In Prince George’s County and the Washington, D.C. metropolitan area, the 2 most important pollutants that threaten human health are ground-level ozone and particle pollution. If you are a typical adult, you'll breathe in close to 3,500 gallons of air in a single day. If your atmosphere is polluted with ozone and particle pollution, you may see your lung function reduced by as much as 20%.

Ozone
Ozone is an extremely reactive gas comprised of 3 atoms of oxygen. Ozone exists naturally in the earth's upper atmosphere, the stratosphere, where it shields the earth from the sun's harmful ultraviolet rays. The ozone layer in the upper atmosphere exists naturally and is essential to life because it filters harmful ultraviolet radiation from the sun, reducing the amount reaching the earth's surface. High concentrations of ozone near ground level, however, can be harmful to people, animals, crops, and other materials.

Ground Level Ozone
Ground level ozone is the main ingredient in urban and regional smog and is found in the air we breathe. It is formed through a complex chemical reaction between volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the presence of sunlight. Sources of man-made VOCs and NOx include:

• Automobiles, trucks and buses
• Consumer products such as paints and cleaners
• Gasoline storage and transfer
• Industrial use of solvents and degreasing agents
• Large combustion and industry sources such as utilities
• Off-road engines such as aircraft, locomotives, boats, construction equipment and lawn and garden equipment

Health Effects of Ozone
High concentrations of ozone can cause shortness of breath, coughing, wheezing, fatigue, headaches, nausea, chest pain, and eye and throat irritation. The most common symptom that people have when exposed to ozone while exercising is pain when taking a deep breath.

The EPA estimates that 5 - 20% of the total U.S. population is especially susceptible to the harmful effects of ozone pollution. The following groups are most vulnerable:

• Athletes and individuals who exercise outdoors
• Children, because their respiratory systems are still developing (They're more active and spend more time outdoors, inhaling more air pollution per pound of body weight than do adults)
• Older adults, because their respiratory and immune systems lose some of their resilience (Damage caused by ground level ozone pollution can aggravate existing conditions or irritate tissues that make them susceptible to infection)
• People with pre-existing respiratory problems

Particulate Matter
You may not be able to see them but "Particulate matter" is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets. These particles come in a wide range of sizes. These particles - the ones under 2.5 micrometers in diameter are called fine particles and they are too small for our respiratory systems to filter out, and end up getting trapped in our lungs where they may adversely affect our health. The very smallest pass through the lungs into the blood stream and can damage the heart. They come from a variety of sources such as:

• Burning of wood
• Buses
• Cars
• Construction sites
• Factories
• Stone crushing
• Tilled fields
• Trucks
• Unpaved roads

Other particles may be formed in the air from the chemical change of gases. They are indirectly formed when gases from burning fuels react with sunlight and water vapor. These can result from fuel combustion in motor vehicles, at power plants, and in other industrial processes.

Unlike ground level ozone, particles are not a seasonal pollutant; high levels can occur any time of the year. Unhealthy levels of particle pollution in the air can cause or trigger significant health problems. These range from coughing and difficult or painful breathing to the possibility of an emergency room visit or even premature death. Exposure to particles can decrease lung function, weaken the heart, and possibly bring on a heart attack. The environment also suffers from particle pollution. Particles are the major source of haze, and can harm the environment by changing the nutrient and chemical balance in soil and water.

Health Effects With Particulate Matter

• When exposed to particulate matter, people with existing heart or lung diseases-such as asthma, chronic obstructive pulmonary disease, congestive heart disease, or ischemic heart disease-are at increased risk of premature death or admission to hospitals or emergency rooms.
• The elderly also are sensitive to particulate matter exposure. They are at increased risk of admission to hospitals or emergency rooms and premature death from heart or lung diseases.
• When exposed to particulate matter, children and people with existing lung disease may not be able to breathe as deeply or vigorously as they normally would, and they may experience symptoms such as coughing and shortness of breath.
• Particulate matter can increase susceptibility to respiratory infections and can aggravate existing respiratory diseases, such as asthma and chronic bronchitis, causing more use of medication and more doctor visits.