Mean Concentrations Of Benzene Research Articles

Acute Suppression of Serum IgM and IgA in Tank Workers Exposed to Benzene

We investigated associations between benzene exposure and alterations of proteins and cells of the immune system among workers maintaining cargo tanks containing crude oil residues. Individual exposure to benzene, benzene in blood and urine, peripheral blood lymphocytes (total lymphocytes, lymphocytes in subpopulations CD3, CD4, CD8, CD19, CD56 and CD4/CD8 ratio), complement factors C3 and C4 and serum concentration of immunoglobulins (IgG, IgA, IgM and IgE) were analysed among 13 tank workers and nine unexposed referents (catering section). Benzene exposure was measured during three consecutive 12-h work days. Blood and urine samples were collected pre-shift on the first day (baseline), post-shift on the third day, and pre-next shift on the following morning. The time spent in the cargo tank was logged. The individual geometric mean benzene exposure in the breathing zone of tank workers over 3 days was 0.15 p.p.m. (range 0.01-0.62 p.p.m.) (n = 26). The geometric mean benzene concentration in blood post-shift was 12.3 nmol/l among tank workers versus 0.7 nmol/l among the referents. Tank workers showed a decline (versus referents) in IgM from baseline to post-shift (t-test, P = 0.04) and IgA from baseline to pre-next shift (t-test, P = 0.01). They also showed a decline in CD4 T cells from baseline to post-shift (t-test, P = 0.04). Suppression correlated with benzene exposure, benzene concentrations in blood and urine and time spent in the tank. The groups did not differ significantly in the change in other immune parameters. The clinical significance is unknown and warrants further studies.

Biological monitoring of benzene exposure during maintenance work in crude oil cargo tanks

We investigated the association between the individual concentrations of benzene in the breathing zone and the concentrations of benzene in the blood and urine among workers maintaining crude oil cargo tanks. Benzene exposure was measured during three consecutive 12h work days among 13 tank workers and 9 unexposed referents (catering section). Blood and urine samples were collected pre-shift on the first day, post-shift on the third day, and pre-next shift on the following morning. The workers used half-mask air-purifying respirators, but not all workers used these systematically. The individual geometric mean benzene exposure in the breathing zone of tank workers over 3 days was 0.15 ppm (range 0.01-0.62 ppm). The tank workers' post-shift geometric mean benzene concentrations were 12.3 nmol/l in blood and 27.0 nmol/l in urine versus 0.7 nmol/l for both blood and urine among the referents. Benzene in the work atmosphere was highly correlated with the internal concentration of benzene both in post-shift blood (r=0.87, P<0.001) and post-shift urine (r=0.90, P<0.001), indicating that the varying use of respirators did not explain much of the variability in absorbed benzene. The results showed that, despite low benzene exposure in this work atmosphere and the use of personal protective equipment to a varying degree, the tank workers had a significant uptake of benzene that correlated highly with benzene exposure. The internal concentration of benzene was higher than expected considering the measured individual benzene exposure, probably due to an extended work schedule of 12h and physical strain during tank work. Control measures should be improved for processes, which impose a potential for increased absorption of benzene upon the workers.

Determination of benzene, toluene, ethylbenzene, and xylenes in urban air of Thessaloniki, Greece

In this study, quasicontinuous measurements of major aromatic volatile organic compounds (VOCs), which include benzene, toluene, ethylbenzene, and xylenes were carried out by means of an automatic gas chromatograph (GC-PID analyzer), in the urban air of Thessaloniki, at a mean level of 27 m above ground, during the years 2003 and 2004. The highest measured concentrations of aromatic hydrocarbons were observed during the winter period of the year. The data indicate that the annual mean benzene concentration levels were around 1 ppb, less than the E.U. annual limit value of 5.0 microg m(-3) (1.44 ppb at STP). The diurnal variation of aromatic hydrocarbons suggests that emissions from motor vehicles are their dominant source, at the commercial center of the city, while meteorological conditions (wind speed and direction) are important variables that control the atmospheric abundance of these pollutants, especially during stagnant weather conditions that favor the development of land-sea breeze circulations.

