Temporal Trend in Accumulation of Microplastics in Decedent Human Lungs

Environmental accumulation and human exposure to micro- and nanoplastics (MNPs) are increasing as plastic production rises, yet whether this has been paralleled by greater bioaccumulation in human lungs remains unclear. We conducted a comparative study of paraffin-embedded lung tissues collected post mortem from two series of autopsy cases from the same tertiary care medical center, including individuals who died in 1991 (n = 42) and in 2024 (n = 57). Microplastic abundance, size, and polymer type were assessed using laser-direct infrared (LDIR) imaging. Confirmatory analyses were performed in representative subsets using pyrolysis–gas chromatography/mass spectrometry and scanning electron microscopy. Collagen I staining and CD68 infiltration were evaluated to assess fibrosis and inflammation. MNPs were identified by LDIR in lung samples from 8 of 42 individuals (19%) who died in 1991 and 44 of 57 (77%) who died in 2024. The median MNP burden per gram of tissue (interquartile range) increased from 12.9 particles (11.3–13.7) to 19.9 (15.5–28.2), while mean particle diameter decreased. Polymer composition shifted from polyethylene predominance (51.7%) in 1991 to a more heterogeneous profile in 2024, including polyethylene terephthalate (28.4%), polyvinyl chloride (14.3%), and polystyrene (14.2%), findings corroborated by pyrolysis–gas chromatography/mass spectrometry and scanning electron microscopy. Lung samples containing MNPs showed greater CD68 and collagen I abundance than samples without detectable MNPs. Over the past three decades, MNP contamination of human lung tissue has become markedly more prevalent, compositionally diverse, and characterized by smaller particles, with accompanying histological features consistent with inflammation and fibrosis.