District of Columbia

How is my grade calculated?

“State of the Air” grades are based on the number of days a county’s air reaches unhealthful levels on the Air Quality Index. Each unhealthy air day is given a weighted score, with orange days given a weight of 1, red days 1.5, purple days 2 and maroon days 2.5. Those daily scores are added up and divided by 3 to get a weighted average that is then assigned a grade. For year-round particle pollution, grading is based on the national standard for annual PM_2.5 of 9 μg/m³. Counties for which EPA lists a design value of at or below the standard are given grades of “Pass.” Counties at or above 9.1 μg/m³ are given grades of “Fail.”

What do these colors mean?

The colors used in “State of the Air" are based on the Air Quality Index, which assigns six different levels of health concern to increasing concentrations of air pollution. Each category has a specific color. “State of the Air” only includes the four levels that are considered unhealthy: Orange for “unhealthy for sensitive groups,” Red for “unhealthy,” Purple for “very unhealthy,” and Maroon for “hazardous.”

High Ozone Days

Ozone air pollution, sometimes known as smog, is one of the most widespread pollutants in the United States. It is a powerful lung irritant. When inhaled into the lungs, it reacts with the delicate lining of the airways, causing inflammation and other damage that can impact multiple body systems. Ozone exposure can also shorten lives.

Particle Pollution - 24 Hour

Particle pollution is a deadly and growing threat to public health in communities around the country. The more researchers learn about the health effects of particle pollution, the more dangerous it is recognized to be. Short-term spikes in particle pollution that last from a few hours to a few days can kill. Most premature deaths are from respiratory and cardiovascular causes. Spikes in particle pollution also have many other harmful effects, ranging from decreased lung function to heart attacks.

Particle Pollution - Annual

Particle pollution is a deadly and growing threat to public health in communities around the country. The more researchers learn about the health effects of particle pollution, the more dangerous it is recognized to be. Breathing particle pollution day in and day out can be deadly. Research has also linked year-round exposure to particle pollution to a wide array of serious health effects at every stage of life.

Populations At Risk

All of the millions of Americans living in places with failing grades for unhealthy levels of ozone or particle pollution are at risk of harm to their health. But some groups of people are especially vulnerable to illness and death from their exposure.

What do INC and DNC Mean?

INC (Incomplete) indicates that some monitoring data was collected for at least one year in the county, but not all three years.

DNC (Data Not Collected) indicates that data on that particular pollutant is not collected in the county.

DNC (Data Not Collected)

Data on this particular pollutant was not collected in this county during the three years covered in this report.

INC (Incomplete)

Monitoring data is available for at least one year in this county, but not all three years. It is incomplete for purposes of calculating a grade.