The Impact of a Nano-Ceria Diesel Additive on Physicochemical and Toxicological Properties of Diesel Exhaust Particles

摘要

Fuel additives incorporating nanosized ceria have been increasingly used in diesel engines as combustion promoters. However, few studies have assessed the impact of these nanotechnology-based additives on pollutant emissions and toxicity. In the Risk Assessment of Manufactured Nano-materials Used in Consumer products (RAMNUC) project, we systematically compare emission rates of particulate and gaseous pollutants from a single-cylinder, four-cycle diesel engine using fuel mixes containing nano-ceria of varying concentrations. The test fuels were made by adding different amounts of a commercial fuel additive Envirox™ into an ultra-low-sulfur diesel fuel at 0 (base fuel), 0.1, 1, and 10-fold the manufacturer-recommended concentration. Our findings on the impact of Envirox on emission rates of particulate and gaseous pollutants have been published, suggesting that risk assessment need not only to consider particle mass reductions and particle number increases but also potential changes in particle toxicity. In this presentation, we report new results on the impact of Envirox on physicochemical and toxicological properties of diesel exhaust particles. We found that increasing fuel ceria concentrations led to decreases in the size of emitted particles, decreases in the fraction of elemental carbon, and increases in the fraction of organic carbon. However, the addition of ceria did not show a clear change pattern in particle electrical charge (zeta potential). Preliminary results from in vitro (in pulmonary cells) and in vivo (mice instillation) experiments snowed decreased pro-inflammatory responses to particles emitted from diesel containing Envirox at the 10-fold recommended concentration. More complete and comprehensive data will be available for presentation concerning the impact of Envirox on cytotoxicity, antibacterial immunity, cellular and tissue inflammation, and lung mechanical function.