Effects of repeated exposure to JP-8 jet fuel vapor on learning of simple and difficult operant tasks by rats

Toxicity and human health assessment of an alcohol-to-jet (ATJ) synthetic kerosene developed under an international agreement with Sweden

Alcohol-to-jet (ATJ) Synthetic Kerosene with Aromatics (SKA) fuels are produced by dehydration and refining of alcohol feed stocks. ATJ SKA fuel known as SB-8 was developed by Swedish Biofuels as a cooperative agreement between Sweden and AFRL/RQTF. SB-8 including standard additives was tested in a 90-day toxicity study with male and female Fischer 344 rats exposed to 0, 200, 700, or 2000 mg/m³ fuel in an aerosol/vapor mixture for 6 hr/day, 5 days/week. Aerosols represented 0.04 and 0.84% average fuel concentration in 700 or 2000 mg/m³ exposure groups. Examination of vaginal cytology and sperm parameters found no marked changes in reproductive health. Neurobehavioral effects were increased rearing activity (motor activity) and significantly decreased grooming (functional observational battery) in 2000 mg/m³ female rats. Hematological changes were limited to elevated platelet counts in 2000 mg/m³ exposed males. Minimal focal alveolar epithelial hyperplasia with increased number of alveolar macrophages was noted in some 2000 mg/m³ males and one female rat. Additional rats tested for genotoxicity by micronucleus (MN) formation did not detect bone marrow cell toxicity or alterations in number of MN; SB-8 was not clastogenic. Inhalation results were similar to effects reported for JP-8. Both JP-8 and SB fuels were moderately irritating under occlusive wrapped conditions but slightly irritating under semi-occlusion. Exposure to SB-8, alone or as 50:50 blend with petroleum-derived JP-8, is not likely to enhance adverse human health risks in the military workplace.

Hydrocarbon-induced hormesis: 101 years of evidence at the margin?

Hydrocarbons are used worldwide for an array of purposes ranging from transportation to making plastics and synthetic fibers. Hydrocarbons pollution can occur from local to global scales, becoming a focus of regulatory authorities since a long time ago. While studies show numerous adverse effects on biota, such effects usually occur at very high doses. This paper collates significant evidence showing that hydrocarbons induce hormesis in biota, with dual effects of low versus high doses. Hydrocarbon-induced hormetic responses should be considered in relevant dose-response studies as well as in risk assessment. Dismissing hormesis could lead to incorrect predictions of hydrocarbons effects, which can occur at doses up to 100 times smaller than the traditional toxicological threshold, and would raise serious concerns regarding human and ecological health safety.

Acquired Central Auditory Processing Disorder in Service Members and Veterans

Purpose A growing body of evidence suggests that military service members and military veterans are at risk for deficits in central auditory processing. Risk factors include exposure to blast, neurotrauma, hazardous noise, and ototoxicants. We overview these risk factors and comorbidities, address implications for clinical assessment and care of central auditory processing deficits in service members and veterans, and specify knowledge gaps that warrant research. Method We reviewed the literature to identify studies of risk factors, assessment, and care of central auditory processing deficits in service members and veterans. We also assessed the current state of the science for knowledge gaps that warrant additional study. This literature review describes key findings relating to military risk factors and clinical considerations for the assessment and care of those exposed. Conclusions Central auditory processing deficits are associated with exposure to known military risk factors. Research is needed to characterize mechanisms, sources of variance, and differential diagnosis in this population. Existing best practices do not explicitly consider confounds faced by military personnel. Assessment and rehabilitation strategies that account for these challenges are needed. Finally, investment is critical to ensure that Veterans Affairs and Department of Defense clinical staff are informed, trained, and equipped to implement effective patient care.

