On Thursday October 30, 2003, Delta, Crested Butte, Mount Crested Butte, and Grand Junction recorded exceedances of the twenty-four-hour PM10 standard with readings of 215 ug/m3 at Delta, 177 ug/m3 at Crested Butte, 165 ug/m3 at Mount Crested Butte, and 234 ug/m3 at Grand Junction. The exceedances were caused by a combination of dense smoke transported from the massive wildfires in Southern California and blowing dust from the desert Southwest and local sources. A local wildfire near Aspen also contributed to elevated particulate levels in the area.
