By: Phil Fellin

The impacts of alternative fuels need to be evaluated before their use becomes more widespread in Canada. Personal exposures to airborne compounds emitted by vehicles operated with diesel, gasoline, methanol- and ethanol-blended fuels have been assessed by AirZOne staff in Medicine Hat, Windsor and Toronto. Source attribution was an important objective in each of these studies, but since the alternative fuel vehicle fleet was so small, only useful exposure information was produced. To allow source apportionment, and to generate exposure data that can be extrapolated to Canadian climatic conditions, we evaluated personal exposures to vehicular emissions (for Health Canada and in conjunction with Stockholm University) on the Stockholm public transit system.

Since oxygenates in fuels reduce VOC and CO emission in urban centres with large motor vehicle populations and also CO2 emissions from non-renewable sources, their use in Canada is projected to increase. Oxygenates in fuels, however, increase significantly the emissions of carbonyls (formaldehyde and acetaldehyde, specifically). Both compounds have detrimental human health effects. Studies are needed in areas with a climate similar to Canadas where oxygenates are currently widely and routinely used as fuel additives. In the U.S., many states including California add ethanol, methanol, and methyl and ethyl tertiary butyl ethers to liquid fuels to mitigate local and regional air quality problems. However, most of these jurisdictions contain a large number of fixed sources of VOC with organic compound emission profiles similar to those of vehicles. Moreover, climatic factors, particularly, high insolation rates, promote the rapid degradation and formation of target compounds (carbonyls) in the atmosphere. For accurate source attribution, the compounds must be stable in the atmosphere for at least as long as the sampling intervals. High rates of photochemical activity do not allow this criterion to be satisfied. Since source attribution is a key objective of this study, interpretation of the data from this perspective becomes complex and uncertain. Furthermore, it is difficult to extrapolate exposure results from such studies to Canadian climatic conditions.

Ethanol and other oxygenates are widely used in Swedish liquid fuels for the motor vehicle fleet and public transit vehicles. In addition, Stockholm has a large motor vehicle population, and its climate, (insolation levels, temperature, wind speed and shoreline diffusion), is similar to that of many large Canadian urban centres. Moreover, ethanol fuel blends in Sweden contain isopropyl and isobutyl alcohols, additives that can serve as additional marker compounds for source apportionment. For these reasons, Stockholm represents a more attractive and useful venue for the study than other locations.