Status of Ozone Pollution in Maryland

T​he Department has developed maps to help you visualize Maryland's air quality impr​ovements. The maps illustrate how lower ozone levels have led to smaller problem areas.

8-Hour Ozone Exceedance Days

The annual list of the 8-hour ozone concentrations exceeding the 2008 health-based National Ambient Air Quality Standard is provided below.  Click on the appropriate check mark to download the data in Excel format.  Be advised that the counts of days reflect all monitors that are part of the non-attainment area (NAA); howe​ver, only Maryland data collected by the Department and the EPA Clean Air Status and Trends Network (CASTNET) are provided in the Excel file.  A map of NAAs shows the Maryland NAAs and surrounding jurisdictions.

Historical air quality data is also accessible at  Clean Air Partners, EPA Air Data,  and other data resources listed below. 

Number of Days 8-Hour Ozone Concentrations Exceeded 2015 Health-Based Standard
	Baltimore, MD NAA	Washington, DC-MD-VA NAA	Philadelphia-Wilmington-Atlantic City, PA-DE-MD-NJ NAA	State-wide	Excel
2023	15	15	15	20
2022	2	3	5	3
2021	15	8	13​​	17
2020	3	2	5	3
2019	12	10	11	14
2018	16	10	17	16
2017	9	8	14	17
2016	21	13	18	26
2015	15	14	25	20
2014	5	10	11	11
2013	9	12	12	19
2012	35	34	39	42
2011	35	38	28	46
2010	50	49	40	61
2009	16	12	14	19
2008	40	37	38	49
Notes: "NAA" denotes non-attainment area, EPA CASTNET data are included since 2011. Table reflects the 2015 70ppb ozone standard.

Data Resources

• EPA Air Pollution Data Sources: https://www.epa.gov/environmental-topics/air-topics
• EPA Air Data: https://www.epa.gov/outdoor-air-quality-data
• EPA Air Trends: https://www.epa.gov/air-trends
• EPA Clean Air Markets: https://www.epa.gov/airmarkets