Relative Contributions of Self-Pollution and On-Road-Pollution to Children’s Exposure in School Buses

Details

• Personal Author:
  Lee E ; Zhu Y
• Description:
  Previous studies have shown children are exposed to high levels of PM2.5, black carbon (BC), and ultrafine particle (UFP, diameter <= 100 nm) inside school buses. Both surrounding vehicle emissions from the roadway (i.e., on-road-pollutions) and school bus' own emissions contribute to the exposure levels. While many studies have reported the presence of self-pollution in schools buses; the relative contributions between on-road-pollution and self-pollution is unknown. This study investigated under what conditions and to what extend self-pollution becomes more important than on-road-pollution. We estimated self-pollution rates inside six school buses and assessed the associated changes of spatial concentration distributions at increased driving speeds. The selected school buses include a wide range of model year, passenger capacity, cabin volume, and engine/exhaust tail-pipe locations. We measured the number concentration and size distributions of UFPs, PM2.5, BC, CO2, and CO levels concurrently in and out of school buses. In-cabin measurements were conducted at breathing zones in the front, center, and back of school buses. Statistical regression analyses were conducted to estimate self-pollution rates for UFPs, PM2.5, and BC. This study found high self-pollution rates of UFPs, PM2.5, and BC in the school buses. On local streets, self-pollution makes in-cabin/on-road concentration (I/O) ratios as high as approximately 1.5 for UFPs and slightly less for PM2.5 and BC. In comparison, on freeways, the I/O ratio was approximately 1.0 because of high air exchange rates and the infiltration of high-concentration of pollutants. Self-pollution dominates spatial concentration distributions of in-cabin pollutants. The spatial concentrations were substantially decreased at all three monitoring points at high driving speeds due to increased air exchange rates. The findings in this study suggest that self-pollution in school buses depends on self-pollution source strength, ambient concentration, and driving speed. [Description provided by NIOSH]
• Subjects:
  Air Pollution Occupational Health Particulate Matter Safety Transportation
• Keywords:
  Air Pollution Automotive Emissions Children Particulates Ultrafine Particles
• Publisher:
  American Association for Aerosol Research
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  California ; OSHA Region 9
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• NIOSHTIC Number:
  nn:20055837
• Citation:
  Proceedings of the AAAR 33rd Annual Conference, October 20-24, 2014, Orlando, Florida. Mount Laurel, NJ: American Association for Aerosol Research, 2014 Oct; :1IA.1
• CAS Registry Number:
  Carbon black (CAS RN 1333-86-4)
• Federal Fiscal Year:
  2015
• Performing Organization:
  University of California Los Angeles
• Peer Reviewed:
  False
• Start Date:
  20050701
• Source Full Name:
  Proceedings of the AAAR 33rd Annual Conference, October 20-24, 2014, Orlando, Florida
• End Date:
  20270630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:647c311dd13a836b0497416f54e5124261861bce80d9bb666ab478e8ed7d75c707dbc43a56d9581fb6e4fdda90aef5a82f2cf7db1bc8451fb106a2d3ff3cd049
• Download URL:
  https://stacks.cdc.gov/view/cdc/213603/cdc_213603_DS1.pdf
• File Type:
  [PDF - 215.76 KB ]