Benzene In Air Research Articles

Benzene, toluene, ethyl benzene and xylenes in ambient air and Pinus sylvestris L. needles: a comparative study between Belgium, Hungary and Latvia

Concentrations of benzene, toluene, ethyl benzene and xylenes (BTEX) in ambient air and in 1 yr old Pinus sylvestris pine needles were monitored along a busy road, petrol station and rural area of Belgium, Hungary and Latvia in a 1 yr period. To test P. sylvestris as a possible biomonitor for the BTEX concentrations, samples were taken in the four seasons. As the distribution of data was not normal, the level of pollution on different sites and seasons was compared and evaluated by non-parametric tests. The measured air concentrations did not differ significantly from one season to another throughout the year. There were, however, differences between sampling places. The C 2-alkylbenzene and toluene concentrations in the needles were similar in the autumn/winter and spring/summer periods but a significant decrease in their concentration was observed in every place between winter and spring. This effect was less obvious for toluene.

A methodology for assessing risk from released hydrocarbon in an enclosed area

This study presents a method for calculating the concentration of hydrocarbon releases in enclosed areas using empirical equations for the evaporation rate. The approach of the method is to estimate the hydrocarbon exposure concentration in the air under conditions assumed. A methodology for assessing risk to individual exposed workers or others using probit expressions is suggested. The toxicity criteria and available human exposure data were examined and guidelines for risk assessment suggested for benzene–air and toluene–air systems. The values of probit constants with mole fractions of lethal concentrations in a mixture of hydrocarbons and a non-toxic substance were predicted. The probit values calculated with mole fractions can be used to estimate guidelines to prevent toxicity within enclosed working areas.

Aldehyde and Monocyclic Aromatic Hydrocarbon Mixing Ratios at an Urban Site in Las Vegas, Nevada

ABSTRACT Linhong Jing completed a master's degree in chemistry at UNLV and is currently enrolled in the Ph.D. program at Purdue University. Her address is Department of Chemistry, Purdue University, West Lafayette, IN 47907. Dr. Spencer Steinberg is an associate professor of chemistry at UNLV. His address is UNLV Department of Chemistry, P.O. Box 454003, Las Vegas, NV 89154-4003. Dr. Brian Johnson is an associate professor of chemistry at UNLV. His address is UNLV Department of Chemistry, P.O. Box 454003, Las Vegas, NV 89154-4003. Oxidation of benzene, toluene, ethylbenzene, and xylenes (BTEX) in air, of significance due to, for example, the potential for O3 formation, is believed to be initiated by OH attack on the ring (addition) or on the alkyl side chain (H abstraction). A series of ring-breaking reactions follows, with major products predicted to be a-dicarbonyls, simple aldehydes, and organic acids. To test this prediction, ambient air mixing ratios of aldehydes (formaldehyde, ac-etaldehyde, benzaldehyde, glyoxal, and pyruvaldehyde), along with some supporting BTEX data, were measured at an urban site in Las Vegas, NV. Samples were collected on sorbents and determined by chromatographic methods; mixing ratios were compared to ambient levels of CO, O3, and NOx. A meteorological analysis (temperature, wind speed, and wind direction) was also included. Statistically significant relationships were noted among the BTEX hydrocarbons (HCs) and among the photochemi-cally derived species (e.g., O3, NO2, and some of the aldehydes), although there was seasonal variation. The observations are consistent with a common primary source (i.e., vehicular exhaust or fuel evaporation) for the BTEX compounds and a common secondary source (e.g., OH attack) for glyoxal and pyruvaldehyde.

Use of expert judgment in exposure assessment. Part I. Characterization of personal exposure to benzene.

