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


Ozone Standard Exceedances in National Parks

Map of 2017 Ozone Exceedances - Season to Date
Map of 2017 Ozone Exceedances (Click photo to enlarge)

The National Park Service (NPS) actively monitors ozone at its parks from April to October. Ozone measurements are compared with the National Ambient Air Quality Standard (NAAQS) for ozone. The Environmental Protection Agency (EPA) sets this standard as the level at which the ozone in the air becomes unhealthy.

On October 1, 2015, the EPA strengthened the national ozone standard by setting the new level at 70 ppb, daily maximum 8-hour average. The NPS tracks the days when the standard is exceeded in the parks. In accordance with the new standard, the table below displays the parks and the ozone values along with the number of days where the daily maximum 8-hour average ozone concentration exceeded 70 parts per billion (ppb). The thumbnail on the right links to a map of parks with ozone exceedances in 2017.

2017 Ozone Standard Exceedances

National Park April May June July Aug. Sept. Oct. 2017 Season
Total Count Max 8-hr O3 (ppb) 4th highest max.
8-hr O3 (ppb)
Acadia National Park– Cadillac Mountain 1 2 3 0 0 0 6 98 80
Acadia National Park– McFarland Hill 0 1 1 0 0 0 2 87 67
Cape Cod– 0 2 3 0 0 0 5 85 72
Chamizal– State Monitor 0 1 2 1 1 1 6 82 72
Chiricahua National Monument– Entrance Station 1 0 0 0 0 0 1 72 67
Death Valley National Park– Park Village 0 0 0 2 0 0 2 72 70
Great Smoky Mountains National Park-Look Rock– Look Rock 1 0 0 0 0 0 1 72 65
Ogden Dunes– Water Treatment Plant 0 0 4 1 0 0 5 80 72
Joshua Tree National Park-Black Rock– Black Rock 6 10 17 14 3 1 51 98 92
Joshua Tree National Park-Cottonwood Canyon– Cottonwood Canyon 3 5 10 1 0 1 20 87 79
Joshua Tree National Park-Pinto Wells– Pinto Wells 2 0 2 0 0 0 4 76 71
Lassen Volcanic National Park– Manzanita Lake Fire Station 0 0 0 0 0 1 1 71 64
Mesa Verde National Park– Resource Management Area 1 0 1 0 0 0 2 72 66
Mojave National Preserve-Kelso Mountains– Kelso Mountains 0 1 4 1 1 3 10 84 74
Mount Rainier– Jackson Visitor's Center 0 0 0 0 2 0 2 78 69
Petrified Forest National Park– South Entrance 0 0 1 0 0 0 1 71 65
Rocky Mountain National Park– Long's Peak 0 0 0 0 0 1 1 74 67
Saguaro– East 2 1 2 0 0 0 5 77 73
Sequoia and Kings Canyon National Parks-Ash Mountain– Ash Mountain 0 4 18 29 20 5 76 92 89
Sequoia and Kings Canyon National Parks-Lower Kaweah– Lower Kaweah 0 2 12 25 10 0 49 87 84
Tonto National Monument– 1 0 0 0 0 0 1 71 67
Yosemite National Park-Turtleback Dome– Turtleback Dome 0 0 0 8 0 3 11 88 78

Validation Level *

2

2

2

2

2

1

0

0

0

0


Annual Exceedance Summaries

2017 | 2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004

2003 (pdf, 137 KB) | 2002 (pdf, 146 KB) | 2001 (pdf, 136 KB) | 2000 (pdf, 133 KB)


Compiled Exceedance Summaries


Last Updated: October 18, 2017