Commuter exposures to VOCs in Boston, Massachusetts.

This study examines the commuter's exposure to six gasoline-related volatile organic compounds (VOCs): benzene, toluene, ethylbenzene, m-/p-xylene, o-xylene, and formaldehyde. The VOC concentrations to which commuters were exposed in four different commuting modes (driving, subway, walking, and biking) in Boston, Massachusetts, are compared. The VOC concentrations in participants' homes and offices were also measured. Factors that could influence in-vehicle VOC concentrations, such as different traffic patterns, car model and vehicle ventilation conditions, were also evaluated. Driving a private car was associated with higher VOC concentrations and commuting on urban roadways resulted in the highest VOC concentrations. The use of car heaters resulted in higher in-vehicle VOC concentrations. The longer the subway commuters stayed underground, the higher their VOC exposures. The home-to-work car or subway commute represented about 10 to 20 percent of an individual's total VOC exposure for these compounds.     

Identifying Influencing Factors on Paved Roads Silt Loading

Abstract

The factors that influence the increase or decrease of silt loadings on paved roadways have not been fully quantitatively investigated. They were identified in this study based on the quarterly silt loading sampling data collected from 20 sites by the Clark County Department of Air Quality and Environmental Management in Southern Nevada for the period from 2000 to 2003. The silt loading and associated data collected over these years at one sampling site may inherently possess site-specific characteristics that can be better incorporated by using panel data models. The factors that are identified as significant are the presence of curbs and gutters, shoulder type, pavement conditions, and the presence of construction activities in the vicinity of roadways. The presence of curbs and gutters, stabilized shoulders, and good pavement conditions would result in decreased silt loadings. Conversely, the presence of construction activities within the immediate vicinity of sampled areas would result in increases of silt loadings on the roadway surfaces. Based on the analysis of the results, it was recommended that constructing curbs, gutters and stabilized shoulders, preventing or reducing construction track-out from construction activity, and improving pavement conditions be the preferred control measures to reduce silt loading on paved roadways.     

Impact of roadside noise barriers on particle size distributions and pollutants concentrations near freeways

Increasing epidemiological evidence has established an association between a host of adverse health effects and exposure to ambient particulate matter (PM) and co-pollutants, especially those emitted from motor vehicles. Although PM and their co-pollutants dispersion profiles near the open freeway have been extensively characterized by means of both experimental measurements and numerical simulations in recent years, such investigations near freeways with roadside barriers have not been well documented in the literature. A few previous studies suggested that the presence of roadside structures, such as noise barriers and vegetation, may impact the decay of pollutant concentrations downwind of the freeway by limiting the initial dispersion of traffic emissions and increasing their vertical mixing due to the upward deflection of airflow. Since the noise barriers are now common roadside features of the freeways, particularly those running through populated urban areas, it is pertinent to investigate the impact of their presence on the particles and co-pollutants concentrations in areas adjacent to busy roadways. This study investigated two highly trafficked freeways (I-710 and I-5) in Southern California, with two sampling sites for each freeway, one with and the other without the roadside noise barriers. Particle size distributions and co-pollutants concentrations were measured in the immediate proximity of freeways and at different distances downwind of the freeways. The results showed the formation of a “concentration deficit” zone in the immediate vicinity of the freeway with the presence of roadside noise barrier, followed by a surge of pollutant concentrations further downwind at 80–100 m away from freeway. The particle and co-pollutants concentrations reach background levels at farther distances of 250–400 m compared to 150–200 m at the sites without roadside noise barriers.     

Identifying influencing factors on paved roads silt loading

The factors that influence the increase or decrease of silt loadings on paved roadways have not been fully quantitatively investigated. They were identified in this study based on the quarterly silt loading sampling data collected from 20 sites by the Clark County Department of Air Quality and Environmental Management in Southern Nevada for the period from 2000 to 2003. The silt loading and associated data collected over these years at one sampling site may inherently possess site-specific characteristics that can be better incorporated by using panel data models. The factors that are identified as significant are the presence of curbs and gutters, shoulder type, pavement conditions, and the presence of construction activities in the vicinity of roadways. The presence of curbs and gutters, stabilized shoulders, and good pavement conditions would result in decreased silt loadings. Conversely, the presence of construction activities within the immediate vicinity of sampled areas would result in increases of silt loadings on the roadway surfaces. Based on the analysis of the results, it was recommended that constructing curbs, gutters and stabilized shoulders, preventing or reducing construction track-out from construction activity, and improving pavement conditions be the preferred control measures to reduce silt loading on paved roadways.     