This paper presents the results of the first phase of a study, conducted as an element of the National Human Exposure Assessment Survey (NHEXAS), to demonstrate the use of expert subjective judgment elicitation techniques to characterize the magnitude of and uncertainty in environmental exposure to benzene. In decisions about the value of exposure research or of regulatory controls, the characterization of uncertainty can play an influential role. Classical methods for characterizing uncertainty may be sufficient when adequate amounts of relevant data are available. Frequently, however, data are neither abundant nor directly relevant, making it necessary to rely to varying degrees on subjective judgment. Since the 1950s, methods to elicit and quantify subjective judgments have been explored but have rarely been applied to the field of environmental exposure assessment. In this phase of the project, seven experts in benzene exposure assessment were selected through a peer nomination process, participated in a 2-day workshop, and were interviewed individually to elicit their judgments about the distributions of residential ambient, residential indoor, and personal air benzene concentrations (6-day integrated average) experienced by both the non-smoking, non-occupationally exposed target and study populations of the US EPA Region V pilot study. Specifically, each expert was asked to characterize, in probabilistic form, the arithmetic means and the 90th percentiles of these distributions. This paper presents the experts' judgments about the concentrations of benzene encountered by the target population. The experts' judgments about levels of benzene in personal air were demonstrative of patterns observed in the judgments about the other distributions. They were in closest agreement about their predictions of the mean; with one exception, their best estimates of the mean fell within 7-11 microg/m(3) although they exhibited striking differences in the degree of uncertainty expressed. Their estimates of the 90th percentile were more varied with the best estimates ranging from 12 to 26 microg/m(3) for all but one expert. However, their predictions of the 90th percentile were far more uncertain. The paper demonstrates that coherent subjective judgments can be elicited from exposure assessment scientists and critically examines the challenges and potential benefits of a subjective judgment approach. The results of the second phase of the project, in which measurements from the NHEXAS field study in Region V are used to calibrate the experts' judgments about the benzene exposures in the study population, will be presented in a second paper.

Experimental upgrades of membrane introduction mass spectrometry for water and air analysis.

Some improvements to the membrane introduction mass spectrometry (MIMS) technique, resulting in low-ppt detection limits for volatile organohalogen compounds (CX) in water (namely, chloroform, bromoform, bromodichloromethane, chlorodibromomethane, tetrachloroethylene, trichloroethylene, 1,1,1-trichloroethane, and carbon tetrachloride) and low-microgram per cubic meter detection limits for benzene, toluene, ethylbenzene, and xylenes (BTEX) in gaseous samples, are shown. A static MIMS configuration was compared to a dynamic one, the former requiring longer time to obtain the analytical response. A cryotrapping preconcentration step is introduced and linearity of response, mixture effects, and detection limits are presented. The instrumental setup consists of a hollow fiber silicone membrane, a water or air container, a cryofocusing trap based on Tenax adsorbent, a Peltier cell, and a Varian ion trap benchtop mass spectrometer is described. This instrumental setup, which we named membrane extraction trap focusing mass spectrometry, allowed the detection of CX in water at a concentration as low as 8 ppt and of benzene in air at 0.1 microg/m3. The whole assembly shows great potential for on-site routine monitoring of drinking water resources and urban and indoor air under current EU and Italian regulations.

Improvement of Catalyst Durability in Benzene Photooxidation by Rhodium Deposition on TiO2

Abstract Photocatalytic oxidation of benzene in air was carried out over TiO2 and metal-loaded TiO2 catalysts at room temperature. Deposition of Rh on TiO2 improved the catalyst durability by inhibiting the formation of carbon deposits on the catalyst surface and accelerating their decomposition.

Environmental and biological monitoring of occupational exposure to organic micropollutants in gasoline

An exposure risk assessment of workers in a refinery production unit was undertaken. Gasoline and its main components were investigated through environmental and biological monitoring. Measured variables were environmental benzene, toluene, pentane and hexane; benzene and toluene in blood and urine; tt-MA (metabolite of benzene) in urine. Multivariate statistical analysis of the data showed that worker's exposure to the above substances fell within the limits specified by organisations such as ACGIH. Also, biological values complied with reference values (RV) for non-occupationally-exposed population. Different values of biological variables were determined by separating smokers from non-smokers: smokers had hematic and urinary benzene values significantly higher than non-smokers. During a 3-yr sampling, it was possible to identify a significant decrease of benzene in the workplace air and of hematic benzene for non-smokers. The most exposed department, one in which tank-lorries were loaded, needs further investigation and extended monitoring.

