Sources of Air Pollution

Various air pollutants can cause detrimental effects on sensitive park resources. These include pollutants emitted directly from sources (primary pollutants) and those that are formed as a result of chemical reactions in the atmosphere (secondary pollutants). Primary pollutants include, sulfur dioxide, nitrogen oxides, particulate matter, and volatile organic compounds, while secondary pollutants include sulfates, nitrates, and ozone.

Types of Pollution Sources

Sources of air pollution include: "stationary sources" such as power plants, industrial facilities, factories, and dry cleaners; "mobile sources" such as cars, buses, planes, trucks, and trains; and "natural sources" such as wind-blown dust, wildfires, and volcanoes. The graphic below illustrates air pollution sources, their transport and transformation, and some of the resources that are affected by air pollution.

Source: Adapted from National Science and Technology Council Committee on Environment and Natural Resources, Air Quality Research Subcommittee, 1999

Sources in Parks

Most air pollution that impacts park resources is emitted from sources outside of the parks. However, air pollution is also emitted directly inside parks as a result of various in-park activities (e.g., visitor automobiles, wildfires). The NPS is committed to complying with all environmental laws and leading by example by applying the highest standards of environmental stewardship to its own operations. To help meet this commitment, the Air Resources Division (ARD), with assistance from park staff, develops air emission inventories for units of the National Park System. The NPS quantifies in-park air emissions in order to: (1) determine the magnitude of in-park emissions relative to those from the surrounding area, (2) identify existing and potential strategies to mitigate in-park emissions, and (3) evaluate and ensure compliance status of our parks relative to local, state, and federal air pollution regulations. Reports for those parks inventoried to date, and a summary report and presentation are available below.

In-Park Emissions Inventory Summary (PDF 377 kb)

In-Park Emission Reports web page

The National Park Service is also concerned about emissions from fire which contribute to air pollution. However, fire also plays an important role in many forest ecosystems. Protecting human health and air resources, including visibility, must be considered fully in fire management planning and operations. Through past fire suppression practices, many wildland areas are now in an unhealthy state due to unnaturally high fuel loadings, the presence of plant species that are not endemic to these areas, and increased susceptibility of plant species to insect infestations and disease. A major challenge is protecting human health and air quality while restoring fire-dependent forest ecosystems to their natural, wilderness character. The NPS is concerned about the increased use of fire as a management tool because it may impede progress being made in restoring visibility to natural conditions and complying with legal and regulatory requirements related to human health, welfare, and safety. For more information regarding fire emissions, smoke management, and related topics, please visit the following websites:

• The National Fire Plan website provides information on the National Fire Plan. This plan was developed to help protect communities and natural resources, and most importantly, the lives of firefighters and the public. It is a long-term commitment based on cooperation and communication among federal agencies, states, local governments, tribes and interested public.
• Division of Fire and Aviation. The Division of Fire and Aviation Management (FAM) is comprised of the Wildland Fire, Structural Fire and Aviation Program areas. Fire and Aviation Management is dedicated to delivering these programs safely, professionally and efficiently in support of the overall vision and mission of the National Park Service.
• The NPS Wildland Fire Management Policy website provides guidance for the development of park Fire Management Plans (FMPs).
• EPA's Interim Air Quality Policy on Wildland and Prescribed Fire contains EPA's interim policy for addressing public health and welfare impacts caused by wildland and prescribed fires that are managed to achieve resource benefits, and related policy documents.
• The Western Regional Air Partnership (WRAP) Fire Emissions Joint Forum makes recommendations to WRAP and related WRAP forums on policies and methodologies for: estimating air pollution emissions and their effects on air quality and visibility due to smoke from various natural and human-caused fires; developing a data set and associated tracking system for those emissions in the region; and recommending strategies and methods to manage emissions from these sources.
• The Wildland Fire Statistics website shows current and historical summary data for prescribed and wild fires on Department of the Interior Lands.

New Source Permit Review

The NPS is also concerned about the emissions associated with new sources proposing to locate near its areas. Under the Clean Air Act, the NPS has an affirmative responsibility to protect air resources at parks from emissions associated with new or modified air pollution sources. One way to meet this responsibility is to review permit applications for these proposed new sources. For more information regarding the NPS new source review program, please visit our Permit Applications webpage.