Evaluation of retrofit crankcase ventilation controls and diesel oxidation catalysts for reducing air pollution in school buses

Trenbath, Kim; Hannigan, Michael P.; Milford, Jana B.

doi:10.1016/j.atmosenv.2009.08.012

Cited by 11 publications

(10 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both DOC and CCVs showed significant reductions in PM 2.5 and UFPs. This is generally consistent with previous invehicle studies, which found reductions of 25-60% for PM 2.5 and 5-70% for UFPs (17,25,27,28). Reductions in UFPs, and to a lesser extent PM 2.5 , with ULSD are also consistent with an earlier in-cabin study using ULSD in combination with DPF (17).…”

Section: Discussionsupporting

confidence: 82%

Adopting Clean Fuels and Technologies on School Buses. Pollution and Health Impacts in Children

Adar

D’Souza

Sheppard

et al. 2015

Am J Respir Crit Care Med

View full text Add to dashboard Cite

Rationale: More than 25 million American children breathe polluted air on diesel school buses. Emission reduction policies exist, but the health impacts to individual children have not been evaluated.Methods: Using a natural experiment, we characterized the exposures and health of 275 school bus riders before, during, and after the adoption of clean technologies and fuels between 2005 and 2009. Air pollution was measured during 597 trips on 188 school buses. Repeated measures of exhaled nitric oxide (FE NO ), lung function (FEV 1 , FVC), and absenteeism were also collected monthly (1,768 visits). Mixedeffects models longitudinally related the adoption of diesel oxidation catalysts (DOCs), closed crankcase ventilation systems (CCVs), ultralow-sulfur diesel (ULSD), or biodiesel with exposures and health.Measurements and Main Results: Fine and ultrafine particle concentrations were 10-50% lower on buses using ULSD, DOCs, and/or CCVs. ULSD adoption was also associated with reduced FE NO (216% [95% confidence interval (CI), 221 to 210%]), greater changes in FVC and FEV 1 (0.02 [95% CI, 0.003 to 0.05] and 0.01 [95% CI, 20.006 to 0.03] L/yr, respectively), and lower absenteeism (28% [95% CI, 216.0 to 20.7%]), with stronger associations among patients with asthma. DOCs, and to a lesser extent CCVs, also were associated with improved FE NO , FVC growth, and absenteeism, but these findings were primarily restricted to patients with persistent asthma and were often sensitive to control for ULSD. No health benefits were noted for biodiesel. Extrapolating to the U.S. population, changed fuel/technologies likely reduced absenteeism by more than 14 million/yr.Conclusions: National and local diesel policies appear to have reduced children's exposures and improved health.

show abstract

Section: Discussionsupporting

confidence: 82%

Adopting Clean Fuels and Technologies on School Buses. Pollution and Health Impacts in Children

Adar

D’Souza

Sheppard

et al. 2015

Am J Respir Crit Care Med

View full text Add to dashboard Cite

show abstract

“…Finally, we only considered the school environment, but other microenvironments and activities may make substantial contributions to the air pollution and noise exposures of school-aged children. For example, children can receive high exposures to some pollutants while commuting on diesel school buses [ 49 ], although exposures depend on a wide range of factors including emissions controls [ 50 ], fuels [ 51 , 52 ], and routes [ 52 ]. The relationship between school location and students' exposures is complicated by the fact that school location may affect accessibility and the amount of time that students spend in transit.…”

