Air pollution is, or at least should be, a major part of every serious public conversation. The human population of the Earth stood at roughly 7 billion as of the end of the second decade of the 21st century; regardless of the rate at which this figure continues to grow, humans will rely on various sources of energy for their activities in order to feed themselves, move themselves around the globe, stay warm, and otherwise build and maintain stable communities. To widely varying extents, much of human industry causes air pollution.
Air pollution often assaults the senses; it looks disgusting and smells foul, and it doesn't help that many of the facilities that produce it make a great deal of noise, too. But air pollution causes and effects are often silent and insidious, yet still thoroughly destructive. Some solid and compelling air-pollution facts just might cajole some readers into delving further into the issue and possibly even having a hand, large or small, in a partial solution.
What Are the Causes of Air Pollution?
The U.S. Environmental Protection Agency (EPA) and the World Health Organization (WHO) list six distinct types of air pollution.
Fine particles are the product of chemical reactions in the atmosphere, consisting of a mixture of solid particles and liquid droplets. These are often called PM, for particulate matter. The size of a given type of PM is indicated by a subscript, which gives the diameter of the particle in millionths of a meter, or microns. Thus, PM2.5 is a type of PM with a diameter of 2.5 microns, about one-thirtieth the width of a human hair. PM can be inhaled, leading to adverse physical consequences.
Some PM is released directly into the atmosphere from fires, smokestacks and construction sites, while in other cases, emitted material, such as automobile exhaust and the output of power plants, reacts with elements already in the air to create PM.
Ground-level ozone is "bad" ozone that forms when two different emitted components react in the air under the influence of sunlight. These two reactants are nitrates of oxygen, or NOx (where x represents an integer number) and volatile organic compounds, or VOC. Both of these are often emitted in automobile exhaust, industrial and electric plants, gasoline vapor and chemicals used as solvents.
Sulfur dioxide, or SO2, is one type of an oxide of sulfur (SOx). It is far more plentiful in the atmosphere than another such oxide, SO3. Most of this gets into the air as a result of the burning of fossil fuels such as gasoline and diesel fuel, whereas lesser amounts are contributed by machines that burn fuel with a significant sulfur content (for example, locomotives and ships) and even volcanic eruptions (it is a myth that air pollution is only caused by human activity, even if the natural contribution is relatively minor).
Nitrogen dioxide has been mentioned already as a component of ground-level ozone. In environmental science, "nitrogen dioxide" is typically used as a stand-in for any oxide of nitrate (NOx). Like sulfur dioxide, most nitrogen dioxide creates air pollution when it is released during fuel combustion. It is a respiratory hazard by itself and creates other problems when it reacts with PM to form derivative polluting compounds.
Lead is often thought of as a contaminant of water and other non-air entities, having famously rendered much of the public water supply in Flint, Michigan, dangerously undrinkable. But it also gets into the air, mainly through the processing of metals and ore, and also through aircraft emissions. Not surprisingly, the highest concentrations in air are found near lead-smelting centers, where the heavy-metal element is melted down.
Carbon monoxide, or CO, is released into the air in large quantities from cars, trucks and other motor vehicles. But this simple and ever-present molecule is also emitted by household appliances such as gas stoves, space heaters and furnaces. Cigarette smoke contains carbon monoxide, although this is only one of the hazards of this type of smoke.
Note that this list does not include the greenhouse gas carbon dioxide, considered by some sources to be the worst air polluter of them all because of its contribution to global warming, more commonly referred to as climate change. That excessive carbon dioxide levels cause a great deal of harm to Earth and its inhabitants is not in dispute; some authorities simply prefer not to classify it as an air pollutant because it is also a by-product of cellular respiration in an enormous number of living things. Other greenhouse gases include methane (CH4), which arises from swamps and the digestive gas emitted by farm animals, and chlorofluorocarbons (CFCs), which were formerly used in aerosols and refrigerants until they were banned owing to their role in the degradation of the Earth's ozone layer.
Climate change itself is a source of air pollution because of the increased tendency of smog to form in warmer air. Thus, the more fossil fuels contribute to climate change, the more pronounced their unchecked effects become over time.
What Are the Effects of Air Pollution?
Air pollution, in addition to being an eyesore, has a number of proven hazardous effects on various systems of the body, chiefly the respiratory system. It can also lead to cardiovascular disease, neuropsychiatric disorders, eye irritation, skin diseases and chronic diseases such as cancer. In different parts of the world, the most severe health effects are realized in different proportions, but worldwide, respiratory and cardiovascular disease are the leading causes of death and debility from air pollution.
