Benzene and naphthalene in air and breath as indicators of exposure to jet fuel

Biomarkers of occupational benzene exposure: A Systematic Review to estimate the exposure levels and individual susceptibility at low doses

Benzene is associated with diverse occupational and public health hazards. It exhibits an ability to rapidly permeate the skin and contaminate water and food sources, leading to dermal and ingestion exposures. Despite numerous studies examining the associations between benzene and various indicators of harm, the findings have yielded inconsistent results. Furthermore, relying solely on air concentration as a measure of benzene exposure is limited, as it fails to account for internal exposure dose and individual susceptibility. This study aimed to conduct a comprehensive review in order to present current knowledge on benzene biomarkers and their significance in evaluating exposure levels and associated health hazards. The search methodology adhered to the PRISMA guidelines and involved the application of specific inclusion and exclusion criteria across multiple databases including PubMed, Embase, and Web of Science. Two researchers independently extracted and evaluated the relevant data based on predetermined criteria. Following the screening process, a total of 80 articles were considered eligible out of the initially retrieved 1053 articles after undergoing screening and assessment for inclusion. As the level of exposure decreased, specific biomarkers demonstrated a gradual increase in limitations, including heightened background concentrations and vulnerability to confounding factors. The advancement of sampling and analysis techniques will yield new biomarkers. Additionally, when conducting practical work, it is crucial to employ a comprehensive utilization of diverse biomarkers while excluding individual metabolic variations and combined exposure factors.

Complex Mixtures: Array PBPK Modeling of Jet Fuel Components

An array physiologically-based pharmacokinetic (PBPK) model represents a streamlined method to simultaneously quantify dosimetry of multiple compounds. To predict internal dosimetry of jet fuel components simultaneously, an array PBPK model was coded to simulate inhalation exposures to one or more selected compounds: toluene, ethylbenzene, xylenes, n-nonane, n-decane, and naphthalene. The model structure accounts for metabolism of compounds in the lung and liver, as well as kinetics of each compound in multiple tissues, including the cochlea and brain regions associated with auditory signaling (brainstem and temporal lobe). The model can accommodate either diffusion-limited or flow-limited kinetics (or a combination), allowing the same structure to be utilized for compounds with different characteristics. The resulting model satisfactorily simulated blood concentration and tissue dosimetry data from multiple published single chemical rat studies. The model was then utilized to predict tissue kinetics for the jet fuel hearing loss study (JTEH A, 25:1-14). The model was also used to predict rat kinetic comparisons between hypothetical exposures to JP-8 or a Virent Synthesized Aromatic Kerosene (SAK):JP-8 50:50 blend at the occupational exposure limit (200 mg/m³). The array model has proven useful for comparing potential tissue burdens resulting from complex mixture exposures.

Assessing the effect of BTEX on blood and spirometry parameters staff in a petroleum refinery

This study aimed to investigate the impact of BTEX compound on blood and spirometry parameters of staff in the Abadan petroleum refinery (Iran). In 80 staff was examined in terms of BTEX exposure (40 exposed and 40 non-exposed). In this study, the air sampling was carried out according to the NIOSH 1,501 method and an automated hematology analyzer was used to analyze all blood samples to evaluate blood parameters and using a Micro Direct automated computerized spirometer. Spss20 software was used to interpret the performance. According to the obtained results, total BTEX concentrations with the recommended standard level showed that, toluene, ethylbenzene, and xylenes, concentrations in Abadan Oil Refining Company Workers' breathing zone were lower than the TLV-TWA recommended by ACGIH. However, the average concentration of benzene was higher than the allowable limit. Therefore, in this study the effect of benzene on the blood and respiratory parameters of the workers was evaluated, the comparison of the blood and respiratory parameters between the groups of exposed and unexposed workers did not reveal any statistical difference between the groups (p > 0.001). The results showed no statistically significant connection between mean blood and spirometry parameters and benzene exposure. Also, based on results the effect of benzene problems needs to be prevented in employees with adequate engineering and management controls and periodic inspection.

A Physiologically Based Pharmacokinetic Model for Naphthalene With Inhalation and Skin Routes of Exposure

Naphthalene, a volatile organic compound present in moth repellants and petroleum-based fuels, has been shown to induce toxicity in mice and rats during chronic inhalation exposures. Although simpler default methods exist for extrapolating toxicity points of departure from animals to humans, using a physiologically based pharmacokinetic (PBPK) model to perform such extrapolations is generally preferred. Confidence in PBPK models increases when they have been validated using both animal and human in vivo pharmacokinetic (PK) data. A published inhalation PBPK model for naphthalene was previously shown to predict rodent PK data well, so we sought to evaluate this model using human PK data. The most reliable human data available come from a controlled skin exposure study, but the inhalation PBPK model does not include a skin exposure route; therefore, we extended the model by incorporating compartments representing the stratum corneum and the viable epidermis and parameters that determine absorption and rate of transport through the skin. The human data revealed measurable blood concentrations of naphthalene present in the subjects prior to skin exposure, so we also introduced a continuous dose-rate parameter to account for these baseline blood concentration levels. We calibrated the three new parameters in the modified PBPK model using data from the controlled skin exposure study but did not modify values for any other parameters. Model predictions then fell within a factor of 2 of most (96%) of the human PK observations, demonstrating that this model can accurately predict internal doses of naphthalene and is thus a viable tool for use in human health risk assessment.

Health Effects of Naphthalene Exposure: A Systematic Evidence Map and Analysis of Potential Considerations for Dose-Response Evaluation

BACKGROUND

Naphthalene is a polycyclic aromatic hydrocarbon that has been associated with health effects, including cancer. As the state of the science on naphthalene toxicity continues to evolve, updated toxicity reference value(s) may be required to support human health risk assessment.

OBJECTIVES

We present a systematic evidence map of studies that could be used to derive toxicity reference value(s) for naphthalene.

METHODS

Human and animal health effect studies and physiologically based pharmacokinetic (PBPK) models were identified from a literature search based on populations, exposures, comparators, and outcomes (PECO) criteria. Human and animal studies meeting PECO criteria were refined to a smaller subset considered most informative for deriving chronic reference value(s), which are preferred for assessing risk to the general public. This subset was evaluated for risk of bias and sensitivity, and the suitability of each study for dose-response analysis was qualitatively assessed. Lowest observed adverse effect levels (LOAELs) were extracted and summarized. Other potentially relevant studies (e.g., mechanistic and toxicokinetic studies) were tracked as supplemental information but not evaluated further. Existing reference values for naphthalene are also summarized.

