Human bioaccumulation of micro- and nanoplastics is primarily determined by the organs' vascular volume

Recent studies have demonstrated the accumulation of micro- and nanoplastics (MNPs) in human organs, particularly in the brain, at an alarming rate (Campen et al., 2024, doi.org/10.21203/rs.3.rs-4345687/v1). This study examines the phenomenon of bioaccumulation in relation to up to six distinct biological and biomedical parameters pertaining to vascular structure and composition in three organ tissues: the brain cortex, kidney, and liver. As anticipated based on fundamental mechanistic considerations of bioaccumulation (washing rate), the MNP content appears to be proportional to the inverse of the capillary volume fraction ($V_c$), exhibiting no correlation with any other geometric variable, such as capillary diameter or capillary segment length. This finding is consistent with the small size spectra of MNPs in comparison to these dimensions. However, contrary to expectations, no correlation was observed between MNP content and biological composition (lipid, water, or carbohydrate content), while a likely non-causal correlation was observed between MNP content and protein content, which may be simply attributed to the non-linear correlation between protein content and $V_c$. The conclusions that point to a possibly exceedingly large number of MNP particles currently in our brains call for urgent further investigation and the revision of the published data.