Response to comments received on PMRL consultations for proposed new maximum residue limits of various pesticides (PMRL2021-15 to PMRL2021-30)

Several comments were received from the general public and two health professionals on the proposed maximum residue limit consultation documents PMRL2021-15 through to PMRL2021-30.^{Footnote 1} While these comments did not result in changes to the new MRLs proposed in these consultation documents, it did highlight the importance of providing further explanation on the purpose of setting maximum residue limits (MRLs), and how MRLs are determined.

In general, these comments opposed the presence of any pesticide residues in food and questioned the definition of acceptable risk and how precaution is applied. There were also questions as to why MRLs differed for the same commodity in different countries, as well as why pesticide regulatory systems differed between various countries and jurisdictions, such as that of the European Union.

Maximum residue limit

A pesticide MRL is the maximum amount of pesticide residue that may legally remain on a food commodity that is either grown and produced domestically, or imported into Canada when the pesticide is used according to label directions. Health Canada routinely sets science-based MRLs to help ensure the food Canadians eat is safe. The MRL for each pesticide-crop combination is set at levels well below the amount that could pose a health concern. (See Understanding acceptable risk below).

Pesticide residues in or on food commodities

Pesticide residues and MRLs are measured in parts per million (or ppm). One part per million is equal to a single granule of sugar in 273 cubes of sugar (or 1 granule in one million granules). Therefore, 1 or even 20 ppm of residue on a food commodity from a pesticide is exceedingly small. Nevertheless, Health Canada must be satisfied that the amount of residue that could be present on a food commodity, once a crop has been treated with a pesticide according to label instructions, is not a health concern.

Health Canada's responsibility in pesticide regulation

Health Canada's priority is to protect the health and safety of Canadians, the environment and the food supply. This includes setting the conditions for approval of each specific pesticide use in Canada, including the levels of pesticide residues that may be present in food commodities grown in Canada or that may be imported into the country. These conditions are set based on Health Canada's independent review of scientific data. The role of Health Canada's Pest Management Regulatory Agency (PMRA) is to make sure that the amount of residues that may be present in or on food commodities grown in Canada does not pose a human health concern to any segment of the Canadian population including infants and toddlers, pregnant and nursing mothers, and the elderly.

Understanding acceptable risk

Before approving the registration of a pest control product for a specific use, Health Canada thoroughly assesses the risks to human health to make sure that the level of human exposure, when used according to the label directions, is well below the level that would be of health concern. Only pesticides for which health risks are shown to be acceptable are approved.
To do this assessment, Health Canada combines scientific information on pesticide toxicity with information on the degree and duration of dietary exposure to the pesticide residue from food. The risk assessment process involves four distinct steps:

1. Identifying the toxicology hazards of a pesticide
2. Determining the "acceptable dietary level" for Canadians (including all vulnerable populations) that is protective of adverse health effects, by setting the acceptable level at least 100-fold below the level where no effects are observed in animal studies;
3. Estimating how much of a pesticide people may be exposed to in their diet from all possible sources (domestic and imported commodities), based on how much residue remains in or on the food and the amount of treated food an individual may consume; and
4. Characterizing human risk by comparing the estimated dietary exposure to the acceptable dietary level set in Step 2.

If estimated human exposure from Step 3 is less than, or equal to the acceptable level (developed in Step 2 above), Health Canada concludes that consuming residues resulting from use according to approved label directions is not a health concern. This quantity of residue is then subject to consultation to legally specify it as an MRL. If risks to human health from the consumption of treated crops are not shown to be acceptable, the pesticide product will not be permitted for sale or use in Canada, and an MRL (or import MRL) will not be established.

An MRL applies to the identified raw agricultural food commodity as well as to any processed food product that contains that commodity. On occasion, and depending on the characteristics of a given pesticide, a different MRL may be specified for a processed product made from that raw agricultural commodity (for example, corn versus corn oil).

As noted above, Health Canada establishes MRLs only when there are no health risks of concern to consumers; in other words, the risks are shown to be acceptable. This approach is consistent with the international approach to health risk assessment and is considered protective, as exposure to pesticide residues in the diet must be below levels that could pose a health concern.

MRL differences between countries

MRLs may vary from one country to another for a number of reasons, including differences in how the pesticide is used on a particular crop in various countries, and the geographical locations of the crop field trials that analyse and measure residue data on these crops. For livestock commodities, differences in MRLs can also be due to different livestock feed items and practices, as well as different legislative requirements in different countries.

Calculating an MRL

An MRL is calculated by a statistical method that is used internationally by Organisation for Economic Co-operation and Development (OECD) countries. Health Canada scientists collaborated with other OECD scientists to develop this OECD calculator. This calculation is based on the amount of residue that may remain on crops when a pesticide is used according to label directions. The calculator compares the lowest residue with the highest residue; the larger that range is, the greater the difference present in the data. This difference is taken into account when computing the MRL and may lead, in some cases, to MRL proposals significantly greater than the highest residue. It is important to note that the MRL does not indicate a target level of residue, but represents the highest residue that could remain on a particular crop at harvest when the pesticide has been applied to the crop according to the approved domestic or foreign pesticide label. Once Health Canada concludes that consuming residues resulting from use according to approved label directions is not a health concern, this quantity is then subject to consultation to legally specify it as an MRL. Health Canada establishes MRLs only when there are no health risks of concern to consumers.

Environmental impacts

For all pesticide registrations in Canada, environmental considerations are taken into account. These assessments may be found in the Proposed Registration Decision Documents and Evaluation Reports for individual pesticides, which are available through the Canada.ca website or Pesticide Product Information Database.

International differences in pesticide regulations

Health Canada works collaboratively with international regulatory authorities such as the United States Environmental Protection Agency (USEPA) and European Food Safety Authority (EFSA), and monitors the regulatory status of pesticides in other OECD member countries. While each regulatory authority considers all the available scientific information, each country conducts independent risk assessments, taking into consideration country-specific legislation, policies and conditions of use. For these reasons, regulatory decisions may differ from country to country.

Conclusion

As dietary risks from the consumption of pesticide residues in or on food commodities noted in the various PMRL consultation documents were shown to be acceptable when the products are used according to the supported label directions, the foods containing these residues are safe to eat, and the MRLs will be established as proposed (PMRL2021-15 to PMRL2021-30^{Footnote 1}).

For more information on the activities of Health Canada's Pest Management Regulatory Agency, you are invited to refer to the Pest Management Regulatory Agency Annual Report (2019-20).