Evaluation of benzene exposure in adults and urinary s-phenylmercapturic acid in children living in Adelaide, South Australia

Benzene Exposure was evaluated in adults and children living in Adelaide, South Australia by measuring benzene and urinary s-phenylmercapturic acid (SPMA). To determine of benzene exposure in each subject the personal passive samplers was used and samples were analyzed by gas chromatography system equipped to flame ionization detector. The level of SPMA was determined by competitive enzymelinked immunosorbent assay (ELISA) in children. The mean concentration of benzene in Summer and Winter were 1.62±1.43 and 1.36±0.87 ppb respectively. There was a significant difference between exposure to benzene for subjects with less and more than 6 hours activity over days of week (p<0.05). The mean urinary concentrations levels of SPMA adjusted to creatinene for children that living less and more than 200 meters distance from main road were 1.56 and 4.67 μmol/mol creatinene, respectively and the significant difference was seen in two groups (p<0.005). Data shows, that SPMA can be utilized as a biomarker for exposure to benzene in children. Exposure to benzene is more for children that living near to main road compare to other children. Adults have more activity in out side of home has more exposure to benzene than other people.

062 Traffic-related air pollution assessed using a dispersion model related to allergie and respiratory health in children

Introduction The impact of traffic-related air pollution (TAP) on respiratory and allergie health is still debated. This might hâve been the resuit of inaccurate classification of exposure. Our cross-sectional study was intended to assess the role of TAP modelled using a dispersion model in the prevalence of allergie and respiratory outeomes in children. Methods 6,683 children aged 9-ll years recruited between 1999 and 2000 from 108 schools randomly selected in 6 French cities underwent a clinical examination including skin prick test and exercise-induced bronchial reactivity (EIB). The prevalence of asthma, allergie rhinitis (AR) and eczema were assessed by a stan-dardised questionnaire completed by the parents. A validated 3-D dispersion model, which combines data on traffic conditions, topo-graphy, meteorology and background air pollution, was used to assign outdoor annual mean concentrations of benzene, VOC, SO2, PM10, NO2, NOx, and CO at the 108 schools attended by the children. For each air pollutant, a 2-categories-exposure variable was defined with respect to the median value of the modelled concentrations at school. Results Adjusted odds ratios (OR) for EIB indicated significant positive associations with ail modelled air pollutants (OR =1.7 (95% CI: 1.3-2.1) with SO2, 1.5 (1.2-1.8) with benzene, 1.3 (1.1-1.7) with PM10), except NO2. Asthma was significantly related to benzene (1.3 (1.0-1.6)), SO2 (1.3 (1.0-1.6)) and PM10 (1.3 (1.0-1.6)), AR to PM10 (1.2 (1.0-1.4), eczema to NO2 (1.2 (1.1 -1.4)) and sensitisation to pollen to benzene (1.2 (1.0-1.5)) and PM10 (1.4 (1.1-1.7)). Positive associations of asthma with VOC and CO, of AR with benzene and SO2, of eczema with PM10, and of sensitisation to pollen with VOC reached borderline statistical significance. Sensitivity analyses suggested stronger associations between sensitisation to pollen and TAP in girls than in boys. Positive associations were more pro-nounced among long-term resident children (current address for at least 8 years). Conclusion Accurate modelization of TAP shows an augmented prevalence of respiratory and allergie diseases in areas with high concentrations of air pollutants.

Evaluation of atmospheric benzene concentrations in the Helsinki Metropolitan Area in 2000–2003 using diffusive sampling and atmospheric dispersion modelling

