Establishing a Microfiber Recovery Rate in Human Lung Tissue

Microplastics (<5 mm) are an increasing concern for environmental and human health, continuously detected in ecosystems worldwide and a variety of human tissues. While health effects remain unclear, experimental studies on microplastic particles have suggested adverse outcomes. Microplastic fibers, which shed from everyday items, are more toxic than particles and twice as prevalent, yet remain understudied. Microplastic studies vary widely and use various extraction techniques, with few validating recovery accuracy. These limited recovery studies primarily examine particles, raising concerns about the true abundance of microfibers. This study establishes baseline recovery rates of polyethylene terephthalate (PET) and polypropylene (PP) microfibers of varying lengths from formalin-fixed human cadaveric lung tissue. Following enzymatic and oxidative digestion, PET microfibers showed a recovery rate of 47%, while 87% of PP microfibers was recovered. Chemical alterations were assessed using laser direct infrared (LDIR) spectroscopy; optical microscopy and scanning electron microscopy (SEM) evaluated physical changes post-digestion. These findings provide insights into microfiber recovery, highlight potential over- and underestimations, and characterize the chemical and physical behavior of fibers within human tissue studies. Establishing accurate recovery methods is essential for advancing microfiber toxicology research and assessing potential health risks.