I'll try to explain it in two parts. Maximum residue limits are based on basic toxicology studies. These look at the product metabolized in the animals and make extrapolation calculations. Toxicity studies in animals are considered. They study the maximum tolerance, the maximum areas where there may be issues. For example, they take into account carcinogenicity and mutagenicity studies to ensure that a person who eats food treated with those particular drugs will not be subjected to levels of exposure that would cause harm in the long term. These types of calculations, these types of study requirements, are internationally harmonized. Therefore, Canada is not asking for any more than what is there internationally.
There are also international organizations such as the Codex Alimentarius Commission that bring people together to talk about where to draw the line in terms of safety, what the maximum limits are. When you look at the maximum residue limits that Health Canada has set for a lot of these veterinary drugs, they are very specific, and they are internationally harmonized.