In an article published on February 23, 2022, in the peer-reviewed journal Science of the Total Environment, Javier López-Vázquez from Universidade de Santiago de Compostela, and co-authors evaluated whether bisphenol A (BPA) and phthalate esters (PAEs) present in microplastics become bioaccessible under simulated physiologically relevant digestion conditions.
For their analysis, López-Vázquez et al. used low-density polyethylene (LDPE) and polyvinyl chloride (PVC) particles with average sizes of 110 µm and 140 µm, respectively, that had eight PAEs and BPA (only in LDPE) added in certified concentrations of either 30,000 µg/g or 3000 µg/g depending on the substance. To simulate the human digestion process, they applied physically relevant extraction conditions that mimic the different digestive fluids of the gastric and small intestine compartments. Subsequently, the scientists measured the leached compounds in the respective gut fluid using gas chromatography-mass spectrometry (GC-MS) and determined the bioaccessible and non-bioacessible fraction of the compounds in microplastics. The bioaccessible fraction is “the maximum amount of compound amenable to be bioavailable and reach the systemic circulation.” They also compared fed and fasted states, PAEs of different polarities, as well as microplastic types with different particle sizes, surface properties, and structural rigidity and how these may influence the release of the target compounds.
The scientists found that “the oral bioaccessibility of PAEs and BPA in the gastric compartment usually accounts for more than 65% of overall bioaccessibility and increases significantly for those compounds with log Kow < 4.0”, meaning those with higher polarity. Dimethyl phthalate (DMP; CAS 131-11-3), diethyl phthalate (DEP; CAS 84-66-2), and BPA leached at the highest levels. However, DMP and DEP were partially hydrolyzed to phthalate monoesters under gastric conditions. Bioaccessibility was observed to be higher under fed- compared to fasted-state gastrointestinal extraction conditions. The authors further reported a larger release of PAEs and BPA from LDPE than PVC, which they attributed to the diverging material characteristics. For instance, PVC’s higher surface polarity may have favored the adherence of polar additives while LDPE’s larger surface area contacting the body fluids may have enhanced additive release.
López-Vázquez and co-authors also calculated potential human health risk of PAEs and BPA via microplastics ingestions by using the microplastic mass ingested daily on average, the assumption that plastics contain 0.1-5% phthalates and by comparing the results against the human safe reference values e.g., based on the oral reference doses (RfDs) provided by the US Environmental Protection Agency (EPA). The scientists found that DMP, di-n-butyl phthalate (DnBP; CAS 84-74-2), and BPA at levels of 0.3% (w/w) of the microplastics “may pose severe risks after oral uptake in contrast to the more hydrophobic congeners for which concentrations above 3% (w/w), except for diethylhexyl phthalate, would be tolerated.” They concluded that “the human uptake of primary microplastics might pose severe health risks” because of the leachability of some endocrine-disrupting additives under gastrointestinal digestion conditions, especially the most polar ones such as DMP, DnBP and BPA.
López-Vázquez, J. et al (2022). “Mimicking human ingestion of microplastics: Oral bioaccessibility tests of bisphenol A and phthalate esters under fed and fasted states.” Science of the Total Environment. DOI: 10.1016/j.scitotenv.2022.154027
This article was originally published by Lisa Zimmermann at the Food Packaging Forum.