<Ul> <Li> Dust from natural sources , usually large areas of land with little or no vegetation </Li> <Li> Methane , emitted by the digestion of food by animals , for example cattle </Li> <Li> 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 . </Li> <Li> Smoke and carbon monoxide from wildfires </Li> <Li> Vegetation , in some regions , emits environmentally significant amounts of Volatile organic compounds ( VOCs ) on warmer days . These VOCs react with primary anthropogenic pollutants -- specifically , NO , SO , and anthropogenic organic carbon compounds -- to produce a seasonal haze of secondary pollutants . Black gum , poplar , oak and willow are some examples of vegetation that can produce abundant VOCs . The VOC production from these species result in ozone levels up to eight times higher than the low - impact tree species . </Li> <Li> Volcanic activity , which produces sulfur , chlorine , and ash particulates </Li> </Ul>
where do some of the natural air pollutants come from
Dust the digestion of food by animals radioactive decay within the Earth 's crust wildfires Vegetation Volcanic activity