Comparison of breath, blood and urine concentrations in the biomonitoring of environmental exposure to 1,3-butadiene, 2,5-dimethylfuran, and benzene

Determination of breast cancer biomarkers with poly acrylic acid/ MIL-88(Fe)-NH2 hydrogel as a coating for stir bar sorptive extraction

The Poly acrylic acid/MIL-88(Fe)-NH2 composite material, carefully prepared, is employed as a sorbent for the stir bar. The best formula of the composite was selected by investigation of two parameters including the cross-linker of PAA and MIL-88(Fe)-NH2 content. The prepared stir bar was used for extraction of 2-pentanone, 2-heptanone, ethyl propionate, para-xylene, 1,2,4-trimethylbenzene, o-cresol, m-cresol in urine samples as breast cancer biomarkers with gas chromatography-flame ionization detector. The prepared Poly acrylic acid / MIL-88(Fe)-NH2 as sorbent for the stir bar demonstrate good repeatability of one bar (relative standard deviation (RSD%) < 4.61 %) and satisfactory reproducibility between two bars (RSD% < 6.85 %). The central composite design method was applied for the optimization of extraction parameters. Under the optimum conditions, linear dynamic ranges for compounds were in the acceptable range with correlation coefficients higher than 0.99. Detection limits of them were less than 1.71 µg L-1.

Method Development for Detecting Low Level Volatile Organic Compounds (VOCs) among Workers and Residents from a Carpentry Work Shop in a Palestinian Village

Volatile organic compounds (VOCs) are considered a major public health concern in industrial location areas. The presence of exposure to (VOCs) has raised concern regarding the health effects caused by chronic human exposure as this will increase cancer diseases in the village. An analytical method has been developed and modified to help us detect 38 VOCs in the blood of 38 volunteers who are related to a carpentry shop at the parts-per-trillion level. To measure and evaluate the potential risk, several devices, such as portable passive monitors and air-collected samples, in addition to blood concentration, were used to study three different occupational groups. Ten of the volunteers are employees at the shop, 10 volunteers live very close to the shop, and 10 of them are students in an elementary school very close to the shop. In this study, we developed an automated analytical method using headspace (HS) together with solid-phase microextraction (SPME) connected to capillary gas chromatography (GC) equipped with quadrupole mass spectrometry (MS). The detection limits for the method used were measured in the range from 0.001 to 0.15 ng/L, using linear calibration curves that have three orders of magnitude. The detected concentrations ranged from 3 ng L^-1 for trichloroethene to 91 ng L^-1 for toluene and 270 ng L^-1 for 2,4-diisocyanate, which was derived from the paint solvents used for the wood in the carpentry shop and the paints on the walls. More than half of all assessed species (80%) had mean concentration values less than 50 ng L^-1, which is the maximum allowed for most VOCs. The major chemical types among the compounds quantified will be those we found in our previous study in the surrounding air of a carpentry workshop in Deir Ballout in Palestine, which were toluene diisocyanate and butyl cyanate. Some were found to be highly present air. Most of the measurements were below the guidelines of the World Health Organization (WHO). Despite the fact that this study only involved a small number of smokers, smoking was found to be connected with several blood and breath components. This group includes unsaturated hydrocarbons (1,3-butadiene, 1,3-pentadiene, 2-butene), furans (2,5-dimethylfuran), and acetonitrile. The proposed classification of measured species into systemic (blood-borne) and exogenous volatiles is strictly hypothetical, as some species may have several origins.

Human biomonitoring of low-level benzene exposures

Historically, benzene has been widely used in a large variety of applications. Occupational exposure limits (OELs) were set for benzene as it was found to be acutely toxic, causing central nervous system depression at high exposures. OELs were lowered when it was discovered that chronic exposure to benzene could cause haematotoxicity. After confirmation that benzene is a human carcinogen causing acute myeloid leukaemia and possibly other blood malignancies, OEL were further lowered. The industrial application of benzene as solvent is almost completely discontinued but it is still used as feedstock for the production of other materials, such as styrene. Occupational exposure to benzene may also occur since it is present in crude oil, natural gas condensate and a variety of petroleum products and because benzene can be formed in combustion of organic material. In the past few years, lower OELs for benzene in the range of 0.05-0.25 ppm have been proposed or were already established to protect workers from benzene-induced cancer. The skin is an important potential route of exposure and relatively more important at lower OELs. Consequently, human biomonitoring - which integrates all exposure routes - is routinely applied to control overall exposure to benzene. Several potential biomarkers have been proposed and investigated. For compliance check of the current low OELs, urinary S-phenylmercapturic acid (S-PMA), urinary benzene and blood benzene are feasible biomarkers. S-PMA appears to be the most promising biomarker but proper validation of biomarker levels corresponding to airborne benzene concentrations below 0.25 ppm are needed.

