The efficiency of EURO 6d car particulate filters is compromised by atmospheric aging: In vitro toxicity of gasoline car exhaust

Tailpipe emissions from road traffic contribute substantially to the burden of fine inhalable particulate matter (PM_2.5) and deteriorate air quality. Exhaust emission standards, forcing improvements in combustion and exhaust after-treatment technology, considerably decreases combustion-related PM_2.5 emitted by modern cars. A549 cancerous alveolar and BEAS-2B normal bronchial epithelial cells were exposed at the air-liquid interface to the total aerosol or gas phase of either fresh or photochemically aged tailpipe emissions from a gasoline EURO 6d car equipped with a gasoline particulate filter. Diluted fresh emissions contained particle number concentrations comparable to low ambient air levels and induced no detectable cytotoxicity. Photochemical aging led to the formation of secondary aerosols and caused significant cytotoxicity. While the aged aerosol induced significant DNA damage, oxidative stress was more associated with volatile secondary species. Our results call for the consideration of the exhaust emission atmospheric transformation processes in future emission standards toward health effect-driven emission regulations.