To assist manufacturers of food packaging materials in recognizing equivalency (and thus interchangeability) between polymer resins, the Food Directorate maintains, on the Health Canada website, positive lists of polymers for which letters of no objection have been issued for use in food packaging and other food contact applications. The intent of the lists is to preclude the need for new requests for letters of no objection in situations where interchanging one resin with a comparable one on the positive lists is the only change made to the composition of a food packaging material that has already been sanctioned by the FD for food contact uses. In such a case, it is only necessary to apprise the FD of the change to maintain the validity of the letter of no objection. However, the FD reserves the right to challenge the equivalency determination made by the manufacturer upon receipt of the notification., Health Canada information for the food packaging industry: Canadian food packaging regulations, pre-market assessments, letters of no objection, food packaging guidance documents, a submission process schematic, interaction with the Canadian Food Inspection Agency (CFIA) and Food Directorate listings for polymers, Requirements for food packaging submissions and technical references for safe food productions systems. How to submit a pre-market assessment on food packaging material. General principles for food hygiene and labelling, food safety and accepted construction and packing materials..