Article

Hazard and risk assessment of a nanoparticulate cerium oxide-based diesel fuel additive-a case study

Oxonica plc, Yarnton, Kidlington, United Kingdom.
Inhalation Toxicology (Impact Factor: 2.34). 05/2008; 20(6):547-66. DOI: 10.1080/08958370801915309
Source: PubMed

ABSTRACT Envirox is a scientifically and commercially proven diesel fuel combustion catalyst based on nanoparticulate cerium oxide and has been demonstrated to reduce fuel consumption, greenhouse gas emissions (CO(2)), and particulate emissions when added to diesel at levels of 5 mg/L. Studies have confirmed the adverse effects of particulates on respiratory and cardiac health, and while the use of Envirox contributes to a reduction in the particulate content in the air, it is necessary to demonstrate that the addition of Envirox does not alter the intrinsic toxicity of particles emitted in the exhaust. The purpose of this study was to evaluate the safety in use of Envirox by addressing the classical risk paradigm. Hazard assessment has been addressed by examining a range of in vitro cell and cell-free endpoints to assess the toxicity of cerium oxide nanoparticles as well as particulates emitted from engines using Envirox. Exposure assessment has taken data from modeling studies and from airborne monitoring sites in London and Newcastle adjacent to routes where vehicles using Envirox passed. Data have demonstrated that for the exposure levels measured, the estimated internal dose for a referential human in a chronic exposure situation is much lower than the no-observed-effect level (NOEL) in the in vitro toxicity studies. Exposure to nano-size cerium oxide as a result of the addition of Envirox to diesel fuel at the current levels of exposure in ambient air is therefore unlikely to lead to pulmonary oxidative stress and inflammation, which are the precursors for respiratory and cardiac health problems.

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    • "or markers of inflammation and oxidative damage (Fall et al., 2007; Park et al., 2007, 2008a). Additional studies have demonstrated that exposure to CeO 2 nanoparticles increase cell cytotoxicity, oxidative stress, inflammation, apoptosis, and autophagy (Eom and Choi, 2009; Gojova et al., 2009; Hussain et al., 2012; Lin et al., 2006; Park et al., 2008b). "
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    • "While particulate emissions as a whole are found to decrease if CeO 2 is used (by approximately 15%), according to Park et al. (2008a). Emissions in the nanoparticle range are found to increase (Park et al., 2008a). Jung et al. (2005) tested the impact of adding Ce to a medium duty diesel engine, discovering that the number of accumulation mode particles decreased while the number of nucleation mode particles increased; they attributed this to the reduction in the available surface area reducing the scavenging of particle precursors, thereby leading to more homogenous nucleation and reduced coagulation of nucleation mode particles with particles in the accumulation mode (Jung et al., 2005). "
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    • "The exposure concentrations in this study were selected considering the future perspective of environmental build-up with elevating production and disposal of nCeO 2 [34] [35] [36]. The TEM image of the nCeO 2 suspension is shown in Fig. 1A and the size, pH and ␨potential of the nCeO 2 and bCeO 2 suspensions have been provided in Table S1 SD. "
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