Air pollution also can be invisible, causing lung damage, cancer or other serious health problems in people who may not realize the potential danger of the unseen gases or particles suspended in the air.
What are you breathing?
The U.S. Environmental Protection Agency (EPA) tracks five major air pollutants that cause significant health effects: ground-level ozone, nitrogen oxides, sulfur oxides, carbon monoxide, and 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 like carbon monoxide or nitrogen dioxide, they are absorbed by the cells that line the airways to the lungs. Once absorbed, the gases pass into the bloodstream and travel to your internal organs, where they can cause damage. If the gases are not entirely absorbed by the airways, they can reach the lungs, where they can do further damage.
Large particles in the air are filtered out by cilia, the small hairs that line your respiratory tract. Smaller particles, however, reach your airways and lungs. Particles of all sizes also land on crops and in water that are eventually consumed by humans and by animals that humans eat.
Sulfur oxides, particulate matter, ozone, and nitrogen dioxide are the most commonly found pollutants that cause health problems. Usually, several of these pollutants occur together, increasing your risk for illness.
Sulfur oxides are formed when sulfur-containing fuels such as coal and oil are burned, when gasoline is extracted from crude oil or when metals are extracted from ore, the EPA says. Sources of sulfur oxides are power plants, oil refineries, smelters, paper pulp mills and, in the home, kerosene space heaters. This gas is easily absorbed by the lining of your upper airways, irritating them and causing them to constrict. In the environment, sulfur oxides are eventually transformed into acid rain, which harms both plants and animals.
Both nitrogen oxide and nitrogen dioxide are formed when fuel is burned at a high temperature. This occurs in motor vehicles, power plants, oil refineries and, in the home, gas stoves, furnaces and kerosene space heaters. Nitrogen oxides are some of the main ingredients involved in the formation of ground-level ozone, which can trigger serious respiratory problems, the EPA says. They also react with ammonia, moisture and certain compounds to form nitric acid and related particles. These can penetrate the lungs and cause or worsen respiratory diseases such as emphysema and bronchitis, and aggravate existing heart disease. In the environment, nitrogen oxides also contribute to acid rain and global warming.
Ground-level ozone (the primary constituent of smog) is different from the protective ozone found in the upper atmosphere. Ground-level ozone is created when ultraviolet irradiation from sunlight interacts with nitrogen oxides and substances called volatile organic compounds, the EPA says. Major sources are industrial plants, electric utility companies, motor vehicle exhaust, and vapors from gasoline and chemical solvents. Ozone is more common during summer heat waves and also is found in aircraft cabins and in the fumes from welding, copiers and ozone generators. It is poorly absorbed by your upper airways, so much of what you inhale reaches your lungs. Ozone can cause lung inflammation, which decreases lung function, and makes allergies worse. Repeated exposure may permanently scar lung tissue.
Particulate matter is a mixture of tiny particles and airborne droplets, the EPA says. The combination can include acids, organic chemicals, metals and dust particles. Particulate matter can be found in motor vehicle exhaust, particularly diesel; power plant emissions; and, in the home, especially tobacco smoke and wood smoke. The size of the particles determines whether they reach the lungs: Those 10 microns or smaller in diameter can get deep into your lungs and some even into your bloodstream. Once in the lungs, they cause irritation that makes existing lung problems worse. In people with healthy lungs, particulate matter increases the chance of developing heart disease and having a heart attack or stroke.