Information Note - PMRA’s conclusion on Notice of Objection 2021-3441 for the imidacloprid re-evaluation decision

Health Canada’s Pest Management Regulatory Agency
27 Jun 2025

On this page

• About Notices of Objection
• Notice of Objection for the imidacloprid re-evaluation decision
• PMRA’s decision on this Notice of Objection (2021-3441)
• How to request our response letter

About notices of objection

Anyone in Canada may formally object to a major registration, re-evaluation or special review decision for scientific reasons by filing a Notice of Objection within 60 days of the date the decision is published.

When a Notice of Objection is submitted, scientists at the Pest Management Regulatory Agency (PMRA), who were not part of the original decision, conduct a thorough scientific review of the objection(s) and supporting information provided.

These scientists review the information provided in the objection(s) to determine whether any part of the original decision should be reassessed by an expert panel external to the PMRA.

When determining whether an external expert review panel is needed, the following factors are considered:

1. whether an objection raises scientific doubt about the evaluation of health or environmental risks, or a pesticide product’s value; and
2. whether the advice from expert scientists would help address the objection.

If an expert panel is established, they will provide their advice on specific parts of the objection(s) that raised any scientific uncertainty. The PMRA will then consider their advice when determining whether the original decision should be:

• confirmed,
• reversed, or
• modified (varied).

Learn more about the Review Panel Regulations.

Notice of Objection (2021-3441) for this imidacloprid re-evaluation decision

The re-evaluation decision on imidacloprid is outlined in the published document titled Re-evaluation Decision for Imidacloprid (RVD2021-05). The PMRA concluded that, with additional risk mitigation measures, many uses of imidacloprid products meet current standards for protection of human health and the environment and have value. However, certain uses of imidacloprid were cancelled to address potential risks to the environment. Supporting information on the pesticide assessment is available in the published document titled Proposed Re-evaluation Decision for Imidacloprid (PRVD2016-20) that underwent a public consultation.

The objector, Dr. Christy Morrissey (Professor of Department of Biology, University of Saskatchewan), raised objections related to the environmental risk and value assessment we used to make our re-evaluation decision on imidacloprid. The objector submitted evidence to support 14 objections, including a reference list of 76 studies. The full objection notice and PMRA’s response letter, can be accessed in the Pesticide Product Information Database under Application Number 2021-3441.

Learn more about:

• Re-evaluation Decision RVD2021-05, Imidacloprid and Its Associated End-use Products
• Proposed Re-evaluation Decision for Imidacloprid (PRVD2016-20)

PMRA’s decision on this Notice of Objection (2021-3441)

PMRA scientists reviewed the objections and supporting information provided by Dr. Christy Morrissey, and concluded that:

1. one aspect of an objection provided in this Notice of Objection raised scientifically founded doubt about the environmental risk assessment for imidacloprid, and
2. advice from external expert scientists would help address the objection raised.

As a result, the PMRA will set up a review panel of external experts.

Reviewing the objections

The specific aspect to be evaluated by an external panel of experts is the assertion that the PMRA placed too much emphasis on mesocosm studies when assessing risk to aquatic invertebrates. Specifically, the objector stated that an uncertainty factor is needed when using mesocosm studies in environmental risk assessments.

Mesocosm studies are controlled, outdoor experiments designed to simulate natural environments. As their use in regulatory decisions is relatively rare, international regulators have not reached agreement on their interpretation or how to apply uncertainty factors in quantitative environmental risk assessments.

All objections were assessed using standard risk assessment approaches. For the objections not resulting in further action, the supporting studies provided by the objector were consistent with our conclusions in the original decision (RVD2021-05), and no further action is warranted. You can find additional information about the objections, as well the PMRA’s responses, in our response letter.

Setting up an expert external review panel

An external Review Panel will be established as the PMRA determined that expert advice would help address the specific concern.

The Review Panel will examine the PMRA’s approach to the use of mesocosm studies in environmental risk assessment for imidacloprid, specifically the consideration and potential application of uncertainty factors when reviewing these types of studies.

While the panel conducts its review, the registration status of imidacloprid will not change. Information about the Review Panel, including their report when it becomes available, will be posted in the Public Registry under Application Number 2025-2565.

The PMRA will then consider the Review Panel’s recommendations to make a final decision for imidacloprid. The length of the PMRA’s review will depend on the complexity of the issue under review and the time required by the Review Panel to provide their recommendation. 

How to request our response letter

Our response to objections is outlined in a letter to the objector that includes technical details and the science review that forms the basis of this regulatory decision.

To request a copy of our response letter:

1. Visit Health Canada’s Public Registry webpage.
2. Click the link to “Pesticide Product Information Database”, review the “Disclaimer” page, then click the “Application search” button.
3. Under Filter, select “Application Number”, leave the Operator “equal” and in the Value field, type “2021-3441”.
4. Click “Search”.
5. Click on the application number in the search results.
6. On the Application Details page, scroll down and click on the tab “Published Documents”.
7. Click on "Response letter” and follow the prompts to request a copy of this document.

If you have any questions about our decision, please submit questions to Information Services Inquiry - Public Engagement Portal (PEP) (canada.ca).