National Weather Service Weather Forecast Office

The U.S Environmental Protection Agency (EPA) and NOAA’s National Weather Service are encouraging Americans to “Be Air Aware” this week as part of Air Quality Awareness Week.  Concentrations of air pollution tend to increase on the tail end of high pressure systems, after the center of the high passes by.  High pressure systems affect a number of weather conditions, which can lead to poor air quality.

• Higher temperatures promote chemical reactions, such as the formation of ground-level ozone and particle pollution.

• Winds become lighter when pressure builds. Light or no wind allows air pollutants to build up. Still conditions also provide a better environment for chemical reactions to occur.
  
• Dry air does not move as much as moist air, allowing pollutants to build up. Days with high ozone pollution levels often occur when humidity is low.  However, on humid days, poor visibility occurs when small particles in the air absorb moisture and swell, reducing visibility.
  
• Sinking air in high pressure systems prevents the air from cooling and forming clouds. This creates sunny days – a key ingredient in the formation of ozone is sunlight.
  
• Inversions, when cooler air is trapped near the ground by a layer of warmer air above, can trap pollution near the Earth’s surface. This can lead to high levels of ozone and particle pollution.

People with heart and lung diseases or asthma, children and older adults can be especially at-risk for health problems related to air pollution. Extremely poor air quality can affect everyone. Stay healthy and reduce your exposure by watching air quality reports from your local media or checking www.airnow.gov.  When conditions reach “Code Orange” or higher, consider rescheduling sports games and other strenuous outdoor activities for another day. If you do go outside, aim for early morning or evening hours, when air pollution levels are likely to be lower.

Test your knowledge about air quality: http://www.earthgauge.net/aqquiz

 (Sources: US EPA. “What Affects My Air Quality?” http://www.epa.gov/airnow/airaware/day2-detail.html; www.airnow.gov)