Riassunto

Background One of the major areas for increasing the use of renewable energy is in traffic fuels e.g. bio-basedfuels in diesel engines especially in commuter traffic. Exhaust emissions from fossil diesel fuelled engines are known to cause adverse effects on human health, but there is very limited information available on how the new renewablefuels may change the harmfulness of the emissions, especially particles (PM). We evaluated the PM emissions from a heavy-duty EURO IV diesel engine powered by three different fuels; the toxicological properties of the emitted PM were investigated. Conventional diesel fuel (EN590) and two biodiesels were used - rapeseed methyl ester (RME, EN14214) and hydrotreated vegetable oil (HVO) either as such or as 30% blends with EN590. EN590 and 100% HVO were also operated with or without an oxidative catalyst (DOC + POC). A bus powered by compressed natural gas(CNG) was included for comparison with the liquid fuels. However, the results from CNG powered bus cannot be directly compared to the other situations in this study.

Results High volume PM samples were collected on PTFE filters from a constant volume dilution tunnel. The PM mass emission with HVO was smaller and with RME larger than that with EN590, but both biofuels produced lower PAH contents in emission PM. The DOC + POC catalyst greatly reduced the PM emission and PAH content in PM with both HVO and EN590. Dose-dependent TNFα and MIP-2 responses to all PM samples were mostly at the low or moderate level after 24-hour exposure in a mouse macrophage cell line RAW 264.7. Emission PM from situations with the smallest mass emissions (HVO + cat and CNG) displayed the strongest potency in MIP-2 production. The catalyst slightly decreased the PM-induced TNFα responses and somewhat increased the MIP-2 responses with HVO fuel. Emission PM with EN590 and with 30% HVO blended in EN590 induced the strongest genotoxic responses, which were significantly greater than those with EN590 + cat or 100% HVO. The emission PM sample from the CNG bus possessed the weakest genotoxic potency but had the strongest oxidative potency of all the fuel and catalyst combinations. The use of 100% HVO fuel had slightly weaker and 100% RME somewhat strongeremission PM induced ROS production, when compared to EN590.

Conclusions The harmfulness of the exhaust emissions from vehicle engines cannot be determined merely on basis of the emitted PM mass. The study conditions and the engine type significantly affect the toxicity of the emittedparticles. The selected fuels and DOC + POC catalyst affected the PM emission from the heavy EURO IV engine both qualitative and quantitative ways, which influenced their toxicological characteristics. The plain HVO fuel performed very well in emission reduction and in lowering the overall toxicity of emitted PM, but the 30% blend of HVO in EN590 was no better in this respect than the plain EN590. The HVO with a DOC + POC catalyst in the EURO IV engine, performed best with regard to changes in exhaust emissions. However some of the toxicological parameters were significantly increased even with these low emissions.

Commento

L’articolo, frutto degli studi coordinati di 4 gruppi di ricerca finlandesi, è stato recentemente pubblicato su una delle più affermate riviste internazionali di tossicologia industriale e ci introduce un argomento di grande attualità e applicabilità nel settore sia professionale che civile.

Dopo una breve introduzione sui nuovi combustibili quali biodisel e metano la ricerca passa ad analizzarne in maniera approfondita le caratteristiche tramite test su un motore diesel. Le analisi vengono incentrate sulle caratteristiche chimiche delle emissioni di scarico e i risultati sono comparati con le risposte tossiche che queste sostanze sono in grado di indurre.

La ricerca dimostra ampiamente che la tipologia di emissioni e la loro tossicità dipendono significativamente oltre che dal tipo di carburante utilizzato anche dal tipo di motore e dalla sua manutenzione.

Interessanti i risultati degli effetti di questi carburanti sul danno citotossico, genotossico e sulla produzione cellulare di mediatori dell’infiammazione, che permangono comunque elevati sia a basse che ad alte dosi di esposizione e indipendentemente dal combustibile utilizzato.

Si sottolinea che, in letteratura, questi parametri cellulari rappresentano i meccanismi attraverso i quali si ritiene che l'inquinamento atmosferico possa indurre o aggravare malattie respiratorie e cardiovascolari.

Keywords

Biodiesel, Compressed natural gas, Emissions, Hydrotreated vegetable oil, In vitro toxicology, Particulate matter

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