| Characteristic | Weighted average days with high ozone |
|---|---|
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
| - | - |
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April 2025
United States
2021 to 2023
The majority of U.S. counties don’t have monitors — which means that many communities, especially rural ones, don’t have official monitored information on their air quality. Please note that the population figures in this statistic are only for those places that collect air pollution data, and do not reflect the entire population of these groups in the U.S.
The 2021, 2022, and 2023 AQS hourly ozone data were used to calculate the daily 8-hour maximum concentration for each ozone-monitoring site. The highest 8-hour daily maximum concentration in each county for 2021, 2022, and 2023, based on EPA-defined ozone season, was identified. The current National Ambient Air Quality Standard for ozone is 70 parts per billion (ppb) measured over eight hours.
