The biological effects of subacute inhalation of diesel exhaust following addition of cerium oxide nanoparticles in atherosclerosis-prone mice

Abstract

BackgroundCerium oxide (CeO2) nanoparticles improve the burning efficiency of fuel, however, little is known about health impacts of altered emissions from the vehicles.MethodsAtherosclerosis-prone apolipoprotein E knockout (ApoE−/−) mice were exposed by inhalation to diluted exhaust (1.7 mg/m3, 20, 60 or 180 min, 5 day/week, for 4 weeks), from an engine using standard diesel fuel (DE) or the same diesel fuel containing 9 ppm cerium oxide nanoparticles (DCeE). Changes in hematological indices, clinical chemistry, atherosclerotic burden, tissue levels of inflammatory cytokines and pathology of the major organs were assessed.ResultsAddition of CeO2 to fuel resulted in a reduction of the number (30%) and surface area (10%) of the particles in the exhaust, whereas the gaseous co-pollutants were increased (6–8%). There was, however, a trend towards an increased size and complexity of the atherosclerotic plaques following DE exposure, which was not evident in the DCeE group. There were no clear signs of altered hematological or pathological changes induced by either treatment. However, levels of proinflammatory cytokines were modulated in a brain region and liver following DCeE exposure.ConclusionsThese results imply that addition of CeO2 nanoparticles to fuel decreases the number of particles in exhaust and may reduce atherosclerotic burden associated with exposure to standard diesel fuel. From the extensive assessment of biological parameters performed, the only concerning effect of cerium addition was a slightly raised level of cytokines in a region of the central nervous system. Overall, the use of cerium as a fuel additive may be a potentially useful way to limit the health effects of vehicle exhaust. However, further testing is required to ensure that such an approach is not associated with a chronic inflammatory response which may eventually cause long-term health effects.

The risks of acute exposure to black carbon in Southern Europe: results from the MED-PARTICLES project

“…In a controlled exposure study to diesel exhaust, Lucking et al 29 observed increases in thrombus formation. In addition, recent toxicological studies have demonstrated that animals exposed to diesel exhaust experienced the promotion of growth of atherosclerotic plaque 30 31…”

The yin: an adverse health perspective of nanoceria: uptake, distribution, accumulation, and mechanisms of its toxicity

“…Following inhalation exposure, nanoceria, being poorly-soluble in body fluids 46, 47 , deposits within the respiratory tract based on physical properties related to its size distribution and agglomeration/ aggregation state 48 . Ceria detected in diesel exhaust emissions from a nanoceria-based fuel additive was found to be of nanoscale size (<100 nm) 3, 49, 50 . Knowledge of the potential health effects associated with the use of nanoceria, including its use as diesel fuel additive, is rather limited 51 .…”

Factors Affecting the Ambient Physicochemical Properties of Cerium-Containing Particles Generated by Nanoparticle Diesel Fuel Additive Use

“…Jung et al (2005) observes that cerium-containing particles at the time of emission consist of cerium oxide nanoparticle aggregates that either decorate the surface of larger soot particles or exist as individual particles. Cassee et al (2012) and Batley et al (2013), on the other hand, characterize the ceria nanoparticle agglomerations as being within the soot matrix/clusters. Using an iron (Fe) fuel borne catalyst similar to the nCe-based additives, Nash et al (2013) reports that the fraction of Fe-containing exhaust particles unassociated with soot increases as the particle size decreases.…”