Exposure to MTBE, TAME and aromatic hydrocarbons during gasoline pump maintenance, repair and inspection

The exposure of gasoline pump repairers and inspectors to gasoline was studied at service stations and repair shops in Finland in April-June 2004. The average air temperature ranged from 7 degrees C to 16 degrees C and wind speed from 2.5 to 7 m/s. The gasoline blends contained mixtures of methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME), the total content of oxygenates being 11-12%. The content of benzene was <1%. Breathing zone air was collected during the work task using passive monitors. The mean sampling period was 4.5 h. The mean TWA-8 h concentrations for MTBE, TAME, hexane, benzene, toluene, ethylbenzene and xylene were 4.5, 1.3, 0.55, 0.23, 2.2, 0.26 and 1.1 mg/m3, respectively. None of the individual benzene concentrations exceeded the binding limit value for benzene (3.25 mg/m3). The sum concentration of MTBE and TAME in urine was between 8.9 and 530 nmol/l in individual post-shift samples. The individual sum concentrations of the metabolites tert-butyl alcohol and tert-amyl alcohol collected the following morning after the exposure ranged from 81 to 916 nmol/l. All individual results were below corresponding biological action levels. Exposure to aromatic hydrocarbons was estimated from post-shift urine samples, with benzene showing the highest concentration (range 4.4 and 35 nmol/l in non-smokers). The exposure levels were similar to those measured in previous studies during unloading of tanker lorries and railway wagons. The results indicated a slightly higher exposure for inspectors, who calibrated fuel pump gauges at the service stations, than for pump repairers. No significant skin exposure occurred during the study.     

Customer exposure to gasoline vapors during refueling at service stations

Gasoline is a volatile complex mixture of hydrocarbon compounds that is easily vaporized during handling under normal conditions. Modern reformulated gasoline also contains oxygenates to enhance octane number and reduce ambient pollution. This study measured the difference in the exposure of customers to gasoline and oxygenate vapors during refueling in service stations with and without vapor recovery systems. Field measurements were carried out at two self-service stations. One was equipped with Stage I and the other with Stage II vapor recovery systems. At Stage I stations there is vapor recovery only during delivery from road tanker, and at Stage II stations additional vapor recovery during refueling. The exposure of 20 customers was measured at both stations by collecting air samples from their breathing zone into charcoal tubes during refueling with 95-octane reformulated gasoline. Each sample represented two consecutive refuelings. The samples were analyzed in the laboratory by gas chromatography using mass-selective detection for vapor components. The Raid vapor pressure of gasoline was 70 kPa and an oxygen content 2 wt%. Oxygenated gasoline contained 7 percent methyl tert-butyl ether (MtBE) and 5 percent methyl tert-amyl ether (MtAE). The geometric mean concentrations of hydrocarbons (C3-C11) in the customers' breathing zone was 85 mg/m3 (range 2.5-531 mg/m3) at the Stage I service station and 18 mg/m3 (range < 0.2-129 mg/m3) at the Stage II service station. The geometric mean of the exposure of customers to MtBE during refueling at the Stage I service station was 15.3 mg/m3 (range 1.8-74 mg/m3), and at the Stage II service station 3.4 mg/m3 (range 0.2-16 mg/m3). The differences in exposure were statistically significant (p < 0.05). The mean refueling times were 57 seconds (range 23-207) at the Stage I and 66 seconds (range 18-120) at the Stage II station. The measurements were done on consecutive days at the various service stations. The temperature ranged from 10 to 17 degrees C, and wind velocity was 2-4 m/s. The climatic conditions were very similar on the measurement days. Based on this study it was found that the Stage II vapor recovery system reduces gasoline emission considerably. The exposure level of customers at the Stage II station during refueling was circa 20-25 percent of the exposure at the Stage I service station when conditions were equal and no other confounding factors such as leaks or spills were present.     

Tank truck driver exposure to vapors from oxygenated or reformulated gasolines during loading and unloading.

