"Respirable particles are a danger to human health, and acute exposure have been linked to respiratory illness and even death," Stone notes.
The EPA regulates the particulates, known as PM2.5. The agency also regulates coarser particles, those with an airborne diameter of roughly 10 microns, which were not part of this study. In 2012, the EPA lowered the primary standard for the annual average concentration of PM2.5 particulates considered safe, as more information became known about their prevalence and danger to human health.
In general, the UI researchers found that the concentration of PM2.5 particulates was higher at the urban monitoring sites than the rural locations. This was true especially for particles associated with exhaust from gasoline- and diesel-powered vehicles. Diesel combustion, in particular, was 230 percent higher in urban areas than rural, the study found.
The rural sites had slightly higher concentrations of secondary nitrateswhich form by chemical reactions in the atmosphere and are most prevalent in wintertimeaccording to the data.
Another particulate, secondary sulfates (formed in the atmosphere from emissions, such as those from coal-fired power plants), had the highest concentration (between 30 and 44 percent) of all pollutants at urban and rural sites, with readings being mostly uniform across locations.
"In general, we see most (urban and rural monitoring) sites have comparable levels of sulfates," notes Stone, a native Iowan. "That suggests it's a regional phenomenon affecting all of Iowa."
Other pollution impacts, such as particulates from cars and diesel vehic
|Contact: Richard Lewis|
University of Iowa