Systemic molecular and cellular changes induced in rats upon inhalation of JP-8 petroleum fuel vapor

Limited information is available regarding systemic changes in mammals associated with exposures to petroleum/hydrocarbon fuels. In this study, systemic toxicity of JP-8 jet fuel was observed in a rat inhalation model at different JP-8 fuel vapor concentrations (250, 500, or 1000 mg/m(3), for 91 days). Gel electrophoresis and mass spectrometry sequencing identified the alpha-2 microglobulin protein to be elevated in rat kidney in a JP-8 dose-dependent manner. Western blot analysis of kidney and lung tissue extracts revealed JP-8 dependent elevation of inducible heat shock protein 70 (HSP70). Tissue changes were observed histologically (hematoxylin and eosin staining) in liver, kidney, lung, bone marrow, and heart, and more prevalently at medium or high JP-8 vapor phase exposures (500-1000 mg/m(3)) than at low vapor phase exposure (250 mg/m(3)) or non-JP-8 controls. JP-8 fuel-induced liver alterations included dilated sinusoids, cytoplasmic clumping, and fat cell deposition. Changes to the kidneys included reduced numbers of nuclei, and cytoplasmic dumping in the lumen of proximal convoluted tubules. JP-8 dependent lung alterations were edema and dilated alveolar capillaries, which allowed clumping of red blood cells (RBCs). Changes in the bone marrow in response to JP-8 included reduction of fat cells and fat globules, and cellular proliferation (RBCs, white blood cells-WBCs, and megakaryocytes). Heart tissue from JP-8 exposed animals contained increased numbers of inflammatory and fibroblast cells, as well as myofibril scarring. cDNA array analysis of heart tissue revealed a JP-8 dependent increase in atrial natriuretic peptide precursor mRNA and a decrease in voltage-gated potassium (K+) ion channel mRNA.

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

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.

Workplace exposures and the risk of amyotrophic lateral sclerosis

BACKGROUND

Occupation has been suggested to play a role in amyotrophic lateral sclerosis (ALS) etiology, but detailed information on the importance of specific workplace exposures is lacking.

OBJECTIVES

Our aim was to assess the relationship between workplace exposures and the risk of ALS and to evaluate potential interactions between these exposures and smoking.

METHODS

We conducted a case-control study in New England between 1993 and 1996, comprising 109 cases and 253 controls who completed a structured interview covering occupations and workplace exposures. Unconditional logistic regression models were used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for ALS. Analyses were conducted among the entire study population and after stratification by smoking.

RESULTS

We observed a higher risk of ALS for construction workers excluding supervisors (OR = 2.9; 95% CI, 1.2-7.2) and precision metal workers (OR = 3.5; 95% CI, 1.2-10.5). Self-reported exposures to paint strippers; cutting, cooling, or lubricating oils; antifreeze or coolants; mineral or white spirits; and dry cleaning agents each appeared to be associated with a 60-90% higher risk. Specific chemicals related to a > 50% increase in risk of ALS included aliphatic chlorinated hydrocarbons, glycols, glycol ethers, and hexane. Relative risks associated with these workplace exposures and chemicals were greater among nonsmokers and persisted in mutually adjusted models.

CONCLUSIONS

Our data suggest that certain occupations and workplace exposures may be associated with increased risk of ALS. These results need to be confirmed in independent populations.

Neuroscience and hormesis: overview and general findings

This article provides a summary of an assessment of the occurrence and impact of hormesis in the neurosciences, including the areas of neuroprotection, neurite outgrowth, and drugs for Alzheimer's disease, Parkinson's disease, anxiety, pain, seizures, stroke, as well as in the areas of behavioral pharmacology, addictive drugs, stress biology including the Yerkes-Dodson law, and p-glycoprotein efflux activity. The findings indicate that the hormetic dose response has a common, if not dominant, presence in each of these diverse areas of neuroscience and further strengthens the conclusion that hormesis is highly generalizable, being independent of biological model, endpoint, and chemical class.

Repeated aerosol-vapor JP-8 jet fuel exposure affects neurobehavior and neurotransmitter levels in a rat model

Four groups of Fischer Brown Norway hybrid rats were exposed for 5, 10, 15, or 20 d to aerosolized-vapor jet propulsion fuel 8 (JP-8) compared to freely moving (5 and 10-d exposures) or sham-confined controls (15 and 20-d exposures). Behavioral testing utilized the U.S. Environmental Protection Agency Functional Observational Battery. Exploratory ethological factor analysis identified three salient factors (central nervous system [CNS] excitability, autonomic 1, and autonomic 2) for use in profiling JP-8 exposure in future studies. The factors were used as dependent variables in general linear modeling. Exposed animals were found to engage in more rearing and hyperaroused behavior compared to controls, replicating prior JP-8 exposure findings. Exposed animals also showed increasing but rapidly decelerating stool output (autonomic 1), and a significant increasing linear trend for urine output (autonomic 2). No significant trends were noted for either of the control groups for the autonomic factors. Rats from each of the groups for each of the time frames were randomly selected for tissue assay from seven brain regions for neurotransmitter levels. Hippocampal DOPAC was significantly elevated after 4-wk JP-8 exposure compared to both control groups, suggesting increased dopamine release and metabolism. Findings indicate that behavioral changes do not appear to manifest until wk 3 and 4 of exposure, suggesting the need for longitudinal studies to determine if these behaviors occur due to cumulative exposure, or due to behavioral sensitization related to repeated exposure to aerosolized-vapor JP-8.