Measurements of benzene and toluene in ambient air using proton-transfer-reaction mass spectrometry: calibration, humidity dependence, and field intercomparison

PTR-MS (proton transfer reaction–mass spectrometry) is a chemical ionization mass spectrometry technique that uses proton transfer reactions with H 3O + ions for on-line measurements of organic trace gases in air. The instrument is calibrated for benzene and toluene, and the humidity dependence is investigated. The observed humidity dependence is explained using a simple model that calculates the distribution of H 3O + · (H 2O) n ( n=0, 1, 2, 3) cluster ions in the reactor. These findings were verified in a field intercomparison by comparing PTR-MS measurements of benzene and toluene with GC (gas chromatograph) analyses of gas samples. Isoprene, acetone, acetonitrile, methanol, dimethyl sulfide, and acetaldehyde were also investigated, and no humidity dependence was found, except for isoprene, when larger clusters were used as primary ions.

LONG-TERM ASSESSMENT OF BENZENE CONCENTRATION IN AIR BY PASSIVE SAMPLING: A SUITABLE APPROACH TO EVALUATE THE RISK TO HUMAN HEALTH

A new model of sampling device (Analyst) based upon molecular diffusion has been tested for determination of benzene and other monoaromatics in air and used for a monitoring campaign performed in Rome in 1998–99.Since the Analyst device provided optimum results when passive samplings were lasted from 4 to 12 weeks, its use seemed to be a very suitable way to assess the health risk for humans arising from organic pollution, because long-term sampling is likely to be coupled with high spatial resolution.

Combining membrane extraction with mobile gas chromatography for the field analysis of volatile organic compounds in contaminated waters

A mobile gas chromatographic device (Airmobtx HC 1000 monitor manufactured by Airmotec, Germany), originally designed for the analysis of benzene, toluene, ethylbenzene and xylenes (BTEX) in air, was connected to a flow cell for dynamic membrane extraction. Volatile organic compounds (VOCs) diffuse out of a water stream through a hollow fibre, are enriched onto sorption tubes integrated in the mobile device, and are then thermally desorbed and analysed by gas chromatography–flame ionisation detection. Battery operation of the device enables continuous on-site analysis of VOCs. Influences of the water flow-rate on system response and memory effects were investigated. The linear range of the method depends on the flow-rate of the water sample and did not exceed two orders of magnitude. The detection limits for trichloroethene, chlorobenzene and the BTEX compounds were found to be between 0.1 and 1.0 μg/l using a water flow-rate of 30 ml/min. Dynamic membrane extraction combined with the mobile gas chromatographic device was used for the on-site analysis of contaminated waters in the area of Leipzig.

The Lagrange Street story: the prevention of aromatics air pollution during the last nine years in a European city

Benzene, toluene and xylenes (BTX) air pollution is a very important topic for environmental health, due to the toxicity and/or mutagenetic or carcinogenetic properties of these aromatics and the commercialisation of the unleaded gasoline containing amount of BTX. We measured BTX in the air of Turin city, the capital of Piedmont region (north-western Italy), during 10 years, from 1989 to 1998. The sampling site selected was Lagrange Street (LS), an “urban canyon” placed in the centre of the city. The behaviour of BTX in LS was conditioned by some local and national legislative measures enforced during 1990s for the reduction of automotive traffic and BTX air pollution, respectively. Taking into account the existence of similar measures undertaken also in several cities in the developed countries, largely described but never discussed, the aim of this study was to verify in LS the preventive effects of these regulatory actions by means of a longitudinal survey extended over 10 years. Results obtained in Lagrange Street highlight seasonal trends, typical of this kind of pollutants, and an important reduction (from 42.6 to 15.9 ppbv) of aromatic hydrocarbons (sum of benzene, toluene and xylenes) in atmospheric air from 1990 to 1997. In particular, the annual level of benzene in air showed a mean from 9.2 ppbv in 1990 to 2.0 ppbv in 1997, almost half of the 3.1 ppbv imposed by law since 31 December 1998. In conclusion, the present findings induce a consistent optimism about the usefulness and the effectiveness of these types of regulatory actions enforced to reduce the human exposure to BTX, which could be extended also to other trafficated sites where the aromatics air pollution has to be reduced.

