Ambient Air Concentrations Of Benzene Research Articles

Simulating the spatiotemporal distribution of BTEX with an hourly grid-scale model.

Modeling approaches have been utilized to simulate ambient pollutant concentrations, but very limited efforts have been made to estimate volatile organic compounds in the atmosphere. For this reason, an hourly grid-scale simulation model was developed to determine ambient air concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX). BTEX data were collected over a one-year time frame from the database of the Taiwan Environmental Protection Administration's photochemical assessment monitoring stations. Multivariate linear regression models were used along with correlation analysis to simulate hourly grid-scale BTEX concentrations, using criteria pollutants and selected meteorological variables as predictors. The simulation model was validated in the southern Taiwan area via a portable micro gas chromatography system (n=121) with significant correlation (r=0.566**, ** indicated p<0.01). Moreover, the grid-scale model was applied to areas covering about 72% of the population in Taiwan. A geographic information system (GIS) was used to visualize the spatial distribution of BTEX concentrations from the modeling results. This new grid-scale modeling strategy, which incorporated the GIS output of the simulated data, provides a useful alternative tool for personal exposure analysis and health risk assessment of ambient air BTEX.

BTEX Emissions from the Largest Landfill in Operation in Rio de Janeiro, Brazil.

The emission rates and the ambient air concentrations of benzene, toluene, ethyl benzene and xylenes (BTEX) were measured over the intermediate cover layer and atmosphere of the Seropédica landfill, Rio de Janeiro, Brazil. BTEX were sampled using coconut shell charcoal cartridges, followed by extraction with dichloromethane and analysis by gas chromatography with mass spectrometry. Thirteen samples were collected in areas with and without cracks in the cover layer, and six samples were collected from the ambient air. The average emission rates were 11.7, 492.2, 153.7, 67.2, and 21.7µg m- 2 day- 1, respectively, for benzene, toluene, ethyl benzene, m + p-xylenes and o-xylene. No benzene concentrations above the detection limit were observed in ambient air samples. The average concentrations of toluene, ethyl benzene, m + p-xylenes and o-xylene in ambient air samples were 2.14, 1.35, 0.49 and 0.08µg m- 3, respectively. Higher emissions were found in locations containing larger cracks during the collection.

Health risk assessment of ambient air concentrations of benzene, toluene and xylene (BTX) in service station environments.

A comprehensive evaluation of the adverse health effects of human exposures to BTX from service station emissions was carried out using BTX exposure data from the scientific literature. The data was grouped into different scenarios based on activity, location and occupation and plotted as Cumulative Probability Distributions (CPD) plots. Health risk was evaluated for each scenario using the Hazard Quotient (HQ) at 50% (CEXP50) and 95% (CEXP95) exposure levels. HQ50 and HQ95 > 1 were obtained with benzene in the scenario for service station attendants and mechanics repairing petrol dispensing pumps indicating a possible health risk. The risk was minimized for service stations using vapour recovery systems which greatly reduced the benzene exposure levels. HQ50 and HQ95 < 1 were obtained for all other scenarios with benzene suggesting minimal risk for most of the exposed population. However, HQ50 and HQ95 < 1 was also found with toluene and xylene for all scenarios, suggesting minimal health risk. The lifetime excess Cancer Risk (CR) and Overall Risk Probability for cancer on exposure to benzene was calculated for all Scenarios and this was higher amongst service station attendants than any other scenario.

Health Risk Assessment and Urinary Biomarkers of VOCs Exposures among Outdoor Workers in Urban Area, Bangkok, Thailand

Volatile organic compounds (VOCs) are major source of ambient air pollutants in Bangkok, Thailand. Humans can be exposed to these pollutants by inhalation, ingestion, and dermal contact but mainly by inhalation. The scientists have paid much attention to the study of exposure to air pollutants in outdoor air because they have realized the seriousness of outdoor air pollution problems of acute and chronic health effects as cancer. The measurements of benzene, toluene, ethylbenzene, xylene (BTEX) and carbonyl compounds (CCs) at 16 sites with 144 subjects of 3 classes (motorcycle drivers, security guardsmen and street venders) were performed in Pathumwan district, central Bangkok during September and October 2012 by Gas Chromatography/Flame Ionized Detector (GC/FID) and High Performance Liquid Chromatography/Ultraviolet-Visible Detector (HPLC/UV-VIS). The ambient air concentrations of benzene, toluene, ethyl benzene, xylene, formaldehyde and acetaldehyde in urban area were 46.13, 91.10, 4.55, 58.27, 11.98 and 5.85 µg/m3 respectively. The outdoor workers had average lifetime cancer risk of benzene, ethylbenzene, formaldehyde and acetaldehyde at 1.67E05, 2.11E-07, 3.38E-06 and 7.93E-07 respectively which cancer risk of benzene and formaldehyde were higher than acceptable limit (1.00E-06). The security guardsmen, motorcycle drivers and street venders who work in the same area had cancer risk at 3.65E-05, 1.76E-05 and 1.01E-05 respectively The hazard quotient (HQ) of benzene, toluene, ethylbenzene, xylene, formaldehyde and acetaldehyde of all workers were 9.43E02, 9.57E-04, 4.43E-04, 4.04E-02, 1.42E-01 and 7.64E-01 respectively which all of them were lower than acceptable limit (HQ<1.00). In addition, the urinary biomonitoring concentrations of outdoor workers of trans,trans-muconic acid (tt-MA), hippuric acid, formaldehyde, acetaldehyde and formic acid were 1.66 mg/gCr, 0.51 g/gCr, 0.85 mg/gCr, 15.9 mg/gCr and 20.57 mg/gCr respectively. The tt-MA was strongly associated with benzene exposure (p<0.001) as well as hippuric acid was associated with toluene (p=0.001).