Methods for the characterization of Jet Propellent-8: vapor and aerosol

Jet Propellant-8 (JP-8) has been responsible for the majority of reported chemical exposures by the US Department of Defense. Concerns related to human exposure to JP-8 are relatively new; therefore, there is a lack of literature data. Additionally, health effects related to the composition of the exposure have only recently been considered. Two major questions exist: (1) what is the compositional difference between the aerosol and vapor portions of JP-8 under controlled conditions and (2) what is the most representative method to sample JP-8 aerosol and vapor? Thirty-seven standards, representing more than 40% of the mass of JP-8, were used for characterization of the neat fuel, vapor and aerosol portions. JP-8 vapor samples at a concentration of 1600 mg/m(3) were prepared in Tedlar bags. A portion of the vapor samples was adsorbed on charcoal, Tenax and custom mixed phase sorbents. These samples were then extracted using organic solvent and analyzed using gas chromatography/mass spectrometry. The vapor samples extracted from the sorbent tubes were directly compared with a vapor bag. The samples collected using Tenax sorbent tubes were found to be most representative of the composition of the vapor bags. In another set of experiments, aerosolized JP-8 was generated using a collision nebulizer. Aerosol samples were collected and the chemical composition was characterized. The entire aerosol distribution was collected on a glass filter, extracted into solvent, and analyzed by GC-MS. Finally, the composition of the vapor and aerosol was compared. The vapor was found to represent the lower molecular weight components of JP-8, while the aerosol was composed of higher molecular weight components. Therefore, the vapor and aerosol should be treated as two discrete forms of exposure to JP-8.

Expression of JP-8–Induced Inflammatory Genes in AEII Cells Is Mediated by NF-κB and PARP-1

Lung epithelial cells are critical in the regulation of airway inflammation in response to environmental pollutants. Altered activation of NF-kappaB is associated with expression of several proinflammatory factors in respiratory epithelial cells in response to an insult. Here we show that a low threshold dose (8 microg/ml) of the jet fuel JP-8 induces in a rat alveolar epithelial cell line (RLE-6TN) a prolonged activation of NF-kappaB as well as the increased expression of the proinflammatory cytokines TNF-alpha and IL-8, which are regulated by NF-kappaB. The up-regulation of IL-6 mRNA in cells exposed to JP-8 appears to be a reaction of RLE-6TN cells to reduce the enhancement of proinflammatory mediators in response to the fuel. Moreover, lung tissues from rats exposed to occupational levels of JP-8 by nasal aerosol also showed dysregulated expression of TNF-alpha, IL-8, and IL-6, confirming the in vitro data. The poly(ADP-ribosyl)ation of PARP-1, a coactivator of NF-kappaB, was coincident with the prolonged activation of NF-kappaB during JP-8 treatment. These results evidenced that a persistent exposure of the airway epithelium to aromatic hydrocarbons may have deleterious effects on pulmonary function.

The last decade of solvent research in animal models of abuse: mechanistic and behavioral studies

The abuse of volatile organic solvents (inhalants) leads to diverse sequelae at levels ranging from the cell to the whole organism. This paper reviews findings from the last 10 years of animal models investigating the behavioral and mechanistic effects of solvent abuse. In research with animal models of inhalant abuse, NMDA, GABA(A), glycine, nicotine, and 5HT(3) receptors appear to be important targets of action for several abused solvents with emerging evidence suggesting that other receptor subtypes and nerve membrane ion channels may be involved as well. The behavioral effects vary in magnitude and duration among the solvents investigated. The behavioral effects of acute and chronic inhalant abuse include motor impairment, alterations in spontaneous motor activity, anticonvulsant effects, anxiolytic effects, sensory effects, and effects on learning, memory and operant behavior (e.g., response rates and discriminative stimulus effects). In addition, repeated exposure to these solvents may produce tolerance, dependence and/or sensitization to these effects.

