The Threshold of Regulation (TOR) Rule permits FDA to exempt a food contact material from regulation based on exposure and toxicology. In 2010, FDA issued a TOR Exemption (No. 2010-002) for all food contact articles used to irradiate pre-packaged food provided that certain conditions are followed. Specifically, the TOR permits the following materials:

1. Food additives listed in Title 21 of the Code of Federal Regulations (C.F.R.) Parts 174 through 186;
2. Substances for which there is an effective food-contact substance notification; and
3. Substances that are the subject of a TOR exemption,

to be used in food-contact articles during the irradiation of prepackaged food. However, this exemption only applies when:

1. The radiation processing is done in compliance with 21 C.F.R. Part 179;
2. The substances are not subjected to radiation doses above 4.5 kGy; and
3. The packaged food is irradiated either in a verifiably oxygen-free environment or while frozen and contained under vacuum.

TOR letters are of general applicability meaning that any food packager may rely on them.