Quantitative tracking of the transformation of micro- and nanoplastics in simulated human body fluid

Micro- and nanoplastics (MNPs) are widespread in the environment and food, posing ingestion risks through various pathways. However, their transformation in human body fluids (SBFs), especially the formation of secondary nanoparticles (NPs), is not well understood due to inadequate quantification methods. This study proposed a robust method for quantifying eight common MNPs using pressurized liquid extraction (PLE) for pretreatment and pyrolysis gas chromatography-quadrupole time-of-flight mass spectrometry (Py-GC-QTOF-MS) for analysis. The method demonstrated high performance with recoveries over 90.9 % and a detection limit down to 0.01 mg/L. Most sample matrices did not interfere with MNP quantification, though poly(3-hydroxybutyrate) and polyethylene required background noise deduction. High recoveries in SBFs (>79.0 %) further confirmed the practicality of this method. Utilizing this method, it was found that only a few MPs were able to release secondary NPs within the simulated digestive system, with the maximum proportion of released NPs less than 2.1 %, suggesting a negligible health risk from secondary NPs. Besides, ester structure was found not to promote the formation of secondary NPs but did affect surface morphology and functional groups to a certain extent. We anticipate that this work will open opportunities for the health risk assessment of MNPs.