Generation and Characterization of Four Dilutions of Diesel Engine Exhaust for a Subchronic Inhalation Study

Abstract

Exposure atmospheres for a rodent inhalation toxicology study were generated from the exhaust of a 2000 Cummins ISB 5.9L diesel engine coupled to a dynamometer and operated on a slightly modified heavy-duty Federal Test Procedure cycle. Exposures were conducted to one clean air control and four diesel exhaust levels maintained at four different dilution rates (300:1, 100:1, 30:1, 10:1) that yielded particulate mass concentrations of 30, 100, 300, and 1000 microg/m3. Exposures at the four dilutions were characterized for particle mass, particle size distribution (reported elsewhere), detailed chemical speciation of gaseous, semivolatile, and particle-phase inorganic and organic compounds. Target analytes included metals, inorganic ions and gases, organic and elemental carbon, alkanes, alkenes, aromatic and aliphatic acids, aromatic hydrocarbons, polycyclic aromatic hydrocarbons (PAH), oxygenated PAH, nitrogenated PAH, isoprenoids, carbonyls, methoxyphenols, sugar derivatives, and sterols. The majority of the mass of material in the exposure atmospheres was gaseous nitrogen oxides and carbon monoxide, with lesser amounts of volatile organics and particle mass (PM) composed of carbon (approximately 90% of PM) and ions (approximately 10% of PM). Measured particle organic species accounted for about 10% of total organic particle mass and were mostly alkanes and aliphatic acids. Several of the components in the exposure atmosphere scaled in concentration with dilution but did not scale precisely with the dilution rate because of background from the rodents and scrubbed dilution air, interaction of animal derived emissions with diesel exhaust components, and day-to-day variability in the output of the engine. Rodent-derived ammonia reacted with exhaust to form secondary inorganic particles (at different rates dependent on dilution), and rodent respiration accounted for volatile organics (especially carbonyls and acids) in the same range as the diesel exhaust at the lowest exhaust exposure concentrations. Day-to-day variability in the engine output was implicated partially for differences of several components, including some of the particle bound organics. Though these observations have likely occurred in nearly all inhalation exposure atmospheres that contain complex mixtures of material, the speciations conducted here illustrate many of them for the first time.

Measuring long chain alkanes in diesel engine exhaust by thermal desorption PTR-MS

“…The diesel engine was a 5.5 kW Yanmar diesel electric generator and the gasoline engine a 1996 model General Motors 4.3-L V-6 mounted to a dynamometer. The emissions from these engines and facility description are described in more detail in McDonald et al (2004McDonald et al ( , 2007McDonald et al ( , 2011. The emissions output from these engines reflect older emission standards with the diesel generator simulating emissions from a medium duty diesel truck engine.…”

Health Effects of Fine Particulate Air Pollution: Lines that Connect

“…Exposure to diesel engine exhaust is an example of a mixture for which the effects are frequently and glibly ascribed to PM. The speciation by McDonald et al 9 of emissions from a contemporary (2000), common on-road diesel engine operated on a simulated duty cycle and burning national-average (certification) fuel provides insight. When concentrations of gases (typically reported as parts per million, which yields small numerical values) were reported as mass concentrations (micrograms per cubic meter), the PM component constituted Ͻ1% of the total emitted mass, even disregarding carbon dioxide and water vapor.…”

Dominant Mechanisms that Shape the Airborne Particle Size and Composition Distribution in Central California

“…Particles released directly from a source (primary PM) have a characteristic size and composition distribution that is determined by the generating mechanism (Hildemann et al 1991;Kleeman et al 1999;Kleeman et al 2000;Allen et al 2001;Wingfors et al 2001;McDonald et al 2003;Sturm et al 2003;Hays 2004;Laschober et al 2004;McDonald et al 2004;Shah et al 2004). Once in the atmosphere, the particle size and composition distribution can be modified by chemical reactions, condensation/evaporation of semi-volatile species, coagulation with other particles, activation during high humidity, wet deposition, and dry deposition.…”