Validation of a gas chromatography/mass spectrometry method for the quantification of aerosolized Jet Propellant 8

Jet Propellant 8 (JP-8) jet fuel is a kerosene-based fuel containing hundreds of hydrocarbons used by the military in NATO countries. Previous rodent inhalation studies carried out with aerosolized JP-8 never evaluated the exposure chamber atmosphere. For this reason, our laboratory developed an analytical method, with an accuracy of better than 80% and precision of better than 20%, for JP-8 aerosol and vapor samples using gas chromatography/mass spectrometry (GC/MS). A method was developed for quantification of selected individual components of JP-8 and for the total amount of JP-8 in aerosolized fuel. A 34 component surrogate hydrocarbon mixture (SHM) was developed and used for simultaneous analysis of the individual components. Three separate runs containing a standard curve and five replicates each at the selected concentrations were analyzed for both the SHM and neat JP-8. The resulting interday accuracy (100-percent relative error) and precision (relative standard deviation) values for the SHM were 86.5% or better and 8.0% or better, respectively. The intraday accuracy and precision values ranged from 99.29% to 84.50% and 0.97% to 12.4%, respectively. For the total amount of JP-8 in aerosol and vapor, the interday accuracy was 83.7% or better and interday precision was 7.0% or better. The intraday accuracy and precision values ranged from 94.8% to 80.4% and 2.4% to 10.5%, respectively. We then used this method to analyze samples collected from an inhalation chamber. From the data obtained, we are able to account for approximately 40-44% of the mass of the aerosol portion and 68-70% of the mass of the vapor portion. The aerosol represented 6-10% of the total mass of the aerosolized JP-8 fuel with the remaining portion being the vapor. From these experiments individual components were identified for further in vivo and in vitro toxicological testing.

Stress induced in heart and other tissues by rat dermal exposure to JP-8 fuel

Limited information is available regarding the development of systemic organ stress by dermal exposure to JP-8 fuel. In this study, the systemic stress potential of this fuel is evaluated in a rat model subjected to dermal applications of JP-8 for 7 days at 300 microl per day. Tissue histology indicated that JP-8 induces morphological alterations that suggest that tissue stress in the heart is more substantial than stress in the kidney and liver. Immunoblot analysis of tissues revealed increased levels of the inducible heat shock protein 70 (HSP70) in the heart, kidney, and liver after this dermal JP-8 exposure. This exposure also leads to increased levels of heme oxygenase-1 (HO-1/HSP3) in the liver. Additionally during this exposure, a negative regulator of inflammation, IkappaBalpha (inhibitor of NF-kappaB), was increased in the liver, slightly increased in the kidney, and not increased in the heart. Two regions of the rat brain were also examined and HSP70 and IkappaBalpha were increased in the cerebellum but not significantly increased in the cortex. This study indicates dermal JP-8 exposure causes systemic alterations that are associated with cytoprotective activities (e.g., in the liver) as well as potentially toxic mechanisms (heart and kidney).

Occupational and Public Health Risks

Symptoms reported by passengers and crewmembers on commercial aircraft are described according to individual air quality-related sources, including: (1) elevated levels of bioeffluents; (2) infectious agents; (3) extreme temperatures; (4) exhaust fumes, deicing fluid, fuel fumes, and cleaning products; (5) heated engine oil and hydraulic fluid; (6) reduced oxygen supply; (7) ozone gas; and (8) insecticides. A brief overview of the aircraft regulatory environment and available sources of data on the hazards and associated health effects is also provided.

Gene expression profiles in the rat central nervous system induced by JP-8 jet fuel vapor exposure

Jet propulsion fuel-8 (JP-8) is the predominant fuel for military land vehicles and aircraft used in the US and NATO. Occupational exposure to jet fuel in military personnel has raised concern for the health risk associated with such exposure in the Department of Defense. Clinical studies of humans chronically exposed to jet fuel have suggested both neurotoxicity and neurobehavioral deficits. We utilized rat neurobiology U34 array to measure gene expression changes in whole brain tissue of rats exposed repeatedly to JP-8, under conditions that simulated possible occupational exposure (6 h/day for 91 days) to JP-8 vapor at 250, 500, and 1000 mg/m(3), respectively. Our studies revealed that the gene expression changes of exposure groups can be divided into two main categories according to their functions: (1). neurotransmitter signaling pathways; and (2). stress response. The implications of these gene expression changes are discussed.

