2008 Ozone Standard Exceedances in National Parks

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.

In the spring of 2007, EPA made the ozone standard more stringent (lowering it from 85 parts per billion (ppb) to 75 ppb). As a result, many more parks were added to the list of exceedances in 2008. The table below displays the parks and the ozone values along with the number of days when the daily maximum 8-hour average ozone concentration exceeded the standard of 75 parts per billion (ppb)†. The fourth highest ozone column has been color-coded for easier viewing. The thumbnail on the right links to a map of parks with 2008 ozone exceedances.

2008 Ozone Standard Exceedances
National Park	April	May	June	July	Aug.	Sept.	Oct.	2008 Season
								Total Count	Max 8-hr O3 (ppb)	4th highest max. 8-hr O3 (ppb)
Acadia– Cadillac Mountain	0	0	0	2	0	0	0	2	90	74
Assateague Island– Maintenance Area	0	0	2	1	0	0	0	3	83	74
Cape Cod– State Monitor	0	0	1	2	0	0	0	3	106	75
Chamizal– State Monitor	0	0	1	0	1	1	0	3	84	73
Cowpens– State Monitor	1	0	2	1	1	0	0	6	85	79
Cumberland Gap– Hensley Settlement	0	0	1	0	0	0	0	1	76	70
Death Valley– Park Village	0	0	4	1	0	0	0	5	94	77
Denali– Headquarters	1	0	0	0	0	0	0	1	76	68
Great Basin– Maintenance Yard	1	0	0	0	0	0	0	1	76	71
Great Smoky Mountains– Cades Cove	0	1	0	0	0	0	0	1	78	71
Great Smoky Mountains– Clingmans Dome	1	1	3	4	0	0	0	9	86	80
Great Smoky Mountains– Cove Mountain	1	0	1	4	1	0	0	7	83	79
Great Smoky Mountains– Look Rock	1	4	1	4	4	0	0	14	87	82
Great Smoky Mountains– Purchase Knob	1	0	0	4	0	0	0	5	89	80
Joshua Tree– Black Rock	6	6	22	17	14	5	0	70	110	105
Joshua Tree– Cottonwood Canyon	1	3	10	3	0	0	0	17	88	84
Joshua Tree– Pinto Wells	3	5	3	2	0	0	0	13	85	82
Lassen Volcanic– Manzanita Lake Fire Stn.	0	0	6	2	0	0	0	8	104	83
Mammoth Cave– Houchin Meadow	0	0	0	0	0	0	0	0	73	70
Mojave– Kelso Mountains	2	5	11	12	3	2	0	35	100	86
Pinnacles– SW of East Entrance Stn.	0	0	4	5	0	3	0	12	94	86
Rocky Mountain– Long's Peak	0	2	0	2	0	0	0	4	81	76
Rocky Mountain– Trail Ridge	0	0	0	1	0	0	0	1	76	67
Saguaro– Pima County	0	0	1	0	0	0	0	1	80	74
Sequoia and Kings Canyon– Ash Mountain	0	11	19	19	4	17	4	74	121	112
Sequoia and Kings Canyon– Lower Kaweah	0	3	18	25	21	6	0	73	113	101
Shenandoah– Big Meadows	2	1	2	0	0	0	0	5	81	78
Yosemite– Mobile	0	0	4	8	3	3	0	18	102	83
Yosemite– School Yard	0	0	0	3	0	0	0	3	105	75
Yosemite– Turtleback Dome	1	1	12	10	6	5	0	35	102	94
Zion National Park– Dalton's Wash	1	0	0	0	0	0	0	1	76	72
Validation Level *	2	2	2	2	2	2	2
*Validation level 0 indicates raw data. Validation level 1 indicates preliminary data. Validation level 2 indicates final, validated data. Counts of days with 8-hr average ozone greater than 75 ppb may change after the data is fully validated. The ozone season runs from April to October for the detailed current ozone conditions. During the winter, more limited numbers of locations and web products are available. †The current NAAQS is 75 ppb, daily maximum 8-hour average. The ozone standard is violated when the 3-year average of the annual fourth-highest daily maximum 8-hour average ozone concentration is greater than 75 ppb, which occurs when the 3-year average exceeds 75 ppb. An exceedance occurs when the daily maximum 8-hour average is greater than 75 ppb.