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Short-term exposure to traffic-related micro- and nanoplastics associated with immature granulocyte mobilization and tissue repair markers.
Summary
Researchers had 23 healthy adults spend four hours at three outdoor sites with differing traffic levels and found that short-term exposure to traffic-related micro- and nanoplastics (primarily tire wear) was associated with subtle immune changes the next morning, including markers suggesting mobilization of immature white blood cells, pointing to delayed resolution-phase rather than acute inflammatory responses.
Traffic-related micro- and nanoplastics (MNPs) from tyre wear are among the largest sources of unintentionally released plastic particles in the air. However, their potential health effects remain understudied. We investigated whether short-term exposure to traffic-related MNPs is associated with systemic immunological changes in healthy adults. Three outdoor sites (stop-and-go high-traffic, highway, urban park) were visited with 23 healthy volunteers for 4-h. Venous blood samples were collected immediately before and after, and the following morning. Plasma cytokine/chemokine levels were determined using an OLINK® Target-48 panel. Expression of maturation marker CD16 and activation markers CD10, CD62L, and CD11b were assessed on granulocytes, and monocytes, using flow-cytometry. On-site traffic-related MNPs within particulate matter with an aerodynamic diameter <10 μm (PM) were collected using a high-volume sampler, and analyzed using pyrolysis-gas chromatography-mass spectrometry. PM, ultrafine particles, black carbon, trace metals, and polycyclic aromatic hydrocarbons were also monitored. Linear mixed models were used to determine associations from baseline to post-exposures, adjusting for meteorological covariates. Immediately post-exposure, traffic-related MNPs were positively associated with small increases in EGF, IL7, and MMP1 (5.2-16.9%), though not significant after multiple testing correction. The following morning we found significant false discovery rate (FDR)-corrected downregulation of CXCL9 and IL18 (2.3-8.5%), and negative associations with CD16 (-5%) on granulocytes, and CD11b on monocytes (-25.5%). Short-term exposure to the traffic-related particle mixture, including tyre-wear MNPs, was associated with changes in circulatory cytokines/chemokines, and patterns that might indicate mobilization of immature granulocytes. The delayed associations with cytokine decreases and reduced activation marker expressions could suggests resolution-phase activities, rather than inflammatory responses.