Discriminant Profiles of Volatile Compounds in the Alveolar Air of Patients with Squamous Cell Lung Cancer, Lung Adenocarcinoma or Colon Cancer

The objective of the present work was to analyze volatile compounds in alveolar air in patients with squamous cell lung cancer, lung adenocarcinoma or colon cancer, to prepare algorithms able to discriminate such specific pathological conditions. The concentration of 95 volatile compounds was measured in the alveolar air of 45 control subjects, 36 patients with lung adenocarcinoma, 25 patients with squamous cell lung cancer and 52 patients with colon cancer. Volatile compounds were measured with ion molecule reaction mass spectrometry (IMR-MS). An iterated least absolute shrinkage and selection operator multivariate logistic regression model was used to generate specific algorithms and discriminate control subjects from patients with different kinds of cancer. The final predictive models reached the following performance: by using 11 compounds, patients with lung adenocarcinoma were identified with a sensitivity of 86% and specificity of 84%; nine compounds allowed us to identify patients with lung squamous cell carcinoma with a sensitivity of 88% and specificity of 84%; patients with colon adenocarcinoma could be identified with a sensitivity of 96% and a specificity of 73% using a model comprising 13 volatile compounds. The different alveolar profiles of volatile compounds, obtained from patients with three different kinds of cancer, suggest dissimilar biological–biochemistry conditions; each kind of cancer has probably got a specific alveolar profile.

Impact of Cognitive Tasks on CO2 and Isoprene Emissions from Humans

The human body emits a wide range of chemicals, including CO₂ and isoprene. To examine the impact of cognitive tasks on human emission rates of CO₂ and isoprene, we conducted an across-subject, counterbalanced study in a controlled chamber involving 16 adults. The chamber replicated an office environment. In groups of four, participants engaged in 30 min each of cognitive tasks (stressed activity) and watching nature documentaries (relaxed activity). Measured biomarkers indicated higher stress levels were achieved during the stressed activity. Per-person CO₂ emission rates were greater for stressed than relaxed activity (30.3 ± 2.1 vs 27.0 ± 1.7 g/h/p, p = 0.0044, mean ± standard deviation). Isoprene emission rates were also elevated under stressed versus relaxed activity (154 ± 25 μg/h/p vs 116 ± 20 μg/h/p, p = 0.041). The chamber temperature was held constant at 26.2 ± 0.49 °C; incidental variation in temperature did not explain the variance in emission rates. Isoprene emission rates increased linearly with salivary α-amylase levels (r² = 0.6, p = 0.02). These results imply the possibility of considering cognitive tasks when determining building ventilation rates. They also present the possibility of monitoring indicators of cognitive tasks of occupants through measurement of air quality.

Analysis of some commonly found inhalants using gas chromatography-mass spectrometry (GC MS) - Effect of substrates on the identification of inhalants

Inhalant abuse is a serious and ever-evolving problem for our society. Inhalants are abused more commonly by teenagers and adolescents. Inhalants such as glue, paint thinners, correction fluid, and nail paint remover are easily available in the market which makes them readily abused. Out of various methods of abuse, huffing (placing a piece of cloth soaked with inhalant is placed in the mouth), bagging (placing head in a polythene bag containing inhalant), and ballooning (balloons filled with inhalant are used for inhaling vapors through the mouth) are most common. Inhalant abuse results in multiple target organ dysfunction with neuritis and brain damage due to the dissolution of the myelin sheath. In acute poisoning cases, it might cause death due to asphyxia and sudden sniffing syndrome. In such cases, various articles containing traces of inhalants could be retrieved from the scene of incidence and to detect these traces become an important facet of the investigation. However, it might be difficult due to the rapid evaporation of inhalants and the formation of reaction product species. In the present study, an attempt has been made to study the effect of three substrates (balloon, cloth, polythene) on component profiles of four paint thinners and four nail paint removers. The study suggests that although some components are retained, there is the formation of a large number of reaction product species and these must be taken into consideration before furnishing the opinion. These reaction product species might also be inhalant specific which must be further explored.

