Risk assessment of packaging materials provides a unique challenge. Human exposure to packaging materials and/or their components occurs from migration into foods. There are various methods for determining migration into foods. Unlike most food additives, these exposures typically are very small. Because of this, and since complete toxicological data sets are not always available for packaging materials, the US Food and Drug Administration (FDA) has developed a process to make the evaluation of packaging materials more efficient, instead of the extensive review normally required for food additives. This process is used to determine 'when the likelihood or extent of migration to food of a substance used in a food-contact article is so trivial as not to require regulation of the substance as a food additive'. This trivial level, also known as the threshold of regulation, was based upon a large database of carcinogenic potencies and was determined to be 1.5 microg/person day(-1). This was determined to 'be low enough to ensure that the public health is protected, even in the event that a substance exempted from regulation as a food additive is later found to be a carcinogen'. Substances not having structural alerts, or that are not known carcinogens or potent toxins, based on existing toxicological information, and are below the threshold value, are considered by the FDA to be exempted from regulation as food additives. The threshold of regulation approach used by the FDA provides an excellent model by which to evaluate the majority of packaging materials.