Health Advisories for National Parks

The National Park Service (NPS) issues ozone and particulate matter health advisories when concentrations exceed, or are forecasted to exceed, the National Ambient Air Quality Standard. NPS staff post health advisories cautioning visitors of the potential health risks associated with exposures to elevated levels. Most air pollution in National Parks is created outside park boundaries. When air quality conditions reach unhealthy levels in parks, conditions in the surrounding areas are usually similar.

Participating Parks

The NPS issues air quality health advisories at several national parks. These parks include:
  • Acadia NP
  • Great Smoky Mountains NP
  • Mammoth Cave NP
  • Pinnacles NM
  • Rocky Mountain NP
  • Sequoia & Kings Canyon NPs
  • Shenandoah NP
  • Yosemite NP
Advisories from all participating parks are available from the NPS Health Advisories Twitter feed.

Ozone Advisories

The NPS issues ozone health advisories when ozone concentrations exceed, or are forecasted to exceed, the National Ambient Air Quality Standard. The ozone health standard is an 8-hour average concentration of 70 parts per billion (ppb). NPS ozone health advisories are based on the EPA air quality index levels shown below.

Image of the Ozone Health Advisory Scale, which assigns colors to different ozone levels from green (good) to purple (unhealthy).

Understanding Ozone Health Advisory Levels

  • Ozone air quality index good condition icon (green) Good (0–54 ppb)
    No cautionary statement.
  • Ozone air quality index moderate condition icon (yellow) Moderate (55–70 ppb)
    Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.
  • Ozone air quality index unhealthy-for-sensitive-groups condition icon (orange) Unhealthy for Sensitive Groups (71–85 ppb)
    Active children and adults, and people with lung disease, such as asthma, should reduce prolonged or heavy exertion outdoors.
  • Ozone air quality index unhealthy condition icon (red) Unhealthy (86–105 ppb)
    Active children and adults, and people with lung disease, such as asthma, should avoid prolonged or heavy exertion outdoors. Everyone else, especially children, should reduce prolonged or heavy exertion outdoors.
  • Ozone air quality index very-unhealthy condition icon (purple) Very Unhealthy (106+ ppb)
    Active children and adults, and people with lung disease, such as asthma, should avoid all outdoor exertion. Everyone else, especially children, should avoid prolonged or heavy exertion outdoors.

Fine Particulate Matter Advisories

Air quality in some parks may at times exceed the National Ambient Air Quality Standard for fine particulate matter (PM2.5), particles less than or equal to 2.5 micrometers (µm). The 24-hour public health standard set at 35 micrograms per cubic meter parts (µg/m3) is used as a basis for health advisories in the parks. Using the EPA air quality index, the NPS PM2.5 health advisories are based on the levels shown below.

Scale bar which describes the health advisory levels for different concentrations of particulate matter, from good (green) to unhealthy (purple).

Understanding PM2.5 Health Advisory levels

  • PM2.5 air quality index good condition icon (green) Good (0–12 µg/m3)
    No cautionary statement.
  • PM2.5 air quality index moderate condition icon (yellow) Moderate (12.1–35.4 µg/m3)
    Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.
  • PM2.5 air quality index unhealthy-for-sensitive-groups condition icon (orange) Unhealthy for Sensitive Groups (35.5–55.4 µg/m3)
    Active children and adults, and people with lung disease, such as asthma, should reduce prolonged or heavy exertion outdoors.
  • PM2.5 air quality index unhealthy condition icon (red) Unhealthy (55.5–150.4 µg/m3)
    Active children and adults, and people with lung disease, such as asthma, should avoid prolonged or heavy exertion outdoors. Everyone else, especially children, should reduce prolonged or heavy exertion outdoors.
  • PM2.5 air quality index very-unhealthy condition icon (purple) Very Unhealthy (150.5+ µg/m3)
    Active children and adults, and people with lung disease, such as asthma, should avoid all outdoor exertion. Everyone else, especially children, should avoid prolonged or heavy exertion outdoors.

Last updated: February 21, 2018

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