The Earth' s atmosphere is composed of a mixture of gases, mostly nitrogen (78 percent) and oxygen (21 percent). Argon, carbon monoxide, methane, ozone, sulfur dioxide, carbon dioxide, and carbon monoxide make up the rest of air. In addition to "pure air," our atmosphere also carries water vapor, solid particles, and the pollution we create.
The atmosphere surrounding the Earth is very thin and fragile. Think about the skin of an apple. Think how thin it is compared to the entire apple. That's about how thin our atmosphere is compared to the Earth.
Our atmosphere is made up of different layers. The layers begin at the Earth's surface and extend into space. Close to the Earth is the troposphere. This layer is warm, contains a lot of oxygen, and extends only 10 miles from the Earth's surface. The outer layers, called stratosphere, mesosphere, and thermosphere, are cooler and have less oxygen. That's why mountain climbers need to breathe harder at higher elevations. There's simply not as much oxygen to breathe the higher up you get.
One of air's most important jobs is to provide living plants and animals (including humans!) with the gases they need. Humans and other animals breathe in oxygen they need; then they use that oxygen to metabolize their food. Oxygen is used to break down a sugar called "glucose" into carbon dioxide, water, and energy. The carbon dioxide and water are released when we exhale. This process is known as "respiration." Plants respire too, but they also use the carbon dioxide, sunlight and water to make their own food, in a process called "photosynthesis." The plants release most of the oxygen produced in this process into the atmosphere through their leaves.
Each day, you breathe in about 35 pounds of air. Try lifting a 35-pound weight to see how heavy it feels. If you could spread your lungs completely flat, they would be as big as a tennis court. When we exercise, our bodies need more oxygen, so we breathe hard and our hearts pump faster. If the air is dirty, our lungs can't absorb as much oxygen as they need. Breathing dirty air has the same kind of effect on our lungs as smoking cigarettes. Air pollution affects us even more when we exercise.
Air pollution has a greater effect on children, the elderly, and people with lung problem such as asthma, allergies, and emphysema. Children with asthma may need to stay inside in the winter when their neighbors are using wood stoves that release smoke into the air. There are more deaths and emergency room visits for lung problems when the air is heavily polluted.
(Source:Washington State Dept. of Ecology)
Updated December 1996
