A Look Back: Ozone in 2012

Many U.S. cities saw an increase in2012 in the number of days when ozone levels reached “code orange” on the Air Quality Index (AQI), or “unhealthy for sensitive groups.” A number of factors influence ozone formation, including emissions from power plants, cars, trucks, buses and industries – and weather conditions. Weather is especially favorable for ozone formation when it’s hot, dry and sunny, and winds are calm and light. A warmer-than-average June and August in 2012, combined with the third-hottest summer on record in the continental U.S.*, made conditions favorable for ozone formation in many regions of the country.

Information sources: Preliminary air quality data as reported to EPA’s Air Quality System and AirNow.gov; weather information from the National Climatic Data Center

2012 Ozone Map