Daily maximum 8-hour concentration of ground-level ozone in parts per billion (monthly average)

Ozone is <sdt id="-868985184" sdttag="goog_rdk_0">an</sdt><sdt id="-2023004410" sdttag="goog_rdk_1" showingplchdr="t"> </sdt>air pollutant linked to <sdt id="854916612" sdttag="goog_rdk_3">poor </sdt>respiratory health outcomes, including diminished lung function, emergency room visits for asthma, hospital admissions, and premature deaths.1, 2 Ozone in the ambient air is created by chemical reactions between pollutants<sdt id="-1463646632" sdttag="goog_rdk_5" showingplchdr="t"> </sdt>such as nitrogen oxides and volatile organic compounds t<sdt id="15745496" sdttag="goog_rdk_7">hat </sdt>are released by cars, power plants, and chemical plants, as well as<sdt id="-993565398" sdttag="goog_rdk_9"> by</sdt> natural sources such as trees and soils. These reactions <sdt id="1530906167" sdttag="goog_rdk_10">occur </sdt>under sunlight and more efficiently <sdt id="-1303691664" sdttag="goog_rdk_12">on hot</sdt><sdt id="-1346474565" sdttag="goog_rdk_13" showingplchdr="t"> </sdt>days. As a result, ground-level ozone pollution is most likely to reach unhealthy levels in the summer.3

In 2020, the United States Environmental Protection Agency (EPA) determined that ozone levels higher than 70 parts per billion (ppb) can cause health problems for otherwise healthy adults while they <sdt id="63919510" sdttag="goog_rdk_14">engage </sdt>in outdoor activities.4, 5 Cities <sdt id="571094826" sdttag="goog_rdk_16">can </sdt>reduce the impacts of ground-level ozone on residents’ health<sdt id="1200975480" sdttag="goog_rdk_18"> by</sdt><sdt id="1125348972" sdttag="goog_rdk_19" showingplchdr="t"> </sdt>adopting clean energy sources, improving use of public transportation, ensuring that fireplace and wood stove use meets EPA standards<sdt id="-748118970" sdttag="goog_rdk_21">, and through other actions</sdt>.6

The Dashboard’s ozone metric shows the average daily maximum 8-hour concentration of ozone in the air (in ppb) over the course of a month.

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			Strengths of Metric
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			Limitations of Metric
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			<ul><li>Monitoring air quality helps target high pollution areas and track progress in reducing pollution, which can lower the risk of mortality.7</li>
				<li> This metric provides the most geographically granular, up-to-date, publicly available data for ozone air pollution.</li>
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			<ul><li>The measure is estimated using data from a network of sensors around the country. It is less accurate in areas with fewer sensors.</li>
				<li>Data for Alaska and Hawaii are not currently available.</li>
				<li>Due to limited geographic resolution, census tracts that are right next to each other might share the same ozone pollution value. Please refer to our <a href="https://www.cityhealthdashboard.com/page/823">technical document</a> for more details.</li>
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For more information on the calculation, please refer to the <a href="https://cityhealthdashboard.com/page/823">City Health Dashboard Technical Document</a>.

The data were created by merging ground observations from the US Environmental Protection Agency (EPA) <a href="https://www.epa.gov/aqs">Air Quality System (AQS) network </a>with computer model prediction from the National Oceanic and Atmospheric Administration (NOAA) <a href="https://airquality.weather.gov">National Air Quality Forecast Capability (NAQFC)</a> by the <a href="https://air.csiss.gmu.edu">George Mason University air quality team</a>. Multi-year data are available for this metric. For more information, please refer to <a href="https://www.cityhealthdashboard.com/multi-year-data">Using Multi-Year Data: Tips and Cautions</a>.

<ol><li class="EndNoteBibliography">Centers of Disease Control and Prevention. Air pollution. <a href="https://www.cdc.gov/climateandhealth/effects/air_pollution.htm">https://www.cdc.gov/climateandhealth/effects/air_pollution.htm</a></li>
	<li>United States Environmental Protection Agency. Ground-level Ozone Pollution. <a href="https://www.epa.gov/ground-level-ozone-pollution">https://www.epa.gov/ground-level-ozone-pollution</a></li>
	<li>United States Environmental Protection Agency. Ground-level Ozone Basics. <a href="https://www.epa.gov/ground-level-ozone-pollution/ground-level-ozone-basics#wwh">https://www.epa.gov/ground-level-ozone-pollution/ground-level-ozone-basics#wwh</a></li>
	<li>FACT SHEET: FINAL DECISION OZONE NATIONAL AMBIENT AIR QUALITY STANDARDS (2020).</li>
	<li>OVERVIEW OF EPA’S UPDATES TO THE AIR QUALITY STANDARDS FOR GROUND-LEVEL OZONE (2015).</li>
	<li>Agency USEP. What You Can Do <a href="https://www.airnow.gov/education/what-you-can-do/">https://www.airnow.gov/education/what-you-can-do/</a></li>
	<li>Jerrett M, Burnett RT, Pope CA, et al. Long-Term Ozone Exposure and Mortality. New England Journal of Medicine. 2009;360(11):1085-1095. doi:10.1056/NEJMoa0803894</li>
</ol> 

Last updated: July 26, 2023

Air Pollution - Ozone

Daily maximum 8-hour concentration of ground-level ozone in parts per billion (monthly average)

Why do we measure ozone?

How do we measure ozone?

Strengths and Limitations

Calculation

Data Source

References