RESULTS

We identified 26 epidemiology studies and 16 animal studies that were considered most informative for further analysis. Eleven PBPK models were identified. The available epidemiology studies generally had significant risk of bias and/or sensitivity concerns and were mostly found to have low suitability for dose-response analysis due to the nature of the exposure measurements. The animal studies had fewer risk of bias and sensitivity concerns and were mostly found to be suitable for dose-response analysis.

CONCLUSION

Although both epidemiological and animal studies of naphthalene provide weight of evidence for hazard identification, the available animal studies appear more suitable for reference value derivation. PBPK models and mechanistic and toxicokinetic data can be applied to extrapolate these animal data to humans, considering mode of action and interspecies metabolic differences. https://doi.org/10.1289/EHP7381.

A review of health effects associated with exposure to jet engine emissions in and around airports

BACKGROUND

Airport personnel are at risk of occupational exposure to jet engine emissions, which similarly to diesel exhaust emissions include volatile organic compounds and particulate matter consisting of an inorganic carbon core with associated polycyclic aromatic hydrocarbons, and metals. Diesel exhaust is classified as carcinogenic and the particulate fraction has in itself been linked to several adverse health effects including cancer.

METHOD

In this review, we summarize the available scientific literature covering human health effects of exposure to airport emissions, both in occupational settings and for residents living close to airports. We also report the findings from the limited scientific mechanistic studies of jet engine emissions in animal and cell models.

RESULTS

Jet engine emissions contain large amounts of nano-sized particles, which are particularly prone to reach the lower airways upon inhalation. Size of particles and emission levels depend on type of aircraft, engine conditions, and fuel type, as well as on operation modes. Exposure to jet engine emissions is reported to be associated with biomarkers of exposure as well as biomarkers of effect among airport personnel, especially in ground-support functions. Proximity to running jet engines or to the airport as such for residential areas is associated with increased exposure and with increased risk of disease, increased hospital admissions and self-reported lung symptoms.

CONCLUSION

We conclude that though the literature is scarce and with low consistency in methods and measured biomarkers, there is evidence that jet engine emissions have physicochemical properties similar to diesel exhaust particles, and that exposure to jet engine emissions is associated with similar adverse health effects as exposure to diesel exhaust particles and other traffic emissions.

Investigation by mass spectrometry and 32P post-labelling of DNA adducts formation from 1,2-naphthoquinone, an oxydated metabolite of naphthalene

Naphthalene is the simplest representative of polycyclic aromatic hydrocarbons (PAHs). It is detected as major pollutant in the different compartments of the environment. This compound is considered by the international agency for research on cancer (IARC), the specialized cancer agency of the World Health Organisation (WHO), as a possible carcinogenic (group 2B) since 2002, mainly based on studies on chronic inhalation in rodent by the national toxicology program of the U.S. department of health and human services. In humans, its main metabolites correspond to derivatives substituted in position and 1 and 2 as 1,2-naphthoquinone (1,2-NphQ). Based on previous studies, 1,2-NphQ is supposed to react with DNA to form mostly depurinating adducts, a possible initiating step of carcinogenicity. To confirm this potentiality, adducts were synthetized by the reaction of 1,2-NphQ with 2'-deoxyguanosine (2'-dG) in N,N-dimethylformamide (DMF), water and calf thymus DNA. 2'-dG adducts were analyzed by ³²P post-labelling, HPLC with ultra-violet detection and ultra-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). We found stable DNA adducts detected in DNA. We proposed a formation mechanism by a 1,4-Michael addition with 2'-dG. Adducts with 2'-deoxyxanthosine are formed after a spontaneous deamination of 2'-dG. These adducts are good candidates as biomarkers allowing evaluation of exposure to naphthalene and its derivatives in the development of pathologies such as cancer.

Development of a method to profile 2- to 4-ring polycyclic aromatic hydrocarbons in saliva samples from smokers and non-smokers by headspace-solid-phase microextraction-gas chromatography-triple quadrupole tandem mass spectrometry

This study reports the development of a method based on headspace (HS)-solid-phase microextraction (SPME)-gas chromatography (GC)-triple quadrupole tandem mass spectrometry (MS/MS) for the quantification of 2- to 4-ring polycyclic aromatic hydrocarbons (PAHs) in saliva samples. Eight unmetabolized compounds (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene) were quantified using six deuterated PAHs as surrogate internal standards. The absence of matrix effect allowed saliva samples to be quantified by external calibration method. The optimized method resulted easy, with minimal sample pre-treatment (homogenization of the sample), and it achieved the highest sensitivity up to date: limits of quantification (LOQ) were in the 0.8-26.4 ng L^-1 range, with a significant improvement in comparison with the few existing methods. Intra- and inter-run precisions provided CV values <18.1%, and accuracies within 20% of the spiked concentration. The application of the method to the analysis of fresh saliva samples collected by spitting from smokers (n = 10) and non-smokers (n = 10) showed that PAHs were quantifiable in all samples and that smokers had higher levels of all compounds than non-smokers. These results show that the method is suitable for quantifying low-boiling PAHs in saliva samples from individuals exposed at different PAH levels.

Characterization of outdoor air pollution from solid fuel combustion in Xuanwei and Fuyuan, a rural region of China

Outdoor air pollution is a growing public health concern, particularly in urban settings. However, there are limited epidemiological data on outdoor air pollution in rural areas with substantial levels of air pollution attributed to solid fuel burning for household cooking and heating. Xuanwei and Fuyuan are rural counties in China where the domestic combustion of locally sourced bituminous (“smoky”) coal has been associated with the highest lung cancer rates in China. We previously assessed indoor and personal air pollution exposures in this area; however, the influence of indoor coal combustion and household ventilation on outdoor air pollution has not been assessed. Therefore, we measured outdoor fine particulate matter (PM_2.5), species of polycyclic aromatic hydrocarbons (PAHs) including naphthalene (NAP) and the known carcinogen benzo(a)pyrene (BaP), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂) over two consecutive 24-h sampling periods in 29 villages. Just over half of the villages were revisited two to nine months after the initial sampling period to repeat all measurements. The overall geometric mean (GM) of outdoor PM_2.5, BaP, NAP, and NO₂ were 45.3 µg/m³, 9.7 ng/m³, 707.7 ng/m³, and 91.5 µg/m³, respectively. Using linear mixed effects models, we found that burning smoky coal was associated with higher outdoor BaP concentrations [GM ratio (GMR) = 2.79] and lower outdoor SO₂ detection rates (GMR = 0.43), compared to areas burning smokeless coal. Areas with predominantly ventilated stoves (> 50% of stoves) had higher outdoor BaP (GMR = 1.49) compared to areas with fewer ventilated stoves. These results show that outdoor air pollution in a rural region of China was associated with the type of coal used for cooking and heating indoors and the presence of stove ventilation. Our findings suggest that efforts of household stove improvement to reduce indoor air pollution have resulted in higher outdoor air pollution levels. Further reducing adverse health effects in rural villages from household coal combustion will require the use of cleaner fuel types.

