Air pollution occurs when chemical, physical or biological substances alter the natural characteristics of the atmosphere, potentially leading to respiratory and other diseases that can be lethal.
The International Agency for Research on Cancer (IARC) at the World Health Organization classifies particulate matter, the main component of air pollution, as carcinogenic and published a study in 2013 definitively linking air pollution and lung cancer.
Industrial cities and densely populated metropolises are home to many sources of air pollution or otherwise fail to counter natural and manmade pollution sources, creating public planning risk scenarios that require mitigation. Of concern to health officials in urban areas are: large open grounds without any trees or grass and that may also lack protection against erosion; motorization, including exhaust and particulates from the residue of tire friction against asphalt; and winterization of roadways, commonly with sands and other reagents. Rural living conditions in the developing world can present uniquely challenging pollutants because reducing the pollutants would require cultural adaptations. For example, the use of biomass for fuel and home construction as well as poor sanitation in highly travel roadways generates air pollution.
*PM10 is used to describe particles of 10 micrometers or less and PM2.5 represents particles less than 2.5 micrometers in aerodynamic diameter.