Title: Pollution in the United States
Content:  Air pollution is caused predominantly from burning fossil fuels, cars and much more. Natural sources of air pollution include forest fires, volcanic eruptions, wind erosion, pollen dispersal, evaporation of organic compounds, and natural radioactivity. These natural sources of pollution often soon disperse and thin settling near their locale. However, major natural events such as volcanic activity can convey throughout the air spreading, thinning and settling over continents. Fossil fuel burning for heating, electrical generation, and in motor vehicles are responsible for about 90% of all air pollution in the United States.
Title: Pollution
Content:  Air pollution comes from both natural and human-made (anthropogenic) sources. However, globally human-made pollutants from combustion, construction, mining, agriculture and warfare are increasingly significant in the air pollution equation. Motor vehicle emissions are one of the leading causes of air pollution. China, United States, Russia, India Mexico, and Japan are the world leaders in air pollution emissions. Principal stationary pollution sources include chemical plants, coal-fired power plants, oil refineries, petrochemical plants, nuclear waste disposal activity, incinerators, large livestock farms (dairy cows, pigs, poultry, etc.), PVC factories, metals production factories, plastics factories, and other heavy industry. Agricultural air pollution comes from contemporary practices which include clear 
Title: Environmental issues in the United Kingdom
Content:  Gases that lead to air pollution include carbon, nitrogen and sulfur oxides. While some of these gases occur naturally, like carbon dioxide in the expulsion of air from the lungs, the serious polluters come from the burning of fossil fuels: coal, oil and natural gas. Poisonous gases are being released in the air through smoke released by factories and chemical industries. Air pollution is known as a mixture of natural and man-made substances in the air we breathe. Some examples of natural substances that contribute to air pollution in the UK are dust and pollen while examples of man-made substances contributing to the problem are gases that come from 
Title: Air pollution in British Columbia
Content:  Air pollution sources in British Columbia may be divided between those external to the province, such as transboundary pollution, and those internal to it; and between anthropogenic (man-made) sources and natural sources. External anthropogenic sources include combustion particles and gases from industrial sources in the province of Alberta or the U.S. state of Washington. Toxic substances form part of these pollutants such as tetrachloroethylene and trichloroethylene as well as nitrogen monoxide and sulfur dioxide, which Canada seeks to minimize through caps and its tradable permit system. Mount St. Helens has been a significant external natural source: although located entirely in the United States, its eruption created air pollution in parts of British Columbia. Exhaust from internal combustion engines (mainly automobiles and trucks, as well as marine vessels in coastal waters) is a major internal anthropogenic source. Other human-caused sources include: Industrial, agricultural (e.g. manure spreading), commercial operations (e.g., dry cleaners and gas stations) and home heating appliances (furnaces, fireplaces). Radionuclides are generally not a concern with regards to air pollution issues in BC, except for radon gas. Background pollution occurs in areas not directly affected by pollution sources.
Title: Air pollution
Content:   A lack of ventilation indoors concentrates air pollution where people often spend the majority of their time. Radon (Rn) gas, a carcinogen, is exuded from the Earth in certain locations and trapped inside houses. Building materials including carpeting and plywood emit formaldehyde (H2CO) gas. Paint and solvents give off volatile organic compounds (VOCs) as they dry. Lead paint can degenerate into dust and be inhaled. Intentional air pollution is introduced with the use of air fresheners, incense, and other scented items. Controlled wood fires in cook stoves and fireplaces can add significant amounts of harmful smoke particulates into the air, inside and out. Indoor pollution 
Title: Air pollution
Content:   Air pollution is the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types of air pollutants, such as gases (including ammonia, carbon monoxide, sulfur dioxide, nitrous oxides, methane, carbon dioxide and chlorofluorocarbons), particulates (both organic and inorganic), and biological molecules. Air pollution can cause diseases, allergies, and even death to humans; it can also cause harm to other living organisms such as animals and food crops, and may damage the natural environment (for example, climate change, ozone depletion or habitat degradation) or built environment (for example, acid rain). Both human activity and natural processes can generate 
Title: Pollution in California
Content:  Air pollution stems from a number of sources, and the amount of pollutant from each source differs from place to place. Particulate pollution sources are shown in the graph at right. Residential wood combustion, such as burning wood in fireplaces, is the largest source of PM 2.5 pollution. The Clean Air Act requires the US EPA to regulate six common pollutants. These air pollutants (also known as "criteria pollutants") are found all over the United States. They are particle pollution, ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead. All of these pollutants have been shown to have adverse health and environmental impacts and some can cause property damage. Of the six pollutants, particle pollution and ground-level ozone 
Title: Air pollution
Content: Dust from natural sources, usually large areas of land with little vegetation or no vegetation ; Methane, emitted by the digestion of food by animals, for example cattle ; Radon gas from radioactive decay within the Earth's crust. Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is considered to be a health hazard. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause of lung cancer, after cigarette smoking. ; Smoke and carbon monoxide from wildfires. During periods of 
Title: Air pollution in Canada
Content:  Fuel production causes majority of the air pollution in New Brunswick. Emissions come from engines, homes and industrial heating systems, from manufacturing operations and power-generating stations. Forest fires also occur and can be a major natural source of air pollution.. Major weather systems reach New Brunswick from the west and up the Atlantic seaboard, bringing pollutants from the more industrialized and densely populated areas of the United States and central Canada. In the southern part of the province, air from the Bay of Fundy can slow the dispersal of air pollutants and trap them close to ground level. There are more than 60 separate locations across the province monitor ambient air quality all year round.
Title: Air pollution
Content:  widespread it is almost always associated with prolonged exposure to asbestos). Biological sources of air pollution are also found indoors, as gases and airborne particulates. Pets produce dander, people produce dust from minute skin flakes and decomposed hair, dust mites in bedding, carpeting and furniture produce enzymes and micrometre-sized fecal droppings, inhabitants emit methane, mold forms on walls and generates mycotoxins and spores, air conditioning systems can incubate Legionnaires' disease and mold, and houseplants, soil and surrounding gardens can produce pollen, dust, and mold. Indoors, the lack of air circulation allows these airborne pollutants to accumulate more than they would otherwise occur in nature.

Question: where do some of the natural air pollutants come from?
Answer: wildfires.
Volcanic activity.
Dust.
Carbon dioxide.
Vegetation.