Recovery and reactivity of polycyclic aromatic hydrocarbons collected on selected sorbent tubes and analyzed by thermal desorption-gas chromatography/mass spectrometry

This article describes the optimization of methodology for extending the measurement of volatile organic compounds (VOCs) to increasingly heavier polycyclic aromatic hydrocarbons (PAHs) with a detailed focus on recent sorbent tube technology. Although PAHs have lower volatility than compounds such as benzene, toluene, ethylbenzene and xylenes, these semi-volatile compounds can be detected in air and breath samples. For this work, PAHs were captured on sorbent tubes and subsequently analyzed using automated thermal desorption gas chromatography - mass spectrometry (ATD-GC/MS). While many different sorbent tubes are commercially available, optimization for airborne PAH sampling using sorbent tubes has not been previously considered. Herein, several commercially available sorbent tubes, including Carbograph 2 TD/1TD, Tenax TA, XRO-440, and inert-coated PAH tubes are compared to determine the relative recovery for eight PAHs commonly found in the environment. Certain types of sorbent materials were found to be better suited for PAH recovery during thermal desorption, and PAH reaction products were observed on several types of sorbent tubes, including graphitized carbon black sorbents with stainless steel tube materials. As such, selection of sorbent tube media should be carefully considered prior to embarking on a PAH study.

JP8 exposure and neurocognitive performance among US Air Force personnel

Petroleum-based fuels such as jet propellant (JP) 4, JP5, JP8, and jet A1 (JetA) are among the most common occupational chemical exposures encountered by military and civilian workforces. Although acute toxicity following high-level exposures to JP8 and similar chemical mixtures has been reported, the relationship between persistent low-level occupational exposures to jet fuels and both acute and longer-term central nervous system (CNS) function has been comparatively less well characterized. This paper describes results of neurocognitive assessments acquired repeatedly across a work week study design (Friday to Friday) as part of the Occupational JP8 Exposure Neuroepidemiology Study (OJENES) involving U.S. Air Force (AF) personnel with varying levels of exposure to jet fuel (JP8). JP8 exposure levels were quantified using both personal air monitoring and urinary biomarkers of exposure. Neurocognitive performance was evaluated using an objective, standardized battery of tests. No significant associations with neurocognitive performances were observed between individuals having regular contact and those with minimal/no direct contact with JP8 (measured by average work week levels of personal breathing zone exposure). Also, no significant findings were noted between repeated measures of absorbed dose (multi-day pre-shift urinary 1- and 2-naphthol) and reduced proficiency on neurocognitive tasks across the work week. Results suggest that occupational exposure to lower (than regulated standards) levels of JP8 do not appear to be associated with acute, measurable differences or changes in neurocognitive performance.

Breath Biomarkers to Measure Uptake of Volatile Organic Compounds by Bicyclists

Breath biomarkers were used to study uptake of traffic-related volatile organic compounds (VOCs) from urban bicycling. Breath analysis was selected because it is one of the least invasive methods to assess urban traveler exposure. Research hurdles that were overcome included considering that factors other than on-road exposure can influence concentrations in the body, and absorbed doses during a trip can be small compared to baseline body burdens. Pre-trip, on-road, and post-trip breath concentrations and ambient air concentrations were determined for 26 VOCs for bicyclists traveling on different path types. Statistical analyses of the concentration data identified eight monoaromatic hydrocarbons potentially useful as breath biomarkers to compare differences in body levels brought about by urban travel choices. Breath concentrations of the biomarker compounds were significantly higher than background levels after riding on high-traffic arterial streets and on a path through a high-exposure industrial area, but not after riding on low-traffic local streets or on other off-street paths. Modeled effects of high-traffic streets on ambient concentrations were 100-200% larger than those of low-traffic streets; modeled effects of high-traffic streets on breath concentrations were 40-100% larger than those of low-traffic streets. Similar percentage increases in breath concentrations are expected for bicyclists in other cities.

Phytonutrients Differentially Stimulate NAD(P)H:Quinone Oxidoreductase, Inhibit Proliferation, and Trigger Mitotic Catastrophe in Hepa1c1c7 Cells

Phytonutrients have rapidly emerged as natural food chemicals possessing multifaceted biological actions that may support beneficial health outcomes. Among the vast array of phytonutrients currently being studied, sulforaphane, curcumin, quercetin, and resveratrol have been frequently reported to stimulate the expression of endogenous detoxification enzymes and may thereby facilitate the neutralization of otherwise harmful environmental agents. Some of these same phytonutrients, however, have also been implicated in disrupting normal cell proliferation and hence may possess toxic properties in and of themselves. In this study, we characterize the respective minimum threshold concentrations of the aforementioned phytonutrients in Hepa1c1c7 cells that stimulate

NAD(P)H

quinone oxidoreductase (NQO1), a key enzyme in the hepatic neutralization of menadione, other biological oxidants, and some environmental carcinogens. Moreover, our findings demonstrate that relatively low concentrations of either sulforaphane or curcumin significantly (P < .05) increase NQO1 protein expression and activity without triggering G2/M cell cycle arrest or mitotic catastrophe. The minimal quercetin concentration inducing NQO1, however, was 100-fold higher than that which disrupted mitosis. Also, while resveratrol modestly stimulated NQO1, the minimally effective resveratrol concentration concomitantly induced evidence of cellular apoptosis. Taken together, these findings indicate that only particular phytonutrients are likely efficacious in upregulating NQO1 activity without also leading to hepatic cytotoxicity.

