Accumulation of micro- and nanoplastic particles in mammalian tissues: a translational study

ABSTRACT The utilization and subsequent disposal of plastics and plastic based products continues to rise exponentially. Current pervasiveness of micro- and nanoplastic particles (MNPs) in the environment results in significant exposure to human populations via inhalation and ingestion. MNP contaminants have been discovered in the air we breathe, the food we eat, and in 81% of tap water samples tested around the globe. Samples taken from human subjects, including our preliminary data, identify MNP deposition in tissues (e.g., lung, heart, blood, thrombi, and placenta) and excreta (e.g., semen, breast milk, bronchoalveolar lavage fluid, and feces). These findings indicate that not only are humans exposed to MNP, but these pervasive part icles bypass protective anatomical barriers, accumulating within systemic tissues. Animal models reproduce these findings in a laboratory environment, resulting in MNP accumulation in systemic tissues and associations with pathologic changes. MNPs have also been identified in the placenta and fetal organs of rodent models after pulmonary or gastric exposure. Our preliminary data suggest maternal transfer of MNP to the offspring, with MNP deposition remaining in offspring tissues for at least 2 weeks after birth, 16 days after the last maternal exposure. Despite the extent of world-wide MNP exposure, the quantified concentration of MNP within systemic tissues is unknown. Analyses have been conducted using microscopic fixed tissue analyses or chemical extraction- based techniques. Unfortunately, these methodologies cannot currently be adequately compared. Currently, there is no “gold standard” methodology that meets all requirements for identifying MNPs in biological tissues. Furthermore, the role of sex, age, and ethnicity in the accumulation of MNPs in human tissues has not yet been explored. This project will investigate inter-tissue MNP accumulation in rodent models of MNP exposure via intratracheal installation or gavage, using overlapping state-of-the-art detection methodologies to quantify and confirm MNP deposition. We will then compare these concentrations to those obtained from human autopsy samples. Innovative statistical methods for integrating calibration samples with results from different analytical methods will be employed to correct for measure errors. These translational studies will provide further rationale to relate human and laboratory MNP translocation and deposition studies. To fully assess MNP toxicities, we must first understand the measured mass deposition based on known exposure doses. Successful completion of these studies will provide the foundational physiological doses to advise fut ure in vitro and ex vivo MNP toxicological studies.