Commuter Exposures to VOCs in Boston,Massachusetts

This study examines the commuter’s exposure to six gasoline-related volatile organic compounds (VOCs): benzene, toluene, ethylbenzene, m-/p-xylene, o-xylene, and formaldehyde. The VOC concentrations to which commuters were exposed in four different commuting modes (driving, subway, walking, and biking) in Boston, Massachusetts, are compared. The VOC concentrations in participants’ homes and offices were also measured. Factors that could influence in-vehicle VOC concentrations, such as different traffic patterns, car model and vehicle ventilation conditions, were also evaluated. Driving a private car was associated with higher VOC concentrations and commuting on urban roadways resulted in the highest VOC concentrations. The use of car heaters resulted in higher in-vehicle VOC concentrations. The longer the subway commuters stayed underground, the higher their VOC exposures. The home-to-work car or subway commute represented about 10 to 20 percent of an individual’s total VOC exposure for these compounds.     

Modeling vehicle interior noise exposure dose on freeways: Considering weaving segment designs and engine operation

Vehicle interior noise functions at the dominant frequencies of 500 Hz below and around 800 Hz, which fall into the bands that may impair hearing. Recent studies demonstrated that freeway commuters are chronically exposed to vehicle interior noise, bearing the risk of hearing impairment. The interior noise evaluation process is mostly conducted in a laboratory environment. The test results and the developed noise models may underestimate or ignore the noise effects from dynamic traffic and road conditions and configuration. However, the interior noise is highly associated with vehicle maneuvering. The vehicle maneuvering on a freeway weaving segment is more complex because of its nature of conflicting areas. This research is intended to explore the risk of the interior noise exposure on freeway weaving segments for freeway commuters and to improve the interior noise estimation by constructing a decision tree learning–based noise exposure dose (NED) model, considering weaving segment designs and engine operation. On-road driving tests were conducted on 12 subjects on State Highway 288 in Houston, Texas. On-board Diagnosis (OBD) II, a smartphone-based roughness app, and a digital sound meter were used to collect vehicle maneuvering and engine information, International Roughness Index, and interior noise levels, respectively. Eleven variables were obtainable from the driving tests, including the length and type of a weaving segment, serving as predictors. The importance of the predictors was estimated by their out-of-bag–permuted predictor delta errors. The hazardous exposure level of the interior noise on weaving segments was quantified to hazard quotient, NED, and daily noise exposure level, respectively. Results showed that the risk of hearing impairment on freeway is acceptable; the interior noise level is the most sensitive to the pavement roughness and is subject to freeway configuration and traffic conditions. The constructed NED model shows high predictive power (R = 0.93, normalized root-mean-square error [NRMSE] < 6.7%).

Implications: Vehicle interior noise is usually ignored in the public, and its modeling and evaluation are generally conducted in a laboratory environment, regardless of the interior noise effects from dynamic traffic, road conditions, and road configuration. This study quantified the interior exposure dose on freeway weaving segments, which provides freeway commuters with a sense of interior noise exposure risk. In addition, a bagged decision tree–based interior noise exposure dose model was constructed, considering vehicle maneuvering, vehicle engine operational information, pavement roughness, and weaving segment configuration. The constructed model could significantly improve the interior noise estimation for road engineers and vehicle manufactures.     

Mobile load simulators – A tool to distinguish between the emissions due to abrasion and resuspension of PM10 from road surfaces

Mechanically produced abrasion particles and resuspension processes are responsible for a significant part of the PM10 emissions of road traffic. However, specific differentiation between PM10 emissions due to abrasion and resuspension from road pavement is very difficult due to their similar elemental composition and highly correlated variation in time. In this work Mobile Load Simulators were used to estimate PM10 emission factors for pavement abrasion and resuspension on different pavement types for light and heavy duty vehicles.From the experiments it was derived that particle emissions due to abrasion from pavements in good condition are quite low in the range of only a few mg·km^?1 per vehicle if quantifiable at all. Considerable abrasion emissions, however, can occur from damaged pavements. Resuspension of deposited dust can cause high and extremely variable particle emissions depending strongly on the dirt load of the road surface. Porous pavements seem to retain deposited dust better than dense pavements, thus leading to lower emissions due to resuspension compared to pavements with a dense structure (e.g. asphalt concrete). Tyre wear seemed not to be a quantitatively significant source of PM10 emissions from road traffic.     

Near-roadway monitoring of vehicle emissions as a function of mode of operation for light-duty vehicles

Determination of the effect of vehicle emissions on air quality near roadways is important because vehicles are a major source of air pollution. A near-roadway monitoring program was undertaken in Chicago between August 4 and October 30, 2014, to measure ultrafine particles, carbon dioxide, carbon monoxide, traffic volume and speed, and wind direction and speed. The objective of this study was to develop a method to relate short-term changes in traffic mode of operation to air quality near roadways using data averaged over 5-min intervals to provide a better understanding of the processes controlling air pollution concentrations near roadways. Three different types of data analysis are provided to demonstrate the type of results that can be obtained from a near-roadway sampling program based on 5-min measurements: (1) development of vehicle emission factors (EFs) for ultrafine particles as a function of vehicle mode of operation, (2) comparison of measured and modeled CO₂ concentrations, and (3) application of dispersion models to determine concentrations near roadways. EFs for ultrafine particles are developed that are a function of traffic volume and mode of operation (free flow and congestion) for light-duty vehicles (LDVs) under real-world conditions. Two air quality models—CALINE4 (California Line Source Dispersion Model, version 4) and AERMOD (American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model)—are used to predict the ultrafine particulate concentrations near roadways for comparison with measured concentrations. When using CALINE4 to predict air quality levels in the mixing cell, changes in surface roughness and stability class have no effect on the predicted concentrations. However, when using AERMOD to predict air quality in the mixing cell, changes in surface roughness have a significant impact on the predicted concentrations.

Implications: The paper provides emission factors (EFs) that are a function of traffic volume and mode of operation (free flow and congestion) for LDVs under real-world conditions. The good agreement between monitoring and modeling results indicates that high-resolution, simultaneous measurements of air quality and meteorological and traffic conditions can be used to determine real-world, fleet-wide vehicle EFs as a function of vehicle mode of operation under actual driving conditions.     

Traffic noise exposure of high-rise residential buildings in urban area

Noise pollution is a major factor of environmental complaints in many cities, which has significant impacts on human health. As a dominating source of environmental noise, the impact of road traffic noise is increasing. Residents living in high-rise buildings along the main road are severely affected by traffic noise. In order to assess the noise level of urban area along the main road in Guangzhou, three buildings were selected to conduct traffic noise measurements, and the questionnaire about traffic noise impact on human being was completed. Through the questionnaire, around 70% of participants consider the traffic noise has negative effect, and about 60% of participants consider the noise has moderate or much higher impact on physical comfort. Around 65% of participants consider the noise had moderately or much higher impact on their psychological comfort. By analyzing the measured data, all of the measured noise levels in three buildings exceed the recommended limit of 55 dB (A) in the daytime and 45 dB (A) in the night for residence, and the exceeded value can be up to 16 dB (A). By comparing the fitting curve of noise level transfer function on each floor relative to the reference floor, the quadratic polynomial was selected to plot the transfer function rather than cubic polynomial.

     

Implementation of a top-down noise control strategy for a liquefied natural gas peak-shaving facility

There have been many previous noise-related studies on liquefied natural gas (LNG) facilities in the United States; however, noise control of these facilities using a top-down approach has not been explored in detail. Most studies have demonstrated noise compliance to applicable standards by focusing on a combination of treatments and specifications, with less consideration on control technology feasibility, ranking, and cost-effectiveness. The Federal Energy Regulatory Commission (FERC) prohibits natural gas facilities from emitting day-night noise levels in excess of 55 dB(A) (equivalent to 24-hr continuous level of 49 dB(A)) at nearby receivers. A case study was conducted to evaluate a top-down approach to reduce noise at a typical LNG peak-shaving facility under normal operating conditions, accounting for technical feasibility, control effectiveness, and cost implications. A modeling approach (International Organization for Standardization standard ISO 9613-2) was used to predict and evaluate the facility’s noise reduction potential. The study found that the strategy could achieve feasible and environmentally effective reductions up to 11 dB(A) at 500 m from the facility by first identifying source groups with highest-emitting sources and then targeting major noise source contributors per group. This approach is cost-effective because the FERC noise goals can still be achieved by avoiding unnecessary control costs associated with lower-ranked sources. The study identified the following four source groups as the highest noise emitters: (1) liquefaction and instrument air, (2) boil-off gas (BOG) compression, (3) glycol water system (air coolers), and (4) pretreatment. Of all the treatments evaluated, installation of enhanced silencers for gas turbine (GT) package—as well as construction of an acoustical building for the BOG compressors and drivers—resulted in the greatest noise reduction at nearby receivers. The study notes that incremental treatment costs presented in this paper are approximate estimates that may vary depending on factors such as facility size and region.