Cigarillo and Little Cigar Mainstream Smoke Constituents from Replicated Human Smoking

Little cigar and cigarillo smoking is increasing in popularity in the U.S., but little is known about the topography and mainstream smoke (MSS) constituents of these types of cigar products. This report describes the quantity of selected MSS toxicants generated from puff-by-puff replication of human laboratory smoking. Participants were dual users of cigarettes and either little cigars ( n = 21) or cigarillos ( n = 23). In the laboratory smoking session, participants of the little cigar group smoked a filtered unflavored Winchester Little Cigar; those in the cigarillo group smoked an unfiltered, unflavored Black & Mild cigarillo. MSS components included both volatiles and semivolatile compounds. The MSS of five representative U.S. domestic cigarettes was generated using smoking topography profiles of the participants smoking their own brand of cigarettes. Machine smoking accurately replicated individual puff profiles as indicated by a high correlation between lab and machine smoked: time to smoke, number of puffs, and total puff volume. There was wide variability in smoking patterns across subjects of both little cigars and cigarillos. For example, total puff volume ranged from 84 to 732 mL after the little cigar and from 270 to 2089 mL after the cigarillo. Qualitatively, cigar smoke from little cigars and cigarillos were similar and resembles cigarette smoke. All analytes (VOC and SVOCs) were greater in cigarillo smoke compared to that of little cigars and cigarettes. However, when the toxicants were adjusted for grams of tobacco burned, little cigar smoke contained more nicotine, tobacco-specific nitrosamines, acetonitrile, and acrylonitrile compared with cigarillo smoke. When the constituents were adjusted for nicotine content, cigarillo MSS contained more of all toxicants compared with little cigar. Cigarillos and little cigars, like cigarettes, deliver nicotine and other toxicants known to be harmful to health; their regulation by the FDA is appropriate for their public health risk.

Quantification of selected volatile organic compounds in human urine by gas chromatography selective reagent ionization time of flight mass spectrometry (GC-SRI-TOF-MS) coupled with head-space solid-phase microextraction (HS-SPME)

Selective reagent ionization time of flight mass spectrometry with NO⁺as the reagent ion in conjunction with gas chromatography and head-space solid-phase microextraction was used to determine 16 volatiles in human urine.

Validation of a radial diffusive sampler for measuring occupational exposure to 1,3-butadiene

1,3-Butadiene (BD) is a major industrial chemical used in the manufacture of rubbers and latexes; it is also a ubiquitous environmental pollutant whose major source is traffic. Occupational exposure to (BD) can occur both during its production and during its use as a raw material. The objective of the study was the laboratory and field validation of a new diffusive sampler for BD. The nominal sampling rate of the Radiello diffusive sampler filled with Carbopack X is 30.5 cm(3)/min, at 0.177 mg/m(3), 20 °C and 50% relative humidity (RH), for an 8-h exposure time. A model can be used for calculating the sampling rate as a function of temperature, time and RH. The concentration does not affect the sampling rate above 30 μg/m(3). The measurement uncertainty (k=2), calculated both by laboratory data and by field comparison according to International Standard Organization (ISO) 13752, satisfies the EN 482:2006 requirement for measurements between 0.1 and 0.5 times the threshold limit value-time weighted average (TLV-TWA) (uncertainty<50%). For field validation study, 38 workers exposed to BD and 20 administrative employees, as the control group, underwent environmental and biological monitoring. Personal exposure to BD was measured by diffusive samplers (Radiello) in comparison with active samplers. The BD exposure levels detected for the exposed subjects were low (mean 0.059, range <0.010-1.340 mg/m(3)) but higher than the controls levels, all below 0.010 mg/m(3). The comparison between diffusive and active (pumped) air sampling showed a good correlation, with no systematic deviation from the ideal values of the intercept and slope of the optimized regression line. The concentrations of two biomarkers were also determined on urine samples, collected at the end of the work-shift: unchanged BD, by GC-MS, and the metabolite dihydroxybutylmercapturic acid (DHBMA), by HPLC-MS/MS. The urinary excretion of the biomarkers was on average higher in the exposed group (urinary BD: mean 8.8, range <1-48.1 ng/l; DHBMA: mean 0.232, range 0.016-0.572 mg/l) than in controls (urinary BD: mean 6.4, range 2.6-14.5 ng/l; DHBMA: mean 0.205, range 0.037-0.602 mg/l), but a statistically significant difference was achieved only for unchanged BD and not for DHBMA. In conclusion, the environmental monitoring measured by diffusive samplers (Radiello) appears to be a reliable method for the assessment of exposure to low levels of airborne BD and a convenient alternative to the conventional active sampling.

