In an article published on October 13, 2022, in the Journal of Analytical and Applied Pyrolysis, Fleurine Akoueson from the French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Boulogne-sur-Mer, France, and co-authors present a general analytical method to assess specific organic plastic additives in food packaging. First, the authors selected 56 additives considered relevant according to their literature search, analyzed them by gas chromatography and high-resolution mass spectrometry (GC–HRMS), and used the mass spectra to generate their own plastic additives database. The mass spectra data can be downloaded from Zenodo. Subsequently, they developed a thermodesorption method using pyrolysis/thermaldesorption (Py/TD) coupled to GC-HRMS to detect and identify the selected plastic additives. Finally, they applied the method to two polypropylene (PP) and two polylactic acid (PLA) food packaging samples from two different suppliers. They used 1 mm diameter cylinders cut from the items for the pyrolysis and identified the selected additives using their previously developed database.
Akoueson and co-authors present a high-resolution spectral database including 56 organic plastic additives that function as plasticizers, flame retardants, antioxidants, and UV stabilizers. For each additive the retention time, retention indices, and quantitative and qualitative ion rations are given. With their developed Py/TD-GC-HRMS method they were able to identify 49 of the 56 additives. According to the scientists the method “may be limiting to certain organic plastic additives harder to mobilize using GC” and, therefore, suggest complementing their method with a liquid extraction analysis.
Over the four food packaging samples, they detected ten of the targeted additives including eight plasticizers and two flame retardants. The plasticizers diethyl phthalate (DEP, CAS 84-66-2) and diisobutyl phthalate (DIBP, CAS 84–69–5) as well as the flame retardant tris(2-chloroisopropyl) phosphate (TCPP, CAS 13674–84–5) were detected in all four samples. While in general PP samples generated higher peak signals, bisphenol B (BPB, CAS 77–40–7) and tributyl phosphate (TBP, CAS 115–86–6) were only detected in PLA samples. However, in both material types, the conventional plastic PP and the bio-based and biodegradable PLA, ten additives were detected. This underlines the result of a previously published study showing that bio-based materials neither contain fewer chemicals nor are they less harmful than those contained in conventional plastics (FPF reported).
The authors further concluded that additive content varies between products of the same application and made of the same polymer type, verifying previous findings (FPF reported and here). Consequently, each product would need to be assessed for its composition and toxicity. The researchers emphasized that their study would outline the “complexity of identifying and generalizing the additive content of plastic materials.”
Another article with Akoueson as first author was published on October 8, 2022, in the journal Science of the Total Environment. Once again, two PP and two PLA food packaging samples were analyzed but this time not only for their chemical composition but also their in vitro toxicity.
The scientists extracted the products for 24 h in methanol as well as leached them for 24 h and 5 days in filtered natural seawater. Specific plastic additives in extracts and leachates were identified and quantified by applying the samples to targeted GC-MS (57 organic plastic additives were targeted). The leachates were also assessed for toxicity using the Microtox assay measuring baseline toxicity and studying pacific oyster Crassostrea gigas fertilization success and embryo-larval development (ISO 17244:2015 assay).
Akoueson et al. detected a total of 21 substances in extracts with the PLA samples containing 17 additives and the PP samples eight or nine. Organic plastic additives were also detected in all leachate samples with a higher number in 5-day leachates (eight or ten/sample) compared to 24 h leachates (eight to ten/sample). Overall, fewer substances were detected in the leachates compared to the extracts. The authors pointed out “differences in the number and concentration of additives between polymers and suppliers” which indicates “that the chemical signature cannot be generalized to a polymer and is rather product dependent.”
In the in vitro bioassays none of the leachates induced acute toxicity at (high) environmental concentrations. However, the authors proposed to also perform tests with other organisms and environmental parameters to gain an “additional understanding of the toxicology associated with the leachates.” They concluded that looking at the chemical composition is not sufficient to predict the toxicity of a product but bioassays can serve as a complementary tool to risk assess food packaging.
References
Akoueson, F. et al. (2022). “Identification of plastic additives: Py/TD-GC-HRMS method development and application on food containers.” Journal of Analytical and Applied Pyrolysis. DOI: 10.1016/j.jaap.2022.105745
Akoueson, F. et al. (2022). “Additives in polypropylene and polylactic acid food packaging: Chemical analysis and bioassays provide complementary tools for risk assessment.” Science of the Total Environment. DOI: 10.1016/j.scitotenv.2022.159318