Biomonitoring of benzene and 1,3-butadiene exposure and early biological effects in traffic policemen

The objective of this study was to determine benzene and 1,3-butadiene exposure through ambient air and personal air monitoring, as well as through biomarkers of exposure, and to evaluate the potential health risk of exposure through the use of biomarkers of early biological effects in central Bangkok traffic policemen. Ambient air concentrations of benzene and 1,3-butadiene at the roadsides were significantly higher than in police offices used as control sites ( p < 0.001). Traffic policemen had a significantly higher exposure to benzene (median 38.62 μg/m 3) and 1,3-butadiene (median 3.08 μg/m 3) than office policemen (median 6.17 μg/m 3 for benzene and 0.37 μg/m 3 for 1,3-butadiene) ( p < 0.001). Biomarkers of benzene exposure, blood benzene, and urinary metabolite, trans, trans-muconic acid were significantly higher in traffic policemen than office policemen ( p < 0.001). No significant difference between traffic and office policemen was found in urinary benzene metabolite, S-phenyl mercapturic acid, or in urinary 1,3-butadiene metabolite, monohydroxy-butenyl mercapturic acid. Biomarkers of early biological effects, 8-hydroxy-2′-deoxyguanosine in leukocytes (8-OHdG), DNA-strand breaks, and DNA-repair capacity, measured as an increase in gamma ray-induced chromosome aberrations were significantly higher in traffic policemen than controls ( p < 0.001 for 8-OHdG, p < 0.01 for tail length, p < 0.001 for olive tail moment, p < 0.05 for dicentrics and p < 0.01 for deletions). Multiple regression model including individual exposure, biomarkers of exposure, ages and years of work as independent variables showed that only the levels of individual 1,3-butadiene exposure were significantly associated with 8-OHdG and olive tail moment at p < 0.0001 indicating more influence of 1,3-butadiene on DNA damage. These results indicated that traffic policemen, who are exposed to benzene and 1,3-butadiene at the roadside in central Bangkok, are potentially at a higher risk for development of diseases such as cancer than office policemen.

Ambient Air Concentrations of Benzene, Toluene, Ethylbenzene and Xylene in Bangkok, Thailand during April–August in 2007

Ambient Air Concentrations of Benzene, Toluene, Ethylbenzene and Xylene in Bangkok, Thailand during April–August in 2007

Ambient Air Concentrations of Benzene, Toluene, Ethylbenzene and Xylene in Bangkok, Thailand during April-August in 2007

Benzene, toluene, ethylbenzene and m-, p-, and o-xylene, the most influential aromatic volatile organic compounds (VOCs), were measured in Bangkok, Thailand, one of the most rapidly developing urban areas in Southern East Asia. The purpose of this study is to characterize the ambient air quality with respect to above mentioned aromatic compounds. The data were monitored in ten sites which cover roadside area, residential area and background area. Canister technique was used to obtain air sample at 24 hour interval per a month during April-August in 2007. GC/MS with three stage preconcentrator was used to analyze these samples. The average concentrations of benzene, toluene, ethylbenzene m-, p-xylene and o-xylene are 5.8, 36.1, 4.1, 11.0 and 3.7 ㎍/㎥, respectively. They were observed to be distributed in a log-normal form. Moreover, o-xylene and m,p-xylene exhibited a very good correlation (r=0.976). The slope of the regression equation between them was 3.07 which consisted with a previous reported value. The average ratio of toluene to benzene was 6.4 in April, May June and August.This value was comparable to the ones measured in other Asian cities. Two types of statistical analyses, cluster and factor analyses, were applied to the data in this study. Well characterization was made to understand the air quality of Bangkok area.