Performance evaluation of a hybrid system comprising silent discharge plasma and manganese oxide catalysts for benzene decomposition

A hybrid system comprising a silent discharge plasma reactor (SDR) and manganese oxide (MnO/sub 2/) catalyst was used for the decomposition of benzene in air. The benzene conversion was greatly enhanced by combining MnO/sub 2/ with the SDR in the latter part. The MnO/sub 2/ catalyst decomposed benzene by using ozone (O/sub 3/) that was formed in the SDR as the oxidant precursor. With an increase in the amount of water vapor in air, the benzene conversion was decreased, due to the deactivation of high-energy electrons, the diminished formation of O/sub 3/ in SDR, and decreased activity of MnO/sub 2/ for the benzene oxidation with O/sub 3/. The only products of the reaction were CO/sub 2/ and CO. The carbon mass balance was not perfect due to the deposition of intermediates on MnO/sub 2/ during the reaction. The intermediates were subsequently decomposed to CO/sub 2/ and CO by MnO/sub 2/ in the presence of O/sub 3/. In dry air, the selectivities to CO/sub 2/ and CO were 70% and 30%, respectively, and were almost independent of specific energy density. The CO/sub 2/ selectivity was improved to 90% by humidifying the background air.

An overview of commonly used methods for measuring benzene in ambient air

Emitted primarily from traffic, benzene has been identified as a carcinogen, inflicting deleterious effects on human health. This has mandated a high degree of scientific attention, both to measure ambient levels in urban regions and to explore mitigation strategies, which can form the basis of policy. In this paper, we present an overview of the most commonly used methods for measurements of atmospheric benzene. The results from field inter-comparisons involving a BTEX monitor as well as with manual pumped tube sampling and diffusive sampling are presented. Finally, monitoring strategies are discussed.

Reductions in human benzene exposure in the California South Coast Air Basin

Benzene typically contributes a significant fraction of the human cancer risk associated with exposure to urban air pollutants. In recent years, concentrations of benzene in ambient air have declined in many urban areas due to the use of reformulated gasolines, lower vehicle emissions, and other control measures. In the California South Coast Air Basin (SoCAB) ambient benzene concentrations have been reduced by more than 70% since 1989. To estimate the resulting effect on human exposures, the Regional Human Exposure (REHEX) model was used to calculate benzene exposures in the SoCAB for the years 1989 and 1997. Benzene concentration distributions in 14 microenvironments (e.g. outdoor, home, vehicle, work) were combined with California time-activity patterns and census data to calculate exposure distributions for 11 demographic groups in the SoCAB. For 1997, the calculated average benzene exposure for nonsmoking adults in the SoCAB was 2 ppb, compared to 6 ppb for 1989. For nonsmokers, about half of the 1997 exposure was due to ambient air concentrations (including their contributions to other microenvironments), but only 4% for smokers. Passive tobacco smoke contributed about one-fourth of all exposure for adult nonsmokers. In-transit microenvironments and attached garages contributed approximately 15 and 10%, respectively. From 1989 to 1997, decreases in passive smoke exposure accounted for about one-sixth of the decrease in exposure for nonsmoking adults, with the remainder due to decreases in ambient concentrations. The reductions in exposure during this time period indicate the effectiveness of reformulated fuels, more stringent emission standards, and smoking restrictions in significantly reducing exposure to benzene.