Tank truck drivers' exposure to gasoline vapors was studied by collecting breathing zone samples during loading and unloading of gasoline. The field studies were conducted at three dispatches and at seven service stations in Finland. The gasolines included in the study (95, 98, 99 research octane number, RON) were of reformulated or oxygenated grade containing about 2% (w/w) oxygen and 0.5-1.5% (v/v) benzene. The sampling times ranged from 16 to 57 min (mean 35 min), and time-weighted average concentrations for a 30-min period were calculated. Using the time-adjusted values, geometric mean concentrations (GM) were calculated for three periods of dispatch measurements (n = 15,20,7) and a period of unloading measurements at service stations (n = 7). The GM for methyl tert-butyl ether ranged from 0.95 to 7.3 mg/m3 and that for tert-amyl methyl ether from 0.30 to 1.1 mg/m3. The GM concentrations of hexane, benzene, and toluene were in the range of 0.25-2.3 mg/m3, 0.15-0.28 mg/m3, and 0.73-1.7 mg/m3, respectively. Multiple regression analysis yielded an r2 value of 0.98 for the daily mean concentration of toluene and correspondingly 0.94 for benzene when daily wind speed (0.1-3.7 m/sec) and daily air temperature (-7.4(-)+17.2 degrees C) were used as independent variables. The average number of gasoline loads per tank truck was 2.5, corresponding to 23,000 L of gasoline.     

Toxicokinetics of methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME) in humans, and implications to their biological monitoring

Healthy male volunteers were exposed via inhalation to gasoline oxygenates methyl tert-butyl ether (MTBE) or tert-amyl methyl ether (TAME). The 4-hr exposures were carried out in a dynamic chamber at 25 and 75 ppm for MTBE and at 15 and 50 ppm for TAME. The overall mean pulmonary retention of MTBE was 43 +/- 2.6%; the corresponding mean for TAME was 51 +/- 3.9%. Approximately 52% of the absorbed dose of MTBE was exhaled within 44 hr following the exposure; for TAME, the corresponding figure was 30%. MTBE and TAME in blood and exhaled air reached their highest concentrations at the end of exposure, whereas the concentrations of the metabolites tert-butanol (TBA) and tert-amyl alcohol (TAA) concentrations were highest 0.5-1 hr after the exposure and then declined slowly. Two consecutive half-times were observed for the disappearance of MTBE and TAME from blood and exhaled air. The half-times for MTBE in blood were about 1.7 and 3.8 hr and those for TAME 1.2 and 4.9 hr. For TAA, a single half-time of about 6 hr best described the disappearance from blood and exhaled air; for TBA, the disappearance was slow and seemed to follow zero-order kinetics for 24 hr. In urine, maximal concentrations of MTBE and TAME were observed toward the end of exposure or slightly (< or = 1 hr) after the exposure and showed half-times of about 4 hr and 8 hr, respectively. Urinary concentrations of TAA followed first-order kinetics with a half-time of about 8 hr, whereas the disappearance of TBA was slower and showed zero-order kinetics at concentrations above approx. 10 micro mol/L. Approximately 0.2% of the inhaled dose of MTBE and 0.1% of the dose of TAME was excreted unchanged in urine, whereas the urinary excretion of free TBA and TAA was 1.2% and 0.3% within 48 hr. The blood/air and oil/blood partition coefficients, determined in vitro, were 20 and 14 for MTBE and 20 and 37 for TAME. By intrapolation from the two experimental exposure concentrations, biomonitoring action limits corresponding to an 8-hr time-weighted average (TWA) exposure of 50 ppm was estimated to be 20 micro mol/L for post-shift urinary MTBE, 1 mu mol/L for exhaled air MTBE in a post-shift sample, and 30 micro mol/L for urinary TBA in a next-morning specimen. For TAME and TAA, concentrations corresponding to an 8-hr TWA exposure at 20 ppm were estimated to be 6 micro mol/L (TAME in post-shift urine), 0.2 micro mol/L (TAME in post-shift exhaled air), and 3 micro mol/L (TAA in next morning urine).     