Seasonal Variation of Toxic Benzene Emissions in Petroleum Refinery

Petroleum refineries are largest chemical industries that are responsible for the emission of several pollutants into the atmosphere. Benzene is among the most important air pollutants that are emitted by petroleum refineries, since they are involved in almost every refinery process. Volatile organic compounds (VOCs) are a major group of air pollutants, which play a critical role in atmospheric chemistry. These contribute to toxic oxidants, which are harmful to ecosystem, human health and atmosphere. The variability of pollutants is an important factor in determining human exposure to these chemicals. The ambient air concentrations of benzene were measured in several sites around the Digboi petroleum refinery, near the city of Gowahati in northeast India, during winter and summer 2004. The seasonal and spatial variations of the ambient air concentrations of this benzene were investigated and analyzed. An estimation of the contribution of the refinery to the measured atmospheric levels of benzene was also performed. The ambient air mixing ratios of benzene in a large area outside the refinery was generally low, in ppbv range, much lower than the ambient air quality standards. This article presents the temporal and spatial variation of air pollution in and around petroleum refinery and showed that no health risk due to benzene is present in the areas adjacent to the refinery.

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.

Benzene: A Secondary Pollutant Formed in the Three-Way Catalyst

Benzene emissions from a relevant proportion of today's gasoline-driven passenger cars and light-duty vehicles can increase by up to 2 orders of magnitude when driving at high engine load (e.g., on highways). Under such conditions, post-catalyst benzene levels exceeded those found pre-catalyst. As a consequence, formation of benzene in the catalyst was postulated. To further reduce ambient air concentrations of benzene,these critical operating conditions must be carefully avoided. Here, we report in detail to what extent and at what operating conditions catalyst-induced benzene and toluene formation can occur. For that purpose, a EURO-1 passenger car (1.8 L, model year 1995)fulfilling the valid regulations, equipped with a new, two-layered, Pd-CeO2-Al2O3/Rh-ZrO2-Al2O3 three-way catalyst was operated at steady state on a chassis dynamometer at 100, 125, and 150 km/h at variable air to fuel ratios. Pre- and post-catalyst exhaust gas concentrations of benzene, toluene, C2-, and C3-benzenes were monitored at a time resolution of 0.5 Hz by means of chemical ionization mass spectrometry. A net benzene formation window, ranging from pre-catalyst exhaust gas temperatures of 600-730 degrees C and lambda-values of 0.83-0.95, with a pronounced minimum at 0.87, was observed. Dealkylation reactions of aromatic hydrocarbons are assumed to be the major pathway leading to benzene.

Investigation of a cluster of leukaemia in the Illawarra region of New South Wales, 1989-1996.

To investigate a cluster of leukaemia among young people and assess the plausibility of a disease-exposure relationship. Descriptive analysis of population-based leukaemia incidence data, review of evidence related to the causation of leukaemia, assessment of environmental exposures to known leukaemogens, and resulting risks of leukaemia. Illawarra region of New South Wales, Australia, focusing on suburbs between the Port Kembla industrial complex and Lake Illawarra (the Warrawong area). Standardised incidence ratios (SIRs) for leukaemia; current measured and past estimated ambient air benzene concentrations; and expected leukaemia cases attributable to estimates of ambient air benzene concentrations. In 1989-1996, 12 leukaemia cases among Warrawong residents aged less than 50 years were observed, more than the 3.49 cases expected from the rate in the rest of the Illawarra region (SIR, 343.8; 99% CI, 141.6-691.7). These people lived in suburbs immediately to the south-southwest of a coke byproducts plant (a major industrial source of benzene, one of the few known leukaemogens). The greatest excess was among 15-24-year-olds (SIR, 1085.6; 99% CI, 234.1-3072.4). In 1996, ambient air concentrations of benzene averaged less than 1 part per billion (ppb). Since 1970, ambient air concentrations of benzene were estimated to have averaged up to 3 ppb, about one-thousandth of the level at which leukaemia risk has been identified in occupational epidemiological studies. Using the risk assessment model developed by the US Environmental Protection Agency, we estimate that past benzene levels in the Warrawong area could have resulted in 0.4 additional cases of leukaemia in 1989-1996. The excess occurrence of leukaemia in the Warrawong area in 1989-1996 is highly unusual. Current environmental benzene exposure and the reconstructed past environmental benzene exposure level are too low to explain the large excess of leukaemia. The cause of the cluster is uncertain.

Chromosome aberrations in lymphocytes of mice after sub-acute low-level inhalation exposure to benzene

Male and female CD-1 mice were exposed to near ambient air concentrations of benzene by inhalation for 22 h per day, 7 days per week for 6 weeks. The concentrations were 0, 40, 100 and 1000 ppb. Significant increases in chromosome aberrations in spleen lymphocytes were observed in exposed compared with control mice except in the high-dose group ( p < 0.05 for female mice in 2 experiments and for male mice in 1 experiment; p < 0.15 for male mice in the second experiment). A lack of increase in aberrations among mice of the high-dose group may be due to an induction of detoxifying enzymes as observed by us in a previous study (Au et al., 1988b). We also found that the female mice were more sensitive to the clastogenic activity of benzene than male mice under our experimental conditions. Our study serves to emphasize the need to conduct subchronic, low-dose in vivo genotoxicity studies using exposure conditions similar to those of humans, for evaluation of potential hazards. Our data suggest that the current occupational exposure concentrations for benzene (< 1000 ppb) may still be hazardous to humans.