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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    ABSTRACT: Diesel exhaust (DE) exposure induces adverse cardiopulmonary effects. Cerium oxide nanoparticles added to diesel fuel (DECe) increases fuel burning efficiency but leads to altered emission characteristics and potentially altered health effects. Here we evaluated whether DECe results in greater adverse pulmonary effects compared to DE. Male Sprague-Dawley rats were exposed to filtered air, DE, or DECe for 5 hrs/day for 2 days. N-acetyl glucosaminidase activity was increased in bronchial alveolar lavage fluid (BALF) of rats exposed to DECe but not DE. There were also marginal but insignificant increases in several other lung injury biomarkers in both exposure groups (DECe>DE for all). To further characterize DECe toxicity, rats in a second study were exposed to filtered air or DECe for 5 hrs/day for 2 days or 4 weeks. Tissue analysis indicated a concentration- and time-dependent accumulation of lung and liver cerium followed by a delayed clearance. The gas-phase and high concentration of DECe increased lung inflammation at the 2 day time point, indicating that gas-phase components, in addition to particles, contribute to pulmonary toxicity. This effect was reduced at 4 weeks except for a sustained increase in BALF γ-glutamyl transferase activity. Histopathology and TEM revealed increased alveolar septa thickness due to edema and increased numbers of pigmented macrophages after DECe exposure. Collectively, these findings indicate that DECe induces more adverse pulmonary effects on a mass basis than DE. In addition, lung accumulation of cerium, systemic translocation to the liver, and delayed clearance are added concerns to existing health effects of DECe.
    Toxicological Sciences 09/2014; 142(2). DOI:10.1093/toxsci/kfu187 · 4.48 Impact Factor
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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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    ABSTRACT: Knowledge of the human health impacts associated with airborne nanoparticle exposure has led to considerable research activity aimed at better characterising these particles and understanding which particle properties are most important in the context of effects on health. Knowledge of the sources, chemical composition, physical structure and ambient concentrations of nanoparticles has improved significantly as a result. Given the known toxicity of many metals and the contribution of nanoparticles to their oxidative potential, the metallic content of the nanoparticulate burden is likely to be an important factor to consider when attempting to assess the impact of nanoparticle exposure on health. This review therefore seeks to draw together the existing knowledge of metallic nanoparticles in the atmosphere and discuss future research priorities in the field. The article opens by outlining the reasons behind the current research interest in the field, and moves on to discuss sources of nanoparticles to the atmosphere. The next section reviews ambient concentrations, covering spatial and temporal variation, mass and number size distributions, air sampling and measurement techniques. Further sections discuss the chemical and physical composition of particles. The review concludes by summing up the current state of research in the area and considering where future research should be focused.
    Atmospheric Environment 09/2014; 94:353–365. DOI:10.1016/j.atmosenv.2014.05.023 · 3.06 Impact Factor
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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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    ABSTRACT: Overwhelming use of engineered nanoparticles demands rapid assessment of their environmental impacts. The transport of cerium oxide nanoparticles (nCeO2) in plants and their impact on cellular homeostasis as a function of exposure duration is not well understood. In this study, kidney bean plants were exposed to suspensions of ∼8±1nm nCeO2 (62.5 to 500mg/L) for 15 days in hydroponic conditions. Plant parts were analyzed for cerium accumulation after one, seven, and 15 days of nCeO2 exposure. The primary indicators of stress like lipid peroxidation, antioxidant enzyme activities, total soluble protein and chlorophyll contents were studied. Cerium in tissues was localized using scanning electron microscopy and synchrotron μ-XRF mapping, and the chemical forms were identified using μ-XANES. In the root epidermis, cerium was primarily shown to exist as nCeO2, although a small fraction (12%) was biotransformed to Ce(III) compound. Cerium was found to reach the root vascular tissues and translocate to aerial parts with time. Upon prolonged exposure to 500mg nCeO2/L, the root antioxidant enzyme activities were significantly reduced, simultaneously increasing the root soluble protein by 204%. In addition, leaf's guaiacol peroxidase activity was enhanced with nCeO2 exposure in order to maintain cellular homeostasis.
    Journal of Hazardous Materials 06/2014; 278C:279-287. DOI:10.1016/j.jhazmat.2014.06.009 · 4.33 Impact Factor