Pollution is the introduction of contaminants into the natural environment that cause harm.
[1] Pollution
can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or
light). Pollutants, the components of pollution, can be either foreign substances/energies or naturally
occurring contaminants.
Although environmental pollution can be caused by natural events, the word pollution generally implies
that the contaminants have a human source – that is, a source created by human activities, such
as manufacturing, extractive industries, poor waste management, transportation or agriculture. Pollution
is often classed as point source (coming from a highly concentrated specific site, such as
a factory, mine, construction site), or nonpoint source pollution (coming from a widespread distributed
sources, such as microplastics or agricultural runoff).
Many sources of pollution were unregulated parts of industrialization during the 19th and 20th centuries
until the emergence of environmental regulation and pollution policy in the later half of the 20th
century. Sites where historically polluting industries released persistent pollutants may have legacy
pollution long after the source of the pollution is stopped. Major forms of pollution include air
pollution, water pollution, litter, noise pollution, plastic pollution, soil contamination, radioactive
contamination, thermal pollution, light pollution, and visual pollution.[2]
Pollution has widespread consequences on human and environmental health, having systematic impact
on social and economic systems. In 2019, pollution killed approximately nine million people worldwide
(about one in six deaths that year); about three-quarters of these deaths were caused by air
pollution.[3][4][5][6][7] A 2022 literature review found that levels of anthropogenic chemical pollution have
exceeded planetary boundaries and now threaten entire ecosystems around the world.[8][9] Pollutants
frequently have outsized impacts on vulnerable populations, such as children and the elderly, and
marginalized communities, because polluting industries and toxic waste sites tend to be collocated with
populations with less economic and political power.[10] This outsized impact is a core reason for the
formation of the environmental justice movement,[11][12] and continues to be a core element
of environmental conflicts, particularly in the Global South.
Because of the impacts of these chemicals, local and international countries' policy have increasingly
sought to regulate pollutants, resulting in increasing air and water quality standards, alongside
regulation of specific waste streams. Regional and national policy is typically supervised
by environmental agencies or ministries, while international efforts are coordinated by the UN
Environmental Program and other treaty bodies. Pollution mitigation is an important part of all of
the Sustainable Development Goals.[13]
Definitions and types
Various definitions of pollution exist, which may or may not recognize certain types, such as noise
pollution or greenhouse gases. The United States Environmental Protection Administration defines
pollution as "Any substances in water, soil, or air that degrade the natural quality of the environment,
offend the senses of sight, taste, or smell, or cause a health hazard. The usefulness of the natural
resource is usually impaired by the presence of pollutants and contaminants."[14] In contrast, the United
Nations considers pollution to be the "presence of substances and heat in environmental media (air,
water, land) whose nature, location, or quantity produces undesirable environmental effects."[15]
Smog in the center of Moscow, Russia in August 2010
The major forms of pollution are listed below along with the particular contaminants relevant to each of
them:
Air pollution: the release of chemicals and particulates into the atmosphere. Common gaseous
pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs) and nitrogen
oxides produced by industry and motor vehicles. Photochemical ozone and smog are created as
nitrogen oxides and hydrocarbons react to sunlight. Particulate matter, or fine dust is
characterized by their micrometre size PM10 to PM2.5.
Electromagnetic pollution: the overabundance of electromagnetic radiation in their non-
ionizing form, such as radio and television transmissions, Wi-fi etc. Although there is no
demonstrable effect on humans there can be interference with radio-astronomy and effects on
safety systems of aircraft and cars.
Light pollution: includes light trespass, over-illumination and astronomical interference.
Littering: the criminal throwing of inappropriate man-made objects, unremoved, onto public and
private properties.
Noise pollution: which encompasses roadway noise, aircraft noise, industrial noise as well as
high-intensity sonar.
