When city skies are thick with smog, people who are sick, injured, elderly or young often die at higher rates.

A University of Delaware scientist says air pollution threatens healthy adults, too, because tiny particles can zoom through human lungs up to two times faster and penetrate deeper than previously assumed.

"Smog kills," says air-pollution expert Anthony S. Wexler, a professor of mechanical engineering at UD, "perhaps partly because pollutant particles are so deeply deposited in our airways."

A study by Ramesh Sarangapani and Wexler, expected to appear in the next Journal of Aerosol Science, reveals how pollutant particles smaller than 2.5 micrometers--a size identified by the U.S. Environmental Protection Agency (EPA) as hazardous--penetrate buildings and people's airways.

From car exhaust and power-plant emissions to fumes from household fireplaces and wood stoves, various human activities fill the air with tiny pollutant particles. In the atmosphere, fine particles also can be generated by gases such as sulfur dioxide, nitrogen oxides and volatile organic compounds.

When they float solo, these particles are so small, they can't be seen without a microscope. Yet, clusters of fine particles produce clouds of dust, black soot and gray haze. And, when ground-level ozone mixes with air pollution, choking smog can blanket U.S. cities, reducing visibility by 70 percent in some regions, the EPA reports.

"Tens of thousands of elderly people die prematurely each year from exposure to ambient levels of fine particles," according to official EPA information. And, because children breathe 50 percent more air per pound of body weight, compared to adults, they're more susceptible to tiny bits of air pollution, especially if they suffer from asthma.

To combat the human health effects of fine pollutant particles, EPA Administrator Carol M. Browner signed new air-quality standards July 16, 1997, recommending lower levels of exposure
'"/>

Contact: Ginger Pinholster
gingpin@udel.edu
302-831-6408
University of Delaware
16-Aug-1999