For more information about National Park Service air resources, please visit http://www.nature.nps.gov/air/.
Air Quality Conditions and Trends
The latest assessment of air quality conditions National Park Service (NPS) units is available in the in the
2005–2009 Air Quality Condition Table (pdf, 422 KB). These conditions, as well as information on air quality trends in parks, will be included the upcoming Air Quality in National Parks: 2010 Annual Performance and Progress Report.
To create the conditions table above, Air Resources Division used all available air quality monitoring data over a five-year period (2005–2009) to estimate air quality for the continental United States, even for areas that do not have direct monitoring. The estimated values were used to determine an index of condition for ozone, wet deposition, and visibility. The condition indices for a specific park may have been adjusted due to nitrogen or sulfur deposition risk, ozone sensitivity, or location with an EPA designated ozone nonattainment county.
For more information on the how these conditions were derived please see the latest guidance on Methods for Determining Air Quality Conditions and Trends (pdf, 220 KB).
For the Air Quality in National Parks; 2009 Annual Performance and Progress Report, which covers the years 1999–2008, 241 NPS units have enough data on-site or nearby to report on one or more air quality indicators. Of these, 97 percent showed stable or improving trends in visibility, 100 percent showed stable or improving trends in ozone concentrations, and 93 percent showed stable or improving trends in atmospheric deposition of sulfate, nitrate, and ammonium ions.
Although these are certainly positive results for air quality in the national parks, a stable trend in air quality may not be sufficient to protect an area that is already experiencing poor air quality. For this reason we have developed an index for assessing current air quality conditions at parks throughout the country that assigns them to one of three categories:
- Condition Red–a Significant Concern,
- Condition Yellow–in Moderate Condition, or
- Condition Blue–in Good Condition.
The NPS Air Resources Division oversees the air resource management program. It is important to measure the program's effectiveness based on outcomes even though the NPS has no authority to regulate sources of air pollution located outside park boundaries.
The NPS can make a difference by: (1) acquiring high quality data, (2) making that information available to the general public, and (3) identifying and seizing opportunities to participate in decisions being made by regulatory agencies that might affect air quality in parks. Several indicators are used to measure progress. One indicator looks at visibility trends on the clearest and haziest days. Another tracks changes in ozone concentrations based on the 3-year average of the annual fourth highest daily maximum 8-hour concentration. The final indicator focuses on wet deposition of sulfate, nitrate, and ammonium ions. An area meets the NPS air quality goals (related to visibility, ozone, and atmospheric deposition) if it does not show statistically significant deterioration in any of the indicators used to measure those goals during the most recent 10-year period for which data is available.
Past Performance and Progress Reports
Last Updated: March 13, 2013