Organophosphate pesticides cumulative health risk assessment fact sheet

Table of contents

• Why Health Canada is conducting a cumulative health risk assessment for the organophosphate insecticides
• Organophosphate pesticides included in the cumulative risk assessment
• How a cumulative health risk assessment differs from a regular re-evaluation
• Why a cumulative health risk assessment takes time
• Cumulative risk assessment of organophosphates by other Regulators
• What this means for people in Canada right now
• Where to learn more

Why Health Canada is conducting a cumulative health risk assessment for the organophosphate insecticides

Health Canada is required to consider available information on potential cumulative human health effects associated with co-exposures to two or more pesticides that have a common mechanism of toxicity as described in the SPN2018-02, Cumulative Health Risk Assessment Framework.

A cumulative health risk assessment (CRA) examines the possibility of exposure to more than one pesticide with a shared mechanism of toxicity at the same time. It considers combined exposures from food, drinking water and non-occupational residential sources. By assessing these exposure pathways together, a CRA helps determine the likelihood and potential impact of cumulative health effects.

The CRA for organophosphate (OP) insecticides is focused on OPs that act similarly in the human nervous system by inhibiting acetylcholinesterase, an enzyme that is essential for normal nerve function.

Organophosphate pesticides included in the cumulative risk assessment

Organophosphate pesticides are a group of pesticides, generally used for insect control, that affect their nervous system in a similar way; by inhibiting acetylcholinesterase, an enzyme that helps nerves function normally.

Health Canada completed a scoping assessment of all 10 OP pesticides registered in Canada and 42 OP pesticides not registered in Canada that could be present on food imported into Canada. A list of all 52 OPs assessed can be found in Tables 1 and 2 of REV2024-02, Organophosphate Pesticides – Cumulative Health Risk Scoping Assessment, Problem Formulation and Planned Approach of Analysis.

Based on this work, Health Canada determined 29 OPs will be evaluated in this CRA, including the 10 OPs registered in Canada and 19 OPs not registered in Canada that could potentially be found on food imported into Canada. The determination of which non-registered OPs will be included in the CRA was reached using the decision tree found in Appendix II of REV2024-02.

How a cumulative health risk assessment differs from a regular re-evaluation

Re-evaluation of a particular active ingredient: Looks at each active ingredient individually, to verify that registered pesticides containing that active ingredient continue to meet current standards with regards to human health effects, environmental effects, and value.

Cumulative Health Risk Assessment of a group of active ingredients: Looks at the combined human health effects from co-exposure to multiple active ingredients with a common mode of toxicity.

As an example, let's look at bensulide:

• Bensulide is currently undergoing a re-evaluation of all registered uses. The re-evaluation includes assessing risks to human health (for example, dietary exposure, occupational and residential exposure) and the environment (for example, fate and ecotoxicology) to determine the continued acceptability of all registered uses of bensulide.
• Bensulide is also included in the OP CRA and it will be assessed with other OP pesticides as part of the cumulative dietary and residential health risk assessments. The toxicological and exposure assessments from the re-evaluation of bensulide must be current before the cumulative risk assessment can be completed.

Why a cumulative health risk assessment takes time

The cumulative health risk assessment can only be completed once an individual active ingredient (in this case the individual OP) assessments are updated. As outlined in Science Policy Note, Cumulative Health Risk Assessment Framework (SPN2018-02), individual pesticide assessments must be current before cumulative assessments can proceed.

Four of the 10 OP pesticides registered in Canada are currently undergoing cyclic re-evaluations, with publication of proposed decisions for public consultation expected in late 2027 into early 2028. For more information on the re-evaluation process and timelines, see Appendix I of DIR2016-04, Management of Pesticides Re-evaluation Policy.

As mentioned in the bensulide example above, the outcomes of each ongoing OP pesticide re-evaluation must be completed first to ensure the most up-to-date information is used in the OP CRA. Based on the ongoing re-evaluation work for the four registered OP pesticides, Health Canada anticipates completing the necessary work and publishing the proposed OP CRA decision for public consultation in early 2030 as outlined in REV2026-01, Project Plan for Cumulative Health Risk Assessment – Organophosphate Pesticides.

It is important to note that if during work on the cumulative risk assessment it is determined that additional areas of focus need to be considered, the proposed public consultation for the OP CRA decision timeline may be affected. Information on any timeline changes will be communicated in the annual Pest Management Regulatory Agency Re-evaluation and Special Review Work Plan posted on Health Canada's Decisions and Updates page.

Cumulative risk assessment of organophosphates by other Regulators

Health Canada regularly leverages assessments and data from other international regulators including publicly available regulatory decision documents and reviews. This approach allows Health Canada to make use of cumulative assessments undertaken by other regulators, in whole or in part, provided that the assessments are relevant to the Canadian context.

Cumulative risk assessments of organophosphate pesticides have been completed by the United States Environmental Protection Agency (USEPA) and the European Food Safety Authority (EFSA).

The USEPA assessment evaluated the cumulative health risks for 31 OPs sharing a common toxic effect. The assessment included food, drinking water and residential exposures. The initial outcome was published in 2002 with updates published in 2006.

Their overall conclusion was that cumulative risks of the OPs assessed did not exceed the USEPA's safety benchmarks (levels of concern) for the general population or any sensitive subpopulations (for example infants and children).

The EFSA retrospective cumulative assessment was completed in 2020 with a focus on dietary exposure only. EFSA grouped pesticides by toxicological effect, (for example, nervous system effects), which means a variety of pesticide types including OP pesticides, n-methyl carbamates and triazoles were included in one cumulative assessment. This approach is different than the approach taken by both Health Canada and the USEPA where only OP pesticides with a common toxic effect were grouped. The overall conclusion of EFSA's assessment is that consumer risk from cumulative dietary exposure did not exceed the safety threshold of the European Commission and European Union member states that trigger regulatory action.

What this means for people in Canada right now

While the cumulative health risk assessment is underway:

• All OP pesticides registered in Canada continue to be regulated under the Pest Control Products Act.
• Existing safeguards, use restrictions, and maximum residue limits remain in place.
• New information is regularly reviewed, and immediate action can be taken if new risks are identified.
• Updates to any of the public consultation timelines mentioned in this factsheet will be communicated in the annual Pest Management Regulatory Agency Re-evaluation and Special Review Work Plan.

Where to learn more

• Cumulative Health Risk Assessment Framework (Science Policy Note SPN 2018-02)
• Cumulative health risk assessment operational planning framework (Information Note)
• Organophosphate pesticides – Cumulative health risk scoping assessment, problem formulation and planned approach of analysis (Re-evaluation Note REV2024-02)
• Project Plan for Cumulative Health Risk Assessment – Organophosphate Pesticides (Re-evaluation Note REV2026-01)
• Re-evaluation and Special Review Work Plan 2025-2030 (Re-evaluation Note REV2025-01)
• Pest Control Products Act