According to EPA’s AIRNow Program, the summer of 2009 had better ozone air quality than years past. Many U.S. cities experienced at least 80 percent fewer days when ozone air pollution reached levels that were Unhealthy for Sensitive Groups (USG) or higher on the Air Quality Index. This trend was especially apparent in the Midwest, Mid-Atlantic and Northeastern U.S., where above average precipitation and below average temperatures helped keep ozone pollution levels lower. A stormy weather pattern kept skies cloudy and the atmosphere well-mixed, which limited the reactions between sunlight, heat and air pollutants that cause ozone formation.
Viewer Tip: Weather conditions may have been the primary driver of better ozone air quality over the summer, but reductions in emissions contribute to better air quality, too. Transportation accounts for more than 28 percent of U.S. energy consumption and 25 percent of our air pollution. Reduce your emissions by giving alternative transportation a try – carpooling, using mass transit, walking or riding your bike to work or school just one day per week can make a difference.
AIRNow has provided a true-color satellite image from July 14, 2009, a representative day from this summer when air quality was good throughout much of the country: http://www.airnowstatus.org/smogstories/uploadimages/Sep23_CleanAir.jpg. The bar charts overlaid on the image show a count of days with AQI levels of USG or higher during May to August 2009 compared with the average from May to August during 2004-2008.
Seasons: Summer, Fall
(Sources: EPA AIRNow Program. “AQ Story: Good Ozone Air Quality in Summer 2009.” http://www.airnowstatus.org/smogstories; U.S. Department of Transportation Federal Highway Administration. “It All Adds Up to Cleaner Air.” www.italladdsup.gov)