Immunological and hematological effects observed in B6C3F1 mice exposed to JP-8 jet fuel for 14 days

JP-8 is the primary jet fuel used by the U.S. Air Force and NATO allies. Exposure is likely to be widespread and to include both military and aviation industry personnel as well as residents living near fuel contaminated sites. This study examines the effects of JP-8 on humoral and cell-mediated and hematological parameters. A suite of immunotoxicological endpoints was evaluated in adult female B6C3F1 mice gavaged with JP-8 (in an olive oil carrier) ranging from 250-2500 mg/kg/d for 14 d. One day following the last exposure, significant increases in liver mass were detected beginning at exposure levels of 1000 mg/kg/d, while thymic mass was decreased at exposure levels of 1500 mg/kg/d and above. Decreases in thymic cellularity, however, were only observed at exposure levels of 2000 mg/kg/d and above. Mean corpuscular volume was increased (1500-2500 mg/kg/d), while the hematocrit, hemoglobin concentration, and red blood cell count were decreased only at the 2500 mg/kg/d exposure level. Natural killer cell (NK) activity and T- and B-cell proliferation were not altered. Decreases in the plaque-forming cell (PFC) response were dose responsive at levels of 500 mg/kg/d and greater, while unexpectedly, serum levels of anti-SRBC immunoglobulin M (IgM) were not altered. Alterations were detected in thymic and splenic CD4/8 subpopulations, and proliferative responses of bone marrow progenitor cells were enhanced in mice exposed to 2000 mg/kg/d of JP-8. This study establishes that humoral immune function is impaired with lower exposure levels of JP-8 than are required to affect primary and secondary immune organ weights and cellularities, CD4/8 subpopulations, and hematological endpoints.

An evaluation of neurobehavioral tests used to assess the neurodevelopmental effects of early ammonium perchlorate exposure

Perchlorate is an anion known to interfere with normal production of thyroid hormones that are integrally involved in the development of the central nervous system and neurobehavioral capacities. Given the identification of drinking water contamination with perchlorate, there are efforts to investigate the effects of exposure in developing fetuses and children in order to guide the establishment of regulatory standards. Systematic neurobehavioral investigations in animal models have been completed to evaluate neurodevelopmental consequences of exposures at different concentrations in drinking water. However, these investigations have not directly addressed the public concern for increased incidences of childhood attention deficit disorders, autism, and lowered IQs of children in areas with known contamination. Although epidemiological data suggest there is not a relationship between drinking-water perchlorate exposure and these childhood disorders, it may be prudent to use animal models to systematically assess the potential for such problems. Given the behavioral complexity of these problems, an appropriate evaluation will require the use of nontraditional neurobehavioral tests such as operant conditioning tasks of varying levels of complexity, and juvenile rat play. Such tests will provide a more direct evaluation of the potential for attention deficits, autism, and lowered IQ scores related to thyroid hormone disruption due to early perchlorate exposure.

Biological and health effects of exposure to kerosene-based jet fuels and performance additives