Breath analysis: technical developments and challenges in the monitoring of human exposure to volatile organic compounds

At present, there is a growing concern about human quality of life. In particular, there is an awareness of the impact of volatile organic compounds (VOCs) on the environment and human health, so the monitoring of human exposure to VOCs is an increasingly urgent need. Biomonitoring is theoretically more accurate compared with traditional ambient air monitoring, and it plays an essential role in human environmental exposure assessment. Breath analysis is a biomonitoring method with many advantages, which is applicable to assessments of human exposure to a large number of VOCs. Techniques are being developed to improve the sensitivity and precision of breath analysis based on in-direct and direct measurements which will be reviewed in this paper. This paper briefly reviews the frequently used methods in both of these categories, specifically highlighting some promising new techniques. Furthermore, this review also provides theoretical background knowledge about the use of breath analysis as a biomonitoring tool for human exposure assessment. A review of the application of breath analysis to human exposure monitoring during last two decades is also provided according to occupational/non-occupational exposure. Obstacles and potential challenges in this field are also summarized. Based on the gradual improvements in the theoretical basis and technology reviewed in this paper, breath analysis is an enormous potential approach for the monitoring of human exposure to VOCs.

Urinary polycyclic aromatic hydrocarbon (OH-PAH) metabolite concentrations and the effect of GST polymorphisms among US Air Force personnel exposed to jet fuel

OBJECTIVE

To evaluate the association between inhalation exposure to jet propulsion fuel 8 (JP-8) and urinary metabolites among US Air Force (USAF) personnel, and investigate the role of glutathione S-transferase polymorphisms.

METHODS

Personal air samples were collected from 37 full-time USAF personnel during 4 consecutive workdays and analyzed for JP-8 constituents and total hydrocarbons. Pre- and postshift urine samples were collected each day and analyzed for polycyclic aromatic hydrocarbon urinary metabolites.

RESULTS

Work shift exposure to total hydrocarbons was significantly associated with postshift urinary 1-naphthol (β = 0.17; P = <0.0001), 2-naphthol (β = 0.09; P = 0.005), and 2-hydroxyfluorene concentrations (β = 0.08; P = 0.006), and a significant gene-environment interaction was observed with glutathione S-transferase mu-1.

CONCLUSIONS

USAF personnel experience inhalation exposure to JP-8, which is associated with absorption of JP-8 constituents while performing typical job-related tasks, and in our data the glutathione S-transferase mu-1 polymorphism was associated with differential metabolism of naphthalene.

The human volatilome: volatile organic compounds (VOCs) in exhaled breath, skin emanations, urine, feces and saliva

Breath analysis is a young field of research with its roots in antiquity. Antoine Lavoisier discovered carbon dioxide in exhaled breath during the period 1777-1783, Wilhelm (Vilém) Petters discovered acetone in breath in 1857 and Johannes Müller reported the first quantitative measurements of acetone in 1898. A recent review reported 1765 volatile compounds appearing in exhaled breath, skin emanations, urine, saliva, human breast milk, blood and feces. For a large number of compounds, real-time analysis of exhaled breath or skin emanations has been performed, e.g., during exertion of effort on a stationary bicycle or during sleep. Volatile compounds in exhaled breath, which record historical exposure, are called the 'exposome'. Changes in biogenic volatile organic compound concentrations can be used to mirror metabolic or (patho)physiological processes in the whole body or blood concentrations of drugs (e.g. propofol) in clinical settings-even during artificial ventilation or during surgery. Also compounds released by bacterial strains like Pseudomonas aeruginosa or Streptococcus pneumonia could be very interesting. Methyl methacrylate (CAS 80-62-6), for example, was observed in the headspace of Streptococcus pneumonia in concentrations up to 1420 ppb. Fecal volatiles have been implicated in differentiating certain infectious bowel diseases such as Clostridium difficile, Campylobacter, Salmonella and Cholera. They have also been used to differentiate other non-infectious conditions such as irritable bowel syndrome and inflammatory bowel disease. In addition, alterations in urine volatiles have been used to detect urinary tract infections, bladder, prostate and other cancers. Peroxidation of lipids and other biomolecules by reactive oxygen species produce volatile compounds like ethane and 1-pentane. Noninvasive detection and therapeutic monitoring of oxidative stress would be highly desirable in autoimmunological, neurological, inflammatory diseases and cancer, but also during surgery and in intensive care units. The investigation of cell cultures opens up new possibilities for elucidation of the biochemical background of volatile compounds. In future studies, combined investigations of a particular compound with regard to human matrices such as breath, urine, saliva and cell culture investigations will lead to novel scientific progress in the field.

Single-nucleotide polymorphisms associated with skin naphthyl-keratin adduct levels in workers exposed to naphthalene

BACKGROUND

Individual genetic variation that results in differences in systemic response to xenobiotic exposure is not accounted for as a predictor of outcome in current exposure assessment models.

OBJECTIVE

We developed a strategy to investigate individual differences in single-nucleotide polymorphisms (SNPs) as genetic markers associated with naphthyl-keratin adduct (NKA) levels measured in the skin of workers exposed to naphthalene.

METHODS

The SNP-association analysis was conducted in PLINK using candidate-gene analysis and genome-wide analysis. We identified significant SNP-NKA associations and investigated the potential impact of these SNPs along with personal and workplace factors on NKA levels using a multiple linear regression model and the Pratt index.

RESULTS

In candidate-gene analysis, a SNP (rs4852279) located near the CYP26B1 gene contributed to the 2-naphthyl-keratin adduct (2NKA) level. In the multiple linear regression model, the SNP rs4852279, dermal exposure, exposure time, task replacing foam, age, and ethnicity all were significant predictors of 2NKA level. In genome-wide analysis, no single SNP reached genome-wide significance for NKA levels (all p ≥ 1.05 × 10(-5)). Pathway and network analyses of SNPs associated with NKA levels were predicted to be involved in the regulation of cellular processes and homeostasis.

CONCLUSIONS

These results provide evidence that a quantitative biomarker can be used as an intermediate phenotype when investigating the association between genetic markers and exposure-dose relationship in a small, well-characterized exposed worker population.

Effects on airways of short-term exposure to two kinds of wood smoke in a chamber study of healthy humans

INTRODUCTION

Air pollution causes respiratory symptoms and pulmonary disease. Airway inflammation may be involved in the mechanism also for cardiovascular disease. Wood smoke is a significant contributor to air pollution, with complex and varying composition. We examined airway effects of two kinds of wood smoke in a chamber study.

MATERIALS AND METHODS

Thirteen subjects were exposed to filtered air and to wood smoke from the start-up phase and the burn-out phase of the wood-burning cycle. Levels of PM(2.5) were 295 µg/m(3) and 146 µg/m(3), number concentrations 140 000/cm(3) and 100 000/cm(3). Biomarkers in blood, breath and urine were measured before and on several occasions after exposure. Effects of wood smoke exposure were assessed adjusting for results with filtered air.

