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
- Joshua Tree NP
- Mammoth Cave NP
- Pinnacles NM
- Rocky Mountain NP
- Sequoia & Kings Canyon NPs
- Shenandoah NP
- Yosemite NP
Advisories from some participating parks are available on park websites and social media channels.
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.
Understanding Ozone Health Advisory Levels
Good (0–54 ppb)
No cautionary statement.
Moderate (55–70 ppb)
Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.
Unhealthy for Sensitive Groups (71–85 ppb)
Children, older adults, active people, and people with lung disease (such as asthma) should reduce prolonged or heavy exertion outdoors.
Unhealthy (86–105 ppb)
Children, older adults, active people, and people with lung disease (such as asthma) should avoid prolonged or heavy exertion outdoors. Everyone else should reduce prolonged or heavy exertion outdoors.
Very Unhealthy (106+ ppb)
Children, older adults, active people, and people with lung disease (such as asthma) should avoid all outdoor exertion. Everyone else 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.
Understanding PM2.5 Health Advisory levels
- Good (0–12 µg/m3)
No cautionary statement.
- Moderate (12.1–35.4 µg/m3)
Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.
- Unhealthy for Sensitive Groups (35.5–55.4 µg/m3)
Children, older adults, active people, and people with heart or lung disease (such as asthma) should reduce prolonged or heavy exertion outdoors.
- Unhealthy (55.5–150.4 µg/m3)
Children, older adults, active people, and people with heart or lung disease (such as asthma) should avoid prolonged or heavy exertion outdoors. Everyone else should reduce prolonged or heavy exertion outdoors.
- Very Unhealthy (150.5–250.4 µg/m3)
Children, older adults, active people, and people with heart or lung disease (such as asthma) should avoid all outdoor exertion. Everyone else should avoid prolonged or heavy exertion outdoors.
Hazardous (250.5+ µg/m3)
Everyone should avoid all physical activity outdoors. Children, older adults, and people with heart or lung disease (such as asthma) should remain indoors and keep activity levels low. Follow tips for keeping particle levels low indoors.
