Effects of Ozone
Concentrations of ozone that measure near or above the National Ambient Air Quality Standards
can have adverse effects on human health and our environment.
Effects on Health
High ozone levels affect children, people with lung disease, and people who are active outdoors. Numerous scientific
studies have linked ozone exposure to a variety of health problems, including:
- airway irritation, coughing, and pain when taking a deep breath;
- wheezing and breathing difficulties during exercise or outdoor activities;
- inflammation, which is much like a sunburn on the skin;
- aggravation of asthma and increased susceptibility to respiratory illnesses like pneumonia and bronchitis;
- permanent lung damage with repeated exposures.
Everyone has some sensitivity to pollutants in the air we breathe. However, EPA has found that certain groups of
people are more sensitive to ozone. Children, people with lung diseases, and adults who are active outdoors are
- Children - Scientists consider children sensitive to the effects of ozone exposure because they
often spend a lot of time outdoors during the summer, when ozone levels are the highest. As children run and
play outside, their quick, deep breaths bring ozone to parts of the lungs that are more vulnerable to injury.
Respiratory illnesses can further contribute to a child's sensitivity to ozone. Asthma is the most common
chronic disease for children and it may be worsened by ozone exposure.
- People with respiratory diseases, such as asthma, chronic bronchitis, and emphysema - There is
no evidence that ozone causes asthma or other chronic respiratory disease, but these diseases do make the lungs
more vulnerable to the effects of ozone. Individuals with these conditions will generally experience the effects
of ozone earlier and at lower levels than less sensitive individuals.
- Adults who are active outdoors - Scientists consider healthy adults of all ages who exercise or
work vigorously outdoors a "sensitive group" because they have a higher level of exposure to ozone than people
who are less active outdoors. Physical activity (such as jogging or outdoor work) causes people to breathe
faster and more deeply. During activity, ozone goes deeper into the parts of the lungs that are more vulnerable
- People with unusual susceptibility to ozone - Scientists don't know why yet, but some healthy
people are simply more sensitive to ozone than others. These individuals may experience more health effects from
ozone exposure than the average person.
Other groups of people have been studied to find out whether they are at increased risk from ozone. So far there is
little evidence to suggest that either the elderly or people with heart disease are more sensitive to ozone.
However, like other adults, these people will be at higher risk from ozone exposure if they suffer from respiratory
disease, are active outdoors, or are unusually susceptible to ozone as described above.
What can I do to avoid exposure?
There are safe ways to limit your exposure to ozone without reducing healthy physical activity.
- Sign up for our ozone forecast so you can plan outdoor work or
exercise during your day to avoid possible high levels of ozone.
- Use these recommendations
for schools and outdoor activities to modify plans for outdoor activities such as recess, lunch, and
physical education class.
- If you're involved in an activity that requires heavy exertion, you can reduce the time you spend on this
activity or substitute another activity that requires more moderate exertion(e.g., go for a walk rather than a
- No matter how fit you are, cutting back on the level or duration of exertion when ozone levels are high will
help protect you from ozone's harmful effects.
- Plan outdoor activities when ozone levels are lower, usually in the morning or evening.
Effects on Environment
Ozone can have detrimental effects on plants and ecosystems. These effects include:
- interfering with the ability of sensitive plants to produce and store food, making them more susceptible to
certain diseases, insects, other pollutants, competition and harsh weather;
- damaging the leaves of trees and other plants, negatively impacting the appearance of urban vegetation, as well
as vegetation in national parks and recreation areas; and
- reducing forest growth and crop yields, potentially impacting species diversity in ecosystems.
Photo of healthy (left) and injured from ozone exposure (right) black cherry foliage at Great Smoky Mountains
National Park in North Carolina and Tennessee. (Images from
U.S. National Park Service)