Environmental weathering induces procoagulant structural changes in microplastics

Introduction Microplastic particles (MPs), formed from wear or degradation of larger polymers, are omnipresent in the environment. MPs are taken up by biota and accumulate in food chains. Human uptake is estimated at 40.000 to 50.000 MPs per person yearly through food and inhalation. These particles mainly remain on the luminal side of intestinal system and airways, excreting through feces and mucociliary clearance. However, 2-3%, especially sub-micrometer particles, can pass through mucous membranes and have been observed in circulation and human organs. Associations exist with conditions like atherosclerosis or liver cirrhosis, with undefined causal relationships. Biological response testing often uses spherical polystyrene beads, not addressing complex shape and chemistry of environmental microplastics. This study analyzed blood activation pathways' response to irregularly shaped and weathered NPs of various commodity polymers [ 1 ]. Method Ten polymers were cryomilled to about 25 µm and exposed to weathering cycles with alternating temperature and humidity under UV radiation, simulating about 1.5 years. Particles were characterized for size, zeta potential, and changes in Raman- and Fourier-Transform Infrared Spectroscopy (FTIR). Coagulation and inflammation activation was probed in whole blood at particle concentrations of 4– 100 µg/ml. Results Polymers with aromatic groups (polystyrene (PS), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET), and plasticized polyvinyl chloride (PVC)) degraded forming carboxylic acid groups, shown by spectroscopic methods and zeta potential measurements. These structural changes were associated with pronounced coagulant response (prothrombin F1+2 fragment formation and platelet activation) to weathered polymers versus pristine polymers. A dose dependency of particle count and weathering intensity was observed. Reported particle concentrations in circulation tend to activate blood coagulation. For PET, biological effects exceeded changes in FTIR and Raman spectra. Fig. 1 Coagulation Coagulation activation by weathered polystyrene microplastics. Conclusion Results show microplastic particles entering blood circulation are not inert, and environmental pre-exposure enhances their reactivity. Publication History Article published online: 17 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany