School bus pollution and changes in the air quality at schools: a case study (original) (raw)
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Airborne particulate matter at a bus station: concentration levels and governing parameters
Proceedings of the 10th …, 2005
Traffic emissions are an important contributor to ambient air pollution, especially in large cities featuring extensive and high density traffic networks. Bus fleets represent a significant part of inner city traffic causing an increase in exposure to general public, passengers and drivers along bus routes and at bus stations. Limited information is available on quantification of the levels, and governing parameters affecting the air pollution exposure at bus stations. The presented study investigated the bus emissions-dominated ambient air in a large, inner city bus station, with a specific focus on submicrometer particles. The study's objectives were (i) quantification of the concentration levels; (ii) characterisation of the spatio-temporal variation; (iii) identification of the parameters governing the emissions levels at the bus station and (iv) assessment of the relationship between particle concentrations measured at the street level (background) and within the bus station. The results show that up to 90% of the emissions at the station are ultrafine particles (smaller than 100 nm), with the concentration levels up to 10 times the value of urban ambient air background (annual) and up to 4 times the local ambient air background. The governing parameters affecting particle concentration at the station were bus flow rate and meteorological conditions (wind velocity). Particle concentration followed a diurnal trend, with an increase in the morning and evening, associated with traffic rush hours. Passengers' exposure could be significant compared to the average outdoor and indoor exposure levels.
Journal of Student Science and Technology
Daily commuters of public transportation and private vehicles are exposed to a wide range of traffic-related air pollution (TRAP). However, evidence of differences between commuting method has been building. In this study, the personal ultrafine particle (UFP) and black carbon (BC) air pollution exposures of a high school student were measured during their daily commute. In total, 39 commutes made between the student’s home and school were measured. These commutes were either by bus or private vehicle. Data was analysed using box plots and T-tests of statistical significance. Levels of BC were not significantly higher on buses (mean(SD) = 849(645) ng/m3) than cars (650(689) ng/m3) (p-value = 0.199). For UFP, levels were significantly higher for bus commutes (9393(6923) pts/cm3) than those of private vehicle (4234(6446) pts/cm3) (p-value = 0.045). Our findings suggest that bus commuters may experience higher exposure to UFP relative to private vehicle commuters. The higher UFP exposu...
Spatial and temporal variations in traffic-related particulate matter at New York City high schools
Atmospheric Environment, 2009
Relatively little is known about exposures to traffic-related particulate matter at schools located in dense urban areas. The purpose of this study was to examine the influences of diesel traffic proximity and intensity on ambient concentrations of fine particulate matter (PM 2.5 ) and black carbon (BC), an indicator of diesel exhaust particles, at New York City (NYC) high schools. Outdoor PM 2.5 and BC were monitored continuously for 4-6 weeks at each of 3 NYC schools and 1 suburban school located 20 kilometers upwind of the city. Traffic count data were obtained using an automated traffic counter or video camera. BC concentrations were 2-3 fold higher at urban schools compared with the suburban school, and among the 3 urban schools, BC concentrations were higher at schools located adjacent to highways. PM 2.5 concentrations were significantly higher at urban schools than at the suburban school, but concentrations did not vary significantly among urban schools. Both hourly average counts of trucks and buses and meteorological factors such as wind direction, wind speed, and humidity were significantly associated with hourly average ambient BC and PM 2.5 concentrations in multivariate regression models. An increase of 443 trucks/buses per hour was associated with a 0.62 μg/m 3 increase in hourly average BC at a NYC school located adjacent to a major interstate highway. Car traffic counts were not associated with BC. The results suggest that
Characterizing the range of children's air pollutant exposure during school bus commutes
2004
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 mg/m 3 for black carbon, 23 to 400 ng/m 3 for particle-bound polycyclic aromatic hydrocarbon (PB-PAH), and 64 to 220 mg/m 3 for NO 2 . Concentrations of benzene and formaldehyde ranged from 0.1 to 11 mg/m 3 and 0.3 to 5 mg/m 3 , respectively. The highest real-time concentrations of black carbon, PB-PAH and NO 2 inside the buses were 52 mg/m 3 , 2000 ng/m 3 , and 370 mg/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.
School Bus In-Cabin Particulate Matter Quantification and Reduction
2010
Public Law 2005, c.219 was signed on Sept 7, 2005. This law was intended to reduce fine particle emissions from diesel mobile sources in New Jersey. The law required the New Jersey Department of Environmental Protection (NJDEP) to conduct a project to (1) evaluate the relative contribution of emissions from both the crankcase and the tailpipe to in-cabin levels of fine particles in school buses; and (2) evaluate the feasibility of requiring, and the environmental and health benefits of, the reduction of fine particle levels from school bus tailpipe emissions through the use of additional retrofit devices. The monitoring study was carried out by Rowan University (Martinez-Morett D., et al., 2009) and overseen by the NJDEP Division of Science, Research and Technology (DSRT). Two size ranges of particulate matter (PM) were measured, PM2.5 (fine particles) and UFPC (ultrafine particulate count). Examples of the adverse health effects from breathing diesel exhaust PM2.5 are exacerbations...
