All pollutants are generated from a variety of sources—some general, others specific—and can be influenced or affected by weather and local topographical conditions. The 21 major-specific types of air pollution sources in this article are as follows:
1. Agricultural activities
The agricultural activities that are air pollution sources and cause air pollution problems, include but are not limited to: animal feeding operations; production and decomposition of animal manure; improper fertilizer, pesticide, and herbicide application; soil erosion, use of agricultural equipment, and handling of bulk materials.
2. Evaporative sources
Evaporative air pollution sources include all volatile liquids that are not confined in a container/tank and are able to evaporate or discharge vapors into the air. Evaporative sources can be found in many areas and may include aerosol sprays, paints, pesticides, solvents, pesticides, hair sprays, gasoline, etc.
3. Activities in the aluminium industry
The primary aluminium industry produces aluminium metal and molten aluminium from ore, for use in creating a variety of products. Substantial amounts of electricity are used in the production processes and air pollution problems are created from the fuels that are being consumed.
The secondary aluminium industry recovers aluminium cans, scraps, and foundry returns; however, it releases toxics during production processes which usually involve melting, shredding, and removal of coating on materials. The toxics include organic compounds, metals, chlorine, hydrogen chloride, chlorinated benzenes, fluorine compounds, dioxins, and furans.
4. Fires and wildfires
Smoke from fires and wildfires (burning grasses, trees, bushes, and houses) consists of gases, fine particles, and contaminants such as greenhouse gases, the six criteria pollutants, and hazardous air pollutants (furans, PAHs, dioxins, formaldehyde, hydrochloric acid, heavy metals including lead, mercury, and arsenic, etc.).
5. Cement kilns and cement production
The production of Portland cement takes up substantial amounts of electricity and contributes substantially to local air pollution whenever cement is being produced by grinding and heating a mixture of materials such as marl, limestone, clay, iron ore, fly ash, slag from blast furnaces used in rotary kilns which are powered by energy sources such as gas, coal, oil, coke, etc.
6. Activities in the chemical industry
The chemical manufacturing activities that are major air pollution sources and contaminate the air, water, and land, include: purification of raw materials; chemical reactions that occur when raw materials are being converted into other products; finishing operations, including the purification of products; handling, storing, transporting, and cleaning of equipment; disposal of unusable waste; manufacturing of artificial fibers, resin, basic chemicals, synthetic rubber, pesticides, fertilizers, pharmaceuticals, agricultural chemicals, paint, adhesives, coating, and soap, along with other cleaning compounds.
7. Controlled burns
Although controlled burns are used in forestry and agriculture to efficiently remove undesirable materials, factors such as weather conditions and the time of the day (when a burn is occurring), contribute to increasing air pollution problems. Controlled burns can cause forest fires if required conditions can no longer be controlled appropriately.
Erosion (the removal and dispersion of rock and soil fragments by water, rain, flooding, wind, snowmelt, gravity, and organisms) can be caused by nature or humans (through construction, agriculture, etc.) and lead to tree removal and drought, thereby creating, propagating, and increasing pollution in many instances.
9. External combustion sources
External combustion sources are major air pollution sources that are formed from fossil fuel (coal, natural gas, oil, residual oil, and distillate oil as their major source of fuel); they include: process heaters or heating systems; coal-fired power plants; electric power plants that use steam; industrial and commercial solid waste incinerators; commercial, industrial, and institutional boilers; and combustion systems for domestic and commercial uses.
10. Hazardous waste
Waste from used oil, drain and oven cleaners, antifreeze (liquids that lower the freezing point in cooling systems), preservatives, batteries, pesticides, solvents used in home improvement, paints, and building materials could consist of hazardous waste which is any type of waste that is toxic, reactive, corrosive, or ignitable, and can even create more air pollution than the original products they originate from.
11. Internal combustion engines
The internal combustion engines of motor or movable vehicles use fossil fuels as a means of transportation and account for approximately 28% of all greenhouse gas emissions. Internal combustion engines are a major part of cars, buses, motorcycles, dirt bikes, heavy-duty vehicles, light-duty vehicles, recreational vehicles, commercial aircraft, semi-trailers, minivans, SUVs, construction and agricultural equipment, a variety of boats and ships, lawn and garden equipment, snowmobiles, etc. All the mobile sources listed above are major specific air pollution sources that pollute the air through combustion of fuel and fuel evaporation.
