Ozone, the main ingredient of smog, presents a serious air quality problem in several National Park Service areas. Even at low levels, ozone can cause health effects.
- What is ozone?
- How can ground-level ozone affect your health?
- Who is at risk?
- What are National Park Service ozone health advisories?
- How does ground-level ozone affect natural resources?
Ozone is mainly formed by chemical reactions between volatile organic compounds (VOCs) and oxides of nitrogen in the presence of sunlight and higher temperatures. The human-caused sources of VOCs and nitrogen oxides are industrial and automobile emissions. Ozone concentrations can be transported hundreds of miles and affect remote areas of the country.
Exposure to ozone can also increase the susceptibility of the lungs to infections, allergens, and other air pollutants. Medical studies have shown that health problems caused by ozone may continue long after exposure has ended.
People particularly sensitive to ozone include:
- People with lung diseases, such as asthma, chronic bronchitis, and emphysema will generally experience more serious health effects at lower ozone levels.
- Children are at higher risk from ozone exposure because they often play outdoors in summer when ozone levels are higher and their lungs are still developing.
- Older adults may be more affected by ozone exposure, possibly because they are more likely to have pre-existing lung disease.
- Active people of all ages who exercise or work outdoors have higher exposure to ozone than people who are less active.
- Some healthy people may experience health effects at lower ozone levels than the average person even though they have none of the risk factors listed above. There may be a genetic basis for this increased sensitivity.
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.