SE il motore Euro IV produce un quantitativo minore di particolato genera un maggior effetto infiammatorio a livello cellulare a causa della forma irregolare del particolato prodotto. Gli esperimenti dimostrano che il particolato di provenienza Euro IV è più citotossico e ha un più elevato potenziale infiammatorio rispetto ad un vecchio motore diesel perché la dimensione media delle pm derivate EuroIV è molto inferiore a quella di confronto. Tutte gli aspetti devono essere presi in considerazione nella valutazione del rischio per la salute. I macrofagi esposti a questo particolato dei motori low-emission ha mostrato caratteristiche di necrosi e degenerazione. I risultati implicano che una riduzione del livello delle emissioni di particelle di fuliggine non porta automaticamente ad una riduzione degli effetti tossici per l'uomo se aumenta, contemporaneamente, la struttura e la attività funzionale a causa delle modifiche superficiali di fuliggine e quindi l'accessibilità biologica e il potenziale infiammatorio della fuliggine. Di conseguenza, lo sviluppo di tecnologie di filtraggio deve essere diretta verso l'eliminazione delle polveri ultrasottili che, per unità di massa, presentano un rischio maggiore per la biosfera delle polveri di dimensioni maggiori.

We evaluated, in vitro, the inflammatory and cytotoxic potential of soot particles from current low-emission (Euro IV) diesel engines toward human peripheral blood monocytederived macrophage cells. The result is surprising. At the same mass concentration, soot particles produced under lowemission conditions exhibit a much higher toxic and inflammatory potential than particles from an old diesel engine operating under black smoke conditions. This effect is assigned to the defective surface structure of Euro IV diesel soot, rendering it highly active. Our experiments show that EuroIV soot particles are more cytotoxic and have a higher inflammatory potential than soot particles from an old diesel engine. Various parameters such as surface area, number of particles, and joint length have been examined to interpret or quantify the lung inflammatory response to nanoparticle exposure (5). The results presented in this work may suggest that the particle size is a proper dose metric for nanotoxicity because the mean particle size of EuroIV soot is much smaller than that of BS soot. However, we strengthen that the reported effects are more likely due to the strongly defective structure, the high abundance of chemically reactive structural elements (edges), and the presence of surface functional groups on the EuroIV soot particles that enabled them to be phagocytized more readily by MDMs than the larger BS particles. The expected hydrophilic surface chemistry due to attached OH groups should also be considered. These properties allow facile chemical and morphological contact with hydrophilic biomolecules. The OH and olefinic surface chemistry is a novel property of the EuroIV soot as opposed to the BS soot with its smooth, inert surface and its hydrophobic character. All theses aspects need to be taken into account in future health risk assessment. Low-emission diesel engines emit a comparatively small amount of soot particulate matter. Our study, however, has shown that, by mass, soot nanoparticles produced under low-emission conditions have a higher cytotoxic and inflammatory potential against human peripheral blood monocytederived macrophage cells than particles from an old diesel engine. The macrophages exposed to soot particles of lowemission engines showed characteristic features of necrosis and degeneration. A high apoptotic cell death rate was observed. This effect is assigned to the functionalized defective surface structure of the low-emission diesel engine soot, rendering it highly active. Moreover, the particles size of EuroIV soot is smaller than that of BS soot that tends to aggregate in bigger clusters. This makes the internalization of a higher amount of EuroIV particles possible, leading to more cytotoxic effects and stimulating a more intensive inflammatory reaction, as compared to BS soot. Our findings imply that a reduction of the emission rate of soot particulates does not automatically lead to a reduction of the toxic effects toward humans if, concurrently, the structure and functionality of the soot changes and therefore the biological accessibility and inflammatory potential of the soot increases. Fortunately, the microstructural features that aggravate the health risk also lead to a more effective oxidation of soot particles to CO2, provided suitable filtering techniques are applied (16). Hence, the development of filtering technology must be directed toward the removal of ultrasmall particles that, per unit mass, pose a higher risk to the biosphere than the more conventional forms of largeparticle soot. Cytotoxicity and Inflammatory Potential of Soot Particles of Low-Emission Diesel Engines DANG SHENG SU, ANNALUCIA SERAFINO, JENS-OLIVER MÜLLER, ROLF E. JENTOFT, † ROBERT SCHLÖGL, AND SILVANA FIORITO