SnifProbe: new method and device for vapor and gas sampling

SnifProbe is based on the use of 15 mm short pieces of standard 0.53 mm I.D. capillary or porous layer open tubular columns for sampling airborne, headspace, aroma or air pollution samples. A miniaturized frit-bottomed packed vial named MicroSPE was also prepared which served for the sampling of solvent vapors and gases as well as liquid water. The short (15 mm) trapping column is inserted into the SnifProbe easy-insertion-port and the SnifProbe is located or aimed at the sample environment. A miniature pump is operated for pumping 10–60 ml/min of the air sample through the short piece of column to collect the sample. After a few seconds up to a few minutes of pumping, the short column is removed from the SnifProbe with tweezers (or gloved hands) and placed inside a glass vial of a direct sample introduction device (ChromatoProbe) having a 0.5 mm hole at its bottom. The ChromatoProbe sample holder with its glass vial and sample in the short column are introduced into the GC injector as usual. The sample is then quickly and efficiently desorbed from the short sample column and is transferred into the analytical column for conventional GC and/or GC–MS analysis. We have explored the various characteristics of SnifProbe and demonstrated its applicability and effectiveness in many applications. These applications include: the analysis of benzene, toluene and o-xylene in air, SO 2 in air, perfume aroma on hand, beer headspace, wine aroma, coffee aroma, cigarette smoke, trace chemical warfare agent simulants, explosives vapors, ethanol in human breath and odorants in domestic cooking gas. SnifProbe can be operated in the field or at a chemical process. The sample columns can be plugged and stored in a small union storage device, placed in a small plastic bag, marked and brought to the laboratory for analysis with the full power of GC and/or GC–MS. Accordingly, we feel that the major and most significant feature of SnifProbe is that it brings the field and process to the laboratory. Thus, SnifProbe can extend the “arm” of the GC and GC–MS laboratory and enable high-quality field and process analysis.

Sampling procedures for intrinsically valid volatile organic compound measurements

The concept of an intrinsically valid volatile organic compound (VOC) measurement is described, whereby the final data contain all the information needed to calibrate and validate the determination. To realise such a system, all modes of failure within the measurement system need to be tested as the analysis proceeds, and the results of the tests incorporated into the final analytical output. The sources of error and uncertainty associated with the seven principal stages of a VOC analysis sequence are considered. In particular, the effect of competitive adsorption, arising from a transient concentration excursion, on the determination of other analytes is highlighted with an example showing a 97.5% reduction in sensitivity towards benzene in air that, in many recommended methods, would remain undetected. An experimental approach is presented which indicates how the problem of validating adsorbent-based VOC measurements may be addressed by adopting an intrinsically valid measurement approach. A sampling manifold is used that enables two internal standards, fluoropentane and fluorononane, to be added to sampled air in a reproducible and traceable manner before the sample is presented to six adsorbent traps. Thus, these internal standards are simultaneously trapped on the adsorbent alongside the airborne VOC. Upon analysis, the internal standards provide a reference within the chromatogram, allowing the validity of the sampling and subsequent steps in the measurement sequence to be assessed. Fluoropentane and fluorononane were chosen because, amongst other reasons, they bracket the adsorbent capacities of Tenax towards benzene, toluene and xylene. Thus, by comparing the behavour of the fluorinated standards within the analysis, it was possible to identify the range of faults that may arise during active sampling, thermal desorption, chromatographic separation and detection. The chromatogram obtained from this approach had associated with it all the features of an intrinsically valid VOC measurement. Furthermore, the system described resulted in 21–51% reductions in the relative standard deviations for the compounds studied, with the exception of 1-xylene.

Preparation of titania-impregnated silica aerogels and their application to removal of benzene in air

Silica–titania aerogels were prepared by impregnating titanium tetraisopropoxide modified with acetylacetone into a silica alcogel followed by supercritical drying. The effects of the impregnation conditions, the supercritical drying medium (ethanol, 2-propanol or CO2) and the calcination temperature on the homogeneity of the aerogel and the nature of the impregnated titania were investigated. Aerogels prepared in this way had large specific surface areas and maximum titanium contents of ca. 32 at%. Ethanol and CO2 dried samples were homogeneous, but 2-propanol dried samples were inhomogeneous because of the extraction of impregnated titania. Ethanol and 2-propanol dried samples contained anatase particles of <10 nm agglomerated into clusters of 100–300 nm size, whereas CO2 dried samples contained amorphous titania. Their application to the removal of benzene from air was attempted. Ethanol dried samples possessed excellent benzene adsorption capacities and the adsorbate could be decomposed to CO2 by photocatalytic reaction.