Over 2 million military and civilian personnel per year (over 1 million in the United States) are occupationally exposed, respectively, to jet propulsion fuel-8 (JP-8), JP-8 +100 or JP-5, or to the civil aviation equivalents Jet A or Jet A-1. Approximately 60 billion gallon of these kerosene-based jet fuels are annually consumed worldwide (26 billion gallon in the United States), including over 5 billion gallon of JP-8 by the militaries of the United States and other NATO countries. JP-8, for example, represents the largest single chemical exposure in the U.S. military (2.53 billion gallon in 2000), while Jet A and A-1 are among the most common sources of nonmilitary occupational chemical exposure. Although more recent figures were not available, approximately 4.06 billion gallon of kerosene per se were consumed in the United States in 1990 (IARC, 1992). These exposures may occur repeatedly to raw fuel, vapor phase, aerosol phase, or fuel combustion exhaust by dermal absorption, pulmonary inhalation, or oral ingestion routes. Additionally, the public may be repeatedly exposed to lower levels of jet fuel vapor/aerosol or to fuel combustion products through atmospheric contamination, or to raw fuel constituents by contact with contaminated groundwater or soil. Kerosene-based hydrocarbon fuels are complex mixtures of up to 260+ aliphatic and aromatic hydrocarbon compounds (C(6) -C(17+); possibly 2000+ isomeric forms), including varying concentrations of potential toxicants such as benzene, n-hexane, toluene, xylenes, trimethylpentane, methoxyethanol, naphthalenes (including polycyclic aromatic hydrocarbons [PAHs], and certain other C(9)-C(12) fractions (i.e., n-propylbenzene, trimethylbenzene isomers). While hydrocarbon fuel exposures occur typically at concentrations below current permissible exposure limits (PELs) for the parent fuel or its constituent chemicals, it is unknown whether additive or synergistic interactions among hydrocarbon constituents, up to six performance additives, and other environmental exposure factors may result in unpredicted toxicity. While there is little epidemiological evidence for fuel-induced death, cancer, or other serious organic disease in fuel-exposed workers, large numbers of self-reported health complaints in this cohort appear to justify study of more subtle health consequences. A number of recently published studies reported acute or persisting biological or health effects from acute, subchronic, or chronic exposure of humans or animals to kerosene-based hydrocarbon fuels, to constituent chemicals of these fuels, or to fuel combustion products. This review provides an in-depth summary of human, animal, and in vitro studies of biological or health effects from exposure to JP-8, JP-8 +100, JP-5, Jet A, Jet A-1, or kerosene.

Adverse respiratory and irritant health effects in airport workers in Taiwan

Airport workers are potentially exposed to aviation fuel or jet stream exhaust. The purpose of this study was to assess if there was an excess of adverse health outcomes among airport workers. Self-reported adverse chronic respiratory symptoms and acute irritative symptoms were assessed in a cross-sectional study among 106 airport workers (exposure group) and 305 terminal or office workers (control group) at the Kaohsiung International Airport (KIA), Taiwan. The prevalence rates for acute irritative symptoms were not significantly different between groups. A possible explanation may be that the concentration of volatile organic compounds (VOCs) that airport workers are exposed to is not sufficient to induce acute irritative symptoms, although this is not known for certain since data on the concentration of VOCs are lacking in this study. Chronic respiratory symptoms (cough and dyspnea), however, were significantly more common among the exposed group.

Identification of target genes responsive to JP-8 exposure in the rat central nervous system

Concern for the health risk associated with occupational exposure to jet fuel has emerged in the Department of Defense. Jet propulsion fuel-8 (JP-8) is the fuel used in most US and North Atlantic Treaty Organization (NATO) jet aircraft, and will be the predominant fuel both for military land vehicles and aircraft into the twenty-first century. JP-8 exhibits reduced volatility and lower benzene content as compared to JP-4, the predominant military aircraft fuel before 1992, possibly suggesting greater occupational exposure safety. However, the higher rates of occupational exposure through fueling and maintenance of increasingly larger numbers of aircraft/vehicles raise concerns with respect to toxicity. Clinical studies of workers experiencing long-term exposure to certain jet fuels demonstrated deficits in CNS function, including fatigue, neurobehavioral changes, psychiatric disorders, and abnormal electroencephalogram (EEG). In the present study, cDNA nylon arrays (Atlas Rat 1.2 Array, Clontech Laboratories, Palo Alto, CA) were utilized to measure changes in gene expression in whole brain tissue of rats exposed repeatedly to JP-8, under conditions that simulated possible real-world occupational exposure (6 h/day for 91 days) to JP-8 vapor at 1,000 mg/m3. Gene expression analysis of the exposure group compared to the control group revealed a modulation of several genes, including glutathione S-transferase Yb2 subunit (GST Yb2); cytochrome P450 IIIAl (CYP3A1); glucose-dependent insulinotropic peptide (GIP); alpha1-proteinase inhibitor (alpha1-AT); polyubiquitin; GABA transporter 3 (GAT-3); and plasma membrane Ca2+-transporting ATPase (brain isoform 2) (PMCA2). The implications of these vapor-induced changes in gene expression are discussed.