Abstract Ambient air concentrations of benzene were both measured and predicted in the Helsinki Metropolitan area. Two-weekly measurements were conducted in 2000, 2002 and 2003 at seven measurement stations using diffusive adsorbent sampling; additional two-hourly measurements were also performed. An urban dispersion modelling system was utilised for modelling the spatial concentration distributions of benzene for 2000. According to both measurements and predictions, the annual mean benzene concentrations were below the upper assessment threshold (3.5 μg m−3) set by the European Union, while the lower assessment threshold (2 μg m−3) was exceeded at one urban station (Toolo) during the year 2000. The concentrations measured in the Helsinki Metropolitan Area were also compared with those at rural and remote stations in Finland. In the winters of 2000 and 2003, the concentrations at the remote and rural stations of Uto, Hyytiala and Pallas were close to the concentrations at the urban background station of Kallio, while in the summers of 2000 and 2003, the concentrations at Kallio were substantially higher. The predicted concentrations in 2000 were highest in the vicinity of major roads and streets, and at their junctions. At all the stations, the predicted yearly averaged concentrations agreed fairly well with the measured data; the differences between measured and predicted values ranged from 10 to 31%. According to the measurements, and also the emission and dispersion computations, the most important source categories were exhaust emissions from local vehicular traffic, and the long-range transported background.

Characterizing the range of children's air pollutant exposure during school bus commutes

Real-time and integrated measurements of gaseous and particulate pollutants were conducted inside five conventional diesel school buses, a diesel bus with a particulate trap, and a bus powered by compressed natural gas (CNG) to determine the range of children's exposures during school bus commutes and conditions leading to high exposures. Measurements were made during 24 morning and afternoon commutes on two Los Angeles Unified School District bus routes from South to West Los Angeles, with seven additional runs on a rural/suburban route, and three runs to test the effect of window position. For these commutes, the mean concentrations of diesel vehicle-related pollutants ranged from 0.9 to 19 microg/m(3) for black carbon, 23 to 400 ng/m(3) for particle-bound polycyclic aromatic hydrocarbon (PB-PAH), and 64 to 220 microg/m(3) for NO(2). Concentrations of benzene and formaldehyde ranged from 0.1 to 11 microg/m(3) and 0.3 to 5 microg/m(3), respectively. The highest real-time concentrations of black carbon, PB-PAH and NO(2) inside the buses were 52 microg/m(3), 2000 ng/m(3), and 370 microg/m(3), respectively. These pollutants were significantly higher inside conventional diesel buses compared to the CNG bus, although formaldehyde concentrations were higher inside the CNG bus. Mean black carbon, PB-PAH, benzene and formaldehyde concentrations were higher when the windows were closed, compared with partially open, in part, due to intrusion of the bus's own exhaust into the bus cabin, as demonstrated through the use of a tracer gas added to each bus's exhaust. These same pollutants tended to be higher on urban routes compared to the rural/suburban route, and substantially higher inside the bus cabins compared to ambient measurements. Mean concentrations of pollutants with substantial secondary formation, such as PM(2.5), showed smaller differences between open and closed window conditions and between bus routes. Type of bus, traffic congestion levels, and encounters with other diesel vehicles contributed to high exposure variability between runs.

The Mobile Source Effect on Curbside 1,3-Butadiene, Benzene, and Particle-Bound Polycyclic Aromatic Hydrocarbons Assessed at a Tollbooth

On-road mobile sources contribute substantially to ambient air concentrations of the carcinogens 1,3-butadiene, benzene, and polycyclic aromatic hydrocarbons (PAHs). The current study measured benzene and 1,3-butadiene at the Baltimore Harbor Tunnel tollbooth over 3-hr intervals on seven weekdays (n = 56). Particle-bound PAH was measured on a subset of three days. The 3-hr outdoor 1,3-butadiene levels varied according to time of day and traffic volume. The minimum occurred at night (12 a.m.–3 a.m.) with a mean of 2 µg/m3 (SD = 1.3, n = 7), while the maximum occurred during the morning rush hour (6 a.m.–9 a.m.) with a mean of 11.9 µg/m3 (SD = 4.6, n = 7). The corresponding traffic counts were 1413 (SD = 144) and 16,893 (SD = 692), respectively. During the same intervals, mean benzene concentration varied from 3 µg/m3 (SD = 3.1, n = 7) to 22.3 µg/m3 (SD = 7.6, n = 7). Median PAH concentrations ranged from 9 to 199 ng/m3. Using multivariate regression, a significant association (p < 0.001) between traffic and curbside concentration was observed. Much of the pollutant variability (1,3-butadiene 62%, benzene 77%, and PAH 85%) was explained by traffic volume, class, and meteorology. Results suggest >2-axle vehicles emit 60, 32, and 9 times more PAH, 1,3-butadiene, and benzene, respectively, than do 2-axle vehicles. This study provides a model for estimating curbside pollution levels associated with traffic that may be relevant to exposures in the urban environment.