Exposure to methyl tert-butyl ether and tert-amyl methyl ether from gasoline during tank lorry loading and its measurement using biological monitoring

Objective and methods: The exposure of Finnish tank lorry drivers to methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME) during loading of gasoline was studied using biological and breathing-zone sampling. During the field measurements – in October 1994 and August 1995 – the gasolines (95, 98, 99 RON) contained MTBE to 5.2–11.8% and TAME to 0–6%. Results: The geometric mean (GM) breathing-zone concentration of MTBE was 4.3 mg/m³ (n= 15) in October and 6.4 mg/m³ (n= 20) in August. The GM concentration of TAME, measured only in August, was 0.98 mg/m³. The mean loading/sampling times were 37 and 35 min, the mean wind speeds were 0.8 and 0.6 m/s, and the mean air temperatures were −4.9° and +14.1 °C, respectively. Blood samples collected on average at 20 min after gasoline loading/exposure showed an MTBE concentration of 143 nmol/l (GM, n= 14) in October and 213 nmol/l (GM, n= 20) in August. Pearson's coefficient of correlation (r) between the MTBE breathing-zone concentrations and MTBE in blood was 0.86 (P= 0.0001) in October and 0.81 (P= 0.00001) in August. No correlation was found between MTBE in air and the metabolite tert-butanol (TBA) in blood. MTBE, but not TBA, in urine samples collected on average at 2.5 h after exposure showed a correlation with MTBE in air. The concentrations of TAME and its metabolite tert-amyl alcohol were below the quantitation limits (<7 and <100 nmol/l, respectively) in most blood and urine samples. Conclusions: The breathing-zone measurements showed low levels of exposure to the two oxygenates, the concentrations being well below the current hygienic standards for MTBE (250–360 mg/m³ for 15 min and 90–180 mg/m³ for 8 h). The linear correlations obtained for MTBE suggest that MTBE in blood or urine can be adopted as a valid biological exposure index. Received: 7 November 1997 / Accepted: 13 February 1998     

Benzene,toluene, ethylbenzene and xylene concentrations in atmospheric ambient air of gasoline and CNG refueling stations

This study aimed to assess workers’ exposure to benzene, toluene, ethylbenzene, and xylene (BTEX) compounds in refueling stations of Ardabil city (Iran). Twenty-four refueling stations including 15 petrol and 9 compressed natural gas (CNG) stations from different regions were selected and monitored for ambient BTEX concentrations. Air samples were taken based on NIOSH Manual of Analytical Method no 1501. Target compounds were extracted using CS₂ and analyzed by GC equipped with FID. Average concentrations of benzene, toluene, ethylbenzene, and xylene were obtained 2.01, 1.80, 2.72, and 1.65 mg/m³, respectively. Benzene concentrations exceeded the occupational exposure limit set by the Iran Ministry of Health and Medical Education. Its concentrations were significantly higher in commercial areas (2.72 mg/m³) compared to suburban areas (1.89 mg/m³). BTEX concentrations in gasoline stations were slightly, but not significantly, higher than those in CNG stations. Long-term exposure cancer risk of 1884?×?10^?6?±?390?×?10^?6 and hazard index of 22.83?±?3.66 were estimated for benzene and BTEX compounds, respectively. The results declare the necessity for controlling BTEX emission (mainly benzene) and monitoring employee’s exposure in refueling stations.     

High-end exposure relationships of volatile air toxics and carbon monoxide to community-scale air monitoring stations in Atlanta,Chicago, and Houston

Evaporative and exhaust mobile source air toxic (MSAT) emissions of total volatile organic compounds, carbon monoxide, BTEX (benzene, toluene, ethylbenzene, and xylenes), formaldehyde, acetaldehyde, butadiene, methyl tertiary butyl ether, and ethanol were measured in vehicle-related high-end microenvironments (ME) under worst-case conditions plausibly simulating the >99th percentile of inhalation exposure concentrations in Atlanta (baseline gasoline), Chicago (ethanol-oxygenated gasoline), and Houston (methyl tertiary butyl either-oxygenated gasoline) during winter and summer seasons. High-end MSAT values as ratios of the corresponding measurements at nearby air monitoring stations exceeded the microenvironmental proximity factors used in regulatory exposure models, especially for refueling operations and MEs under reduced ventilation. MSAT concentrations were apportioned between exhaust and evaporative vehicle emissions in Houston where methyl tertiary butyl ether could be used as a vehicle emission tracer. With the exception of vehicle refueling operations, the results indicate that evaporative emissions are a minor component of high-end MSAT exposure concentrations.     

