11.3: Air Pollution

Air Pollution Defined

Air pollution is the release of gases that cause harm to all of Earth's other spheres (lithosphere/geosphere, biosphere, hydrosphere), which include humans, into the air. Air pollution causes millions of people to die every year. According to the World Health Organization (WHO), 99% of humans breathe air that exceeds the guideline limits for pollutants. People living in second- and third-world countries suffer the most. The Clean Air Act was established in the United States in 1970. It authorizes the U.S. Environmental Protection Agency (EPA) to safeguard public health by regulating the emissions of these harmful air pollutants. Progress has been made, but there is more to go.

Causes and Types of Air Pollution

Most air pollution comes from energy use and production. This includes driving a gasoline powered car, heating a home with natural gas, running a plant on fracked or otherwise sourced gas, etc. In all these examples a fossil fuel is burned, and gases are released into the atmosphere. More information on specific types of pollution is below.

Greenhouse Gases and Ozone

Greenhouse gases are gases that trap the Earth’s heat in the atmosphere, leading to warmer temperatures, which in turn lead to things like rising sea levels and more extreme weather. Common greenhouse gases are water vapor (H₂O), carbon dioxide (CO₂), methane (CH₄), and ozone (O₃). In 2021, carbon dioxide accounted for about 80% of the US's total greenhouse gas emissions, and methane made up more than 11%. Carbon dioxide comes from the burning of fossil fuels. Methane comes from natural (cows produce methane as they digest food) and industrial (decomposition of waste) sources, and include large amounts released during oil and gas drilling. While carbon dioxide emissions are very high, methane is more potent, so it is very dangerous.

Ozone is ozone no matter where it is in the atmosphere. Good ozone is good only because it is in the stratosphere where we cannot breathe it and it absorbs ultraviolet (UV) rays. Bad ozone is near the Earth's surface where we can breathe it. It also absorbs solar ultraviolet light, but but the dangers outweigh the benefits. For UV protection, we are interested in the total number of ozone molecules between us and the Sun. 90% of ozone molecules are in the stratosphere and 10% are in the troposphere - some down near Earth's surface where we can breathe them. There are important issues affecting human and ecological health for both good ozone and bad ozone. For good ozone, the most important issues are the reduction of ozone globally, the Antarctic Ozone Hole, and Arctic ozone loss that is caused by chlorofluorocarbons. Chlorofluorcarbons were widely used in various applications like refrigerants, aerosol propellants, and foam blowing agents, but are now largely phased out due to their significant contribution to ozone depletion in the Earth's atmosphere. Reduced ozone means more solar UV gets to the ground causing more skin cancer. For bad ozone, the most important issues include the production of too much ozone in cities and nearby regions that is caused by too many pollutants from traffic, industrial processes, power generation, and other human activities. Increased ozone means more people have respiratory and heart problems. It is important to note that in October 2016 (2022 for the US), more than 140 countries signed the Kigali Agreement to reduce the use of chlorofluorocarbons and develop greener alternatives over time.

Smog and Soot

Smog is the bad ozone written about above. Soot is made from tiny particles of chemicals, soil, smoke, dust, or allergens carried in the air. They are the two most prevalent types of air pollution. The sources of smog and soot are similar as they occur with emissions from cars and trucks, factories, power plants, incinerators, and engines generated by combusting fossil fuels.

Smog irritates eyes and throats and damages the lungs. Children, elderly, and people who work or exercise outdoors are at higher risk. It’s even worse for people who have asthma or allergies; these extra pollutants can intensify their symptoms and trigger asthma attacks. The tiniest airborne particles in soot are especially dangerous because they can penetrate the lungs and bloodstream and worsen bronchitis, lead to heart attacks, and even hasten death.

Because some sources of these pollutants have been preferentially located in or next to low-income neighborhoods, the negative effects of this pollution are experienced at a higher rate by the people who live in these communities. This has become an important environmental justice issue.

Hazardous Pollutants

Several pollutants, even in tiny amounts, pose sometimes fatal health risks. Common pollutants include mercury, lead, dioxins, and benzene which are emitted as fossil fuels combust or are found in gasoline. Large amounts of lead can damage children’s brains and kidneys, and small amounts can affect children’s ability to learn. This is why pediatricians regularly test children for lead exposure. Mercury damages the central nervous system. Dioxins are usually found in food but can also be found in the air and is a carcinogen that affects the liver, immune system, nervous system, endocrine system, and reproductive functions. Benzene is also a carcinogen and causes eye, skin, and lung irritation, as well as blood disorders.

Another category of pollutants, polycyclic aromatic hydrocarbons (PAHs), are by-products of smoke generated by wildfires and exhaust by traffic. PAHs have been correlated to eye and lung irritation, blood and liver issues, and cancer.

Air Pollution in the United States

According to the American Lung Association (ALA), more than 33% of the people in the U.S. live in counties with unhealthy air. The Clean Air Act, enacted in 1970, has been critical in reducing air pollution by reducing harmful emissions from transportation, power plants, and manufacturing. Fossil fuel interests, often supported by industry-friendly lawmakers, have continuously sought to weaken its protections but maintaining the integrity of this law is crucial to improving and safeguarding air quality.

The latest findings reveal that climate change-driven wildfires and extreme heat are exacerbating the challenges to public health. Recent studies by the ALA focus on ozone levels, year-round particle pollution, and short-term particle pollution, revealing that people of color are 61% more likely than white people to live in counties with a failing grade in at least one of these categories, and three times more likely to live in areas where all three pollution types fail to meet health standards.

In the rankings for these pollution categories, central California cities (Bakersfield, Visalia, Fresno) occupy the top three spots for the worst air quality, despite the state's progress in reducing emissions over the past five decades. On the other end of the spectrum, cities like Burlington, Vermont; Honolulu; and Wilmington, North Carolina, consistently rank among the best for air quality in the country.

The most effective strategy to reduce air pollution is promoting the transition to cleaner fuels and industrial practices. By shifting to renewable energy sources like wind and solar, increasing fuel efficiency in vehicles, and replacing gasoline-powered cars with electric vehicles (assuming the electricity is not generated by fossil fuels), we can address pollution at its source while also mitigating the global warming that exacerbates its harmful health effects.

As for the economic costs of controlling air pollution, a report commissioned by the Natural Resources Defense Council (NRDC) shows that the benefits of cleaner air far outweigh the costs. Each year, the Clean Air Act's regulations result in benefits that are up to 32 times greater than the cost of enforcement. These benefits include preventing up to 370,000 premature deaths, reducing hospital admissions for respiratory and cardiac diseases by 189,000, and generating up to $3.8 trillion in net economic gains for the U.S. economy annually.