Evaluation of cerium oxide and cerium oxide based fuel additive safety on organotypic cultures of lung slices

Among the various technological proposals under consideration to limit diesel exhaust particles (DEP) emissions, the use of a particulate filter in conjunction with a fuel-borne catalyst is currently the primary focus and likely to be introduced over the coming years. One specific catalyst is a cerium-based compound Envirox (TM) developed by Oxonica (Kidlington, UK) and used as a fuel additive to reduce particulate matter ( PM) emissions from diesel engines. Prior to any commercialization it is necessary to undertake an assessment of any potential adverse health effects resulting from exposure to cerium oxide particles especially via the inhalation route, i.e., on the lung. Since the composition of engine exhaust emissions from additized fuel might be different to those emissions from un-additized diesel fuel, the second phase of the current investigation compared the potential biological impact of engine emissions from cerium oxide additized fuel to that of a reference fuel. An experimental procedure developed in our laboratory using an organotypic culture of lung slices was used. Biological endpoints were chosen in order to evaluate cell viability (ATP, intracellular GSH), pro-inflammatory reaction (TNF alpha) and anti-oxidant enzyme activity (total GPx, Mn SOD, catalase). No impact of nanoparticulate cerium oxide aerosol on lung tissue biological parameters was observed with one exception, an increased catalase activity which was not associated with a concomitant loss in cell viability. It is therefore concluded, on the basis of this study and from the prospective potential exposure to cerium oxide, that a very low prospective risk is associated with the expected dissemination of cerium oxide in the atmosphere. Concerning the biological impact of Envirox (TM) additized-diesel fuel, the observed effects are of very limited incidence in that the observed trend on organotypic culture viability and TNF alpha is beneficial, while a limited oxidant activity is observed through catalase induction. Emissions from diesel fuel additized with the tested cerium oxide catalyst do not induce any increase in the known adverse biological effects caused by diesel fuel engine emissions alone in our experimental set-up.