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 μm, depending on the generator and mixture utilized. A/V hydrocarbon concentrations ranged from ∼200 to 1300 mg/m³, 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.

Keywords:

•  Inhalation
• jet fuel
• JP-8
• nebulizer
• nose-only
• S-8

Acknowledgments

The authors would like to thank Drs. Rudolph Jaeger, Jerry L. Campbell Jr., Eva D. McLanahan, W. Matthew Henderson, Babatope Fatuyi, and Oluseye Ogunmoroti, Mr. James Reboulet, and Mrs. Libby Myers for their help during this work, also Dr. Anne Marie Zimeri for kindly editing this document.

Declaration of interest

This work was supported by Air Force Office of Scientific Research (AFOSR) grant FA9550-07-1-0132. The authors alone are responsible for the content and writing of the paper.