Project-Level Air Toxics Analysis

As part of an environmental impact statement for a new interstate river crossing near Stillwater, MN, agency and environmental community concerns over the health impacts of transportation air toxics prompted the Minnesota Department of Transportation to perform an unprecedented project-level analysis. Various studies have shown a correlation between health impacts and proximity to transportation sources of air toxics. Six pollutants (termed priority mobile source air toxics, or MSATs) are considered by the Environmental Protection Agency (EPA) to dominate health risks: diesel particulate matter, Benzene, 1,3-Butadiene, Formaldehyde, Acetaldehyde, and Acrolein. Because of a lack of meaningful standards for permissible concentrations of MSATs, dispersion analysis (such as is done for CO and NOx) was not done. Instead, total emissions were quantified on three scales: regional, local, and corridor. The EPA MOBILE 6.2 emissions model was run to determine emission rates for the six priority MSATs for various roadway types, speeds, and future analysis years. These were then combined with output from the regional travel demand forecasts to determine the emission of each MSAT for each link in the regional highway transportation network. The following are selected findings from this research: (1) Emission rates of 1,3-butadiene, acetaldehyde, acrolein, benzene, and formaldehyde are generally lower under higher operating speeds. Emissions are therefore sensitive to changes in vehicle miles traveled (VMT) and vehicle hours traveled. (2) Direct emission rates of diesel particulates are not sensitive to roadway speed. Emissions are therefore sensitive only to changes in VMT. (3) Long-term projected decreases in emission rates 144 over time are much larger than the difference between any alternatives, even on a regionally significant project. (4) Differences in total emissions between alternatives can be significant and quantifiable on a small area or corridor scale. (5) A well-validated regional travel forecasting model is necessary to perform this type of analysis. Transportation-related air toxics have become a great concern in the environmental community as a result of the threat to public health that they pose. Assessment of the air quality implications of highway projects will increasingly become dominated by air toxics issues. This study provides a valuable method for quantifying air toxics emissions associated with a project.


  • English

Media Info

  • Media Type: Print
  • Features: Tables;
  • Pagination: 9p
  • Monograph Title: Proceedings of the 2005 Mid-Continent Transportation Research Symposium

Subject/Index Terms

Filing Info

  • Accession Number: 01004318
  • Record Type: Publication
  • ISBN: 9780965231084
  • Files: TRIS
  • Created Date: Sep 21 2005 1:47PM