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Published on: February 25, 2013
Analyses of school commuting data for exposure modeling purposes
Jianping Xue1, Thomas McCurdy, Janet Burke
1Human Exposure and Atmospheric Sciences, Division National Exposure Research Laboratory US Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
Journal of Exposure Science & Environmental Epidemiology
|February 26, 2009
Summary
Most Philadelphia students commute outside their home census tract. Accurate exposure modeling requires detailed home, school, and commuting path data, not broad time intervals.
Area of Science:
- Environmental Health
- Exposure Science
- Geographic Information Systems (GIS)
Background:
- Human exposure models often simplify school children's commutes, assuming they attend school within their residential census tract.
- This assumption overlooks the significant spatial and temporal distributions of daily school commuting patterns.
- Accurate exposure assessment for children necessitates understanding their movement between home and school.
Purpose of the Study:
- To analyze the assumption that school children attend school in their home census tract.
- To provide detailed information on the temporal and spatial distributions of school commuting in Philadelphia.
- To evaluate the impact of commuting path resolution on exposure modeling accuracy.
Main Methods:
- Utilized Oak Ridge National Laboratory's LandScan USA population distribution model for high-resolution data in Philadelphia, PA.
- Allocated individual school-aged children to home and school locations.
- Devised minimum-time home-to-school commuting paths ('traces') using Geographic Information System (GIS) data.
Main Results:
- The vast majority of Philadelphia students do not attend school in their home census tract.
- 32% of students walk across multiple census tracts, and 60% drive across multiple census tracts.
- Using broad time intervals (e.g., 5 minutes) misclassifies actual commuting paths, while a 1-minute resolution is needed.
- 50% of homes and 64% of schools are located near highly traveled roads, increasing exposure risk.
Conclusions:
- The simplifying assumption of children attending school in their home census tract is invalid for Philadelphia.
- Detailed modeling of home, school locations, and commuting paths at a fine temporal resolution (1-minute) is crucial for accurate exposure assessments.
- Children's proximity to major roads and their commuting patterns significantly influence exposure to pollutants like benzene and particulate matter.
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