Implications: This study assessed potential noise reductions associated with implementing a top–down noise control strategy on a typical LNG peak-shaving facility. The study determined the top–down noise control strategy could achieve feasible and environmentally effective reductions up to 11 decibels at receivers within 500 m from the facility’s center. As LNG suppliers need to support potential supply disruptions, some regions of the US, including New England and Gulf Coast with projected increase in LNG exports and growing needs from power sector, may find information in this study useful with regard to evaluating and prioritizing noise reduction potential of their LNG peak-shaving facilities.     

Prediction of Traffic Noise: A Screening Technique

Abstract

Traffic noise is ubiquitous in many communities and is an important environmental concern, especially for persons located near major roadways. Several different methods are available to estimate noise levels resulting from roadway traffic. These include computational, graphical, and computer modeling techniques.

The prediction methodology presented here is a simplified technique that can be used for estimating noise resulting from traffic and for screening traffic noise impacts. This Traffic Noise Screening (TNS) approach consists of a series of traffic noise level prediction graphs developed for different roadway configurations. The graphs are based on the results from using the Federal Highway Administration (FHWA) STAMINA2.0 computerized noise prediction model for various scenarios. Data inputs to the TNS approach include roadway geometries, traffic volumes, vehicle travel speed, and centerline distance to the receptors.

The TNS graphs allow easy estimation of traffic noise levels for use in predicting traffic-related noise impacts. This TNS approach is not intended as a substitute for detailed modeling, such as with STAMINA2.0, but as a screening tool to aid in determining when detailed modeling may be necessary. If screening results indicate that noise estimates are significant, or if the scenario is rather complex, then additional, more detailed modeling can be performed.     

Environmental interactions of Sulphlex pavement

Sulphlex, a mixture of elemental sulfur and plasticizers, has been considered for use as an asphalt substitute in road construction. Because this material contains substantial quantities of elemental sulfur, it is a potential substrate for growth of sulfur-oxidising bacteria. Experiments, performed to determine the susceptibility of Sulphlex in Sulphlex-containing media to degradation by Thiobacillus thiooxidans, resulted in breakdown of the Sulphlex material and concomitant production of acid. In concurrent studies, plants were grown in Sulphlex-amended soils. These plants exhibited higher sulfur content and reduced productivity as compared with plants grown in unamended soils, indicating that Sulphlex was being broken down in the soil and that the breakdown products were apparently having a detrimental effect on plant productivity. These experiments indicate that naturally occurring sulfur-oxidising bacteria have the potential to break down Sulphlex paving material, resulting in adverse effects on both the structural integrity of the pavement and the local environment.     

Characteristics of carbonyl compounds in public vehicles of Beijing city: Concentrations,sources, and personal exposures

The characteristics of carbonyl compounds (carbonyls) including concentrations, major sources, and personal exposure were investigated for 29 vehicles including taxi, bus and subway in Beijing. It was found that the taxis (Xiali, TA) and buses (Huanghe, BA) fueled by gasoline with longer service years had the higher indoor carbonyl levels (178±42.7 and 188±31.6 μg m⁻³) while subways energized by electricity without exhaust and the jingwa buses (BB) driven in the suburb had the lower levels with total concentrations of 98.5±26.3 and 92.1±20.3 μg m⁻³, respectively. Outdoor carbonyls of taxi cars and buses were nearly at the same level with their total concentrations varying from 80 to 110 μg m⁻³. The level of outdoor subways carbonyls was equal with the ambient air levels. Exhaust leakage, indoor material emissions, photochemical formation, and infiltration of outdoor air were considered to be the major sources to in-vehicle carbonyls. Personal exposures and cancer risk to formaldehyde and acetaldehyde were calculated for professional bus and taxi drivers, respectively. Taxi drivers had the highest cancer risk with personal exposure to formaldehyde and acetaldehyde of 212 and 243 μg day⁻¹, respectively. The public concern should pay considerable attention to professional drivers’ health.     

