Chemical characterization and in vitro toxicity of diesel exhaust particulate matter generated under varying conditions

Abstract

Epidemiologic studies have linked diesel exhaust (DE) to cardiovascular and respiratory morbidity and mortality, as well as lung cancer. DE composition is known to vary with many factors, although it is unclear how this influences toxicity. We generated eight DE atmospheres by applying a 2×2×2 factorial design and altering three parameters in a controlled exposure facility: (1) engine load (27 vs 82 %), (2) particle aging (residence time ~5 s vs ~5 min prior to particle collection), and (3) oxidation (with or without ozonation during dilution). Selected exposure concentrations of both diesel exhaust particles (DEPs) and DE gases, DEP oxidative reactivity via DTT activity, and in vitro DEP toxicity in murine endothelial cells were measured for each DE atmosphere. Cell toxicity was assessed via measurement of cell proliferation (colony formation assay), cell viability (MTT assay), and wound healing (scratch assay). Differences in DE composition were observed as a function of engine load. The mean 1-nitropyrene concentration was 15 times higher and oxidative reactivity was two times higher for low engine load versus high load. There were no substantial differences in measured toxicity among the three DE exposure parameters. These results indicate that alteration of applied engine load shifts the composition and can modify the biological reactivity of DE. While engine conditions did not affect the selected in vitro toxicity measures, the change in oxidative reactivity suggests that toxicological studies with DE need to take into account engine conditions in characterizing biological effects.

Sex and genetic differences in the effects of acute diesel exhaust exposure on inflammation and oxidative stress in mouse brain

“…Exposures to either FA or DE were conducted simultaneously under SPF conditions in our diesel exposure facility (Gould et al, 2008; Fox et al, 2015), using an Allentown caging system (Allentown, NJ) with racks modified to receive either diluted DE or FA through their air intakes. DE was derived as described (Gould et al, 2008; Fox et al, 2015), from a Yanmar YDG5500 diesel generator, with a load bank maintaining 75% of rated capacity, using No. 2 undyed, ultra-low sulfur on-highway fuel and Royal Purple Duralec 15W-40 Synthetic crankcase oil.…”

“…2 undyed, ultra-low sulfur on-highway fuel and Royal Purple Duralec 15W-40 Synthetic crankcase oil. During exposures, DE concentrations were continuously measured and maintained at steady concentrations using a feedback controller monitoring fine particulate levels (Gould et al, 2008; Fox et al, 2015). DE was composed of PM 2.5 or smaller, with a mean aerodynamic diameter of 100 nm.…”

“…DE was composed of PM 2.5 or smaller, with a mean aerodynamic diameter of 100 nm. The DE characteristics have been described in detail previously (Fox et al, 2015). For assays of lipid peroxidation, inflammatory cytokine levels and Western blots, mice were euthanized by CO 2 asphyxiation within 2 h after the end of the exposure, and brain regions were dissected immediately, flash-frozen in liquid nitrogen, and stored at −80° C. For Iba1 immunohistochemistry and measurement of TSPO binding, mice were euthanized 18 h after the end of exposure.…”

Microglia mediate diesel exhaust particle-induced cerebellar neuronal toxicity through neuroinflammatory mechanisms

“…DEP was collected from the outflow duct, as previously described (Gould et al, 2008; Weldy et al 2011) and consisted of previously characterized PM 2.5 particles (Gould et al, 2008; Fox et al, 2015). Stock solutions were prepared by suspending particles in PBS (2.5% DMSO) at a concentration of 10 mg/mL.…”

Neurotoxicity of traffic-related air pollution

“…2 undyed, on-highway fuel and Royal Purple Duralec 15W-40 Synthetic crankcase oil. During exposures, DE concentrations were continuously measured and maintained at steady concentrations using a feedback controller monitoring fine particulate levels (Gould et al 2008; Fox et al 2015). DE was composed of PM 2.5 or smaller, with a mean aerodynamic diameter of 100 nm.…”