Characterization of a nose-only inhalation exposure system for hydrocarbon mixtures and jet fuels

Abstract

A directed-flow nose-only inhalation exposure system was constructed to support development of physiologically based pharmacokinetic (PBPK) models for complex hydrocarbon mixtures, such as jet fuels. Due to the complex nature of the aerosol and vapor-phase hydrocarbon exposures, care was taken to investigate the chamber hydrocarbon stability, vapor and aerosol droplet compositions, and droplet size distribution. Two-generation systems for aerosolizing fuel and hydrocarbons were compared and characterized for use with either jet fuels or a simple mixture of eight hydrocarbons. Total hydrocarbon concentration was monitored via online gas chromatography (GC). Aerosol/vapor (A/V) ratios, and total and individual hydrocarbon concentrations, were determined using adsorbent tubes analyzed by thermal desorption-gas chromatography-mass spectrometry (TDS-GC-MS). Droplet size distribution was assessed via seven-stage cascade impactor. Droplet mass median aerodynamic diameter (MMAD) was between 1 and 3 mum, depending on the generator and mixture utilized. A/V hydrocarbon concentrations ranged from approximately 200 to 1300 mg/m(3), with between 20% and 80% aerosol content, depending on the mixture. The aerosolized hydrocarbon mixtures remained stable during the 4-h exposure periods, with coefficients of variation (CV) of less than 10% for the total hydrocarbon concentrations. There was greater variability in the measurement of individual hydrocarbons in the A-V phase. In conclusion, modern analytical chemistry instruments allow for improved descriptions of inhalation exposures of rodents to aerosolized fuel.

Development of a physiologically based pharmacokinetic model for inhalation of jet fuels in the rat

“…For the jet fuels, the GC oven Percent aerosol and percent vapor were determined based on the mean of aerosol/vapor data collected with TDS charcoal tubes (see Methods). Aerosol size characteristics for the current study were determined using a cascade impactor, via the method and conditions reported by Martin et al (2010). *The percent of total hydrocarbon concentration, minus the marker chemical concentrations from within the lumps, is listed for each lump.…”

“…The hydrocarbon compositions of vaporized JP-8 and aerosolized JP-8, S-8, and the blended fuel constituents have been reported in previous work Martin et al, 2010;Tremblay et al, 2010b). Six representative hydrocarbons were selected as marker chemicals for JP-8 (n-octane, n-decane, n-tetradecane, toluene, m-xylene, and ethylbenzene) and 3 hydrocarbon markers for S-8 (n-octane, n-decane, and n-tetradecane).…”

“…Martin et al (2010) described in detail the inhalation exposure system and the techniques for generating atmospheric levels of hydrocarbons. Tremblay et al (2010b) and Martin et al (2010) described the analytical methods used to characterize the chamber atmosphere for aerosolized fuel exposures.…”

“…Martin et al (2010) described in detail the inhalation exposure system and the techniques for generating atmospheric levels of hydrocarbons. Tremblay et al (2010b) and Martin et al (2010) described the analytical methods used to characterize the chamber atmosphere for aerosolized fuel exposures. In brief, individual hydrocarbon concentrations, lumped hydrocarbon concentrations (described later), and the total hydrocarbon concentration (THC) within the exposure chamber were quantified using a combination of thermal desorption tubes and gas chromatography (GC), with mass spectrometry (MS) used for individual and lump fractions, and flame ionization detector (FID) for the THC Tremblay et al, 2010b).…”

“…Four rats were killed at each time point (end of exposure and at post-exposure time points: 15, 45, 75 and 120 min) for collection of blood and tissues. Methods for generating the aerosolized tetradecane exposure utilized a Collison nebulizer as described in Martin et al (2010). The total flow rate through the system was 12 L/min.…”