For more information about National Park Service air resources, please visit https://www.nature.nps.gov/air/.
Air Quality Conditions & Trends
The most recent assessment of air quality trends and conditions in National Park Service (NPS) units at a national level is available in the in the Air Quality in National Parks: Trends (2000–2009) and Conditions (2005–2009) (pdf, 2.2 MB) report. More current information about park air quality is available through the Air Quality Conditions & Trends by Park web-page.
The National Park Service (NPS) Air Resources Division measures progress toward clearer skies, cleaner air, and healthier ecosystems by examining key air quality indicators, including:
- visibility – how well and how far visitors can see;
- ozone – which affects human health and vegetation;
- sulfur and nitrogen deposition – affect ecosystem health through acidification and nutrient enrichment of soils, surface waters, and vegetation; and
- mercury deposition – which affects human and wildlife health through bioaccumulation to toxic levels in food webs.
The NPS monitors one or more of these indicators in 58 parks. In addition, many state and local air quality monitoring stations are located in or near parks and collect data that provide valuable information about air quality in parks. Air quality trends and conditions for one or more indicators have been calculated for 347 parks using these data.
Unfortunately, a large proportion of parks warrant significant concern for visibility, ozone, and deposition. Very few parks have air quality that is considered to be in good condition for these indicators. Understanding air quality trends is especially important for protecting park resources in areas where the air quality conditions warrant significant concern.
In parks where visibility warrants significant concern, the vast majority show statistically significant improvement. However, the same cannot be said for parks where ozone, sulfur deposition, and/or nitrogen deposition is of significant concern. Most of these parks show no significant trend, likely indicating that unless pollution levels are reduced they will remain in the significant concern category.
For more information on the how conditions and trends were derived for this report please see: Methods for Determining Air Quality Conditions and Trends (pdf, 220 KB).
Past Performance and Progress Reports
Last Updated: September 01, 2015