The metropolitan Washington region has made tremendous progress in its air quality thanks to more than a decade of actions at the federal, state, and local government levels. To learn more, click through the dashboard slides below and download the Air Quality Trends Report.
2023 - Daily Air Quality Index
This chart shows the Air Quality Index (AQI) of each day during 2023. Conditions on the index include Code Green (good), Code Yellow (moderate), Code Orange (unhealthy for sensitive groups), Code Red (unhealthy), and Code Purple (very unhealthy).
*2023 data is preliminary as of September 30, 2023.
**On June 7, 2023, a health advisory was issued when forecasters expected Code Purple air quality for the region based on current conditions. However, the final recording of air quality for the day (based on the 24-hour average) was short of meeting the criteria for Code Purple.
Number of Unhealthy Air Days (2006 24-Hour PM2.5 Standard)
The number of unhealthy air days due to fine particle pollution (PM 2.5) has significantly decreased over the years in the region. The region now meets the daily and annual federal fine particle standards.
2023 data is preliminary as of September 30, 2023.
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24-Hour PM 2.5 Design Values
The daily fine particle (PM2.5) design value for the region has been declining over the years. Currently, the level of daily PM2.5 design value in the region is below the daily PM2.5 standard, so the region meets the federal standard. The region also meets the annual fine particle standard.
Note: A measure called design value is used by the EPA to evaluate the region’s attainment status for air pollutants. It is based on an average data for three consecutive years.
Number of Unhealthy Air Days (2015 Ozone Standard)
The number of unhealthy air days (Code Orange and worse) has significantly decreased over the years in the region. There has been a decline of approximately 96 percent in such days between 1997 and 2022.
2023 data is preliminary as of September 30, 2023.
8-Hour Ozone Design Values
While data shows the region met the federal standard for all five air pollutants, including fine particles, it does not yet meet officially the 2015 8-hour standard for ozone.
Note: A measure called design value is used by the EPA to evaluate the region’s attainment status for air pollutants. It is based on average data for three consecutive years. Ozone levels have been decreasing over the years.
Improving the Region's Air
All six pollutants regulated by the Clean Air Act have shown a downward trend in the region, and all but one pollutant, ground-level ozone, meet federal health-based air quality standards. Federal, state, and local measures that have improved the region's air quality, include:
- Acid Rain program (Phase 1 -1996/Phase 2 -2000,
- Tier 2/3 (2004/2017)
- Heavy-Duty Diesel Vehicle rule (2004/2007)
- NOx SIP Call (2004)
- Clean Air Interstate Rule (CAIR)/Cross-State Air Pollution Rule (CSAPR)/CSAPR Update (2009/2015/2017)
- District of Columbia, Maryland, and Virginia’s Vehicle Inspection & Maintenance programs
- Local gas can replacement program
- Local renewable energy & energy efficiency programs
For additional information about air pollution and its impact, visit the Air Quality and Your Health page.
For draft air quality data from this year, visit the Air Quality Data page.