Urban roadside aromatic hydrocarbons in three cities of the Pearl River Delta, People's Republic of China

Urban roadside levels of benzene, toluene, ethylbenzene and xylenes (BTEX) were investigated in three typical cities (Guangzhou, Macau and Nanhai) in the Pearl River Delta Region of south China. Air samples were collected at typical ground level microenvironments by multi-bed adsorbent tubes. The BTEX concentrations were determined by thermal desorption–gas chromatography–mass selective detector (TD–GC–MSD) technique. The mean concentrations of benzene, toluene, ethylbenzene and xylenes were, respectively, 51.5, 77.3, 17.8 and 81.6 μg/m 3 in Guangzhou, 34.9, 85.9, 24.1, 95.6 μg/m 3 in Macau, and 20.0, 39.1, 3.0 and 14.2 μg/m 3 in Nanhai. The relative concentration distribution pattern and mutual correlation analysis indicated that in Macau BTEX were predominantly traffic-related while in Guangzhou benzene had sources other than vehicle emission. In Nanhai, both benzene and toluene had different sources other than vehicle emission. The samples collected from Guangzhou showed that BTEX had significant higher concentrations in November than those in July.

Personal exposure to benzene and the influence of attached and integral garages.

Benzene is an air pollutant that is a recognised human carcinogen. An air quality standard has been established for ambient air in the UK to reduce the population's exposure. It has been estimated that about 70% of benzene emissions to air in the UK come from petrol vehicles. A number of studies, including the Avon Longitudinal Study of Pregnancy and Childhood in the UK, have found that benzene concentrations in homes with attached or integral garages tend to be higher than in those without such garages. The present paper reviews these studies and reports a detailed investigation of five homes with either an attached or an integral garage. Indoor and outdoor locations were monitored using diffusive sampling to determine the average benzene concentration over approximately 28 days each month for 18 consecutive months (June 1998-November 1999). For one of these homes, ten years of data had shown the indoor benzene concentration to be consistently higher than outdoors. Personal exposure monitoring of one adult in this home showed that the benzene concentration in the main bedroom was a better predictor of personal exposure than the concentration outdoors. In the homes where a car was regularly parked in the garage, 18-month average benzene concentrations of up to 101.3 micrograms m-3 were measured in the garage, which is more than six times the ambient air quality standard for benzene (16.25 micrograms m-3 running annual average). Mean benzene values in all cars and most of the garages studied exceeded the benzene standard. Mean benzene concentrations in the room above the garage ranged from 3.7 micrograms m-3 in one home, where the car was rarely parked in the garage, to 39.9 micrograms m-3 in another home where a car with high benzene emissions was parked in the garage for six of the 18 months monitored. The mean benzene concentration in the room above the garage in this latter home was nearly 2.5 times the ambient air standard. The study demonstrates that there is a potential for people to have a higher exposure to benzene as a result of living in a home with an attached or integral garage. An understanding of routes of personal exposure is important to develop effective policies to reduce risks to health.

Biological Monitoring of Benzene in Residents Living near Petrochemical Industrial Areas in Korea

Biological Monitoring of Benzene in Residents living near Petrochemical Industrial Areas: Yoonho Choi, et al. Department of Preventive Medicine and Public Health, Yonsei University, Korea—Residents who live near petrochemical industrial areas risk exposure to a variety of petrochemicals, including benzene and benzene‐containing liquids. It is a serious concern because benzene is a human carcinogen naturally present in petroleum and gasoline. The aim of this study was to assess the exposure to benzene, measured by personal/indoor/outdoor air sampling, and to estimate the relationship between the air samples and biological monitoring data. Through biological monitoring, we investigated s‐phenylmercapturic acid (s‐PMA), minor urinary metabolites of benzene, and benzene in blood. The external benzene exposure of 115 subjects was measured with passive dosimeters and urinary s‐PMA and blood‐benzene were determined by GC/MS. The mean concentration of benzene in the breathing zone of residents was 6.3 μg/m3, slightly higher than indoor or outdoor concentrations. Personal, indoor and outdoor concentrations of benzene were significantly correlated to each other. s‐PMA was affected by personal exposure (p&lt;0.05) and was differed according to age (p&lt;0.01) and residence time (p&lt;0.05). Blood benzene was not affected by external benzene during these periods.

