Very small (fine) particulate matter (PM) concentrations approach or exceed the National Ambient Air Quality Standard in several National Park Service (NPS) areas. The NPS therefore issues fine particulate health advisories at several areas.
- What is particulate matter?
- How can particulate matter affect your health?
- What are the symptoms of particle exposure?
- Who is at risk?
- How can I avoid unhealthy exposure?
- What are the NPS PM2.5 health advisories?
- How does particulate matter affect national parks?
Particle size is directly linked to the potential for causing health problems. Particles smaller than 10 micrometers in diameter pose the greatest problems because they can get deep into your lungs and some may even get into your bloodstream. Larger particles are can irritate your eyes, nose, and throat, but are less concerning for health impacts.
Particles of concern are classified as “fine particles” (found in smoke and haze), which are 2.5 micrometers in diameter or less, and “coarse particles” (found in wind-blown dust), which have diameters between 2.5 and 10 micrometers.
Healthy children and adults have not been reported to suffer serious effects from short-term exposures, although they may experience temporary minor irritation when particle levels are elevated.
People sensitive to particulate matter include:
- People with heart or lung diseases such as coronary artery disease, congestive heart failure, and asthma or chronic obstructive pulmonary disease (COPD) are at increased risk, because particles can aggravate these diseases.
- People with diabetes also may be at increased risk, possibly because they are more likely to have underlying cardiovascular disease.
- Older adults are at increased risk, possibly because they may have undiagnosed heart or lung disease or diabetes.
- Children are likely at increased risk for several reasons: their lungs are still developing, they spend more time outside participating in physical activities, and they are more likely to have asthma or acute respiratory diseases which can be aggravated when particle levels are high.
The PM2.5 public health standard is based on both a 24-hour and an annual concentration. The 24-hour standard is used as a basis for health advisories in the parks. The 24-hour standard is set at 35 micrograms per cubic meter (µg/m3). 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.