The group then simulated temperature and wind fields throughout the country using a weather research and forecasting model similar to those used to predict short-term weather. Barrett and Yim entered emissions data into the model to see how weather might disperse the emissions. They then ran another simulation a chemistry transport model to see how emissions from different sectors interacted.
Finally, the group overlaid their simulation results on population density maps to see which locations had the greatest long-term exposure to combustion emissions. Barrett observed that most of the emissions studied were composed of particles less than 2.5 microns in diameter, a size that epidemiologists have associated with premature death.
After road transport, the researchers found that emissions from shipping and aviation were the second greatest contributor to premature deaths, causing 1,800 early deaths annually, followed by powerplant emissions, which cause an estimated 1,700 premature deaths each year.
Barrett and Yim found that powerplant emissions have larger health impacts in northern England, where emissions from five major plants tend to congregate. In London, the researchers found that shipping and aviation emissions had a greater impact on health, possibly due to the proximity of major airports to the city.
Emissions from the country's powerplants, which are mostly northeast of major cities and emit pollution well above ground level, are less damaging to the general population than other sources of pollution, Barrett says. In contrast, he says emissions from cars and trucks, which occur closer to where people live and work, pose a more serious risk to human health.
"People have a number of risk factors in their life," Barrett says. "Air pollution is another risk factor. And it can be significant, especially for people who live in cities."
|Contact: Caroline McCall|
Massachusetts Institute of Technology