Pollution

Pollution is the introduction of contaminants into the natural environment that cause harm. These contaminants, known as pollutants, can be physical substances or forms of energy. Substances can exist as solids, liquids, or gases. Energy-based pollution includes radioactivity, heat, sound, or light.

While natural events can cause pollution, the term usually implies human sources. These sources often include manufacturing, transportation, agriculture, or poor waste management. Pollution can degrade the quality of an environment. It can also offend the senses of sight, taste, or smell.

Scientists and agencies categorize pollution by how it enters an ecosystem. Point source pollution comes from a highly concentrated, specific site. Examples include a factory, a mine, or a construction site. Nonpoint source pollution comes from widespread, distributed sources. This includes microplastics or agricultural runoff that spreads across large areas.

Some pollutants are also persistent. This means they remain in the environment long after the source has stopped. These are often called legacy pollution. They can stay at sites where polluting industries once operated.

There are many distinct types of pollution affecting the planet. Air pollution involves releasing chemicals and particulates into the atmosphere. Common gases include carbon monoxide, sulfur dioxide, and nitrogen oxides. Photochemical ozone and smog form when nitrogen oxides react with sunlight.

Water pollution occurs when industrial wastewater, untreated sewage, or chemical runoff enters surface waters. Soil contamination happens when chemicals like heavy metals or pesticides leak into the ground.

Other types include noise pollution, light pollution, and thermal pollution. Thermal pollution is a temperature change in water caused by human influence, such as using water as a coolant in a power plant.

Historically, the concept of pollution has changed significantly. Before the 1860s, the term was rarely used in an environmental sense. It often referred to the desecration of something sacred. During the 19th and 20th centuries, industrialization led to unregulated emissions. People often called air pollution "the smoke nuisance" or "the smoke plague."

It was not until the later half of the 20th century that environmental regulation and pollution policy emerged to manage these issues.

Pollution has massive global significance for health and the economy. In 2019, pollution killed approximately nine million people worldwide. This accounted for about one in six deaths that year. Roughly three-quarters of these deaths were caused by air pollution.

Furthermore, a 2022 review found that human-made chemical pollution has exceeded planetary boundaries. This means it now threatens entire ecosystems around the world. One specific concern involves per- and polyfluoroalkyl substances, or PFAS. These are often called "forever chemicals" because of their persistence.

Certain populations face much higher risks from these contaminants. Vulnerable groups include children, the elderly, and marginalized communities. This happens because polluting industries and toxic waste sites are often located near people with less economic or political power.

This inequality is a core reason for the environmental justice movement. This movement focuses on the disproportionate impact of pollution on these communities. It remains a central element of environmental conflicts, particularly in the Global South.

Managing pollution requires cooperation at many levels of society. Local, national, and international policies work to regulate various pollutants. This leads to higher standards for air and water quality. Regional and national policies are usually supervised by environmental agencies or ministries. On a global scale, the UN Environmental Program helps coordinate international efforts. Reducing pollution is also a key part of the Sustainable Development Goals.

By regulating waste streams and emissions, society works to protect the natural world.