RESULTS

After exposure to wood smoke from the start-up, but not the burn-out session, Clara cell protein 16 (CC16) increased in serum after 4 hours, and in urine the next morning. CC16 showed a clear diurnal variation. Fraction of exhaled nitric oxide (FENO) increased after wood smoke exposure from the burn-out phase, but partly due to a decrease after exposure to filtered air. No other airway markers increased.

CONCLUSIONS

The results indicate that relatively low levels of wood smoke exposure induce effects on airways. Effects on airway epithelial permeability was shown for the start-up phase of wood burning, while FENO increased after the burn-out session. CC16 seems to be a sensitive marker of effects of air pollution both in serum and urine, but its function and the significance need to be clarified.

Characterization of inhalation exposure to jet fuel among U.S. Air Force personnel

BACKGROUND

Jet propulsion fuel-8 (JP-8) is the primary jet fuel used by the US military, collectively consuming ~2.5 billion gallons annually. Previous reports suggest that JP-8 is potentially toxic to the immune, respiratory, and nervous systems. The objectives of this study were to evaluate inhalation exposure to JP-8 constituents among active duty United States Air Force (USAF) personnel while performing job-related tasks, identify significant predictors of inhalation exposure to JP-8, and evaluate the extent to which surrogate exposure classifications were predictive of measured JP-8 exposures.

METHODS

Seventy-three full-time USAF personnel from three different air force bases were monitored during four consecutive workdays where personal air samples were collected and analyzed for benzene, ethylbenzene, toluene, xylenes, total hydrocarbons (THC), and naphthalene. The participants were categorized a priori into high- and low-exposure groups, based on their exposure to JP-8 during their typical workday. Additional JP-8 exposure categories included job title groups and self-reported exposure to JP-8. Linear mixed-effects models were used to evaluate predictors of personal air concentrations.

RESULTS

The concentrations of THC in air were significantly different between a priori exposure groups (2.6 mg m(-3) in high group versus 0.5 mg m(-3) in low, P < 0.0001), with similar differences observed for other analytes in air. Naphthalene was strongly correlated with THC (r = 0.82, P < 0.0001) and both were positively correlated with the relative humidity of the work environment. Exposures to THC and naphthalene varied significantly by job categories based on USAF specialty codes and were highest among personnel working in fuel distribution/maintenance, though self-reported exposure to JP-8 was an even stronger predictor of measured exposure in models that explained 72% (THC) and 67% (naphthalene) of between-worker variability. In fact, both self-report JP-8 exposure and a priori exposure groups explained more between-worker variability than job categories.

CONCLUSIONS

Personal exposure to JP-8 varied by job and was positively associated with the relative humidity. However, self-reported exposure to JP-8 was an even stronger predictor of measured exposure than job title categories, suggesting that self-reported JP-8 exposure is a valid surrogate metric of exposure when personal air measurements are not available.

Urinary biomarkers of occupational jet fuel exposure among Air Force personnel

There is a potential for widespread occupational exposure to jet fuel among military and civilian personnel. Urinary metabolites of naphthalene have been suggested for use as short-term biomarkers of exposure to jet fuel (jet propulsion fuel 8 (JP8)). In this study, urinary biomarkers of JP8 were evaluated among US Air Force personnel. Personnel (n=24) were divided a priori into high, moderate, and low exposure groups. Pre- and post-shift urine samples were collected from each worker over three workdays and analyzed for metabolites of naphthalene (1- and 2-naphthol). Questionnaires and breathing-zone naphthalene samples were collected from each worker during the same workdays. Linear mixed-effects models were used to evaluate the exposure data. Post-shift levels of 1- and 2-naphthol varied significantly by a priori exposure group (levels in high group>moderate group>low group), and breathing-zone naphthalene was a significant predictor of post-shift levels of 1- and 2-naphthol, indicating that for every unit increase in breathing-zone naphthalene, there was an increase in naphthol levels. These results indicate that post-shift levels of urinary 1- and 2-naphthol reflect JP8 exposure during the work-shift and may be useful surrogates of JP8 exposure. Among the high exposed workers, significant job-related predictors of post-shift levels of 1- and 2-naphthol included entering the fuel tank, repairing leaks, direct skin contact with JP8, and not wearing gloves during the work-shift. The job-related predictors of 1- and 2-naphthol emphasize the importance of reducing inhalation and dermal exposure through the use of personal protective equipment while working in an environment with JP8.

The possibilities will take your breath away: breath analysis for assessing environmental exposure

Human breath is the gaseous exchange with the blood and thus contains trace organic contaminants and metabolites representative of environmental doses. Sampling and analysis of gaseous components in human breath offers a noninvasive and quick means of qualitatively and quantitatively assessing internalized doses of environmental contaminants. Although the humid and complex nature of breath is a challenge for detection of part-per-trillion to part-per-billion concentrations of environmental contaminants, recent advances in chemical analysis and instrumentation are allowing determination of environmental exposure and disease detection.

The utility of naphthyl-keratin adducts as biomarkers for jet-fuel exposure

We investigated the association between biomarkers of dermal exposure, naphthyl-keratin adducts (NKA), and urine naphthalene biomarker levels in 105 workers routinely exposed to jet-fuel. A moderate correlation was observed between NKA and urine naphthalene levels (p = 0.061). The NKA, post-exposure breath naphthalene, and male gender were associated with an increase, while CYP2E1*6 DD and GSTT1-plus (++/+-) genotypes were associated with a decrease in urine naphthalene level (p < 0.0001). The NKA show great promise as biomarkers for dermal exposure to naphthalene. Further studies are warranted to characterize the relationship between NKA, other exposure biomarkers, and/or biomarkers of biological effects due to naphthalene and/or PAH exposure.

