Pollutants

Pollutants are substances or energy released into the environment that can cause harm or discomfort. They may be solids, liquids, gases, or forms of energy such as heat or noise, and they can originate from intentional releases or accidents and natural processes. Pollutants are often categorized by the environment they affect and whether they are primary pollutants or form secondary pollutants through environmental reactions. Common categories include air, water, and soil pollutants.

Air pollutants include particulate matter, sulfur dioxide, nitrogen oxides, carbon monoxide, and ground-level ozone. They arise from burning fossil fuels, industry, and transport, with natural sources such as wildfires also contributing. Exposure affects respiratory and cardiovascular health and can influence climate.

Water pollutants include nutrients such as nitrogen and phosphorus, heavy metals, pesticides, organic compounds, and plastics. They reach water bodies via runoff, wastewater, leaching, and industrial discharges. Soils accumulate heavy metals, pesticides, hydrocarbons, and salts from mining, farming, and waste.

Impacts depend on concentration, exposure duration, and sensitivity of organisms. They can affect health, harm ecosystems, and alter chemical cycles. Some pollutants persist and bioaccumulate.

Monitoring and regulation aim to limit exposure and environmental damage. Agencies establish air and water quality standards, permit discharges, and require controls. Environmental monitoring networks measure pollutant levels to assess trends and inform policy decisions.

Mitigation strategies include reducing emissions at the source, treating polluted water and soil, and adopting cleaner technologies. Public awareness and international cooperation also address transboundary pollution.