For more information about National Park Service air resources, please visit http://www.nature.nps.gov/air/.


Air Atlas–Estimated Ozone

Estimated annual average ozone values for the 2008–2012 time period are shown on the map below:

  • 4th Highest 8-hour – The annual fourth highest daily maximum eight-hour average ozone concentration.
  • SUM06 – Ozone concentrations equaling or exceeding 0.060 parts per million (ppm) summed over daylight hours for 3 months during the growing season.
  • W126 – Ozone concentrations summed over daylight hours for 3 months during the growing season, with higher concentrations weighted more heavily.

Click the map legend to turn parks, monitors, or ozone statistic layers on and off. Click on parks on the map to find park specific estimates. Ozone estimates for 2008–2012 are also avaiable in table form (pdf, 526 KB). Ozone estimates are based on air quality data from monitors in the Environmental Protection Agency’s Air Quality System (AQS).


What is Ozone?

Ground-level ozone is an air pollutant that can harm both human health and plants. EPA has set a standard of 75 parts per billion (ppb), based on the 4th high 8-hour average concentration, to protect human health. Unfortunately, this standard is often exceeded in summer months in urban areas and even in national parks. EPA has considered setting standards to protect plants based on the W126 or SUM06, cumulative ozone metrics related to plant response. effects on health »    effects on vegetation »


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Last Updated: July 28, 2014