A comparison of benzene, toluene and C 2-benzenes mixing ratios in automotive exhaust and in the suburban atmosphere during the introduction of catalytic converter technology to the Swiss Car Fleet

Time-resolved chemical ionization mass spectrometry (CIMS) has been used to investigate the variations of the mixing ratios of benzene, toluene and the C 2-benzenes (xylenes and ethyl benzene) in automotive exhaust during transient engine operation. A significant increase of the benzene/toluene ratios from 0.35 to 1.31 (median) was found upon introduction of a catalytic converter system. A preliminary emission model was developed from these test stand measurements to simulate benzene/toluene ratios of passenger car fleets with variable proportions of three-way catalyst vehicles. Although only the emissions of gasoline-driven passenger cars have been considered so far, the predicted increase of the benzene/toluene ratios during the introduction period of the three-way catalyst from 1980 to 2000 is in good agreement with the observed increase of the atmospheric benzene/toluene ratio measured at a suburban monitoring site (Dübendorf, Switzerland) which is strongly influenced by road traffic emissions. At this site, the atmospheric concentrations of benzene and alkyl benzenes have been detected at hourly intervals since 1993. A steady decrease of the yearly mean from 3.54 to 2.00 ppb for toluene and from 2.87 to 1.33 ppb for the sum of C 2-benzenes was found from 1994 to 1998, respectively, when the proportion of three-way catalyst passenger cars increased from 60 to 82%. Nevertheless, the mean benzene concentration was only affected to a small degree (from 1.10 to 0.97 ppb) within the same period of time. Thus, the observed increase of the atmospheric benzene/toluene-mixing ratios from 0.32 to 0.58 (mean) is in good agreement with the predicted values from the presented emission model. Reduced catalyst conversion efficiency for benzene with respect to alkylated benzenes can explain most of the observed increase of the benzene/toluene and benzene/C 2-benzenes mixing rations. In addition, benzene emissions e.g. from the class of light duty vehicles, which are operated more frequently at sub-optimal combustion conditions, may also contribute to the unexpectedly stable atmospheric benzene concentration at the investigated suburban monitoring site.

Benzene and toluene levels measured with a commercial DOAS system in Thessaloniki, Greece

Benzene, toluene and p-xylene were measured above the buildings level in Thessaloniki, Greece for around eight months during the period December 1993–August 1994 by means of a commercial differential optical absorption spectrometer (OPSIS DOAS). Daily mean mixing ratios for benzene and toluene varied between 1–6 and 1–32 ppb, respectively. The data indicate that the annual mean benzene concentrations most probably lie in the range 2–3 ppb, which is below the guide values but above the target values of European countries that have set limits for benzene. Mean diurnal variations of benzene and toluene during summer and winter months reflect the effects of emission, photochemical degradation and mixing. Benzene and toluene hourly values correlated well with each other and with NO 2. Toluene and benzene hourly values were negatively correlated with ozone during summertime. During wintertime, considerable enhancements of benzene and toluene mixing ratios might be associated with the passage of synoptic weather systems of fair weather. Although the measurement of p-xylene is, in principle, efficiently performed with the DOAS technique, the OPSIS instrument p-xylene measurements contradict current understanding of its sources and sinks and are thus attributed to errors of the instrument in the evaluation of this substance.