Blood 2,5-dimethylfuran as a sensitive and specific biomarker for cigarette smoking

OBJECTIVE

We evaluated the validity of blood 2,5-dimethylfuran (DMF) for determining smoking status using population-based data.

METHODS

We obtained blood DMF concentrations and smoking status from National Health and Nutrition Examination Survey 2003-2006 and computed sensitivity, specificity and Kappa statistic.

RESULTS

Self-reported smoking showed very high agreement (Kappa = 92.8-93.3%) in daily smokers and fair agreement in non-daily smokers (Kappa = 33.7-36.4%). Coffee intake did not influence the detection of blood DMF.

CONCLUSIONS

Blood DMF has comparable sensitivity and specificity with serum cotinine for identifying current daily smokers, which may make it a useful biomarker in epidemiologic studies.

Clinical breath analysis: discriminating between human endogenous compounds and exogenous (environmental) chemical confounders

Volatile organic compounds (VOCs) in exhaled breath originate from current or previous environmental exposures (exogenous compounds) and internal metabolic (anabolic and catabolic) production (endogenous compounds). The origins of certain VOCs in breath presumed to be endogenous have been proposed to be useful as preclinical biomarkers of various undiagnosed diseases including lung cancer, breast cancer, and cardio-pulmonary disease. The usual approach is to develop difference algorithms comparing VOC profiles from nominally healthy controls to cohorts of patients presenting with a documented disease, and then to apply the resulting rules to breath profiles of subjects with unknown disease status. This approach to diagnosis has a progression of sophistication; at the most rudimentary level, all measurable VOCs are included in the model. The next level corrects exhaled VOC concentrations for current inspired air concentrations. At the highest level, VOCs exhibiting discriminatory value also require a plausible biochemical pathway for their production before inclusion. Although these approaches have all shown some level of success, there is concern that pattern recognition is prone to error from environmental contamination and between-subject variance. In this paper, we explore the underlying assumptions for the interpretation and assignment of endogenous compounds with probative value for assessing changes. Specifically, we investigate the influence of previous exposures, elimination mechanisms and partitioning of exogenous compounds as confounders of true endogenous compounds. We provide specific examples based on a simple classical pharmacokinetic approach to identify potential misinterpretations of breath data and propose some remedies.

Blood and breath levels of selected volatile organic compounds in healthy volunteers

Gas chromatography with mass spectrometric detection (GC-MS) was used to identify and quantify volatile organic compounds in the blood and breath of healthy individuals. Blood and breath volatiles were pre-concentrated using headspace solid phase micro-extraction (HS-SPME) and needle trap devices (NTDs), respectively. The study involved a group of 28 healthy test subjects and resulted in the quantification of a total of 74 compounds in both types of samples. The concentrations of the species under study varied between 0.01 and 6700 nmol L(-1) in blood and between 0.02 and 2500 ppb in exhaled air. Limits of detection (LOD) ranged from 0.01 to 270 nmol L(-1) for blood compounds and from 0.01 to 0.7 ppb for breath species. Relative standard deviations for both measurement regimes varied from 1.5 to 14%. The predominant chemical classes among the compounds quantified were hydrocarbons (24), ketones (10), terpenes (8), heterocyclic compounds (7) and aromatic compounds (7). Twelve analytes were found to be highly present in both blood and exhaled air (with incidence rates higher than 80%) and for 32 species significant differences (Wilcoxon signed-rank test) between room air and exhaled breath were observed. By comparing blood, room air and breath levels in parallel, a tentative classification of volatiles into endogenous and exogenous compounds can be achieved.

