127 Photochemical Aging Increases Toxicity of EURO 6 Gasoline Car Exhaust in Lung Epithelial Cells at the Air-Liquid Interface

Abstract

Traffic emissions contribute to ambient air pollution, posing a threat to human health. The installation of stricter exhaust emission standards and particle filters led to a significant decrease of particulate matter emissions by cars. However, little is known about how atmospheric transformation changes the toxicity of exhaust emissions from modern cars. We evaluated the physico-chemical properties and toxicological effects of fresh and photochemically aged aerosols from a gasoline EURO 6 car equipped with a particulate filter. A549 alveolar and BEAS-2B bronchial epithelial cells were exposed for 4h to aerosols at the air-liquid interface. The toxicity was determined by measuring cell viability, cytotoxicity, oxidative stress, primary and oxidative DNA damage. Particle number concentration (PN) in fresh aerosol was negligible while photochemical aging with an equivalent photochemical age of 5 days led to PN of 6.6´106 cm-3 with a mean size of 35 nm. Secondary aerosol particles predominantly consisted of organic matter, nitrate, and ammonium, which were formed by the oxidative gas-to-particle conversion of volatile organic compounds (VOCs), particularly aromatic hydrocarbons, and NOx in the exhaust. Significant levels of oxygenated VOCs were also detected. Fresh aerosol caused no cytotoxicity in lung cells, but led to slight DNA damage whereas aged aerosol caused toxicity to both cell models, oxidative stress and oxidative DNA damage mainly due to the gas phase. Our results indicate a significant toxification of the emissions by photochemical aging. This calls for considering atmospheric processes in future exhaust emission standards for the transport sector toward health effect-driven emission regulations.