The Occupational JP8 Exposure Neuroepidemiology Study (OJENES): repeated workday exposure and central nervous system functioning among US Air Force personnel

One of the most prevalent workplace chemical exposures historically and currently confronting the global military and civilian workforce is jet propellant (JP) fuel (e.g., JP4, JP5, JP8, jet A1), a complex mixture of numerous hydrocarbon compounds and additives. To date, numerous protective and preventive strategies (e.g., federal exposure limits, workplace procedure protocols, protective gear such as goggles, respirator use, gloves, and coveralls) have been put in place to minimize acutely toxic exposure levels. However, questions remain regarding the effect of repeated exposures at lower (than regulated) levels of JP fuel. The Occupational JP8 Exposure Neuroepidemiology Study (OJENES) was designed to examine the relationships between occupational JP8 exposure over multiple, repeated workdays and specific aspects of central nervous system (CNS) functioning among Air Force (AF) personnel. In this report, we present the OJENES methodology, descriptive findings related to participant characteristics, JP8 exposure levels observed over a work week among higher and lower exposure groups, and neuropsychological task performances at the first study assessment. Results indicated minimal differences between participants in the high and lower exposure groups in terms of descriptive characteristics, other than daily JP8 exposure levels (p<0.001). In addition, neuropsychological task performances for most task measures were not found to be significantly different from reported reference ranges. These findings demonstrated that confounding and misclassification of exposure and outcome status are not major concerns for the study. Therefore, future OJENES analyses targeting the more focused research questions regarding associations between JP8 exposure and CNS functioning are likely to provide valid conclusions, as they will be less influenced by these research biases.

Observing the human exposome as reflected in breath biomarkers: heat map data interpretation for environmental and intelligence research

Over the past decade, the research of human system biology and the interactions with the external environment has permeated all phases of environmental, medical and public health research. Similar to the fields of genomics and proteomics research, the advent of new instrumentation for measuring breath biomarkers and their associated meta-data also provide very useful, albeit complex, data structures. The biomarker research community is beginning to invoke tools from system biology to assess the impact of environmental exposures, as well as from internal health states, on the expression of suites of chemicals in exhaled breath. This new approach introduces the concept of the exposome as a complement to the genome in exploring the environment-gene interaction. In addition to answering questions regarding health status for the medical community, breath biomarker patterns are useful for assessing public health risks from environmental exposures. Furthermore, breath biomarker patterns can inform security risks from suspects via covert interrogation of blood borne chemical levels that reflect previous activities. This paper discusses how different classes of exhaled breath biomarker measurements can be used to rapidly assess patterns in complex data. We present exhaled breath data sets to demonstrate the value of the graphical 'heat map' approach for hypothesis development and subsequent guidance for stochastic and mixed effect data interpretation. We also show how to graphically interpret exhaled breath measurements of exogenous jet fuel components, as well as exhaled breath condensate measurements of endogenous chemicals.

Review of pesticide urinary biomarker measurements from selected US EPA children's observational exposure studies

Children are exposed to a wide variety of pesticides originating from both outdoor and indoor sources. Several studies were conducted or funded by the EPA over the past decade to investigate children’s exposure to organophosphate and pyrethroid pesticides and the factors that impact their exposures. Urinary metabolite concentration measurements from these studies are consolidated here to identify trends, spatial and temporal patterns, and areas where further research is required. Namely, concentrations of the metabolites of chlorpyrifos (3,5,6-trichloro-2-pyridinol or TCPy), diazinon (2-isopropyl-6-methyl-4-pyrimidinol or IMP), and permethrin (3-phenoxybenzoic acid or 3-PBA) are presented. Information on the kinetic parameters describing absorption and elimination in humans is also presented to aid in interpretation. Metabolite concentrations varied more dramatically across studies for 3-PBA and IMP than for TCPy, with TCPy concentrations about an order of magnitude higher than the 3-PBA concentrations. Temporal variability was high for all metabolites with urinary 3-PBA concentrations slightly more consistent over time than the TCPy concentrations. Urinary biomarker levels provided only limited evidence of applications. The observed relationships between urinary metabolite levels and estimates of pesticide intake may be affected by differences in the contribution of each exposure route to total intake, which may vary with exposure intensity and across individuals.

Inhalation exposure to jet fuel (JP8) among U.S. Air Force personnel

As jet fuel is a common occupational exposure among military and civilian populations, this study was conducted to characterize jet fuel (JP8) exposure among active duty U.S. Air Force personnel. Personnel (n = 24) were divided a priori into high, moderate, and low exposure groups. Questionnaires and personal air samples (breathing zone) were collected from each worker over 3 consecutive days (72 worker-days) and analyzed for total hydrocarbons (THC), benzene, toluene, ethylbenzene, xylenes, and naphthalene. Air samples were collected from inside the fuel tank and analyzed for the same analytes. Linear mixed-effects models were used to evaluate the exposure data. Our results show that the correlation of THC (a measure of overall JP8 inhalation exposure) with all other analytes was moderate to strong in the a priori high and moderate exposure groups combined. Inhalation exposure to all analytes varied significantly by self-reported JP8 exposure (THC levels higher among workers reporting JP8 exposure), a priori exposure group (THC levels in high group > moderate group > low group), and more specific job task groupings (THC levels among workers in fuel systems hangar group > refueling maintenance group > fuel systems office group > fuel handling group > clinic group), with task groupings explaining the most between-worker variability. Among highly exposed workers, statistically significant job task-related predictors of inhalation exposure to THC indicated that increased time in the hangar, working close to the fuel tank (inside > less than 25 ft > greater than 25 ft), primary job (entrant > attendant/runner/fireguard > outside hangar), and performing various tasks near the fuel tank, such as searching for a leak, resulted in higher JP8 exposure. This study shows that while a priori exposure groups were useful in distinguishing JP8 exposure levels, job task-based categories should be considered in epidemiologic study designs to improve exposure classification. Finally, the strong correlation of THC with naphthalene suggests that naphthalene may be an appropriate surrogate of JP8 exposure. [Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a pdf file containing a table detailing concentrations of JP8 components.].

Exposure to naphthalene induces naphthyl-keratin adducts in human epidermis in vitro and in vivo

We observed naphthyl-keratin adducts and dose-related metabolic enzyme induction at the mRNA level in reconstructed human epidermis in vitro after exposure to naphthalene. Immunofluorescence detection of 2-naphthyl-keratin-1 adducts confirmed the metabolism of naphthalene and adduction of keratin. We also observed naphthyl-keratin adducts in dermal tape-strip samples collected from naphthalene-exposed workers at levels ranging from 0.004 to 6.104 pmol adduct microg(-1) keratin. We have demonstrated the ability of the human skin to metabolize naphthalene and to form naphthyl-keratin adducts both in vitro and in vivo. The results indicate the potential use of keratin adducts as biomarkers of dermal exposure.