12. Activities in the iron and steel manufacturing industry
Iron and steel production consists of various processes and activities that generate criteria air pollutants and numerous other types of pollutants. The processes in the industry include: handling and treatment of raw materials, waste materials, and intermediate materials; iron preparation and sulfur removal; steel production; sintering (recovering of raw materials from waste materials); iron production from original ore; steel pickling (using acid solution to remove oxides); production of semi-finished products; and preparation of finished products.
13. Activities in the natural gas and crude oil extraction industry
Petroleum and natural gas production from oil wells, along with activities such as drilling, processing, storage, transmission or transportation and distribution, consists of processes that release emissions and pollute the atmosphere.
14. Building construction and land development
Land development and building construction activities produce significant amounts of air pollution over short periods of time within and around an area; the activities include: excavation and hauling of materials; site preparation; paving of surfaces; erection or construction of new structures and buildings; demolition of old or existing structures and buildings and structures; tarring of roofs; waterproofing of materials; and painting of structures and buildings.
15. Natural sources
Natural sources of air pollution vary in terms of the type, intensity, and quantity of pollutants they consist of, individually, and they include: the digestive processes in cattle, marine life, and other animals; forest fires caused by any self-generated or induced combustion that produces nitrogen oxides, smoke, ash, carbon dioxide, and other air pollutants; lightning that converts atmospheric nitrogen into nitrogen oxides; dust from areas that have little or no vegetation; geysers that produce arsenic, hydrogen sulfide, other types of heavy metals, etc.; sea salt which releases NaCl and other particles into the atmosphere from the action of wind over salt water; trees and plants which release VOCs into the atmosphere; radioactive materials which discharge radon gas from the Earth’s crust; soil microbial action which forms and discharges nitrogen oxides; volcanoes which produce ash, smoke, sulfur dioxide, carbon dioxide, and other air pollutants; wetlands which, through microbial action, produce and release significant amounts of methane into the air.
16. Petroleum refining: refineries
Refineries process crude oil to produce lubricants, diesel fuel, automobile gasoline, and other petroleum-based products. Air toxics are emitted during production, storage, transportation, separation, and upgrading; leaks occur from pumps, valves, compressors, flanges, and other equipment used in natural gas and oil production. Toxic air pollutants are discharged from petroleum storage tanks, process vents, equipment leaks, wastewater collection, and treatment systems in refinery facilities.
17. Public sewage treatment plants/works
Wastewater from industrial, commercial, and residential sources is treated in sewage treatment plants, and usually, the following are released: methylene chloride, VOCs, chloroform, xylene, toluene, ethylbenzene, tetrachloroethylene, and naphthalene.
18. Paper and pulp and mills
When using chemicals and mechanical grinding to convert wood and non-wood sources of fiber into pulp, process gases are emitted along with other types of emissions that are discharged during the heating of materials and energy-producing processes.
19. Solid waste landfills
The waste in solid waste landfills contains microorganisms which, along with chemical reactions, contribute to discharge of landfill gas including ammonia, sulfides, methane, and carbon dioxide into the ambient air.
20. Solid waste incinerators
Solid waste incinerators are used to reduce the quantity of waste generated from municipal, commercial, institutional, and industrial areas. A number of pollutants are discharged during incineration; they include: lead, dioxin, sulfur dioxide, cadmium, mercury, nitrogen dioxide, hydrogen chloride, and particulate matter.
21. Spills and runoff from stored chemicals and storage tanks
Spills could occur and chemicals or substances could leak into the ground, contaminate it, and cause long-term air pollution after people mishandle certain products, and storage tanks corrode, leak, don’t undergo proper maintenance, and are overfilled with substances that end up being a waste and polluting the air.
The chemicals that seep into the ground become part of water runoff and surface bodies of water. A single leakage or spill can seep into the ground and groundwater and cause air and environmental pollution for many years.