Actual car fleet emissions estimated from urban air quality measurements and street pollution models

A method to determine emissions from the actual car fleet under realistic driving conditions has been developed. The method is based on air quality measurements, traffic counts and inverse application of street air quality models. Many pollutants are of importance for assessing the adverse impact of the air pollution, e.g. NO 2, CO, lead, VOCs and particulate matter. Aromatic VOCs are of special great concern due to their adverse health effects. Measurements of benzene, toluene and xylenes were carried out in central Copenhagen since 1994. Significant correlation was observed between VOCs and CO concentrations, indicating that the petrol engine vehicles are the major sources of VOC air pollution in central Copenhagen. Hourly mean concentrations of benzene were observed to reach values of up to 20 ppb, what is critically high according to the WHOs recommendations. Based on inverse model calculation of dispersion of pollutants in street canyons, an average emission factor of benzene for the fleet of petrol fuelled vehicles was estimated to be 0.38 g/km in 1994 and 0.11 in 1997. This decrease was caused by the reduction of benzene content in Danish petrol since summer 1995 and increasing percentage of cars equipped with three-way catalysts. The emission factors for benzene for diesel-fuelled vehicles were low.

New high resolution maps of estimated background ambient NO x and NO 2 concentrations in the U.K.

Maps of estimated annual mean background surface concentrations of NO x and NO 2 in the U.K. have been calculated on 1 km x 1 km grid for 1994. These maps have been calculated using a multi-stage approach which includes the interpolation of rural measurements and the empirical modelling of the local source contribution to ambient concentrations. The empirical regression models were calibrated with reference to automatic monitoring data and then validated by comparison with diffusion tube measurements of NO 2 at several hundred sites. Estimates of the population potentially exposed to annual mean concentrations of pollutants above certain thresholds were calculated from these maps. These threshold annual mean concentrations can be approximately equated with proposed and existing air quality standards for NO 2, benzene and 1,3 butadiene. These estimates indicate that about 8% of the population live in regions where the annual mean NO 2 concentration is above the European Union Directive Guide Value for a median concentration of 26 ppb; about 23% live in areas at risk of exceeding the U.K. Government proposed 99.9th percentile target for NO 2 of 104.6 ppb and about 30% live in areas with running annual mean benzene concentrations exceeding 1 ppb.

97/04185 Immobilization of heavy metals in ashes

We investigated the association between the individual concentrations of benzene in the breathing zone and the concentrations of benzene in the blood and urine among workers maintaining crude oil cargo tanks. Benzene exposure was measured during three consecutive 12 h work days among 13 tank workers and 9 unexposed referents (catering section). Blood and urine samples were collected pre-shift on the first day, post-shift on the third day, and pre-next shift on the following morning. The workers used half-mask air-purifying respirators, but not all workers used these systematically. The individual geometric mean benzene exposure in the breathing zone of tank workers over 3 days was 0.15 ppm (range 0.01–0.62 ppm). The tank workers’ post-shift geometric mean benzene concentrations were 12.3 nmol/l in blood and 27.0 nmol/l in urine versus 0.7 nmol/l for both blood and urine among the referents. Benzene in the work atmosphere was highly correlated with the internal concentration of benzene both in post-shift blood (r = 0.87, P < 0.001) and post-shift urine (r = 0.90, P < 0.001), indicating that the varying use of respirators did not explain much of the variability in absorbed benzene. The results showed that, despite low benzene exposure in this work atmosphere and the use of personal protective equipment to a varying degree, the tank workers had a significant uptake of benzene that correlated highly with benzene exposure. The internal concentration of benzene was higher than expected considering the measured individual benzene exposure, probably due to an extended work schedule of 12 h and physical strain during tank work. Control measures should be improved for processes, which impose a potential for increased absorption of benzene upon the workers.

Determination of Benzene, Toluene and Xylene in Ambient Air Inside Three Major Steel Plant Airsheds and Surrounding Residential Areas

