Last week, Dan Jaffe’s atmospheric research group at the University of Washington released the results of a study of particulate emissions associated with rail traffic here in Seattle and along the Columbia River. That study was motivated by the controversy over coal exports, and was funded by contributions from the Sierra Club and through crowdfunding. We have been watching how this study has been received by the public and used by both sides of the coal export debate, and thought it would be useful to provide some context for Dr. Jaffe’s research, especially because this research is a good example of how science, policy, and law interact.
The paper is fairly readable even by someone who lacks a scientific background and is worth the read. To summarize, Dr. Jaffe and his group sampled particulate matter at two locations in Washington, a porch of a house located about 25 meters from train tracks in the Blue Ridge neighborhood in Seattle, and a location along the Columbia River. The Blue Ridge site is the subject of the most analysis. What the researchers observed there was a spike in fine particles as trains passed by. For passenger and freight trains, that spike occurred when the beginning of the train passed the site, and was attributed to diesel emissions from the locomotive. Coal trains had two spikes, one associated with the locomotive and a second associated with larger particles attributed to the coal contained in open-topped cars.
The part of the paper that is receiving the most media coverage is a back-of-the-envelope calculation in the final paragraphs where the authors conclude that a 50% increase in train traffic “would bring the PM2.5 concentrations at [the Blue Ridge] site up to about 14 ug/m3, which is higher than the new U.S. National Ambient Air Quality Standard (NAAQS) of 12 ug/m3 (annual average).” Media and bloggers are using this conclusion to proclaim that coal trains are “degrading” air quality, such as this article in The Olympian, and Cliff Mass’s blog post from March 3rd.
This theme emerging in media in reaction to Dr. Jaffe’s research is what we wanted to explore in more detail.