Full title of this study: "Identification of potential migrants into food simulants from commercially-manufactured, thermoformed virgin and post-consumer polyethylene terephthalate packaging."
Food packaging is considered an indirect food additive according to the Code of Federal Regulations; therefore, risk assessment requires an understanding of packaging-component toxicities and predicted levels of human exposure [1-4]. Although the initial composition of the packaging may be known, the final composition can vary depending on physical and chemical degradation during the packaging’s life cycle prior to consumption of the product; this leads to recycling feed-stocks with large variations in composition . The suitability of a recycled material for direct food contact therefore strongly depends on the source of the waste, and the recycling method [5, 6].
Migration of contaminants from packaging can adversely affect food quality giving it off-odors and flavors, and the contaminants may be toxic to consumers [4, 7, 8]. The degree of migration of a polymer component into food will depend on its initial concentration, mobility through the polymer matrix, duration of exposure at a particular temperature, and solubility of the component in the food [4, 8, 9].
Glass, steel, aluminum, and paper are commonly recycled for food contact applications. Contamination of these materials, except paper, due to consumer use and post-consumer handling is generally very low and the conditions of the recycling processes reduce contaminant concentration . The Food and Drug Administration (FDA) categorizes recycling as: primary recycling -- the use of pre-consumer industrial waste to form a new product; secondary recycling -- the physical reprocessing and reformation of post-consumer materials; and, tertiary recycling -- the chemical treatment of post-consumer materials to isolate components to be reprocessed . A majority of the post-consumer reprocessing done in the United States is secondary recycling. Secondary recycling involves grinding, washing, melting, and reforming packaging which removes some contaminants that absorbed into the polymer matrix during product use [5, 6].
Ideally, post-consumer waste should be sorted by polymer type and packaging sector, as an additive that is not approved for direct food-contact could become incorporated into a package that is in direct contact with food. This, however, is difficult to achieve due to the increase in curbside reclamation programs and the increasing use of common polymers, such as PET (used for beverage bottles and food packaging) for non-food applications (cleaners, personal care) . Poor sorting can result in the incorporation of non-food-contact polymers into the recycling feed-stock for direct food-contact packaging. Although the FDA believes that acute consumer exposure to chemical contaminants from plastic food containers produced via secondary and tertiary recycling is low (due to low initial concentrations within the materials), trace amounts of toxic compounds have the potential to migrate into food items [5, 8]. As a result, the FDA recommends that worst-case contamination assumptions be made for non-food-contact packaging that enters the recycling stream due to the increasing probability that recycling feed-stock can be comprised of 100% non-food containers .
The FDA believes that secondary recycling processes will not remove all unapproved additives (colors, antioxidants, and other additives with relatively high molecular weights) because such compounds are incorporated into the polymer matrix during fabrication [5, 10, 11]. Other plastic components with lower molecular weights, such as plasticizers, oligomers, and monomers, have a much higher potential to migrate into food and can comprise up to 20% or more of a polymer’s mass [7, 8, 11]. In food-grade packages, the lipophilic nature of ester plasticizers favors their migration into oily and fatty food components . The adverse effects of some plasticizers to human health are well known and can include negative effects on the reproductive and endocrine systems as well as respiratory and dermatological problems .