Section: Discussionmentioning

confidence: 99%

Proximity of public elementary schools to major roads in Canadian urban areas

et al. 2011

View full text Add to dashboard Cite

BackgroundEpidemiologic studies have linked exposure to traffic-generated air and noise pollution with a wide range of adverse health effects in children. Children spend a large portion of time at school, and both air pollution and noise are elevated in close proximity to roads, so school location may be an important determinant of exposure. No studies have yet examined the proximity of schools to major roads in Canadian cities.MethodsData on public elementary schools in Canada's 10 most populous cities were obtained from online databases. School addresses were geocoded and proximity to the nearest major road, defined using a standardized national road classification scheme, was calculated for each school. Based on measurements of nitrogen oxide concentrations, ultrafine particle counts, and noise levels in three Canadian cities we conservatively defined distances < 75 m from major roads as the zone of primary interest. Census data at the city and neighborhood levels were used to evaluate relationships between school proximity to major roads, urban density, and indicators of socioeconomic status.ResultsAddresses were obtained for 1,556 public elementary schools, 95% of which were successfully geocoded. Across all 10 cities, 16.3% of schools were located within 75 m of a major road, with wide variability between cities. Schools in neighborhoods with higher median income were less likely to be near major roads (OR per $20,000 increase: 0.81; 95% CI: 0.65, 1.00), while schools in densely populated neighborhoods were more frequently close to major roads (OR per 1,000 dwellings/km2: 1.07; 95% CI: 1.00, 1.16). Over 22% of schools in the lowest neighborhood income quintile were close to major roads, compared to 13% of schools in the highest income quintile.ConclusionsA substantial fraction of students at public elementary schools in Canada, particularly students attending schools in low income neighborhoods, may be exposed to elevated levels of air pollution and noise while at school. As a result, the locations of schools may negatively impact the healthy development and academic performance of a large number of Canadian children.

show abstract

“…Hammond et al measured the in-cabin number concentrations of particles 20 nm to 1 μm in diameter, and reported a 15–26% decrease between retrofitted and nonretrofitted buses. Trenbath et al tested three school buses for in-cabin particles ranged from 10 nm to greater than1 μm, and found a 33–41% average reduction of particle number concentration. Three school buses were measured in Round Rock, TX for the in-cabin particles 20 nm to 1 μm in diameter, and the change of particle number concentration ranged from 7% higher to 60% lower after retrofitting .…”

Section: Introductionmentioning

confidence: 99%

Performance of School Bus Retrofit Systems: Ultrafine Particles and Other Vehicular Pollutants

Zhang

Zhu

2011

Environ. Sci. Technol.

View full text Add to dashboard Cite

This study evaluated the performance of retrofit systems for diesel-powered school buses, a diesel oxidation catalyst (DOC) muffler and a spiracle crankcase filtration system (CFS), regarding ultrafine particles (UFPs) and other air pollutants from tailpipe emissions and inside bus cabins. Tailpipe emissions and in-cabin air pollutant levels were measured before and after retrofitting when the buses were idling and during actual pick-up/drop off routes. Retrofit systems significantly reduced tailpipe emissions with a reduction of 20-94% of total particles with both DOC and CFS installed. However, no unequivocal decrease was observed for in-cabin air pollutants after retrofitting. The AC/fan unit and the surrounding air pollutant concentrations played more important roles for determining the in-cabin air quality of school buses than did retrofit technologies. Although current retrofit systems reduce children's exposure while waiting to board at a bus station, retrofitting by itself does not protect children satisfactorily from in-cabin particle exposures. Turning on the bus engine increased in-cabin UFP levels significantly only when the wind blew from the bus' tailpipe toward its hood with its windows open. This indicated that wind direction and window position are significant factors determining how much self-released tailpipe emissions may penetrate into the bus cabin. The use of an air purifier was found to remove in-cabin particles by up to 50% which might be an alternative short-to-medium term strategy to protect children's health.

show abstract

Evaluation of retrofit crankcase ventilation controls and diesel oxidation catalysts for reducing air pollution in school buses

Cited by 11 publications

References 17 publications

Adopting Clean Fuels and Technologies on School Buses. Pollution and Health Impacts in Children

Adopting Clean Fuels and Technologies on School Buses. Pollution and Health Impacts in Children

Proximity of public elementary schools to major roads in Canadian urban areas

Performance of School Bus Retrofit Systems: Ultrafine Particles and Other Vehicular Pollutants

Contact Info

Product

Resources

About