Atmospheric Environment, 2005
Variables affecting children's exposure during school bus commutes were investigated using real-time measurements of black carbon (BC), particle-bound polycyclic aromatic hydrocarbons (PB-PAH) and nitrogen dioxide (NO2) inside 3 conventional diesel school buses, a particle trap-outfitted (TO) diesel school bus and a compressed natural gas (CNG) school bus, while traveling along an urban Los Angeles Unified School District bus route. A video camera was mounted at the front of each bus to record roadway conditions ahead of the bus during each commute. The videotapes from 12 commutes, in conjunction with pollutant concentration time series, were used to determine the influence of variables such as vehicles being followed, bus type and roadway type on pollutant concentrations inside the bus. For all buses tested, the highest concentrations of BC, PB-PAH and NO2 were observed when following a diesel school bus, especially if that bus was emitting visible exhaust. This result was important because other diesel school buses were responsible for the majority of the diesel vehicle encounters, primarily due to caravanning with each other when leaving a school at the same time. Compared with following a gasoline vehicle or no target, following a smoky diesel school bus yielded BC and PB-PAH concentrations inside the cabin 8 and 11 times higher, respectively, with windows open, and ∼1.8 times higher for both pollutants with windows closed. When other diesel vehicles were not present, pollutant concentrations were highest inside the conventional diesel buses and lowest inside the CNG bus, while the TO diesel bus exhibited intermediate concentrations. Differences in pollutant concentrations between buses were most pronounced with the bus windows closed, and were attributed to a combination of higher concentrations in the exhaust and higher exhaust gas intrusion rates for the conventional diesel buses. Conventional diesel school buses can have a double exposure impact on commuting children: first, exposures to the exhaust from other nearby diesel school buses and, second, exposure to the bus's own exhaust through “self-pollution”.
Fine particle concentrations in buses and taxis in Florence, Italy
Atmospheric Environment, 2008
On October 2004, a sampling survey was carried out in Florence to estimate urban fine particle exposure concentrations inside commuting vehicles during workdays characterized by heavy traffic. Portable samplers were positioned inside four regularly scheduled diesel-powered buses and four taxis during eight weekdays. Each sampler consisted of a 2.5 mm size pre-separator cyclone, a direct-reading data logging photometer (pDR-1200), and a 4 L min À1 filter sampler for the determination of PM 2.5 mass concentration. Based on reflectance analysis measurements, a PM 2.5 Black Smoke Index was determined for each filter, and the elemental composition of the PM 2.5 was analyzed by Particle Induced X-ray Emission (PIXE). PM 2.5 mass concentrations inside the vehicles correlated well with the urban ambient air PM 2.5 concentrations measured at the fixed-site monitoring stations.
Many metropolitan school districts worldwide operate bus fleets with older diesel school buses. Emission reduction strategies such as the diesel retrofits promise substantial reductions in particulate mass emissions for older diesel engines. Recent studies suggest, however, that particle number concentration is a more important factor than particle mass in developing emissions standards and predicting adverse health effects. In-vehicle particle number concentration measurements on clean diesel, retrofitted diesel, and non-retrofitted diesel school buses were compared to estimate retrofit effectiveness in reducing in-vehicle passenger particle exposures. The retrofits were shown to provide a 15% to 26% decrease in in-vehicle particle number concentration levels between the retrofitted and non-retrofitted buses. Furthermore, the retrofitted diesel buses had average in-vehicle particle number concentrations near the average concentrations for the newer model, clean diesel buses. The average particle number concentrations for the non-retrofitted diesel buses were 1.5 to 2 times higher than the concentration measured from the retrofitted diesel buses. Moreover, a twofold increase was observed for the morning commute samples over the afternoon commuter samples. Particle number concentrations were also significantly affected by engine age, bus idling behavior, and ambient particle concentrations along bus routes. Keywords diesel buses. diesel emissions. particulate matter. exposure assessment. urban air quality 1 Background Current research in the field of environmental epidemiology has consistently established that there is a direct correlation between several adverse health outcomes with increased exposure to diesel emissions (
Exposure to Aerosols Particles on an Urban Road
Journal of Ecological Engineering
Traffic-related emissions, apart from emissions from fuel combustion for heating purposes, significantly deteriorate air quality in cities. The above mainly concerns areas located close to busy traffic routes. According to epidemiological studies, traffic-related emissions have an adverse health effect. This specifically affects commuters (drivers and car passengers) as well as pedestrians. The aim of this study was to determine the variations of particle number and mass concentrations along a busy road in Lublin, Poland and their impact on the particle exposure for commuters and pedestrians. On-route and fixed-site measurements were performed in the summer (June) with a focus on peak and off-peak traffic hours and road sections with low and high traffic intensity. During peak hours, the average number concentration of ultrafine particles (PN 0.1) in the road section near 4-way traffic intersections (TIs) was about 2 times higher than during off-peak hours. The average mass concentration of fine particles (PM 2.5) was also approximately twice as high than in off-peak hours. Similar relations were found for other measured aerosol particles as well as with respect to particle exposure. The obtained results indicate the need for further extended research on traffic-related emissions and exposure and the ways of limiting them.
Risk Analysis, 2005
Fine particle (PM 2.5 ) emissions from traffic have been associated with premature mortality. The current work compares PM 2.5 induced mortality in alternative public bus-transportation strategies as being considered by the Helsinki Metropolitan Area Council, Finland. The current bus fleet and transportation volume is compared to four alternative hypothetical bus fleet strategies for the year 2020: (i) the current bus fleet for 2020 traffic volume; (ii) modern diesel buses without particle traps, (iii) diesel buses with particle traps, and (iv) buses using natural gas engines.