proposed amendment to the food and drug regulations 1347 - sulfonamides under the canadian food and drug regulations the regulations all veterinary drugs must be authorized by health canada prior to their sale and administration to prevent and treat diseases in animals. some drugs are only permitted in certain species not intended to be used for foods while others are used in food-producing animals. these amendments to the regulations establish safe limits for residues of various sulfonamides in foods originating from animals treated with these particular drugs. these veterinary drugs are an important tool in the production of healthy animals which are destined for use as food. acceptable limits of residues of veterinary drugs in food commodities are called maximum residue limits mrls . mrls are the maximum concentrations of residues expressed in parts per million p.p.m. on a fresh weight basis in edible tissues of food-producing animals as a result of the treatment of those animals with veterinary drugs. an mrl is based on the type and amount of residue considered to pose no adverse health effects if ingested daily by humans over a lifetime. the proposed amendments would list the following new individual mrls for authorized sulfonamide compounds to be used in food-producing animals sulfabenzamide sulfacetamide sulfachlorpyridazine sulfadiazine sulfadimethoxine sulfadoxine sulfaethoxypyridazine sulfaguanidine sulfamerazine sulfamethazine sulfanilamide sulfanitran sulfapyridine sulfaquinoxaline and sulfathiazole. in addition these amendments propose that sulfonamides may be used singly or in combination. in cases where more than one sulfonamide drug residue is being detected the combined residues of all sulfonamides listed in the amendments should not exceed 0.1 p.p.m. in edible tissues and 0.01 p.p.m. in milk. extensive studies have determined that the food commodities containing residues of sulfonamides at levels u to the mrls listed in the amendments are safe for consumption. these mrls apply to foods produced domestically or imported into canada