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Partition coefficients (PCs) are used in physiologically based pharmacokinetic (PBPK) models to estimate the free concentration of a chemical in specific blood or organs. Biological PC(tissue:blood) (tissue to blood) values were determined for a series of nonvolatile herbicides, insecticides, and fungicides in liver, brain, skin, fat, kidneys, and muscle of male Sprague-Dawley rats using two different analytical methods. The free phase concentration (in phosphate-buffered saline) of a given chemical was measured in the presence and absence of tissue (including blood) and used to calculate the PC, defined as the ratio of the concentration of the chemical in saline to the concentration in the tissue. PCs were determined for 13 compounds with aqueous solubility ranging from 20 to 4100 mg/L, molecular weights from 187.3 to 342.2 g/mol, and log K (ow) values from -0.18 to 3.9. An ultrafiltration high-performance liquid chromatography (HPLC) method was implemented for compounds with log K (ow) near 0.1 or less and a negligible depletion solid-phase microextraction (nd-SPME) method for compounds with higher log K (ow). PC(tissue:saline) coefficients of variation were 0.13 (n = 3 compounds) on average for the HPLC method and 0.29 (n = 10 compounds) for the nd-SPME method. Presented here is one of the most comprehensive data sets of biological partition coefficients for herbicides, insecticides, and fungicides.

The pharmacokinetic behavior of the majority of jet fuel constituents has not been previously described in the framework of a physiologically based pharmacokinetic (PBPK) model for inhalation exposure. Toxic effects have been reported in multiple organ systems, though exposure methods varied across studies, utilizing either vaporized or aerosolized fuels. The purpose of this work was to assess the pharmacokinetics of aerosolized and vaporized fuels, and develop a PBPK model capable of describing both types of exposures. To support model development, n-tetradecane and n-octane exposures were conducted at 89 mg/m(3) aerosol+vapor and 1000-5000 ppm vapor, respectively. Exposures to JP-8 and S-8 were conducted at ~900-1000 mg/m(3), and ~200 mg/m(3) to a 50:50 blend of both fuels. Sub-models were developed to assess the behavior of representative constituents and grouped unquantified constituents, termed "lumps", accounting for the remaining fuel mass. The sub-models were combined into the first PBPK model for petroleum and synthetic jet fuels. Inhalation of hydrocarbon vapors was described with simple gas-exchange assumptions for uptake and exhalation. For aerosol droplets systemic uptake occurred in the thoracic region. Visceral tissues were described using perfusion and diffusion-limited equations. The model described kinetics at multiple fuel concentrations, utilizing a chemical "lumping" strategy to estimate parameters for fractions of speciated and unspeciated hydrocarbons and gauge metabolic interactions. The model more accurately simulated aromatic and lower molecular weight (MW) n-alkanes than some higher MW chemicals. Metabolic interactions were more pronounced at high (~2700-1000 mg/m(3)) concentrations. This research represents the most detailed assessment of fuel pharmacokinetics to date.

Jet Fuel 8 (JP-8) is a major fuel source used by US and NATO military. JP-8 is a complex mixture of aliphatic and aromatic isomers of hydrocarbons. Tissue/blood partition coefficient (PC) values are chemical-specific parameters used in modeling the kinetic behavior of chemicals. The partition coefficient values for n-alkanes tend to increase with the increasing carbon number, but less is known about the trend for isomers of n-alkanes. PC values were obtained for the n-alkane nonane (C9) and five of its isomers, namely 3-methyloctane, 4-ethylheptane, 2,3-dimethylheptane, 2,2,4-trimethylhexane, 2,2,4,4-tetramethylpentane. The blood:air and tissue:air PC values correlated with the published log octanol/water (O:W) PC values for n-nonane and its isomers. Experimentally determined blood:air and tissue:air PC values for n-nonane with the largest O:W value were greatest and smallest for the isomer 2,2,4,4-tetramethylpentane with the lowest O:W value. As expected the fat tissue had the highest PC values and muscle the lowest for n-nonane and its isomers. For each tissue, a linear relationship was observed between the tissue/blood PC values for the isomers of n-nonane and n-nonane. This suggests that tissue/blood PC values for all isomers of an alkane could be estimated using data collected from only a sub-set of alkanes of equal carbon number. These reported tissue/blood PC values will support the development of a jet fuel physiologically-based pharmacokinetic (PBPK) model.