1098.フォールアウトSr-90の骨への蓄積と日本人の発癌リスク評

The mathematical model was developed for evaluating a fallout 90Sr accumulation in Japanese bone through its dietary intake, and was validated by comparing the estimates of 90Sr concentration in bone with the observed. The mortality risk by the radiation-induced leukemia and bone cancer was evaluated based on the NUREG/CR4214 model. The main results obtained in this study under the limited assumptions are as follows: (1) The mathematical model was developed to relate 90Sr concentration in an environment with the mortality risk due to the radiation-induced leukemia and bone cancer through dietary intake of fallout 90Sr. (2) The leukemia mortality risk due to the fallout 90Sr is about one order larger than the bone cancer mortalit risk, and is evaluated to be larger than 10-6 for Japanese who were born before early 1970' (3) The leukemia mortality risk due to the fallout 90Sr is about 10% level in 1992 of the leukemia mortality risk expected by the benzene in ambient air.

Monitoring and Assessment of Exhaust Emission in Bangkok Street Air

Measurement of the exhaust emission from gasoline-powered motor vehicles in Bangkok were performed on chassis dynamometer. A fleet of 10 vehicles of different model, years and manufacturers were selected to measure the air pollutants in the exhaust effluent. The study revealed that the carbon monoxide and hydrocarbon emissions averaged 32.3–64.2 and 1.82–2.98 g km−1, respectively, for 1990–1992 cars and decreased to 17.8–40.71 and 0.75–1.88 g km−1, respectively, for 1994–1995 cars. A monitoring program for air pollutant concentrations in ambient air was also conducted to evaluate the air pollution problems in Bangkok arising from vehicle exhaust emission. Four air sampling stations were strategically established to cover the Bangkok Metropolitan Region (BMR). Composite air samples in this study area were collected during the day/night times and weekday/weekend. The average concentrations of suspended particulate matter, carbon monoxide, and nitrogen dioxide in Bangkok street air were found to be 0.65 mg/m3 (24 hr ave.), 19.02 mg/m3 (8 hr ave.) and 0.021 mg/m3 (1 hr ave.), respectively. The average concentrations of benzene and toluene in the ambient air of the study area were found to be 15.07–50.20 and 25.76–130.95 μg/mf3, respectively, for 8 hr average. These results indicated that there was a significant increase in air pollutant emissions with increasing car mileage and model year. Subsequent analysis of data showed that there were only 20% of the test vehicles complied to approved emission standard. The finding also revealed that there was a correlation between the average air pollutant concentrations with average traffic speed in each traffic zone of the Bangkok Metropolitan Region (BMR).

Benzene and non-Hodgkin's lymphoma.

Incidence rates for non-Hodgkin's lymphoma (NHL) have been rising throughout the world for several decades, and no convincing explanation exists for the majority of this increase. The commonest subtypes of NHL have no well-defined aetiological factors but lymphoma development has been linked with exposure to a variety of chemicals, including nitrates, pesticides, herbicides, and solvents. Benzene, a solvent and important constituent of petrochemical products, is a potent lymphomagen in experimental animals and high-dose exposure in humans is associated with both acute myeloid leukaemia and NHL. Much current interest centres on the possibility that environmental benzene exposure in the general public may underlie a proportion of the increase in NHL. Seventy per cent of benzene exposure in the environment is derived from vehicle exhaust emissions, whose increase has closely paralleled the rise in frequency of the disease. Mathematical modelling has been used to calculate an acceptable concentration of benzene in air based on risk estimates derived from industrial exposure, but the recommended target concentration in the U.K. of 1 ppb is regularly exceeded in urban locations. Detailed investigation of the health effects of low-level benzene exposure awaits an accurate assay for quantifying long-term human exposure. The (32)P post-labelling technique for the detection of toxin-specific DNA adducts is extremely sensitive and has been applied in the biomonitoring of exposure to a number of carcinogens, but benzene-DNA adducts have to date proved elusive of detection.