• Why are we concerned about Ground-Level Ozone? 
• Who is most at risk from exposure to Ground-Level Ozone? 
• What causes Ozone? 
• What measures can be taken to reduce the amount of Ozone in the air?

Why are we concerned about Ground-Level Ozone?

Ozone is an odorless, colorless gas that is a respiratory health hazard. Though it occurs naturally in the stratosphere to provide a protective layer high above the earth, at ground-level it is a respiratory tract irritant.

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 and pneumonia.

Who is most at risk from exposure to Ground-Level Ozone?

Children

The average adult breathes 13,000 liters of air per day. Children breathe even more air per pound of body weight than adults. 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 backyards.

Asthmatics and Asthmatic Children

As you know, 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.

Healthy Adults

Even moderately exercising healthy adults can experience 15 to over 20 percent reduction 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 causes Ozone?

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.

What measures can be taken to reduce the amount of Ozone in the air?

To avoid unnecessarily contributing to ozone pollution, the following steps may be taken to reduce emissions of smog-forming compounds.

• Limit driving. Share rides, carpool. Combine errands.
• Take public transportation.
• Avoid excessive idling of your automobile.
• Keep your car well-tuned.
• Refuel your car carefully and in the evening when it's cooler.
• Defer lawn and gardening chores that use gasoline-powered equipment.
• Postpone using oil-based paints and solvents.
• Defer use of household consumer products that release fumes or evaporate easily.
• Conserve energy, at home, at work, everywhere. 

Government of the District of Columbia
Department of Health
Environmental Health Administration
Anthony A. Williams Mayor