Using Hoover vacuum cleaners as well as more traditional air-collection devices, UC Davis researchers are studying airborne dust along California highways and at busy intersections. Known as "PM10," particulate matter smaller than 10 microns in diameter, such as road dust, can be a health hazard when it becomes lodged in lungs, causing respiratory infections. In work for Caltrans, Lowell Ashbaugh and other researchers with the Crocker Nuclear Lab on campus are learning more about suspected "hot spots" of PM10 on state roadways. Caltrans wants to learn more about the potential air-quality impacts of new surface or freeway intersections for better compliance with certain state and federal environmental guidelines. "Caltrans wants to be able to look at a project and say, 'Does it or doesn't it have a PM10 effect?' We're trying to help them predict PM10 concentrations by generating better scientific information on an emissions inventory," says Ashbaugh, an associate research ecologist working with the UC Davis Air Quality Group based at Crocker. So far, the researchers have found lower PM10 emissions than estimated by the state Air Resources Board. These lower emission readings may mean that paved roads produce less PM10 air pollution than researchers previously thought. Ashbaugh and colleagues also are examining other sources of PM10, such as unpaved roads, agricultural operations and windblown dust.