WASHINGTON, D.C. – Air quality continues to improve in metropolitan Washington, according to preliminary data released by the Metropolitan Washington Council of Governments (COG).

The region recorded just thirteen days in 2016 when the region’s air quality exceeded healthy levels for ground-level ozone—known as Code Orange days. None of this year’s exceedance days reached more serious Code Red unhealthy levels, despite record-breaking stretches of heat and a stricter federal standard for measuring ground-level ozone that took effect this year. The region has reached this milestone four summers in a row (2013-2016).

Ground-level ozone is a colorless gas created when air pollutants react on hot, sunny summer days. Sensitive groups such as people with lung disease (including asthma, emphysema, and chronic bronchitis), children and older adults, and people who are active outdoors may experience adverse health effects when air pollution levels are elevated for a prolonged period of time.

“We’ve seen a dramatic improvement in the quality of the region’s air,” said Brianne Nadeau, Metropolitan Washington Air Quality Committee (MWAQC) Chairperson and District of Columbia Councilmember. “I want to commend our government leaders across the region who have been working for more than a decade to reduce emissions from power plants and passenger vehicles, and implement programs that help our residents improve energy efficiency and enhance renewable energy use.”

MWAQC, which is staffed by COG, coordinates air quality planning in the region. Its members include area elected officials, environmental directors, and state air management and transportation officials.

More: View the Ozone Season Summary presentation