What Is Air Pollution?

Definition, Facts, and Environmental Risks

shanghai air pollution

DuKai photographer / Getty Images

The term "air pollution" is used so commonly that you may not think definitions are necessary. But the issue is more complicated than it first appears. 

Ask most people to define air pollution, and their first response is to describe smog, the smelly stuff that turns the air brown or gray and hovers over urban centers like Los Angeles, Mexico City, and Beijing. Even here, though, definitions vary. Some sources define smog as the presence of unnatural levels of ground-level ozone, while other sources say things like "fog mixed with smoke." A more modern and precise definition is "a photochemical haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen especially from automobile exhaust."

Officially, air pollution can be defined as the presence of harmful substances in the air, either particulates or microscopic biologic molecules, that pose health hazards to living organisms, such as people, animals or plants. Air pollution comes in many forms and may include a number of different pollutants and toxins in various combinations.

Air pollution is far more than a nuisance or inconvenience. According to the World Health Organization, air pollution causes the deaths of approximately 4.2 million people annually worldwide.

What Constitutes Air Pollution?

The two most widespread types of air pollution are the ozone and particle pollution (soot), but air pollution also may include serious pollutants such as carbon monoxide, lead, nitrogen oxides, and sulfur dioxide, volatile organic compounds (VOCs) and toxins such as mercury, arsenic, benzene, formaldehyde, and acid gases. Most of these pollutants are man-made, but some air pollution is due to natural causes, such as ash from volcanic eruptions. 

The specific composition of air pollution in a particular location depends primarily on the source or sources of pollution. Automobile exhaust, coal-fired power plants, industrial factories, and other pollution sources all spew different types of pollutants and toxins into the air.

While we think of air pollution as a condition describing outside air, the air quality within your home is equally important. Cooking vapors, carbon monoxide from heating appliances, off-gassing of formaldehyde and other chemicals from furniture and construction materials, and secondhand tobacco smoke are all potentially dangerous forms of indoor air pollution. 

Air Pollution and Your Health

Air pollution hovers at unhealthy levels in almost every major U.S. city, interfering with people’s ability to breathe, causing or aggravating many serious health conditions, and placing lives at risk. Many cities worldwide face the same issues, especially in so-called emerging economies such as China and India, where cleaner technologies are not yet in standard usage. 

Breathing ozone, particle pollution or other types of air pollution can seriously damage your health. Inhaling ozone can irritate your lungs, "resulting in something like a bad sunburn within the lungs," according to the American Lung Association. Breathing particle pollution (soot) can increase your risk of heart attack, stroke and early death, and it may necessitate emergency-room visits for people with asthma, diabetes and cardiovascular disease. A great many cancers are traced to chemical air pollutants. 

Air pollution is also a problem in developing countries that are not yet fully industrialized. More than half the world's population still cook their meals with wood, dung, coal or other solid fuels over open fires or on primitive stoves inside their homes, breathing high levels of pollutants such as particulate pollution and carbon monoxide, which results in 1.5 million unnecessary deaths every year.

Who Is Most at Risk?

The health risks of air pollution are greatest among infants and young children, older adults and people with respiratory diseases such as asthma.

People who work or exercise outside also face increased health risks from the effects of air pollution, along with people who live or work near busy highways, factories or power plants. In addition, minorities and people with low incomes are often disproportionately affected by air pollution because of where they live, which places them at higher risk for illnesses related to air pollution. Low-income populations often live near industrial or inner-city zones where factories, utilities, and other industrial sources may create unusually high levels of air pollution. 

Air Pollution and the Planet

If air pollution affects humans, it of course also may also have an impact on animals and plant life. Many animal species are threatened by high levels of air pollution, and weather conditions created by air pollution affect both animal and plant life. For example, acid rain caused by the burning of fossil fuels has radically changed the nature of forests in the U.S. Northeast, upper Midwest, and Northwest. And it is now indisputable that air pollution causes shifts in global weather patterns — the raising of global temperatures, the melting of polar ice sheets and the coming rise in ocean water levels. 

How Can Air Pollution Be Reduced?

The evidence is clear that our personal choices and industrial practices can affect the levels of air pollution. Cleaner industrial technologies are shown to lower air pollution levels, and it can be demonstrated that anytime more primitive industrial practices increase, so do levels of dangerous air pollution. Here are some of the obvious ways that humans can, and have reduced air pollution: 

  • Reduction of fossil fuel burning in favor of renewable energy sources. Nations that obtain their electrical power from nuclear, hydroelectric, solar and wind power have lower pollution levels than those that favor the burning of coal or natural gas. 
  • Improved gas mileage in automobiles and the introduction of electric-powered vehicles. California, for example, once plagued with dangerous smog, has greatly improved its air quality through tight controls on automobile emissions standards. Similarly, reduction in the use of other internal combustion engines can reduce air pollution. The shift to battery-operated or electric lawn mowers and lawn equipment, for example, has a demonstrable effect on air quality. 
  • Reduction in agricultural burning — the method of clearing forested areas for agriculture — can reduce the level of smoke and carbon dioxide in the air. This is a particular problem in developing countries. 
  • Reducing wood burning can also reduce levels of smoke in the air. In some communities, wood fireplaces are now outlawed, greatly reducing dangerous levels of smoke in the air. Gas fireplaces are better than wood-burners, and even better are electric fireplaces that burn no fuels at all. 
  • Indoor air quality is improved when tobacco smoking is restricted by ordinance. Citizen pressure to restrict smoking in public places has a real effect on air quality. 
  • Reduction of chemical compounds in paints, adhesives, and solvents has improved the quality of indoor and outdoor air. Always look for low VOC materials for home improvements, and where practical, opt for water-based rather than solvent-based paints and other materials. Look for carpets, fabrics, and furniture that don't off-gas dangerous fumes. 

Controlling pollution is possible, but it requires the individual and political will to do so, and these efforts must constantly be balanced with economic realities, as green technologies are often more expensive, especially when they are first introduced. Such choices are in the hands of each individual: for example, do you buy a cheap but dirty automobile or an expensive electric car? Or are jobs for coal miners more important than clean air? These complex questions are not easily answered by individuals or governments, but they are questions that should be considered and debated with eyes open to the real effects of air pollution.