Exposure to ultrafine and fine particles and noise during cycling and driving in 11 Dutch cities

Recent studies have suggested that exposures during traffic participation may be associated with adverse health effects. Traffic participation involves relatively short but high exposures. Potentially relevant exposures include ultrafine particles, fine particles (PM_2.5) and noise.Simultaneously, detailed real time exposure of particle number concentration (PNC), PM_2.5 and noise has been measured while driving and cycling 12 predefined routes of approximately 10–20 min duration. Sampling took place in eleven medium-sized Dutch cities on eleven weekdays in August till October 2006. To investigate variability in cyclists exposure, we systematically collected information on meteorology, GPS coordinates, type of road, traffic intensity, passing vehicles and mopeds while cycling.The overall mean PNC of car drivers was 5% higher than the mean PNC of cyclists. The overall mean concentration of PM_2.5 in the car was 11% higher than during cycling. Slightly higher 1-min peak concentrations were measured in the car (PNC 14%; PM_2.5 29% for 95-percentiles). Shorter duration peaks of PNC were higher during cycling (43% for 99-percentile of 1-s averages). Peaks in PNC typically last for less than 10 s. A large variability of exposure was found within and between routes. Factors that significantly predicted PNC variability during cycling were: passing vehicles (mopeds, cars), waiting for traffic lights, passing different types of (large) intersections and bicycle lanes and bike paths close to motorized traffic. No relation was found between PM_2.5 and those predictor variables. The correlation between PNC and noise was moderate (median 0.34). PM_2.5 had very low correlations with PNC and noise.PNC and PM_2.5 exposure of car drivers was slightly higher than that of cyclists. PNC was largely uncorrelated with PM_2.5 and reflected local traffic variables more than PM_2.5. Different factors were associated with high PNC and high noise exposures.     

Ambient Air Pollution and Daily Pediatric Hospitalizations for Asthma (5 pp)

Background, Aim and Scope A series of severe air pollution episodes in Europe and North America prior to 1960 have focused scientific and regulatory attention on the adverse effects of air pollution on human health. As a consequence of significant reductions in ambient air pollution levels in the intervening years, scientists and public health officials have become more concerned with the potential health effects of exposure to routine concentrations of air pollution. Several recent time series studies conducted world-wide have found relatively low levels of air pollutants that are below national standards were associated with adverse effects on mortality and morbidity. This study examined the effects of ambient air pollution indicators on the daily rate of pediatric hospital admissions for asthma in the Oklahoma City Metropolitan area from 2001-2003. Results: Negative binomial regression analysis revealed significant relationships between the total number of hospitalizations per day and the one-hour maximum NO2 level, the proportion of susceptible children < 5 years old, and the ratio of temperature to humidity. Discussion: This study of the total number of children aged ≤ 14 years old experiencing hospitalizations on a daily basis in the Oklahoma City area from 2001-2003 underscores factors other than ambient air pollution, especially when concentrations are low, affect hospitalizations for pediatric asthma. For example, information related to indoor air quality, health care, family history, and exposure to environmental tobacco smoke and other irritants are not obtainable. Yet, those factors are risk drivers for asthma. Similarly, health privacy requirements prevented obtaining data on physiological factors specific to each child such as differentials in airways functional capacity or other impairments influenced asthma exacerbation. This makes calculating relative risk inappropriate. Conclusions: Although ambient air pollution concentrations and meteorological conditions influence pediatric asthma hospitalizations, they are not the major predictors in the Oklahoma City metropolitan area. This is consistent with other research that finds limited effects associated with low levels for concentrations of the criteria pollutants.     

