In an article published on May 11, 2023, in the journal Environmental Pollution, Ruize Zhou from China Agricultural University, Beijing, China, and co-authors, assessed the presence of organophosphite antioxidants (OPAs) and organophosphate esters (OPEs) in plastic and paper single-use food packaging and their migration into food simulants.
OPAs are widely used as antioxidants, and OPEs substitute brominated flame retardants and may also act as plasticizers. OPE exposure has been linked to neurotoxicity and endocrine disruption (FPF reported).
Zhou and co-authors analyzed 123 plastic and 189 paper products, such as straws, cups, and food trays available on the Chinese market for four OPAs and 23 OPEs. To study the substances’ occurrence in the products they extracted them with acetonitrile for 60 min via ultrasound, and to study their migration they incubated them for 2 h in three types of food simulants (4% acetic acid, 10% ethanol, hexane) at 70 °C. Targeted chemical analysis was performed by high-performance liquid chromatography coupled with electrospray triple quadrupole mass spectrometry.
The scientists detected at least one OPA in 94% of the samples and all four targeted OPAs in at least one. The total mean concentration of OPAs was 1966 ng/g packaging. Out of the 24 OPEs, they detected 19 with a total mean concentration of 189 ng/g. Comparing plastic and paper packaging, the authors reported that “OPAs and OPEs were present at higher concentrations in the plastic packaging.” This confirms the findings of an article published in 2022 which compared OPE presence in plastic and paper food contact materials in Southern China (FPF reported).
Concerning migration, Zhou et al. found all four OPAs and 17 OPEs to migrate into food simulants with OPA migration efficiency being higher. Generally, migration levels were highest in hexane that simulates fatty foods. Therefore, the authors concluded that OPAs and OPEs “are likely to migrate into fatty foods.” Among the tested compounds, the levels of the antioxidant Irgafos 168 (CAS 31570-04-4) and its oxidation product were highest in the extracts as well as in hexane food simulant. Based on the migration levels, the researchers estimated their dietary intake and the potential risk of selected substances. They reported that “the dietary risks of OPAs and OPEs that migrated from single-use food packaging were low.” However, they also pointed out that further analysis of Irgafos 168 and its oxidation product is needed to clarify their toxicity and that reference doses for many of the analyzed compounds are not yet available.
The work of Zhou and co-authors confirms previous assumptions from another group of scientists from Beijing. They had found that OPE levels in packaged food were higher than those in fresh foods, which led them to hypothesize that food packaging may be a source of OPEs (FPF reported).
Ruifeng Bi and co-authors from the University of Science and Technology, Nanjing, China, also looked at the occurrence and migration of OPEs, but they focused on plastic food packaging. In their article published on June 2, 2023, in the journal Environment International, the authors described that they evaluated 106 samples from the Nanjing region by a combined target, suspect, and nontarget screening strategy for OPEs. To do so, they performed a total extraction as well as migration experiments with 10% and 20% ethanol, 3% acetic acid, and isooctane at 40°C for 10 days. Subsequently, they applied the received solutions to ultrahigh-performance liquid chromatography–high-resolution mass spectrometry (UHPLC–HRMS).
The researchers tentatively identified 42 OPEs “of which seven were reported for the first time.” Out of the 42 OPEs, 26 were detected in at least one of the four food simulants demonstrating their migration into foodstuffs by which they become available for human ingestion. Especially in isooctane, a wide variety of OPEs were present in higher concentrations illustrating that the chemicals are prone to transfer into fatty foods (and confirming the findings of Zhou et al.). As already previously suggested, Bi and colleagues’ results led them to conclude that the oxidation of OPAs could be a source of OPEs in plastics.
Furthermore, the authors concluded that their study “suggests that the number of OPEs that humans are exposed to could be much larger than the number of OPEs currently recognized.” As a way forward to get a more comprehensive understanding of OPEs in a wide variety of samples, they recommend their applied method.
The Food Packaging Forum’s (FPF’s) Fact Bite on OPEs illustrates the amount of OPEs that have been detected together in all types of food contact materials until the time of publishing in October 2022.
References
Bi, R. et al. (2023). “Organophosphate esters (OPEs) in plastic food packaging: non-target recognition, and migration behavior assessment. ” Environment International. DOI: 10.1016/j.envint.2023.108010
Zhou, R. et al. (2023). “Occurrence and migration of organophosphite and organophosphate esters into food simulants from single-use food packaging in China. ” Environmental Pollution. DOI: 10.1016/j.envpol.2023.121782