Sampling of benzene in environmental and exhaled air by solid-phase microextraction and analysis by gas chromatography-mass spectrometry

Benzene is classified as a Group I carcinogen by the International Agency for Research on Cancer (IARC). The risk assessment for benzene can be performed by monitoring environmental and occupational air, as well as biological monitoring through biomarkers. The present work developed and validated methods for benzene analysis by GC/MS using SPME as the sampling technique for ambient air and breath. The results of the analysis of air in parks and avenues demonstrated a significant difference, with average values of 4.05 and 18.26 microg m(-3), respectively, for benzene. Sampling of air in the occupational environment furnished an average of 3.41 and 39.81 microg m(-3). Moreover, the correlations between ambient air and expired air showed a significant tendency to linearity (R (2) = 0.850 and R (2) = 0.879). The results obtained for two groups of employees (31.91 and 72.62 microg m(-3)) presented the same trend as that from the analysis of environmental air.

Identification of surrogate measures of diesel exhaust exposure in a controlled chamber study

Exposure to diesel exhaust (DE) has been associated with acute cardiopulmonary and vascular responses, chronic noncancer health effects, and respiratory cancers in humans. To better understand DE exposures and eventually their related health effects, we established a controlled chamber experiment wherein human volunteer subjects were exposed to approximately 100 microg/m3 DE. In general, human exposure assessment for DE is based on ambient air measurements of surrogates such as elemental carbon (EC) or total organic carbon (OC) collected on filters. As specific health effect mechanisms and dose-response are obscured bythe complex composition of DE, the linkage from exposure to internal dose can presumably be improved by use of specific biomarkers and metabolites in blood, breath, or urine. Because EC and OC are not suitable as biomarkers, in this study, we focus on identifying compounds that are demonstrated indicators of DE and can also be found in biological fluids. We measured an assortment of volatile, semivolatile, and particle-bound aromatic compounds in the chamber air and report their airborne concentrations in DE and purified air, as well as the estimated values of the corresponding exposure ratios (mean DE air concentration:mean purified air concentration). These estimated exposure ratios were used to identify naphthalene (Nap) and phenanthrene (Phe) as potentially useful surrogates for DE exposure that could also serve as biomarkers. Estimated mean levels of Nap and Phe associated with the nominal 100 microg/m3 DE were 2600 and 765 ng/m3 with estimated exposure ratios of 252 and 92.4, respectively. Nap levels were significantly correlated with OC and total particle-bound polycyclic aromatic hydrocarbons (PAHs); Phe levels were significantly correlated with total volatile + semivolatile PAHs. These results suggest that Nap and Phe may be particularly useful surrogates for DE concentrations. While Nap and Phe are not validated here as internal biomarkers of DE exposure, we are currently assessing human biological specimens collected during this study and will discuss those results in ensuing papers.

Role of exhaled breath biomarkers in environmental health science

As a discipline of public health, environmental health science is the study of the linkage from environmental pollution sources to eventual adverse health outcome. This progression may be divided into two components, (1) "exposure assessment," which deals with the source terms, environmental transport, human exposure routes, and internal dose, and (2) "health effects," which deals with metabolism, cell damage, DNA changes, pathology, and onset of disease. The primary goal of understanding the linkage from source to health outcome is to provide the most effective and efficient environmental intervention methods to reduce health risk to the population. Biomarker measurements address an individual response to a common external environmental stressor. Biomarkers are substances within an individual and are subdivided into chemical markers, exogenous metabolites, endogenous response chemicals, and complex adducts (e.g., proteins, DNA). Standard biomarker measurements are performed in blood, urine, or other biological media such as adipose tissue and lavage fluid. In general, sample collection is invasive, requires medical personnel and a controlled environment, and generates infectious waste. Exploiting exhaled breath as an alternative or supplement to established biomarker measurements is attractive primarily because it allows a simpler collection procedure in the field for numerous individuals. Furthermore, because breath is a gas-phase matrix, volatile biomarkers become more readily accessible to analysis. This article describes successful environmental health applications of exhaled breath and proposes future research directions from the perspective of U.S. Environmental Protection Agency (EPA) human exposure research.

Occupational exposures associated with petroleum-derived products containing trace levels of benzene

Benzene may be present as a trace impurity or residual component of mixed petroleum products due to refining processes. In this article, the authors review the historical benzene content of various petroleum-derived products and characterize the airborne concentrations of benzene associated with the typical handling or use of these products in the United States, based on indoor exposure modeling and industrial hygiene air monitoring data collected since the late 1970s. Analysis showed that products that normally contained less than 0.1% v/v benzene, such as paints and paint solvents, printing solvents and inks, cutting and honing oils, adhesives, mineral spirits and degreasers, and jet fuel typically have yielded time-weighted average (TWA) airborne concentrations of benzene in the breathing zone and surrounding air ranging on average from <0.01 to 0.3 ppm. Except for a limited number of studies where the benzene content of the product was not confirmed to be <0.1% v/v, airborne benzene concentrations were also less than current occupational exposure limits (e.g., threshold limit value of 0.5 ppm and permissible exposure limit of 1.0 ppm) based on exceedance fraction calculations. Exposure modeling using Monte Carlo techniques also predicted 8-hr TWA near field airborne benzene concentrations ranging from 0.002 to 0.4 ppm under three hypothetical solvent use scenarios involving mineral spirits. The overall weight-of-evidence indicates that the vast majority of products manufactured in the United States after about 1978 contained <0.1% v/v benzene, and 8-hr TWA airborne concentrations of benzene in the workplace during the use of these products would not have been expected to exceed 0.5 ppm under most product use scenarios. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a document containing exposure modeling scenarios and results, historical benzene content of petroleum-derived products, and air monitoring results.].

Relationships between levels of volatile organic compounds in air and blood from the general population

The relationships between levels of volatile organic compounds (VOCs) in blood and air have not been well characterized in the general population where exposure concentrations are generally at parts per billion levels. This study investigates relationships between the levels of nine VOCs, namely, benzene, chloroform, 1,4-dichlorobenzene, ethylbenzene, methyl tert-butyl ether (MTBE), tetrachloroethene, toluene, and m-/p- and o-xylene, in blood and air from a stratified random sample of the general US population. We used data collected from 354 participants, including 89 smokers and 265 nonsmokers, aged 20-59 years, who provided samples of blood and air in the National Health and Nutrition Examination Survey (NHANES) 1999-2000. Demographic and physiological characteristics were obtained from self-reported information; smoking status was determined from levels of serum cotinine. Multiple linear regression models were used to investigate the relationships between VOC levels in air and blood, while adjusting for effects of smoking and demographic factors. Although levels of VOCs in blood were positively correlated with the corresponding air levels, the strength of association (R(2)) varied from 0.02 (ethylbenzene) to 0.68 (1,4-DCB). Also the blood-air relationships of benzene, toluene, ethylbenzene, and the xylenes (BTEX) were influenced by smoking, exposure-smoking interactions, and by gender, age, and BMI, whereas those of the other VOCs were not. Interestingly, the particular exposure-smoking interaction for benzene was different from those for toluene, ethylbenzene, and the xylenes. Whereas smokers retained more benzene in their blood at increasing exposure levels, they retained less toluene, ethylbenzene, and xylenes at increasing exposure levels. Investigators should consider interaction effects of exposure levels and smoking when exploring the blood-air relationships of the BTEX compounds in the general population.