Concentration of benzene, toluene and xylene were measured in three steel plants and the nearby residential areas. A simple packed column Gas Chromatograph was used for analysis and samples were collected using fabricated activated carbon traps. The study was carried out over a two year period of 4 to five months. Mean concentration of benzene µg/m3 inside the three plants were found to be 717 µg/m3, 918 µg/m3 and 576 µg/m3. For toluene the concentrations were 183 µg/m3, 258 µg/m3 and 198 µg/m3 and for xylene they were 6 µg/m3, 124 µg/m3 and 32 µg/m3 respectively. Concentration of benzene in the nearby residential areas were 228 µg/m3, 783 µg/m3 and 552 µg/m3. For toluene they were 160 µg/m3, 412 µg/m3 and 155 µg/m3 and for xylene thay were 9 µg/m3, 265 µg/m3 and 33 µg/m3 respectively. The compositional pattern was found to be very different from that found in other studies. The projected lifetime cancer risk from exposure to atmospheric benzene has been estimated to vary from 2.92 per 1000 to 5.92 per 1000 for plant workers and 1.62 per 1000 to 4.02 per 1000 respectively for the people living in the nearby residential areas.

Diffusive monitoring of C6—C9hydrocarbons in urban air in Sweden

A method for diffusive monitoring of C6–C9 hydrocarbons was evaluated. This technique, based on passive sampling of urban air during a 7 d period followed by analysis via thermal desorption and gas chromatography with a flame ionization detector, has been used to monitor urban air quality in a network of Swedish municipalities during the winter months (October–March) since October 1992. Detection limits, precision, bias, sources of error and sample stability during storage are presented. Parallel measurements made using a different method (on-site gas chromatography) confirm the validity of this method. Mean concentrations of benzene in 30 Swedish cites for the sampling season October 1994–March 1995 range from 2.4 to 6.2 µg m–3. Average benzene concentrations, measured over a 3 year period in 12 Swedish municipalities, have been steadily decreasing, in some cases by 50% or more.

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

A sensitive and rapid method for the determination of benzene, toluene, ethylbenzene and the xylenes (BTX) in ambient and exhaled air is described. After sampling of 1-4 l of ambient or exhaled air on graphitized charcoal tubes, the analytes were thermally desorbed by a microwave device coupled to a gas chromatograph interfaced to a mass spectrometer (GC-MS). The detection limits for benzene, toluene, ethylbenzene m- + p-xylene and o-xylene were 1.6, 3.0, 0.2, 1.4 and 0.4 μg/m 3, respectively, when 1 l of air is sampled. In five smoking households a mean benzene concentration of 13.4 (range: 4.2–18.1) μg/m 3 was measured. In five homes without smokers, the average concentration of benzene was 8.8 (5.5–12.8) μg/m 3. The mean benzene concentrations in the exhalates were 50.2 (19.1–98.0) and 3.9 (0.5–8.8) μg/m 3 for ten smokers and ten non-smokers, respectively. The method was found to be suitable for the determination of environmental BTX exposure in field studies.

Student’s Exposure to Volatile Organic Compounds While Commuting by Motorcycle and Bus in Taipei City

This study examined student's exposure to volatile organic compounds (VOCs) while commuting by bus and motorcycle in Taipei, Taiwan in the winter of 1992. A total of 19 target C5-C10 VOCs on three most frequently used commuting routes were collected on Tenax-GC adsorbent tubes. The VOCs were desorbed by thermal desorption method and analyzed by GC-MS. The most abundant VOC exposure experienced by commuters was to toluene. Several alkylated benzenes, such as propyl benzenes, ethyl-methyl-benzenes and trimethyl-benzenes, were relatively abundant on the roads in Taipei. The mean benzene concentration measured in buses was 173 micrograms/m3 and motorcycles. On the average, the commuters in Taipei experienced about three to eight times higher VOC concentrations than the commuters in Los Angeles, California. Higher VOC concentrations were measured on motorcycles than in buses. The VOC concentrations were not significantly different between morning and afternoon commutes, nor among the three commuting routes. VOC concentrations measured in classroom at three schools in downtown Taipei did not vary significantly on each sampling day. However, at each school the in-classroom VOC concentrations varied significantly over the six consecutive sampling days. The VOC concentrations measured on the roads were about five times higher than those measured in the school classrooms in the city. Moderate to high correlations were found among most of the measurements of the 19 VOCs. The survey questionnaire indicated that daily commuting time ranged from 45 minutes for elementary school students to 95 minutes for vocational school students.(ABSTRACT TRUNCATED AT 250 WORDS)