Determination of benzene and alkylated benzenes in ambient and exhaled air by microwave desorption coupled with gas chromatography-mass spectrometry

Airborne Toluene Detection Using Metal-Organic Frameworks

The pollution of indoor air is a major worldwide concern in our modern society for people's comfort, health, and safety. In particular, toluene, present in many substances including paints, thinners, candles, leathers, cosmetics, inks, and glues, affects the human health even at very low concentrations throughout its action on the central nervous system. Its prevalence in many workplace environments can fluctuate considerably, which led to firm regulation with exposure limits varying between 50 and 400 ppm depending on exposure time. This therefore requires the development of technologies for an accurate detection of this contaminant. Metal-organic frameworks have been proposed as promising candidates to detect and monitor a series of molecules at even extremely low concentrations owing to the high tunability of their functionality. Herein, a high-throughput Monte Carlo screening approach was devised to identify the best MOFs from the computation-ready, experimental (CoRE) metal-organic framework (MOF) density-derived electrostatic and chemical (DDEC) database for the selective capture of toluene from air at room temperature, with the consideration of a ternary mixture composed of extremely low-level concentration of toluene (10 ppm) in oxygen and nitrogen to mimic the composition of air. An aluminum MOF, DUT-4, with channel-like micropores was identified as an excellent candidate for the selective adsorption of toluene from air with a predicted adsorption uptake of 0.5 g/g at 10 ppm concentration and room temperature. The toluene adsorption behavior of DUT-4 at low equivalent concentrations, alongside its sensing performance, was further experimentally investigated by its incorporation in a quartz crystal microbalance sensor, confirming the promises of DUT-4. Decisively, the resulting high sensitivity and fast kinetics of our developed sensor highlight the applicability of this hand-in-hand computational-experimental methodology to porous material screening for sensing applications.

Short and long range surface plasmon polariton waveguides for xylene sensing

Nanostructured plasmonic sensors are fabricated as sinusoidal surface plasmon metallic gratings (SPGs) embedded in a functional and porous hybrid sol-gel material, phenyl-bridged polysilsesquioxane (ph-PSQ). The metal layer is in contact with the environment through the sol-gel film, which works as sensitive element, changing its dielectric properties upon interaction with aromatic hydrocarbons. The combination of sensitivity, transparency and patternability offered by ph-PSQs gives the exceptional possibility to fabricate innovative optical sensors with straightforward processes. An embedded SPG is a thin metal slab waveguide, in which the surface plasmon polaritons (SPPs) at the two metal-dielectric interfaces superpose, resulting in two physical coupled modes: the long range SPPs (LRSPPs) and the short range SPPs (SRSPPs). An extended experimental and theoretical characterization of the optical properties of the plasmonic device was performed. The sensor performance was tested against the detection of 30 ppm xylene, monitoring the influence of the target gas on the SPPs modes. A reversible red-shift of the reflectance dips of both LRSPP and SRSPP resonances in the 1.9-2.9 nm range was observed and correlated to the interaction with the analyte. An enhancement in sensitivity associated with the rotation of the grating grooves with respect to the scattering plane (azimuthal rotation) was verified within the experimental errors. Collected data are compatible with theoretical predictions assuming a variation of the film refractive index of 0.011 ± 0.005.

Carboxyhemoglobin and thiocyanate as biomarkers of exposure to carbon monoxide and hydrogen cyanide in tobacco smoke

The determination of biomarkers in human body fluids is a useful tool, which allows the quantitative assessment of the exposure to chemicals or complex mixtures of chemicals and of early biological effects as a result of the exposure. Biomarkers require validation before their successful application in human studies. This review describes some general purposes of human biomonitoring and biomarkers including the requirements for validation. Risk assessment and harm reduction of smoking and tobacco products, respectively, is a very suitable field for the application of biomarkers. A brief historical review shows that the application of biomarkers of exposure and effect in human smoking goes back more than 150 years. Two 'classical' biomarkers of exposure to tobacco, namely carboxyhemoglobin (COHb and its equivalent carbon monoxide in exhalate, COex) and thiocyanate (SCN) in body fluids are discussed in terms of sources of exposure, metabolism, disposition kinetics and influencing host factors. Data on COHb/COex and SCN in nonsmokers and smokers as well as the power to discriminate between smokers and nonsmokers are presented. Both biomarkers are significantly correlated with the daily cigarette consumption. Smoking machine-derived yields of the precursors carbon monoxide and hydrogen cyanide were not correlated with COHb/COex and SCN, respectively. It is concluded that, while COHb/COex is a useful biomarker for assessing the smoke inhalation, preferably in controlled studies, the application of SCN in body fluids as a biomarker for smoking is limited, mainly due to the abundance of other sources for SCN.