Selection and identification of bacterial strains with methyl-tert-butyl ether, ethyl-tert-butyl ether, and tert-amyl methyl ether degrading capacities

Nine bacterial strains isolated from two hydrocarbon-contaminated soils were selected because of their capacity for growth in culture media amended with 200 mg/L of one of the following gasoline oxygenates: Methyl-tert-butyl ether (MTBE), ethyl-tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). These strains were identified by amplification of their 16S rRNA gene, using fDl and rD1 primers, and were tested for their capacity to grow and biotransform these oxygenates in both mineral and cometabolic media. The isolates were classified as Bacillus simplex, Bacillus drentensis, Arthrobacter sp., Acinetobacter calcoaceticus, Acinetobacter sp., Gordonia amicalis (two strains), Nocardioides sp., and Rhodococcus ruber. Arthrobacter sp. (strain MG) and A. calcoaceticus (strain M10) consumed 100 (cometabolic medium) and 82 mg/L (mineral medium) of oxygenate TAME in 21 d, respectively, under aerobic conditions. Rhodococcus ruber (strain E10) was observed to use MTBE and ETBE as the sole carbon and energy source, whereas G. amicalis (strain T3) used TAME as the sole carbon and energy source for growth. All the bacterial strains transformed oxygenates better in the presence of an alternative carbon source (ethanol) with the exception of A. calcoaceticus (strain M10). The capacity of the selected strains to remove MTBE, ETBE, and TAME looks promising for application in bioremediation technologies.     

Fate of gasoline oxygenates in conventional and multilevel wells of a contaminated groundwater table in Düsseldorf, Germany

In a gasoline-contaminated site in Düsseldorf, Germany a two-year monitoring program was carried out to determine the presence, behavior, and fate of 12 gasoline additives in a total of 96 samples from 14 groundwater wells. The origin of contamination was suspected to be a gasoline spill at a gas station. Target compounds were methyl-tert-butyl ether (MTBE), its main degradation products, tert-butyl alcohol (TBA) and tert-butyl formate (TBF); other gasoline additives, oxygenate dialkyl ethers: Ethyl-tert-butyl ether (ETBE), tert-amyl methyl ether (TAME) and diisopropyl ether (DIPE); aromatics: Benzene, toluene, ethylbenzene and xylenes (BTEX), and other compounds causing odor problems: Dicyclopentadiene and trichloroethylene. Purge and trap coupled with gas chromatography-mass spectrometry permitted detection of ng/L concentrations. Ninety of the 96 samples analyzed contained MTBE at levels varying between 0.01 to 645 microg/L. Five contaminated hot spots were identified with levels up to U.S. Environmental Protection Agency (U.S. EPA) drinking water advisory values (20-40 microg/L) and one of them doubling Danish suggested toxicity level of 350 microg/L at a depth of 11 m. No significant natural attenuation was found in MTBE degradation, although samples with high levels of MTBE contained 0.1 to 440 microg/L of TBA. These levels were attributed to its presence in the contamination source more than MTBE degradation. tert-Butyl alcohol was found to be recalcitrant in groundwater. In all cases, BTEX were at low concentrations or not detected, showing less persistence than MTBE. The monitoring of the contamination plume showed that the distribution of the MTBE and TBA in the aquifer formed a similar vertical concentration profile that was influenced by the groundwater flow direction.     

