From the ABC 7 Weather team

Code orange: Air quality alert across D.C. area

June 17, 2014 - 09:37 AM
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Air quality expected to reach unhealthy levels next few days.

As temperatures continue to rise in D.C., we have more to worry about than just overheating. Monday was the first time this year that Washington, D.C.'s air quality degraded to Orange - the level considered unhealthy for sensitive groups. An air quality alert has been issued for today and Wednesday for much of the metro area as warm temperatures, stagnant air and light winds hover over the Mid-Atlantic.

(Wednesday's code orange)

Air quality in our area primarily depends upon the level of two pollutants: extremely small particles of dust,  like metals and chemicals and ground-level ozone. Most of the very small particles, referred in the environmental world as particulate matter, originate from our use of fossil fuels like gasoline and diesel for transportation and coal for the production of electricity. Ground-level ozone also has it’s origins in our use of gasoline and diesel to get around town, this form of ozone is not associated with the ozone layer in the atmosphere that protects us from UV light.

Poor air quality for the D.C. area is mainly seasonal (May through September) and is worst during the hours of 3 p.m and 7 p.m. when temperatures are warmest and there is the most activity/industry.
It’s during our summer months where weather patterns often lose their progressive characteristics: the large-scale movement of weather systems and ultimately wind, and it’s this lack of air movement that increases the amount of pollution in the air. Those really windy conditions that develop as strong cold fronts move through are fantastic at pushing and diluting air pollutants away thus we usually see fewer air quality issues during the fall, winter, and spring.

(Stagnant pattern this afternoon)

When gasoline and diesel are burned in the engine of a car, several of the chemicals that are given off in the exhaust are nitrogen oxides. These nitrogen oxides go into the air, and through a series of chemical reactions involving sunlight, ozone is produced. It usually takes several hours of sunlight to form higher levels of ozone thus air quality around D.C. is at its worst during the afternoon and evening.

Breathing air that contains higher levels of particle matter and ozone is unhealthy for many reasons. Younger children and older adults are more susceptible to the ill effects of exposure as pollution levels increase (thus the alert today for “unhealthy air for sensitive groups”), we are all at risk for developing respiratory health issues as air pollution levels rise and go beyond the code orange thresholds.

(Clean Air Partners action guide)

So today’s abundant sunshine and lack of wind will unfortunately couple with the pollutants produced by our daily activities to degrade the air we breath. You can always monitor air quality conditions through a variety of resources: and are great websites to stay informed. 

Meteorologists Ryan Miller and Jacqui Jeras contributed to this report.

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