Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of chemical substances or energy, such as noise, heat, or light. Pollutants, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants. Pollution is often classed as point source or nonpoint source pollution. In 2015, pollution killed 9 million people worldwide.

Major forms of pollution include air pollution, light pollution, litter, noise pollution, plastic pollution, soil contamination, radioactive contamination, thermal pollution, visual pollution, and water pollution.

The major forms of pollution are listed below along with the particular contaminant 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 PM₁₀to PM₅.
• Electromagnetic pollution: the overabundance of electromagnetic radiation in their non-ionizing form, like radio waves, etc, that people are constantly exposed at, especially in large cities. It’s still unknown whether or not those types of radiation have any effects on human health, though.
• 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.
• Plastic pollution: involves the accumulation of plastic products and microplastics in the environment that adversely affects wildlife, wildlife habitat, or humans.
• Soil contamination occurs when chemicals are released by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, MTBE,^[4]herbicides, pesticides and chlorinated hydrocarbons.
• Radioactive contamination, resulting from 20th century activities in atomic physics, such as nuclear power generation and nuclear weapons research, manufacture and deployment. (See alpha emitters and actinides in the environment.)
• Thermal pollution, is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant.
• Visual pollution, which can refer to the presence of overhead power lines, motorway billboards, scarred landforms (as from strip mining), open storage of trash, municipal solid waste or space debris.
• Water pollution, by the discharge of industrial wastewater from commercial and industrial waste (intentionally or through spills) into surface waters; discharges of untreated sewage, and chemical contaminants, such as chlorine, from treated sewage; release of waste and contaminants into surface runoff flowing to surface waters (including urban runoff and agricultural runoff, which may contain chemical fertilizers and pesticides; also including human feces from open defecation – still a major problem in many developing countries); groundwater pollution from waste disposal and leaching into the ground, including from pit latrines and septic tanks; eutrophication and littering.

The major forms of pollution are also listed below

Air

Acid rain, Air quality index, Atmospheric dispersion modeling, Chlorofluorocarbon, Exhaust gas, Haze, Indoor air, Internal combustion engine, Global dimming, Global distillation, Ozone depletion, Particulates, Persistent organic pollutant, Smog , Aerosol, Soot, Volatile organic compound.

Electromagnetic

Ecological light pollution, Over illumination, Radio spectrum pollution

Natural

Ozone, Radium and radon in the environment, Volcanic ash, Wildfire

Noise

Transportation – Land, Water, Air, Rail, Sustainable transport, Urban, Sonar, Marine mammals and sonar, Industrial, Military, Abstract Noise control

Radiation

Actinides, Bioremediation, Fission product, Nuclear fallout, Plutonium, Poisoning, Radioactivity, Uranium, Electromagnetic radiation and health, Radioactive waste.

Soil

Agricultural pollution, Herbicides, Manure waste, Pesticides, Land degradation, Bioremediation, Defecation, Electrical resistance heating, Guideline values, Phytoremediation

Soild waste

 Biodegradable waste, Brown waste, Electronic waste, Battery recycling, Food waste, Green waste, Hazardous waste, Biomedical waste, Chemical waste, Construction waste, Lead poisoning, Mercury poisoning, Toxic waste

Industrial waste, Lead smelting, Litter, Mining, Coal mining, Gold mining, Surface mining, Deep sea mining, Mining waste, Uranium mining, Municipal solid waste, Garbage, Nanomaterials, Plastic pollution, Microplastics, Packaging waste, Post-consumer waste

Waste management, Landfill, Thermal treatment

Water

Agricultural wastewater, Diseases, Eutrophication, Firewater, Freshwater, Groundwater, Hypoxia, Industrial wastewater, Marine debris.

Monitoring, Nutrient pollution, Ocean acidification, Oil spill, Pharmaceuticals, Septic tanks, Sewage, Shipping, Stagnation, Sulfur water, Surface runoff, Turbidity, Urban runoff, Water quality