粉煤灰资源化特性及路面工程应用技术研究

对粉煤灰的各项技术参数进行了试验研究,揭示出粉煤灰的不同成分和形貌对其资源化特性的影响规律,初步完成了消除不利于粉煤灰资源化的有害成分炭的优化实验工作,进行了脱炭粉煤灰混凝土配合比等试验研究,并在路面修复工程中予以应有,结果表明,经脱炭处理的粉煤灰应用于混凝土工程可以明显改善混凝土的工作性能,实际道路运营和技术性能符合路面工程的要求,具有重大的经济效益和环境效益。     

道路交通噪声预测模式预测结果的比较

为了分析实际环境影响评价中常用的各种公路交通噪声预测模型预测结果之间存在的差异,并验证各预测方式与实测值之间的相符性,通过对选取的高速公路和市政快速公路采用各种预测模型计算比较,并用实际监测值对各模型预测结果进行验证,结果发现,不同的预测方式会造成预测结果之间昼间4～9 dB、夜间5～10 dB的差异,采用2006版规范计算车速和单车噪声源强,距离衰减考虑车流量大小的预测方式得到的预测结果与实测值最为接近。     

Types,sources, socioeconomic impacts,and control strategies of environmental noise: a review

Noise exposure has reached an alarming degree over the years because of rapid growth in the industry, transportation, and urbanization. Therefore, it is a dire need to provide awareness of the sources and mitigation strategies of noise, and to highlight the health, and socio-economic impacts of noise. A few research studies have documented this emerging issue; however, there is no comprehensive document describing all types of noise, their impacts on living organisms, and control strategies. This review article summarizes the sources of noise; their effects on industrial workers, citizens, and animals; and the value of property in noisy areas. The plethora of literature is showing an increased level of noise in various cities of the world, which have various health consequences such as high blood pressure, insomnia, nausea, heart attack, exhaustion, dizziness, headache, and triggered hearing loss. Apart from humans, noise also affects animal habitat, preying, and reproduction ability; increases heart rate and hearing loss to even death and loss in property value; and impairs the hospital environment. Finally, we have discussed the possible strategies to mitigate the noise problem, policy statements, and regulations to be followed, with future research directions based on the identified research gaps.

     

Use of noise attenuation modeling in managing missile motor detonation activities

The Sound Intensity Prediction System (SIPS) and Blast Operation Overpressure Model (BOOM) are semiempirical sound models that are employed by the Utah Test and Training Range (UTTR) to predict whether noise levels from the detonation of large missile motors will exceed regulatory thresholds. Field validation of SIPS confirmed that the model was effective in limiting the number of detonations of large missile motors that could potentially result in a regulatory noise exceedance. Although the SIPS accurately predicted the impact of weather on detonation noise propagation, regulators have required that the more conservative BOOM model be employed in conjunction with SIPS in evaluating peak noise levels in populated areas. By simultaneously considering the output of both models, in 2001, UTTR detonated 104 missile motors having net explosive weights (NEW) that ranged between 14,960 and 38,938 lb without a recorded public noise complaint. Based on the encouraging results, the U.S. Department of Defense is considering expanding the application of these noise models to support the detonation of missile motors having a NEW of 81,000 lb. Recent modeling results suggest that, under appropriate weather conditions, missile motors containing up to 96,000 lb NEW can be detonated at the UTTR without exceeding the regulatory noise limit of 134 decibels (dB).     

Vehicle Occupants’ Exposure to Aromatic Volatile Organic Compounds While Commuting on an Urban-Suburban Route in Korea

Abstract

This study identified in-auto and in-bus exposures to six selected aromatic volatile organic compounds (VOCs) for commutes on an urban-suburban route in Korea. A bus-service route was selected to include three segments of Taegu and one suburban segment (Hayang) to satisfy the criteria specified for this study. This study indicates that motor vehicle exhaust and evaporative emissions are major sources of both auto and bus occupants' exposures to aromatic VOCs in both Taegu and Hayang. A nonparametric statistical test (Wilcoxon test) showed that in-auto benzene levels were significantly different from in-bus benzene levels for both urban-segment and suburban-segment commutes. The test also showed that the benzene-level difference between urban- segment and suburban-segment commutes was significant for both autos and buses. An F-test showed the same statistical results for the comparison of the summed in-vehicle concentration of the six target VOCs (benzene, toluene, ethylbenzene, and o,m,p-xylenes) as those for the comparison of the in-vehicle benzene concentration. On the other hand, the in-vehicle benzene level only and the sum were not significantly different among the three urban- segment commutes and between the morning and evening commutes. The in-auto VOC concentrations were intermediate between the results for the Los Angeles and Boston. The in-bus VOC concentrations were about one-tenth of the Taipei, Taiwan results.