Evolution of occupational exposure to environmental levels of aromatic hydrocarbons in service stations

During refuelling, people may easily be exposed to extremely high levels of gasoline vapour for a short time, although such exposure takes on more importance in the case of service station attendants. The volume of gasoline sold in refuelling operations and the ambient temperature can significantly increase the environmental level of benzene, toluene and xylene (BTX) vapours and, subsequently, the occupational risk of service station attendants. This is especially true in the case of benzene, the most important component of gasoline vapours from a toxicological point of view. The European Directive 98/70/EC, limiting the benzene composition of gasoline, and 94/63/EC, concerning the use of vapour recovery systems in the delivery of gasoline to services stations, were applied in Spain from January 2000 and 2002, respectively. In addition, a new limit value for occupational exposure of 3.25 mg/m(3) was fixed for benzene in Directive 97/42/EC, applied from June 2003. However, recent years have seen the growing use of diesel as well as of unleaded and reformulated gasoline. In this study, we analyse the differences found between air concentration levels of BTXs in 2000 and 2003, analysing samples taken from the personal breathing-zone of occupationally exposed workers in service stations. The results are compared with those obtained in a similar study carried out in 1995 (before the new regulations came into force). The study was carried out in two phases. The first phase was carried out in 2000, after application of the new legal regulation limiting the benzene concentration in gasoline. In this case, an occupationally exposed population of 28 service station attendants was sampled in July, with a mean ambient temperature of 30-31 degrees C. In the second phase, 19 exposed subjects were sampled in July 2003, one of the warmest months in recent years with mean temperatures of 35-36 degrees C during the time of exposure monitoring. The results were then compared with those obtained in 1995, for similar summer weather conditions (environmental temperature between 28 and 30 degrees C). A significant relationship between the volume of gasoline sold and the ambient concentration of aromatic hydrocarbons was found for each worker sampled in all three of the years. Furthermore, a significant decrease in the environmental levels of BTXs was observed after January 2000, especially in the case of benzene, with mean time-weighted average concentrations for 8 h of 736 microg/m(3) (range 272-1603) in 1995, 241 microg/m(3) (range 115-453) in 2000 and 163 microg/m(3) (range 36-564) in 2003, despite the high temperatures reached in the last mentioned year.     

甲基叔丁基醚对加油站职业人群血清淋巴细胞DNA的损伤

[目的]探索汽油添加剂甲基叔丁基醚（methyltert—butylether,MTBE）对加油站职业暴露人群DNA的损伤。[方法]选择华南地区8家加油站工作人员100名为调查对象（其中暴露组61人,对照组39人）,进行健康检查和问卷调查;调查对象各抽取外周静脉血样5mL,分离血清和淋巴细胞,运用气相色谱一质谱（GC／MS）联用技术测定血清MTBE含量;运用彗星试验（cometassay）,分析外周静脉血淋巴细胞DNA损伤情况;运用Pearson相关分析探索样本人群血清MTBE含量与淋巴细胞DNA损伤的相关性。[结果]接受体检的加油站调查对象未发现身体健康状况不合格者,均符合汽油从业人员的职业卫生要求;暴露组血清MTBE含量平均值为（6．230±2．369）μg／L,高于对照组[（5．164±2．139）μg/L]（P〈O．05）;暴露组0live尾矩平均值为（0．060±0．045）gm,也高于对照组I（0．039±0．038）μm]P〈0．05）;Pearson相关分析显示,暴露组血清MTBE含量与淋巴细胞DNA损伤程度之间呈正相关关系（r=0．859,P〈0．05）。[结论]血清MTBE含量与淋巴细胞DNA损伤可能存在相关性。     

The MTBE air concentrations in the cabin of automobiles while fueling.