The use of biomonitoring data in exposure and human health risk assessment: benzene case study

Abstract A framework of "Common Criteria" (i.e. a series of questions) has been developed to inform the use and evaluation of biomonitoring data in the context of human exposure and risk assessment. The data-rich chemical benzene was selected for use in a case study to assess whether refinement of the Common Criteria framework was necessary, and to gain additional perspective on approaches for integrating biomonitoring data into a risk-based context. The available data for benzene satisfied most of the Common Criteria and allowed for a risk-based evaluation of the benzene biomonitoring data. In general, biomarker (blood benzene, urinary benzene and urinary S-phenylmercapturic acid) central tendency (i.e. mean, median and geometric mean) concentrations for non-smokers are at or below the predicted blood or urine concentrations that would correspond to exposure at the US Environmental Protection Agency reference concentration (30 µg/m(3)), but greater than blood or urine concentrations relating to the air concentration at the 1 × 10(-5) excess cancer risk (2.9 µg/m(3)). Smokers clearly have higher levels of benzene exposure, and biomarker levels of benzene for non-smokers are generally consistent with ambient air monitoring results. While some biomarkers of benzene are specific indicators of exposure, the interpretation of benzene biomonitoring levels in a health-risk context are complicated by issues associated with short half-lives and gaps in knowledge regarding the relationship between the biomarkers and subsequent toxic effects.

Predicted toxicity of the biofuel candidate 2,5-dimethylfuran in environmental and biological systems

Although not mutagenic by Ames test, 2,5-dimethylfuran (DMF), a leading biofuel candidate, was found to induce chromosomal damage in cultured murine cells, suggesting that it may be genotoxic. We sought to prioritize the environmental and biological impacts of using DMF as a combustible biofuel. First, we assessed DMF and its combustion intermediates for potential persistence, bioaccumulation, and aquatic toxicity (PBT) using PBT profiler. Our findings predict DMF to have moderate-level aquatic toxicity; however, a greater subset of the combustion intermediates is predicted to have moderate- and high-level aquatic toxicity with bioaccumulation and persistence concerns. Second, we assessed the biological impact of DMF by testing for statistically significant chemical-disease associations. No direct associations for DMF were found; however, indirect associations were identified from two structurally similar analogs. Curated associations between furfuryl alcohol to kidney neoplasm and adenoma, and significant inferred associations between furan to lung neoplasm, drug-induced liver injury, and experimentally induced liver cirrhosis were found, based on 21 furan-gene interactions. Nine of 49 DMF combustion intermediates analyzed, including benzene and 1,3-butadiene, were found to have associations with 26 tumors and systemic diseases. Although inadequate for a stand-alone risk assessment, our data suggest that DMF combustion intermediates pose a much broader range of hazards than DMF itself, and that both should be further investigated.

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.

Breath biomarkers for lung cancer detection and assessment of smoking related effects--confounding variables, influence of normalization and statistical algorithms

BACKGROUND

Up to now, none of the breath biomarkers or marker sets proposed for cancer recognition has reached clinical relevance. Possible reasons are the lack of standardized methods of sampling, analysis and data processing and effects of environmental contaminants.

METHODS

Concentration profiles of endogenous and exogenous breath markers were determined in exhaled breath of 31 lung cancer patients, 31 smokers and 31 healthy controls by means of SPME-GC-MS. Different correcting and normalization algorithms and a principal component analysis were applied to the data.

RESULTS

Differences of exhalation profiles in cancer and non-cancer patients did not persist if physiology and confounding variables were taken into account. Smoking history, inspired substance concentrations, age and gender were recognized as the most important confounding variables. Normalization onto PCO2 or BSA or correction for inspired concentrations only partially solved the problem. In contrast, previous smoking behaviour could be recognized unequivocally.

