Qualitative and quantitative analysis of microplastics and nanoplastics in healthy human central nervous system and its blood-brain barrier transmission efficiency-A pilot study

Microplastics (MPs) and nanoplastics (NPs) have become critical anthropogenic pollutants of the ecological environment. Accurate data concerning MPs/NPs in the healthy human central nervous system (CNS) are still lacking. This study aims to qualitatively and quantitatively measure MPs/NPs in healthy human CNS and investigate their blood-brain barrier (BBB) transmission efficiency. Synchronous plasma and cerebrospinal fluid (CSF) samples of healthy subjects and postmortem brains without brain disease were collected in this study. Pyrolysis gas chromatography-mass spectrometry was used to quantify 11 types of common MPs/NPs, and laser direct infrared (LDIR) imaging spectroscopy was employed to identify polymer particles. Polyethene (PE) and polyvinyl chloride (PVC) were the main components of MPs/NPs in human plasma and CNS. The concentrations of PE and PVC in the brain were significantly higher than those in plasma and CSF. The BBB transmission efficiencies of polystyrene (PS), PVC, and PE that cross the BBB into the CSF were about 84.08 %, 100.94 %, and 62.86 %. The ratios of different types of MPs detected using LDIR varied among plasma, CSF, and brain tissue. In contrast, the physical characteristics of MPs in plasma and the CNS are similar. This work highlights that PVC, PS, and PE can effectively cross the BBB and enter the CSF in healthy individuals. PE and PVC are the most prevalent MPs/NPs in human plasma and the CNS. Therefore, it is important to consider the neurotoxic effects of high concentrations of PE and PVC on the human CNS in future research.