In a review article published on September 7, 2023, in the journal Foods, Celia Muzeza and co-authors from the University of South Africa, Johannesburg, discuss the migration of plastic monomers from food packaging into food and the associated implications for health.
Monomers are polymerized to produce polymers, such as plastics. However, polymerization reactions are rarely complete, and therefore residual, unreacted monomers might still be present in finished plastic products in concentrations of up to 4% (by weight). Muzeza and co-authors describe that these unreacted monomers can migrate into the packaged food in a four-step process: (1) diffusion through the polymer, (2) the desorption from the polymer surface, (3) the sorption at the plastic-food-interface, (4) and the desorption into the food. According to their review, this migration has been demonstrated for polystyrene, polyamides, polycarbonates, polyvinyl chloride, and polyurethane. Further, they summarize the different pathways of migration and highlight that some of these monomers are known endocrine-disrupting chemicals (EDCs), adding that their migration would “deteriorate the nutritional value, safety, and organoleptic qualities of packaged foods.”
While discussing the human health risk associated with EDC monomer presence in food, Muzeza et al. focus on bisphenol A (BPA, CAS 80-05-7), bisphenol A diglyceride ether (BADGE, CAS 1675-54-3), and caprolactam (CAS 105-60-2), their uses, evidence for migration, and concentrations in food. Their comprehensive 38-page review further touches upon factors influencing monomer migration and includes many useful tables such as on the known health effects of EDCs contained in food packaging materials. The authors conclude that “monomers contained within plastic food packaging are a significant source of food chemical contamination, with endocrine-disrupting effects that affect current and future human generations and environmental health,” which spurs them to call for more research and consumer awareness campaigns.
In 2021, Wiesinger and co-authors mapped 10,547 chemicals intentionally used in plastics, including monomers, additives, and processing aids, and also provided their hazard classification where available (FPF reported). And, researchers from the Food Packaging Forum (FPF) identified 388 chemicals intentionally used in food contact materials (FCMs) that are harmful according to the EU’s Chemicals Strategy for Sustainability (FPF reported), and therefore of high concern. Among them are 30 monomers with empirical evidence for their presence in FCMs and 22 with evidence for migration from finished food contact articles, like packaging. Most of them are known to be carcinogenic, mutagenic, or toxic to reproduction (CMRs), and four are EDCs (FPF reported). This underlines that hazardous monomers in FCMs are a relevant source of human exposure and that assuming all monomers have reacted and are not of relevance for human exposure is not based on scientific evidence.
Reference
Muzeza, C. et al. (2023). “The Mechanisms of Plastic Food-Packaging Monomers’ Migration into Food Matrix and the Implications on Human Health.” Foods. DOI: 10.3390/foods12183364
