In a perspective article published on August 31, 2023, in the journal Environment & Health, Changzhi Shi from Fudan University, Shanghai, China, and co-authors call for more research on oligomers arguing that this group of compounds is inadequately addressed.
More and more scientific articles report the migration of oligomers from different types of food contact plastics, including polyethylene terephthalate (PET) and Tritan™ (FPF reported), polybutylene terephthalate (PBT; FPF reported), polyamide (PA; FPF reported), as well as polycarbonate and biodegradable food ware (FPF reported). Besides plastic packaging, oligomers can also migrate from the coating of metal cans (FPF reported). The limited research available suggests that oligomers can have negative health impacts (FPF reported and here) but large knowledge gaps still exist.
Shi et al. compared the number of studies published on oligomers versus microplastics over the past 20 years on Web of Science and found that 8325 papers addressed microplastics while only 368 addressed oligomers. Considering the continuous development of polymers and “discovery of new oligomers, it is imperative to assess them as distinct polymer-based substances and individual compounds,” they stated.
The authors emphasized that for most oligomers there is limited understanding of their structures and functional properties which is the prerequisite for developing effective analysis methods. Besides expanding this foundational knowledge base, the authors called for database development and research on the environmental behavior of oligomers as well as their absorption, distribution, metabolism, and excretion in the human body to understand their toxicity.
Oligomers are one type of many non-intentionally added substances (NIAS) that are present in plastics, and other types of food contact materials (FCMs). They are composed of two to 40 repeating monomer units. Monomers are used in the synthesis of polymeric materials such as plastics. Oligomers can form as a reaction by-product during the manufacture of the polymeric material or when polymers degrade.
Scientists in Switzerland, including from the Food Packaging Forum (FPF), collected exposure and hazard information for 34 oligomers that have been found to migrate from PET FCMs (FPF reported) and found that most of them have not been tested for their safety (FPF reported). In addition, assumptions made on the toxicity of oligomers are not supported by scientific evidence, such as the assumption that oligomers degrade into monomers and therefore do not require dedicated toxicological assessment. FPF’s FCCmigex database includes evidence from over 40 studies on all types of oligomers migrating from different plastic polymers, silicones, and can coatings. Hazard data on oligomers on the other hand is very scarce.
Reference
Shi, C. et al. (2023). “Oligomers from the synthetic polymers: Another potential iceberg of new pollutants” Environment & Health. DOI: 10.1021/envhealth.3c00086