During the fall of 1998, the US Environmental Protection Agency and the Florida Department of Environmental Protection sponsored a 7-day study at the Ft. McHenry tunnel in Baltimore, MD with the objective of obtaining PM 2.5 vehicle source profiles for use in atmospheric mercury source apportionment studies. PM 2.5 emission profiles from gasoline and diesel powered vehicles were developed from analysis of trace elements, polycyclic aromatic hydrocarbons (PAH), and condensed aliphatic hydrocarbons. PM 2.5 samples were collected using commercially available sampling systems and were extracted and analyzed using conventional well-established methods. Both inorganic and organic profiles were sufficiently unique to mathematically discriminate the contributions from each source type using a chemical mass balance source apportionment approach. However, only the organic source profiles provided unique PAH tracers (e.g., fluoranthene, pyrene, and chrysene) for diesel combustion that could be used to identify source contributions generated using multivariate statistical receptor modeling approaches. In addition, the study found significant emission of gaseous elemental mercury (Hg 0 ), divalent reactive gaseous mercury (RGM), and particulate mercury (Hg(p)) from gasoline but not from diesel powered motor vehicles. Fuel analysis supported the tunnel measurement results showing that total mercury content in all grades of gasoline (284±108 ng L −1 ) was substantially higher than total mercury content in diesel fuel (62±37 ng L −1 ) collected contemporaneously at local Baltimore retailers.

PM2.5 and size-segregated aerosols were collected in May 2002 as part of the Bay Regional Atmospheric Chemistry Experiment (BRACE), Florida, USA. Aerosol organic composition was used to estimate sources of a series of alkanes and polycyclic aromatic hydrocarbons (PAHs) using chemical indices, hierarchical cluster analysis (HCA) and a chemical mass balance receptor model (CMB). Aerosols were collected on quartz fiber filters (QFF) using a PM2.5 high volume sampler and on aluminum foil discs using a Micro-Orifice Uniform Deposit Impactor (MOUDI, 50% aerodynamic cut diameters were 18, 10, 5.6, 3.2, 1.8, 1.0, 0.56, 0.315 and 0.171 μm). Target compounds included alkanes and PAHs and were solvent extracted using a mixture of dichloromethane, acetone and hexane, concentrated and then analyzed using a gas chromatograph/mass spectrometer (GC/MS). The target compounds in PM2.5 were dominated by six sources during the study period: mobile sources (39±5%), coal burning (33±5%), biogenic primary emission (20±2%), oil combustion (5±2%), biomass burning (1.0±0.3%) and an unidentified source (3±2%). Results obtained from the chemical indices, HCA and CMB were in very good agreement with each other. PAH size distributions are presented for days dominated by a same source. Seventy-five percent and 50% of the PAH were found below 1.8 and 0.56 μm, respectively (monthly PAH geometric diameters averaged 0.43 μm). Coarse size PAHs were observed on 1 day (15 May) and were correlated with nitrate and sodium size distribution. It is hypothesized that the PAHs, sodium and nitrate were internally mixed and that the PAHs deposited onto a pre-existing marine aerosol. This transfer process has significant implications for PAH deposition and lifetime and warrants further study.

Sampling of 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) at the Gandy Bridge monitoring site between May and August 2002 provided preliminary ambient air concentrations and dry deposition rates for Tampa Bay. The HiC-IOGAPS dramatically improved the recovery of lower molecular weight gas and particle PAHs, as evidenced by the recoveries of PAHs in back-up denuders and filter packs. Total PAH (gas+particle) concentrations ranged from 80 to 190 ng m −3 . Concentrations of naphthalene, acenaphthene, fluorene, phenanthrene, fluoranthene, and pyrene were consistently higher than concentrations of the remaining 10 PAHs. Assuming an unidirectional flux of these compounds from air to water, the estimated total (gas+particle) dry deposition flux was 11.5 μg m −2 d −1 , or 6.7 μg m −2 d −1 if naphthalene is excluded.

Few robust methods are available to characterize the composition of aerosolized complex hydrocarbon mixtures. The difficulty in separating the droplets from their surrounding vapors and preserving their content is challenging, more so with fuels, which contain hydrocarbons ranging from very low to very high volatility. Presented here is a novel method that uses commercially available absorbent tubes to measure a series of hydrocarbons in the vapor and droplets from aerosolized jet fuels. Aerosol composition and concentrations were calculated from the differential between measured total (aerosol and gas-phase) and measured gas-phase concentrations. Total samples were collected directly, whereas gas-phase only samples were collected behind a glass fiber filter to remove droplets. All samples were collected for 1 min at 400 ml min(-1) and quantified using thermal desorption-gas chromatography-mass spectrometry. This method was validated for the quantification of the vapor and droplet content from 4-h aerosolized jet fuel exposure to JP-8 and S-8 at total concentrations ranging from 200 to 1000 mg/m(3). Paired samples (gas-phase only and total) were collected every approximately 40 min. Calibrations were performed with neat fuel to calculate total concentration and also with a series of authentic standards to calculate specific compound concentrations. Accuracy was good when compared to an online GC-FID (gas chromatography-flame ionization detection) technique. Variability was 15% or less for total concentrations, the sum of all gas-phase compounds, and for most specific compound concentrations in both phases. Although validated for jet fuels, this method can be adapted to other hydrocarbon-based mixtures.

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.