Biomonitoring of inhaled complex mixtures--ambient air, diesel exhaust and cigarette smoke

Human biomonitoring comprises the determination of biomarkers in body-fluids, cells and tissues. Biomarkers are generally assigned to one of three classes, namely, biomarkers of exposure, effect or susceptibility. Since biomarkers represent steps in an exposure-disease continuum, their application in epidemiological studies ('molecular epidemiology') shows promise. However, to be a predictor of disease, a biomarker has to be validated. Validation criteria for a biomarker include intrinsic qualities such as specificity, sensitivity, knowledge of background in the population, existence of dose-response relationships, degree of inter- and intra-individual variability, knowledge of the kinetics, confounding and modifying factors. In addition, properties of the sampling and analytical procedures are of relevance, including constraints and non-invasiveness of sampling, stability of sample as well as simplicity, high sensitivity, specificity and speed of the analytical method. It is of particular importance to prove by suitable studies that the biomarker of exposure indicates the actual exposure, the biomarker of effect strongly predicts the actual risk of disease and the biomarker of susceptibility actually modifies the risk. Biomonitoring of the exposure to complex mixtures such as polluted ambient air, diesel exhaust or tobacco smoke is a particular challenge since these exposures have many constituents in common and many people were exposed to more than one of these mixtures. Data on the exposure to polycyclic aromatic hydrocarbons (PAH) and benzene from ambient air, diesel exhaust and tobacco smoke will be presented. In addition, some source-specific biomarkers such as nitro-arenes and nicotine metabolites as well as their application in population groups will be discussed. The second part of the presentation addresses the application of biomarkers for assessing so called 'potentially reduced exposure products' (PREPs). According to a recent report of the Institute of Medicine (USA), "reducing risk of disease by reducing exposure to tobacco toxicants is feasible" and "surrogate biological markers that are associated with tobacco-related diseases could be used to offer guidance as to whether or not PREPs are likely to be risk-reducing." In general, the same validation criteria apply as discussed above. In addition, it is suggested that a panel of biomarkers should be used, representing both smoke phases (gas and particulate phase) and the various chemical classes of smoke constituents (e.g., carbonyls, benzene, PAH, tobacco-specific nitrosamines, aromatic amines). Also, a panel of biomarkers of effect should cover the major known adverse effects of smoking (e.g., oxidative stress, inflammatory processes, lipid peroxidation, lipometabolic disorders, mutagenic effects). Biomarkers of nicotine and carbon monoxide uptake are of interest for evaluating the smoking and inhalation behavior, respectively. Finally, suitable study designs for evaluating PREPs are discussed. It is concluded that suitable biomarkers for assessing the exposure to complex mixtures such as ambient air, diesel exhaust and tobacco smoke as well as for evaluating the exposure-reducing properties of PREPs are already available. Future efforts should focus on the development and validation of biomarkers of effect.

Occupational Exposure to Aromatic Hydrocarbons at a Coke Plant: Part I. Identification of Hydrocarbons in Air and their Metabolites in Urine by a Gas Chromatography‐Mass Spectrometry Method

A method for the qualitative analysis of aromatic hydrocarbons in air and their various urinary metabolites is presented. The air was sampled in charcoal tubes and extracted with carbon disulfide. The hydrocarbons were identified as being aliphatic hydrocarbons (C(9)-C(19)), aromatic hydrocarbons and heterocyclic compounds. The urinary metabolites after enzymatic hydrolysis were analyzed by solid-phase extraction with a styrene-divinylbenzene resin, silylation with N,O-bis(trimethylsilyl)acetamide and GC/MS for separation and detection. Satisfactory separation of all compounds investigated was achieved without interference due to matrix peaks. The following compounds were identified in the urine of workers: dimethylphenol isomers, 4-ethyl-1,3-benzenediol, 2-ethoxybenzoic acid and methoxyphenols. Trimethylsilyl derivatives of aromatic hydroxyacids and hydroxymethoxyacids were found in the urine of occupationally exposed workers by means of a silylation procedure.

