Air pollution is the black cloud belching from an industrial smokestack. It's the smog that settles over some cities, dimming the skyline. It's the smelly exhaust of an old car that burns oil.
Air pollution also can be invisible and odorless. It can cause lung damage, cancer, or other serious health problems in people who may not realize the possible danger of the unseen gases or particles in the air.
The U.S. Environmental Protection Agency (EPA) tracks 6 major air pollutants that cause major health effects:
Microscopic particles called particulate matter
Both the outside air and the air in your home or workplace can have these pollutants. The amount of pollutant in the air and the length of time you are exposed to it determine how the pollutant will affect you.
When you breathe in gases such as carbon monoxide or nitrogen dioxide, the cells that line the airways to the lungs absorb them. Once taken in, the gases can pass into your blood and travel to your internal organs. There, they can cause damage. If the pollution isn't absorbed into the blood, damage can still be done to the lungs.
Large particles in the air are filtered out by the small hairs (cilia) that line your respiratory tract. But smaller particles reach your airways and lungs. Particles of all sizes also land on crops and in water. Over time, they are eaten by humans, and by animals that humans eat.
The effects of air pollution vary from person to person. A healthy adult who is exposed to these pollutants for a short time or at low dose may not have long-term problems. But it's different for people with a heart or respiratory condition. For these people, even a small dose or a short exposure can make symptoms worse. Longer exposure or a higher dose can lead to serious illness. In some cases, it can lead to death. Children and older adults are more likely to be affected by air pollution than others. They can suffer the effects at lower pollution levels.
The Air Quality Index (AQI) is a national index for 6 major air pollutants regulated by the Clean Air Act:
The index tells you how clean or polluted your air is. It also tells you what health effects you may have in a few hours or days after breathing polluted air.