Diesel exhaust particulate emissions and in vitro toxicity from Euro 3 and Euro 6 vehicles.

Incomplete combustion processes in diesel engines produce particulate matter (PM) that significantly contributes to air pollution. Currently, there remains a knowledge gap in relation to the physical and chemical characteristics and also the biological reactivity of the PM emitted from old- and new-generation diesel vehicles. In this study, the emissions from a Euro 3 diesel vehicle were compared to those from a Euro 6 car during the regeneration of a diesel particulate filter (DPF). Different driving cycles were used to collect two types of diesel exhaust particles (DEPs). The particle size distribution was monitored using an engine exhaust particle sizer spectrometer and an electrical low-pressure impactor. Although the Euro 6 vehicle emitted particulates only during DPF regeneration that primarily occurs for a few minutes at high speeds, such emissions are characterized by a higher number of ultrafine particles (<0.1 µm) compared to those from the Euro 3 diesel vehicle. The emitted particles possess different characteristics. For example, Euro 6 DEPs exhibit a lower PAH content than do Euro 3 samples; however, they are enriched in metals that were poorly detected or undetected in Euro 3 emissions. The biological effects of the two DEPs were investigated in human bronchial BEAS-2B cells exposed to 50 µg/mL of PM (corresponding to 5.2 µg/cm2), and the results revealed that Euro 3 DEPs activated the typical inflammatory and pro-carcinogenic pathways induced by combustion-derived particles, while Euro 6 DEPs were less effective in regard to activating such biological responses. Although further investigations are required, it is evident that the different in vitro effects elicited by Euro 3 and Euro 6 DEPs can be correlated with the variable chemical compositions (metals and PAHs) of the emitted particles that play a pivotal role in the inflammatory and carcinogenic potential of airborne PM.

In vitro pulmonary and vascular effects induced by different diesel exhaust particles.

Diesel exhaust particles (DEP) are responsible for both respiratory and cardiovascular effects. However many questions are still unravelled and the mechanisms behind the health effects induced by the exposure to ultrafine particles (UFP) need further investigations. Furthermore, different emission sources can lead to diverse biological responses. In this perspective, here we have compared the effects of three DEPs, two standard reference materials (SRM 1650b and 2975) and one DEP directly sampled from a EuroIV vehicle without Diesel Particulate Filter (DPF). For the biological investigations, different in vitro lung models involving both epithelial and vascular endothelial cells, were used. Cell viability, oxidative stress, inflammation, DNA damage and endothelial activation markers were investigated at sub-cytotoxic DEP doses. The data obtained have shown that only DEP EuroIV, which had the major content of polycyclic aromatic hydrocarbons (PAHs) and metals, was able to induce oxidative stress, inflammation and consequent endothelial activation, as demonstrated by the expression of adhesion molecules (ICAM-1 and VCAM-1) and the release of inflammatory markers (IL-8) from endothelial cells. Standard reference materials were not effective under our experimental conditions. These data suggest that oxidative stress, endothelial activation and systemic inflammatory cytokines release are crucial events after DEP exposure and that the source of DEP emission, responsible of the particle chemical fingerprint, may have a key role in the resulting adverse biological outcomes.