Available data on naphthalene exposures: strengths and limitations

Exposures to naphthalene occur from a number of sources. Data on these exposures have been reported by a number of researchers; however, these data have not been organized into a consistent framework. In addition, while naphthalene has been identified as an animal inhalation carcinogen there has been no attempt to define the ranges of long-term average inhalation exposures for the general population or sub populations that are relevant to the assessment of the risk of the occurrence of chronic effects. This paper attempts to organize the available data on naphthalene levels in air and provide ranges for the long-term average concentrations experienced by different populations. The paper also discusses the limitations of available data and identifies areas for future research.

PBTK modeling demonstrates contribution of dermal and inhalation exposure components to end-exhaled breath concentrations of naphthalene

BACKGROUND

Dermal and inhalation exposure to jet propulsion fuel 8 (JP-8) have been measured in a few occupational exposure studies. However, a quantitative understanding of the relationship between external exposures and end-exhaled air concentrations has not been described for occupational and environmental exposure scenarios.

OBJECTIVE

Our goal was to construct a physiologically based toxicokinetic (PBTK) model that quantitatively describes the relative contribution of dermal and inhalation exposures to the end-exhaled air concentrations of naphthalene among U.S. Air Force personnel.

METHODS

The PBTK model comprised five compartments representing the stratum corneum, viable epidermis, blood, fat, and other tissues. The parameters were optimized using exclusively human exposure and biological monitoring data.

RESULTS

The optimized values of parameters for naphthalene were a) permeability coefficient for the stratum corneum 6.8 x 10(-5) cm/hr, b) permeability coefficient for the viable epidermis 3.0 x 10(-3) cm/hr, c) fat:blood partition coefficient 25.6, and d) other tissue:blood partition coefficient 5.2. The skin permeability coefficient was comparable to the values estimated from in vitro studies. Based on simulations of workers' exposures to JP-8 during aircraft fuel-cell maintenance operations, the median relative contribution of dermal exposure to the end-exhaled breath concentration of naphthalene was 4% (10th percentile 1% and 90th percentile 11%).

CONCLUSIONS

PBTK modeling allowed contributions of the end-exhaled air concentration of naphthalene to be partitioned between dermal and inhalation routes of exposure. Further study of inter- and intraindividual variations in exposure assessment is required to better characterize the toxicokinetic behavior of JP-8 components after occupational and/or environmental exposures.

Breath air analysis and its use as a biomarker in biological monitoring of occupational and environmental exposure to chemical agents

The analysis of exhaled air has several advantages since it is a noninvasive method applicable to a large number of toxic agents, in addition to being a simpler matrix than those of other biological samples such as urine and blood. However, it presents some challenges, such as the necessity of a more sensitive sampling procedure, since the chemical substances eliminated through exhaled air are unchanged in form, not being metabolized, and exhaled compounds are present at extremely low concentrations, i.e. in the nanomolar range. To improve the sensitivity and precision of measurement of the concentration of these substances in exhaled air, the sample usually has to be concentrated before assay by gas chromatography. To this end, the use of the solid-phase microextraction (SPME) technique has been proposed as an efficient sampling method. This paper presents a revision of breath analysis as a biomarker for occupational and environmental exposure to chemicals. The sampling methods and the potential use of SPME for determining chemical substances in exhaled air are discussed.

Experimental wood smoke exposure in humans

Experimental studies are used to evaluate effects of human exposure to diesel exhaust and concentrated ambient particles. This article describes a system for studying exposure of humans to wood smoke. Wood smoke was generated using a wood stove placed outside an exposure chamber that can hold at least 10 subjects. A partial flow of the generated wood smoke from the stove was mixed with filtered indoor air. Personal and stationary measurements were performed of PM2.5 and PM1 mass concentrations and various volatile organic compounds (VOCs): 1,3-butadiene, benzene, and aldehydes. In addition, particulate matter (PM) mass, number concentrations, and size distributions of particles (0.007-6.7 microm), as well as nitrous oxides, CO2, and CO, were measured online. Filters were analyzed for trace elements and black smoke. Polycyclic aromatic compounds, toluene, and xylenes were determined in stationary samples. Results of the first experiment showed no differences between personal and stationary measurements for particles or VOCs. Consequently, stationary measurements can be used to predict personal exposure. All PM mass (about 250 microg/m3) was in the PM1 fraction. Subjective symptoms were generally weak, while clear objective signs were found, for example, in biomarkers of inflammation. With careful control of the combustion process, relatively constant mass and number concentrations were obtained over each exposure session. By varying the combustion and dilution of the wood smoke, different exposure scenarios can be achieved and thus, knowledge about which of the properties of particles and gaseous compounds are crucial for the effects.

Dermal absorption and penetration of jet fuel components in humans

Jet propulsion fuel 8 (JP-8) is the largest source of chemical exposures on military bases. Dermal exposure to JP-8 has been investigated in vitro using rat or pig skin, but not in vivo in humans. The purpose of this study was to investigate the absorption and penetration of aromatic and aliphatic components of JP-8 in humans. A surface area of 20 cm2 was delineated on the forearms of human volunteers and 1 ml of JP-8 was applied to the skin. Tape-strip samples were collected 30 min after application. Blood samples were taken before exposure (t=0 h), after exposure (t=0.5 h), and every 0.5 h for up to 4 h past exposure. The tape-strip samples showed evidence of uptake into the skin for all JP-8 components. The blood data was used to estimate an apparent permeability coefficient (Kp). The rank order of the apparent Kp was naphthalene>1-methyl naphthalene=2-methyl naphthalene>decane>dodecane>undecane. This rank order is similar to results from rat and pig-skin studies. However, this study demonstrates that rat and pig models of the skin over predict the internal dose of JP-8 components in humans.