Because it is so small, PM poses a special problem to the respiratory system because the smallest PM can be inhaled deep into the bronchial tubes of the lungs. This is one of many types of air pollution that can worsen existing conditions, such as asthma and chronic bronchitis, especially in the very young, the elderly and the already ill.
Ground-level ozone can produce a variety of health problems, among them chest pain, coughing, throat irritation and inflammation of the airway. Some people have a greater genetic susceptibility to ozone's effects than others, as do individuals deficient in vitamins C and E.
Sulfur dioxide in the short term is a respiratory irritant that, like PM, primarily affects children and the elderly, and makes breathing more difficult for anyone who has asthma. SO2 and SO3 both react with other substances to form PM, the damaging effects of which have been described. The effects of nitrogen dioxide are similar, and NO2 can also make people more prone to respiratory infections in the longer term.
Lead affects the body in ways that differ markedly from other air pollutants. Like other so-called heavy metals, lead can be extremely toxic to a variety of organ systems. Once taken up from the environment, lead circulates in the blood and accumulates in the bones. It can damage the nervous system, kidneys, immune system, reproductive system and the cardiovascular system. In the U.S., its most commonly encountered negative effects are on the nervous systems of children and the cardiovascular systems of adults.
In contrast to other air pollutants, the acute effects of carbon dioxide are more dangerous than any chronic effects, since high levels of CO are not typically encountered outdoors, and the molecule degrades relatively quickly. However, at very high levels, which are possible indoors or in other poorly ventilated environments, CO can cause dizziness, confusion, unconsciousness and even death, as with car exhaust in a garage. Because people exposed to CO may become confused and fall unconscious, they are unable to even perceive, much less escape, the threat.
How Does Air Pollution Affect the Environment?
Air pollution affects living things other than animals. Some of these effects are "merely" aesthetic. For example, tiny fine particles (PM2.5) are the leading main cause of reduced visibility caused by haze in parts of the U.S., including in many national parks and wilderness areas. Efforts to prevent oil extraction and similar industrial ventures close to national parks were far from complete as of 2018.
Ozone can affect sensitive types of vegetation within a number of ecosystems, including forests, wildlife refuges, parks and wilderness areas. Ozone has particularly damaging effects on vegetation during the growing season.
At high concentrations, gaseous SOx can harm trees and plants by damaging foliage and decreasing growth. SO2 and other sulfur oxides can contribute to acid rain, which can harm sensitive ecosystems. The effects of oxides of nitrate are similar.
Elevated environmental lead levels are associated with decreased growth and reproductive rates in plants just as they are in animals.
Considering greenhouse gases as an air pollutant, the sweeping effects of human-caused climate change on the environment, already considered to be serious, are expected to become catastrophic to coastal cities around the world within decades. Much of the world's population lives on its coasts, and many will be ill-equipped to stave off the flooding anticipated to result from rising sea levels consequent to the melting of polar ice.
How Does Air Pollution Affect Businesses?
In addition to poisoning water around the globe and damaging the supply of other natural resources, and impacting business through the simple effect of leading to an increase in health problems and infirmity, air pollution has been shown to directly reduce consumer spending. For example, in 2018, researchers with Yale University analyzed daily spending, air pollution and climate data from 12 Spanish provinces. Their findings were drastic, with consumers spending $29 million to $48 million less in U.S. dollars on days when ground-level ozone pollution was "only" 10 percent worse than the norm. Similarly, spending fell by $23 million to $35 million on days when PM pollution was 10 percent worse than usual. They concluded that a 10 percent reduction in ozone and PM2.5 could increase consumer spending in Spain by up to $30 billion annually. Bear in mind that this is the effect on business in one relatively small European nation.
It would be a mistake to portray the issue of air pollution as one that has been allowed to worsen unchecked. Attempts to fight air pollution have in fact existed for a long time. The EPA's Clean Air Act of 1970 is one of many air pollution solutions put into effect around the globe. In the interim, air pollution levels have fallen while the U.S. economy has continued to grow. Total emissions of the six common pollutants dropped an average of 73 percent, while gross domestic product grew by more than a factor of three. Concerns about the slowing or reversal of this progress began to increase in 2017 under the leadership of President Donald Trump, who sought to withdraw the country from a worldwide climate agreement and made a number of moves to visibly weaken the EPA in the context of pro-fossil-fuel industry regulatory activity.
About the Author
Kevin Beck holds a bachelor's degree in physics with minors in math and chemistry from the University of Vermont. Formerly with ScienceBlogs.com and the editor of "Run Strong," he has written for Runner's World, Men's Fitness, Competitor, and a variety of other publications. More about Kevin and links to his professional work can be found at www.kemibe.com.