On March 5, 2024, Sarah Stevens and Molly McPartland from the Norwegian University of Science and Technology published two studies investigating chemical extractions from plastic food contact articles and how those chemical mixtures affect parts of the hormone system, specifically the proteins responsible for direct cell communication.  

Both studies sampled from the same 36 food contact articles purchased in the US, UK, South Korea, Germany, and Norway and made of common polymers including high- and low-density polyethylene (HDPE, LDPE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polyurethane (PUR), and polyvinyl chloride (PVC).  

Stevens led the characterizing the chemical make-up of the articles which varied considerably between polymer types and even individual samples. The samples were placed in methanol which can extract chemicals from the plastic into solution. When dehydrated, the resulting chemical mixture is placed in a mass spectrometer to try and distinguish the number of chemicals present. The results from the mass spec are called a chemical feature. Several “features” may represent a single chemical, but the measurement still allows for comparisons of chemical complexity. The number of chemical features ranged from 37 in one HDPE container to 9,936 from a sample of PVC cling film.  

When samples were grouped by polymer, the number of chemical features per polymer was distinctly different, “with a gradient ranging from HDPE (616 features), PET (1320), PS (2284), PP (2711), LDPE (5495), and PVC (12,683) to PUR (13,004).”  PVC and PUR “require more additives in their production compared to other polymers” (FPF reported). Non-targeted studies, like this one, can help to discover the broad range of chemicals intentionally and non-intentionally used in plastics production.   

Extracts from all the articles were tested for endocrine-disruption and metabolism-disruption, with 33 out of 36 interfering with at least one receptor. The more chemicals in the polymer, the greater the effect, “chemicals present in food packaging made of PVC, PUR, and LDPE induced most effects, whereas the extracts of HDPE, PET, and PP were less active.” 

McPartland, et al. further individual food contact chemicals as well as the chemical mixtures extracted from PVC and PU to discover any effects on G protein-coupled receptors (GPCRs). GPCRs are a critical part of cell communication. When a message (which can be a hormone, a neurotransmitter, or something else) arrives at a cell, it attaches to a GPCR on the cell surface which will then send a signal inside the cell, telling it what to do. There are thousands of different GPCRs.  

The authors found that both PVC and PUR extracts can activate the tested GPCRs. This finding “reinforces existing evidence that PUR and PVC plastics are chemically problematic and should be substituted with safer alternatives.” 

Both studies found that polymer complexity, and thus the mixtures of chemicals that come out, increased biological activity. McPartland et al. conclude, “[a] fundamental reconsideration and redesign of the way we make and use plastics are imperative if plastics are to be considered safe. By adopting strategies that reduce the number and hazard of chemicals used in plastics, we can minimize exposure and reduce their contribution to the burden of disease.” 

FPF’s Chief Scientific Officer, Jane Muncke, together with 20 other scientists recently published a vision for safer food contact materials that discusses some of the same concerns (FPF reported). Muncke et al. developed the six clusters of disease concept, which highlights prevalent and increasingly concerning non-communicable diseases linked to chemical exposures: cancers, cardiovascular diseases, as well as reproductive, brain-related, immunological, and metabolic disorders. The vision proposes a novel approach for testing Food contact chemicals that includes assessing the health impacts of individual food contact chemicals and real-life mixtures with respect to the most prevalent non-communicable diseases in the human population.   

References 

McPartland, M., et al. (2024). “.” Environmental Science and Technology. DOI: 10.1021/acs.est.3c08392 

Stevens, S., et al. (2024). “.” Environmental Science and Technology. DOI: 10.1021/acs.est.3c08250 

Read more 

Katherine Bourzac (March 19, 2024). “.” Chemical and Engineering News.