Methyl tertiary-butyl ether (MTBE) is the most commonly used oxygenated compound added to gasoline to reduce ambient carbon monoxide levels. Complaints about perceived MTBE exposures and adverse health symptoms have been registered in several states, including New Jersey (NJ). Fueling automobiles is the activity thought to cause the highest environmental MTBE exposures. The current study was conducted to determine the MTBE concentrations inside automobile cabins during fueling, which represents the peak exposure that can occur at full service gasoline service stations, such as those that exist in NJ. Air samples were collected at service stations located on the NJ and PA turnpikes from March 1996 to July 1997 during which the MTBE content in gasoline varied. A bimodal distribution of MTBE concentrations was found in the cabin of the cars while fueling. The median MTBE, benzene and toluene in cabin concentrations were 100, 5.5 and 18 ppb, respectively, with the upper concentrations of the distribution exceeding 1 ppm for MTBE and 0.1 ppm for benzene and toluene. The highest in cabin concentrations occurred in a car that had a malfunctioning vapor recovery system and in a series of cars sampled on an unusually warm, calm winter day when the fuel volatility was high, the evaporation maximal and the dispersion by wind minimal. The in-cabin concentrations were typically higher when the car window was opened during the entire fueling process. Thus, exposure to MTBE during fueling can be reduced by properly maintaining the integrity of the fuel system and keeping the windows closed during fueling.     

中山市某石油运输服务企业加油站作业工人血常规和血糖调查

目的 了解中山市某石油运输服务企业加油站作业环境的职业病危害以及人员的职业健康状况。
方法 选择中山市某石油运输服务企业18~40岁的在职人员作为研究对象, 以油枪作业岗位315名工人为研究组, 307名非油枪作业岗位人员为对照组; 收集其一般情况和职业史等资料, 以及职业性体检结果进行分析。
结果 该企业加油站存在的化学毒物有苯、甲苯、二甲苯、溶剂汽油和正己烷, 其中加油作业岗位空气中苯、溶剂汽油、甲苯、二甲苯、正己烷的时间加权平均浓度(C_TWA)值分别为(0.25 ±0.03) mg/m3、(76.73 ±7.03) mg/m3、(0.63 ±0.13) mg/m3、(0.26 ±0.04) mg/m3、(1.25 ±0.09) mg/m3, 办公人员岗位空气中苯、溶剂汽油、甲苯、二甲苯、正己烷浓度均未检出。所有检测点空气中苯、溶剂汽油的C_TWA值均未超标。研究组工人的血红蛋白水平低于对照组(P < 0.05), 血红蛋白异常率高于对照组(P < 0.05);研究组工人的血糖浓度和异常率高于对照组(P < 0.05)。
结论 该石油运输服务企业员工职业病防护管理未到位, 工人血糖、血红蛋白浓度异常检出率升高, 长期接触汽油对作业人员健康造成一定损害, 应加强加石油作业工人的职业健康监护。
     

通信机房作业环境空气污染及特征研究

目的 了解通信作业环境空气的污染状况,为制定防治措施提供依据。方法 选择某通信站的一个地面站、两个地下站共9个作业环境,应用气体传感器、沉降法以及气相色谱－质谱联用技术,现场测定了一氧化碳、二氧化碳、可吸入颗粒物（IP）、细菌总数、二氧化氮、二氧化硫、硫化氢以及4种苯系物等11项空气污染指标。结果 地面站污染物浓度范围分别为：二氧化碳：0.053-0.055%,一氧化碳：2.06-3.31mg/m^3;可吸入颗粒物：未检出－0.08mg/m^3;细菌总数：414－1007CFU／^3;苯：未检出－ 33.48mg/m^3;甲苯：9.75-29.40mg/m^3;乙苯：2.84-6.00mg/m^3;二甲苯：7.82-20.21mg/m^3;地下站污染物浓度范围分别为：二氧化碳：0.032-0.107%,一氧化碳：未检出－34.47mg/m^3;可吸入颗粒物：未检出-0.04mg/m^3;细菌总数：847－1391CFU／m^3;甲苯：16.54-345.54mg/m63;乙苯：未检出－6.29mg/m^3;二甲苯：10.90-313.87mg/m^3;二氧化氮：0.32-0.67mg/m^3;硫化氢：未检出－0.78mg/m^3;二氧化硫：未检出-1.26mg/m^3;苯未检出。结论 通信机房特别是地下作业环境存在空气污染问题,而以苯系物为代表的VOCs 污染应引起重视。     

Environmental and biological monitoring of benzene during self-service automobile refueling

