Plastic burning particulate matter as a source of environmentally persistent free radicals and reactive oxygen and chlorine species

Burning plastic waste releases massive amounts of atmospheric particulate matter (PM), but its chemical composition and health-related properties are largely unelucidated. Here we characterize chemical composition of PM generated from burning common types of plastics and quantify reactive oxygen/chlorine species and PM oxidative potential (OP). We find that plastic burning PM contains high levels of environmentally persistent free radicals (EPFRs), transition metals, and polycyclic aromatic hydrocarbons. In the aqueous phase, PM generates hydrogen peroxide, •OH radicals, and carbon-centered organic radicals, exhibiting high levels of OP as characterized by dithiothreitol (DTT) and OH assays. Remarkably, plastic burning PM is associated with high concentrations of hypochlorous acid. Kinetic model simulations demonstrate that the PM respiratory deposition leads to •OH formation via complex redox reactions among its constituents and antioxidants in lung lining fluid. Our study highlights significant atmospheric and health implications for unregulated plastic burning, particularly common in many areas of developing countries.