Air Pollution - Definition, Causes, Effects And Control

Air pollution
1. What Is Air Pollution?
Air pollution refers to the release of pollutants into the air—
pollutants which are detrimental to human health and the planet
as a whole. According to the World Health Organization (WHO),
each year air pollution is responsible for nearly seven million
deaths around the globe. Nine out of ten human beings currently
breathe air that exceeds the WHO’s guideline limits for
pollutants, with those living in low- and middle-income countries
suffering the most. In the United States, the Clean Air Act,
established in 1970, authorizes the U.S. Environmental Protection Agency (EPA) to safeguard public health by
regulating the emissions of these harmful air pollutants.
1.1. Types of air pollution
The most common and harmful pollutants outdoors include:
particulate matter
nitrogen dioxide
ozone
sulfur dioxide
2. What Causes Air Pollution?
“Most air pollution comes from energy use and
production,” says John Walker, director of the Clean Air
Project, part of the Climate and Clean Energy program at
NRDC. “Burning fossil fuels releases gases and chemicals
into the air.” And in an especially destructive feedback
loop, air pollution not only contributes to climate change
but is also exacerbated by it. “Air pollution in the form of
carbon dioxide and methane raises the earth’s
temperature,” Walker says. “Another type of air pollution, smog, is then worsened by that increased heat,

forming when the weather is warmer and there’s more ultraviolet radiation.” Climate change also increases the
production of allergenic air pollutants, including mold (thanks to damp conditions caused by extreme weather
and increased flooding) and pollen (due to a longer pollen season).
“We’ve made progress over the last 50 years improving air quality in the United States thanks to the Clean Air
Act,” says Kim Knowlton, senior scientist, and deputy director of the NRDC Science Center. “But climate change
will make it harder in the future to meet pollution standards, which are designed to protect health.”
3. Effects of Air Pollution
The effects of air pollution on the human body vary depending on the type of pollutant and the length and level
of exposure—as well as other factors, including a person’s individual health risks and the cumulative impacts of
multiple pollutants or stressors.
3.1. Smog and soot
These are the two most prevalent types of air pollution. Smog (sometimes referred to as ground-level ozone)
occurs when emissions from combusting fossil fuels react with sunlight. Soot (also known as particulate matter)
is made up of tiny particles of chemicals, soil, smoke, dust, or allergens—in the form of either gas or solids—that
are carried in the air. The sources of smog and soot are similar. “Both come from cars and trucks, factories,
power plants, incinerators, engines, generally anything that combusts fossil fuels such as coal, gas, or natural
gas,” Walker says.
Smog can irritate the eyes and throat and also damage the lungs, especially those of children, senior citizens,
and people who work or exercise outdoors. 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,
whether gaseous or solid, are especially dangerous because they can penetrate the lungs and bloodstream and
worsen bronchitis, lead to heart attacks, and even hasten death. In 2020 a report from Harvard’s T. H. Chan
School of Public Health showed COVID-19 mortality rates in areas with more soot pollution were higher than in
areas with even slightly less, showing a correlation between the virus’s deadliness and long-term exposure to
fine particulate matter and illuminating an environmental justice issue.
Because highways and polluting facilities have historically been sighted in or next to low-income neighborhoods
and communities of color, the negative effects of this pollution have been disproportionately experienced by the
people who live in these communities. In 2019 the Union of Concerned Scientists found that soot exposure was

34 percent higher for Asian Americans, on average, than for other Americans. For Black people, the exposure
rate was 24 percent higher; for Latinos, 23 percent higher.
3.2. Hazardous air pollutants
A number of air pollutants pose severe health risks and can sometimes be fatal even in small amounts. Almost
200 of them are regulated by law; some of the most common are mercury, lead, dioxins, and benzene. “These
are also most often emitted during gas or coal combustion, incinerating, or—in the case of benzene—found in
gasoline,” Walker says. Benzene, classified as a carcinogen by the EPA, can cause eye, skin, and lung irritation in
the short term and blood disorders in the long term. Dioxins, more typically found in food but also present in
small amounts in the air, can affect the liver in the short term and harm the immune, nervous, and endocrine
systems as well as reproductive functions. Mercury attacks the central nervous system. In large amounts, lead
can damage children’s brains and kidneys, and even minimal exposure can affect children’s IQ and ability to
learn.
Another category of toxic compounds, polycyclic aromatic hydrocarbons (PAHs), are by-products of traffic
exhaust and wildfire smoke. In large amounts they have been linked to eye and lung irritation, blood, and liver
issues, and even cancer. In one study, the children of mothers exposed to PAHs during pregnancy showed
slower brain-processing speeds and more pronounced symptoms of ADHD.
3.3. Greenhouse gases
By trapping the earth’s heat in the atmosphere, greenhouse gases lead to warmer temperatures, which in turn
lead to the hallmarks of climate change: rising sea levels, more extreme weather, heat-related deaths, and the
increased transmission of infectious diseases. In 2018 carbon dioxide accounted for 81 percent of the country’s
total greenhouse gas emissions, and methane made up 10 percent. “Carbon dioxide comes from combusting
fossil fuels, and methane comes from natural and industrial sources, including large amounts that are released
during oil and gas drilling,” Walker says. “We emit far larger amounts of carbon dioxide, but methane is
significantly more potent, so it’s also very destructive.” Another class of greenhouse gases, hydrofluorocarbons
(HFCs), are thousands of times more powerful than carbon dioxide in their ability to trap heat. In October 2016
more than 140 countries reached an agreement to reduce the use of these chemicals—which are found in air
conditioners and refrigerators—and develop greener alternatives over time. Though President Trump was
unwilling to sign on to this agreement, a bipartisan group of senators overrode his objections in 2020 and set the
United States on track to slash HFCs by 85 percent by 2035. According to David Dungier, senior strategic director