Although automobile refueling represents the major source of benzene exposure among the nonsmoking public, few data are available regarding such exposures and the associated uptake of benzene. We repeatedly measured benzene exposure and uptake (via benzene in exhaled breath) among 39 self-service customers using self-administered monitoring, a technique rarely used to obtain measurements from the general public (130 sets of measurements were obtained). Benzene exposures averaged 2.9 mg/m(3) (SD = 5.8 mg/m(3); median duration = 3 min) with a range of < 0.076-36 mg/m(3), and postexposure breath levels averaged 160 microg/m(3) (SD = 260 microg/m(3)) with a range of < 3.2-1,400 microg/m(3). Log-transformed exposures and breath levels were significantly correlated (r = 0.77, p < 0.0001). We used mixed-effects statistical models to gauge the relative influences of environmental and subject-specific factors on benzene exposure and breath levels and to investigate the importance of various covariates obtained by questionnaire. Model fitting yielded three significant predictors of benzene exposure, namely, fuel octane grade (p = 0.0011), duration of exposure (p = 0.0054), and season of the year (p = 0.032). Likewise, another model yielded three significant predictors of benzene concentration in breath, specifically, benzene exposure (p = 0.0001), preexposure breath concentration (p = 0.0008), and duration of exposure (p = 0.038). Variability in benzene concentrations was remarkable, with 95% of the estimated values falling within a 274-fold range, and was comprised entirely of the within-person component of variance (representing exposures of the same subject at different times of refueling). The corresponding range for benzene concentrations in breath was 41-fold and was comprised primarily of the within-person variance component (74% of the total variance). Our results indicate that environmental rather than interindividual differences are primarily responsible for benzene exposure and uptake during automobile refueling. The study also demonstrates that self-administered monitoring can be efficiently used to measure environmental exposures and biomarkers among the general public.     

Aerobic degradation of ethyl-tert-butyl ether by a microbial consortium: selection and evaluation of biodegradation ability

A microbial consortium that degrades ethyl-tert-butyl ether (ETBE) as the sole source of carbon and energy under aerobic conditions was selected from a gasoline-polluted soil. This consortium consists of a variety of microorganisms with a predominance of filamentous morphology. Degradation of ETBE was found to be solely related to bacterial activity. After prolonged cultivation followed by successive transfers, the consortium's degradation ability was improved and reached a specific degradation rate of 95 mg/g(protein)/h (about 146 mg/g(dry wt)/h). This exceeds the previously reported rates in the literature for ETBE-degrading microorganisms as pure or mixed cultures. Furthermore, a stoichiometric balance of chemical oxygen demand (COD) removal and oxygen uptake with ETBE removal provides indirect evidence of complete degradation. The consortium's activity was not inhibited by high ETBE concentrations (< or = 1,600 mg/L), and large inoculum sizes (> or = 120 mg(protein)/L) were desirable for a faster and complete degradation of ETBE. The enriched consortium was also able to completely degrade methyl-tert-butyl ether (MTBE), tert-amyl methyl ether (TAME), and tert-butyl alcohol (TBA). both alone and in mixture with ETBE, without any measurable release of major degradation intermediates. In each case, MTBE and TAME exhibited the most significant resistance to degradation while TBA was rapidly degraded.     

甲基叔丁基醚无铅汽油肾脏毒性的实验研究

目的：了解甲基叔丁基醚（MTBE）无铅汽油对肾脏的毒性及毒作用机制。方法：昆明种小鼠经呼吸道静式染毒，MTBE无铅汽油22．9、11．4及2．3g/m^3每天一次，连续2h，共22d亚急性染毒。日立－7150型全自动生化仪检测血清中尿素氮（BUN）、肌酐（Cr）含量；肾组织均浆中丙二醛（MDA）和超氧化物歧化酶（SOD）含量分别用荧光法，邻苯三酚自氧化固定时间法测定；电镜观察肾皮质区超微结构的变化，结果：22.9g/m^3染毒组雌性小鼠血清中BUN含量与阴性对照组间比较差异有显著性（P＜0．05）；电镜观察到22.9g/m^3染色毒对照组雌雄性小鼠的肾小球基底膜，肾小管细胞线粒体及绒毛均未见显著异常改变。结论：MTBE无铅汽油对肾小球的滤过功能有一定的影响，雌性小鼠可能更为敏感。     