Simultaneous determination of ethylbenzene, indan, indene and acenaphthene in air by capillary gas chromatography

An attempt was made to establish a method for the simultaneous determination of ethylbenzene, indan, indene and acenaphthene by capillary gas chromatography with flame ionization detection. The air was sampled on charcoal tubes and extracted with carbon disulfide-methanol (60:1, v/v). The four analytes were separated by gas chromatography using a capillary column of cross-linked 5% phenylmethylsilicone. Under the applied conditions the method showed detection limits of 1.8 microg/m3 for ethylbenzene, 2.1 microg/m3 for indan, 2.8 microg/m3 for indene and 3.4 microg/m3 for acenaphthene. Relative standard deviations were as follows: ethylbenzene, 6.2%; indan, 9.9%; indene, 13.6%; and acenaphthene, 14.4%. The recoveries for these compounds were 98.6, 97.9, 55.7 and 52.1%, and the accuracies were 2.5, 3.0, 44.3 and 47.8%, a working range of 1.5-30 ng/microl for ethylbenzene and 0.75-15 ng/microl for indan, indene and acenaphthene. The method was found to be suitable for the determination of environmental and occupational analysed ethylbenzene, indan, indene and acenaphthene exposure.

Assessment of the exposure of children to environmental tobacco smoke (ETS) by different methods

1. In order to elucidate the role of exposure to environmental tobacco smoke (ETS) in various acute and chronic illnesses in children, it is important to assess the degree of exposure by suitable methods. For this purpose, we determined the exposure to ETS in 39 children (4-15 years) and 43 adults (16+ years) by questionnaires, personal diffusion samplers for nicotine, and cotinine measurements in saliva and urine. In addition, the influence of the smoking status and the location of the home (urban or suburban) on the benzene exposure of the children was investigated. 2. On average, the 24 children living in homes with at least one smoker were exposed to ETS for 3.1 h/d. This is significantly longer (P<0.001) than the daily exposure time of the 15 children from nonsmoking homes (0.3 h/d). The nicotine concentrations on the personal samplers worn over 7 days were 0.615 and 0.046 microg/m3 for children from smoking and nonsmoking homes, respectively (P<0.001). Average salivary cotinine levels were 1.95 ng/ml in children from smoking homes and 0.11 ng/ml in children from nonsmoking homes (P< 0.01). The corresponding urinary cotinine levels were 29.4 and 4.5 ng/mg creatinine (P< 0.001). There was no difference in the extent of ETS exposure between children and adults from smoking households. Adults from nonsmoking homes tended to have higher ETS exposure than children from nonsmoking homes. 3. Exposure to benzene, which was determined by means of personal samplers, measurements of benzene in exhaled air and of the urinary benzene metabolite trans, trans-muconic acid, was not significantly related to the smoking status of the home but primarily dependent on the location of the home.

Simultaneous determination of benzene, toluene, ethylbenzene, and xylenes in urine by thermal desorption-gas chromatography

The determination of metabolites of benzene, toluene, ethylbenzene, and xylenes in urine has been used to assess human exposure to these compounds. The analyses of urine samples for these metabolites are tedious and time consuming. The determination of unmetabolized individual compounds in urine has been studied previously with some success. A simultaneous determination of several unmetabolized VOC compounds in urine by thermal desorption-gas chromatography was conducted to assess the exposure of smokers and nonsmokers to these compounds. The method of thermal desorption-GC was sensitive enough to detect a significant difference in exposure levels due to the contribution of light smoking in the environmentally-exposed group.

Biomonitoring exposure to environmental tobacco smoke (ETS): a critical reappraisal

1 The most frequently used biomarkers for exposure to environmental tobacco smoke (ETS) are cotinine and thiocyanate in body fluids, carboxyhaemoglobin in red blood cells (COHb) and carbon monoxide in the expired air. Although not ideal, cotinine in blood, saliva or urine is an established biomarker for ETS exposure within the past 1-3 days. Comparison with cotinine concentrations in cigarette smokers reveals that passive smokers take up less than 1/100 of the nicotine dose of smokers. 2 Biomonitoring data available for the ETS-related exposure to genotoxic substances comprise uptake of benzene, polycyclic aromatic hydrocarbons (PAH), aromatic amines, tobacco-specific nifrosamines (TSNA), electrophilic compounds giving rise to urinary thioethers, mutagens causing urinary mutagenic activity and the formation of various DNA adducts. With the exception of TSNA, these biomarkers are related to chemicals occurring ubiquitously in the environment and in the food. As a consequence, the background levels in unexposed nonsmokers are high compared to the observed increases (if any) associated with ETS exposure. 3 Some markers of biological effects, which, by definition, are non-specific with regard to the underlying exposure, have also been investigated in relation to ETS exposure. These markers comprise cytogenetic effects, aryl hydrocarbon hydroxylase (AHH) induction, urinary hydroxyproline excretion and various factors indicative of cardiovascular risks. The available data suggest that passive smoking is associated with a small induction of placental AHH and also with effects on cardiovascular risk markers. The latter findings in particular may be confounded by other risk factors, which have been observed to be more frequent in passive smokers than in unexposed nonsmokers.