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: 2.26). 05/2008; 20(6):547-66. DOI: 10.1080/08958370801915309
Source: PubMed


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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    • "A study by Zhu et al. (2005), also conducted on residents at different distances from REE mining sites, showed that residents in contaminated areas with heavy (HREE) or light (LREE) REE had significantly lower serum total protein and globulin levels compared to controls, and residents in the HREE area had significantly elevated IgM levels vs. LREE residents. Beyond the so far scanty literature on environmental REE exposures , one should consider that REE and, in particular, Ce compounds are used, among many other applications, as diesel fuel additives (Park et al., 2008) and as abrasives in glass and in printed circuit manufacture (Du and Graedel, 2011; USEPA, 2012), thus "
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    ABSTRACT: Background: A number of applications have been developed using rare earth elements (REE), implying several human exposures and raising unsolved questions as to REE-associated health effects. Methods: A MedLine survey was retrieved from early reports (1980s) up to June 2015, focused on human and animal exposures to REE. Literature from animal models was selected focusing on REE-associated health effects. Results: Some REE occupational exposures, in jobs such as glass polishers, photoengravers and movie projectionists showed a few case reports on health effects affecting the respiratory system. No case-control or cohort studies of occupational REE exposures were retrieved. Environmental exposures have been biomonitored in populations residing in REE mining areas, showing REE accumulation. The case for a iatrogenic REE exposure was raised by the use of gadolinium-based contrast agents for nuclear magnetic resonance. Animal toxicity studies have shown REE toxicity, affecting a number of endpoints in liver, lungs and blood. On the other hand, the use of REE as feed additives in livestock is referred as a safe and promising device in zootechnical activities, possibly suggesting a hormetic effect both known for REE and for other xenobiotics. Thus, investigations on long-term exposures and observations are warranted. Conclusion: The state of art provides a limited definition of the health effects in occupationally or environmentally REE-exposed human populations. Research priorities should be addressed to case-control or cohort studies of REE-exposed humans and to life-long animal experiments.
    Full-text · Article · Jul 2015 · Environmental Research
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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.
    Full-text · Article · Sep 2014 · Toxicological Sciences
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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.
    Full-text · Article · Sep 2014 · Atmospheric Environment
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