OAQPS Fact Sheet
July 17, 1997
Health and Environmental Effects of Ground-Level Ozone
Why are We Concerned about Ground-Level Ozone?
Who is Most at Risk from Exposure to Ground-Level Ozone?
- Ozone is the prime ingredient of smog in our cities and
other areas of the country. Though it occurs naturally in the
stratosphere to provide a protective layer high above the earth,
at ground-level it is the prime ingredient of smog.
- When inhaled, even at very low levels, ozone can:
- cause acute respiratory problems;
- aggravate asthma;
- cause significant temporary decreases in lung capacity
of 15 to over 20 percent in some healthy adults;
- cause inflammation of lung tissue;
- lead to hospital admissions and emergency room visits
[10 to 20 percent of all summertime respiratory-related
hospital visits in the northeastern U.S. are associated
with ozone pollution]; and
- impair the body's immune system defenses, making people
more susceptible to respiratory illnesses, including bronchitis
How does Ground-Level Ozone Harm the Environment?
- Children are most at risk from exposure to ozone:
- The average adult breathes 13,000 liters of air per day.
Children breathe even more air per pound of body weight than
- Because children's respiratory systems are still developing,
they are more susceptible than adults to environmental threats.
- Ground-level ozone is a summertime problem. Children are
outside playing and exercising during the summer months at
summer camps, playgrounds, neighborhood parks and in
- Asthmatics and Asthmatic Children:
- Asthma is a growing threat to children and adults.
Children make up 25 percent of the population and comprise
40 percent of the asthma cases.
- Fourteen Americans die every day from asthma, a rate three
times greater than just 20 years ago. African-Americans die
at a rate six times that of Caucasians.
- For asthmatics having an attack, the pathways of the
lungs become so narrow that breathing becomes akin to
sucking a thick milk shake through a straw.
- Ozone can aggravate asthma, causing more asthma attacks,
increased use of medication, more medical treatment and more
visits to hospital emergency clinics.
- Healthy Adults:
- Even moderately exercising healthy adults can experience
15 to over 20 percent reductions in lung function from
exposure to low levels of ozone over several hours.
- Damage to lung tissue may be caused by repeated exposures
to ozone -- something like repeated sunburns of the lungs --
and this could result in a reduced quality of life as people
age. Results of animal studies indicate that repeated
exposure to high levels of ozone for several months or more
can produce permanent structural damage in the lungs.
- Among those most at risk to ozone are people who are
outdoors and moderately exercising during the summer months.
This includes construction workers and other outdoor workers.
What Improvement Would Result from EPA's New Standards?
- Ground-level ozone interferes with the ability of plants
to produce and store food, so that growth, reproduction and
overall plant health are compromised.
- By weakening sensitive vegetation, ozone makes plants more
susceptible to disease, pests, and environmental stresses.
- Ground-level ozone has been shown to reduce agricultural
yields for many economically important crops (e.g., soybeans,
kidney beans, wheat, cotton).
- The effects of ground-level ozone on long-lived species
such as trees are believed to add up over many years so that
whole forests or ecosystems can be affected. For example, ozone
can adversely impact ecological functions such as water movement,
mineral nutrient cycling, and habitats for various animal and
- Ground-level ozone can kill or damage leaves so that they
fall off the plants too soon or become spotted or brown. These
effects can significantly decrease the natural beauty of an area,
such as in national parks and recreation areas.
- One of the key components of ozone, nitrogen oxides,
contributes to fish kills and algae blooms in sensitive
waterways, such as the Chesapeake Bay.
EPA's new ozone standards will provide increased protection beyond
that provided by the previous standard from the following effects:
Background: What is Ground-level Ozone?
- Reduced risk of significant decreases (15% to over 20%) in
children's lung functions (such as difficulty in breathing or
shortness of breath), approximately 1 million fewer incidences
each year, which can limit a healthy child's activities or result
in increased medication use, or medical treatment, for children
- Reduced risk of moderate to severe respiratory symptoms in
children, hundreds of thousands of fewer incidences each year of
symptoms such as aggravated coughing and difficult or painful
- Reduced risk of hospital admissions and emergency room visits
for respiratory causes, thousands fewer admissions and visits for
individuals with asthma
- Reduced risks of more frequent childhood illnesses and more
subtle effects such as repeated inflammation of the lung,
impairment of the lung's natural defense mechanisms, increased
susceptibility to respiratory infection, and irreversible changes
in lung structure. Such risks can lead to chronic respiratory
illnesses such as emphysema and chronic bronchitis later in life
and/or premature aging of the lungs
- Reduce the yield loss of major agricultural crops, such as
soybeans and wheat, and commercial forests by almost $500,000,000.
- Ozone is not emitted directly into the air, but is formed
by gases called nitrogen oxides (NOx) and volatile organic
compounds (VOCs) that in the presence of heat and sunlight react
to form ozone. Ground-level ozone forms readily in the atmosphere,
usually during hot weather.
- NOx is emitted from motor vehicles, power plants and other
sources of combustion. VOCs are emitted from a variety of sources,
including motor vehicles, chemical plants, refineries, factories,
consumer and commercial products, and other industrial sources.
- Changing weather patterns contribute to yearly differences
in ozone concentrations from city to city. Also, ozone and the
pollutants that cause ozone can be carried to an area from
pollution sources located hundreds of miles upwind.