CONCLUSION

Exhaled substance concentrations may depend on a variety of parameters other than the disease under investigation. Normalization and correcting parameters have to be chosen with care as compensating effects may be different from one substance to the other. Only well-founded biomarker identification, normalization and data processing will provide clinically relevant information from breath analysis.

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.

Determination of S-phenylmercapturic acid by GC-MS and ELISA: a comparison of the two methods

S-phenylmercapturic acid (PMA) is a specific urinary biomarker of benzene at exposure levels lower than 1 ppm. However, measuring PMA in urine is an expensive task by either GC or HPLC due to the necessity of extensive sample pretreatment. In the present study, a commercial chemiluminescence enzyme-linked immunosorbent assay (ELISA) test for PMA and GC-MS were used for screening urine samples of 60 workers employed in petrochemical settings. The ELISA results were evaluated by comparison with the GC-MS. Overall, the ELISA test proved sensitive (limit of detection=0.1 microg l(-1)), rapid, robust and reliable, affording results in good agreement with the GC-MS (54% of measurements) and no false-negatives. On the other hand, 46% of the ELISA assays were assigned as false-positives (arbitrarily established when ELISA >5 microg l(-1), GC-MS <5 microg l(-1) and a correlation coefficient of 0.687 was calculated between the two methods. It appears that urinary PMA routine biomonitoring on large numbers of samples is carried out in a cost-effective and rapid approach by preliminary screening with the ELISA assay followed by GC-MS confirmation of concentrations exceeding the biological exposure index for PMA.

Biological monitoring in occupational exposure to low levels of 1,3-butadiene

Exposure to 1,3-butadiene (BD), a probable carcinogen to humans, was investigated in two groups of subjects working in a petrochemical plant where BD is produced and used to prepare polymers: 42 occupationally exposed workers and 43 internal non-occupationally exposed controls. BD personal exposure was very low but significantly different in the two groups (median airborne BD 1.5 and 0.4 microg/m(3) in exposed and controls, respectively). Similarly, BD in blood and urine, but not in exhaled air, was higher in the exposed workers than in controls (blood BD 3.7 ng/l versus <1.8 ng/l, urinary BD 2.4 ng/l versus <1.0 ng/l). These three biomarkers correlated significantly with personal exposure ( 0.283 < or = Pearson's r < or = 0.383) and between them (0.780 < or = r < or = 0.896). Excretion of urinary mercapturic acids N-acetyl-S-(3,4-hydroxybutyl)-l-cysteine (MI), N-acetyl-S-(1-hydroxymethyl-2-propenyl)-l-cysteine and N-acetyl-S-(2-hydroxy-3-butenyl)-l-cysteine (MII), chromosomal aberrations (CA), and sister chromatid exchanges (SCE) in peripheral blood lymphocytes were not influenced by occupational exposure. Our results show that unmetabolised BD in biological fluids, and particularly urinary BD, represents the biomarker of choice for assessing occupational exposure to low airborne concentrations of BD.

Rapid and sensitive static headspace gas chromatography–mass spectrometry method for the analysis of ethanol and abused inhalants in blood

A sensitive and specific method using static headspace gas chromatography coupled with mass spectrometry (GC/MS) has been developed for the quantitative determination of ethanol in biological fluids using n-propanol as internal standard. Gas chromatography was performed in isothermal mode with a GC run time of 2.6 min. The quantification was performed using scan mode abstracting a quantitative ion and a qualifier ion for ethanol and for the internal standard. The method was linear (r(2), 0.999, in the concentration range of 5-200 mg/dl), specific (no interference from methanol acetaldehyde, acetone or from endogenous materials), sensitive (limit of quantification and limit of detection of 0.2 and 0.02 mg/dl, respectively) and robust (less than 5% inter- and intra-assay coefficient of variation). A slightly modified method was also developed for the quantification of five commonly abused inhalants (dichloromethane, ethyl acetate, benzene, toluene and xylene) in blood. The method used a gradient GC program with a run time of 8 min. The quantification was performed using scan mode and integrating the area under the peak using trichloroethane as an internal standard. Without optimization, the method was linear (from 5 to 100 mg/l) and sensitive.