三种汽油增氧剂对小鼠成纤维细胞DNA损伤的研究

目的 比较3种汽油增氧剂对小鼠成纤维细胞DNA的损伤作用。方法 采用单细胞凝胶电泳试验（彗星试验）对3种汽油增氧剂甲基叔丁基醚（MTBE）、无水乙醇（EA）和碳酸二甲酯（DMC）所致的L－929小鼠成纤维细胞的DNA损伤进行了研究。结果 在一定浓度范围内（37.500-150.000mg/ml)，MTBE可直接引起L－929小鼠成纤维细胞的DNA损伤，出现拖尾的彗星细胞。其拖尾细胞百分率和DNA迁移长度均随受试物浓度的增加而增加，且有明显的剂量－效应关系，即MTBE浓度从9.375mg/ml增加到150.000mg/ml时，彗星率从接受阴性对照组的4％增加到接近阳性对照组的85％,彗尾长度也发生了相应的改变。而EA和DMC无此关系。结论 在本试验条件下（浓度为150.00mg/ml)，MTBE对DNA具有明显的损伤作用；未发现EA和DMC对DNA的损伤作用。     

Liquid-Gas Partitioning of the Gasoline Oxygenate Methyl tert-Butyl Ether (MTBE) Under Laboratory Conditions and Its Effect on Growth of Selected Algae

The partitioning of the widely used gasoline additive methyl tert-butyl ether (MTBE) between liquid growth media and gaseous phase was measured daily under laboratory conditions to determine how closely dissolved MTBE concentrations matched nominal concentrations. Total (gaseous and dissolved) MTBE averaged across 6 days for 29.6, 503.2, and 1005.7 mg L⁻¹ MTBE treatments were 89.9, 90.3, and 73.0% of nominal, respectively, and mean dissolved MTBE in these same treatments were 74.6, 73.8, and 69.6% of total MTBE, respectively. This suggests that dissolved MTBE concentrations can vary substantially from nominal. The effect of MTBE on the growth of selected algae was also evaluated under laboratory conditions. Three unicellular algae, Selenastrum capricornutum (Chlorophyta), Navicula pelliculosa (Bacillariophyta), and Synechococcus leopoliensis (=Anacystic nidulans, Cyanophyta = Cyanobacteria), representative of three taxonomic groups, were used as test organisms. Toxicity tests were acute and increase in cell number was used as an indicator of growth. Algal species were exposed by injection of MTBE into sealed vessels containing defined liquid growth media. The growth of N. pelliculosa and S. leopoliensis was negatively affected at nominal 2400 mg L⁻¹ MTBE, whereas the growth of S. capricornutum was negatively affected at nominal 4800 mg L⁻¹ MTBE and positively affected at nominal 600 mg L⁻¹ MTBE. The differential sensitivity of the growth of these representative species suggests that MTBE may alter algal community composition in the natural environment. Received: 29 January 1997/Accepted: 22 May 1997     

Gasoline vapor exposures at a high volume service station

Gasoline vapor concentrations were measured at a high volume service station for one week in May, 1983, for service station attendants, self-service customers and for various area locations. To facilitate the retention of highly volatile, low-molecular weight gasoline vapor components, 100/50 mg charcoal adsorption tubes were used with flow rates of 100 cc/min for long-term exposure samples and 900 cc/min for short-term exposures. Methylene chloride was selected as the desorption solvent. Desorbed hydrocarbons were analyzed and quantitated by capillary column gas chromatography using a flame ionization detector and a 0-100 degrees C temperature program. The data proved that the predominant ambient air hydrocarbons are those of C4 and C5 compounds. Monitoring results showed that the total gasoline vapor TWA exposures for service station attendants ranged from 0.6 to 4.8 ppm with a geometric mean of 1.5 ppm. Short-term personal samples collected while refueling ranged from not detectable to 38.8 ppm with a geometric mean of 5.8 ppm.