same manner as done to date. Well-characterized biological agents that have had a toxin risk assessment completed by the Public Health Agency of Canada and/or the Canadian Food Inspection Agency under the Health of Animals Act will continue to be assigned a toxin regulatory status, human toxin trigger quantity (as necessary), and a containment level. This information can be found in the online Registry or ePATHogen database. In addition, the Public Health Agency of Canada will continue to consult and seek the expertise of the external Advisory Committee on Human Pathogens and Toxins when conducting risk assessments and determining trigger quantities.

It is important to note that the regulatory status or Biosafety Level classifications of toxins determined by entities other than the Public Health Agency of Canada or the Canadian Food Inspection Agency (for example, culture collections, distributors, manufacturers, other countries, etc.) have no regulatory significance under the Human Pathogens and Toxins Act or the Health of Animals Act. You should always consult the Registry, ePATHogen database, and the “schedule” to determine the regulatory status of any biological agent(s).

I can’t find a toxin in either the Registry or ePATHogen. What do I do next?

Thousands of well-characterized biological agents that have had a pathogen or toxin risk assessment completed by the Public Health Agency of Canada and/or the Canadian Food Inspection Agency can be found in the online Registry or ePATHogen database with an assigned Risk Group or regulatory status and containment level. However, given the rapidly evolving nature of biological agents and new scientific discoveries, there may always be something that has not yet been assessed or is currently under assessment.

Should you wish to know the regulatory status of a toxin that is not listed in the ePATHogen database or the Registry, or if you would like to further discuss a toxin that is listed, please contact us at pathogens.pathogenes@phac-aspc.gc.ca.

There is a pathogen risk assessment guideline and template available on-line to request the risk group classification of a pathogen. Is there a toxin risk assessment guideline and template available?

A toxin risk assessment template and supporting guidance document will be available. These documents will be also supported with an on-line and self-paced Toxin Risk Assessment training course. To request a toxin regulatory status, complete the toxin risk assessment template using the guidance and peer-reviewed publications and scientific literature as sources of information. Completed toxin risk assessment templates may be submitted to the Centre for Biosecurity at pathogens.pathogenes@phac-aspc.gc.ca for validation, confirmation of regulatory status, and subsequent addition to the Registry or ePATHogen database, as appropriate. The Centre for Biosecurity is available to help with any questions that you may have.

In addition to the above, we are planning a Toxin Risk Assessment webinar that will take place in the coming months.

Unsure About Toxins? Ask Us!

Should you have any questions regarding toxins, including biological agents not listed, please do not hesitate to contact us at pathogens.pathogenes@phac-aspc.gc.ca.

Interested parties should consider subscribing here for updates from the Public Health Agency of Canada on biosafety and biosecurity. These include notifications about new or updated Advisories, biosafety training opportunities, changes in regulatory information including risk group classifications or microbial toxin regulatory status, and other regulatory information.