ABSTRACT
Urban air quality has become a critical public health concern in many parts of the globe with the increase of urbanization and industrialization during the last few decades. Almost half of the world’s population now live in the urban areas, and their number will increase to 4 billion by the end of this decade. Particulate matter (PM) (or aerosols) and ozone are two of the major pollutants affecting the air quality in urban areas throughout the world. PM is a complex mixture of solid and liquid particles that vary in size and composition and remain suspended in the air. Many chemical, physical, and biological components of atmospheric aerosols are identižed as being potentially harmful to respiratory and cardiopulmonary human health. Aerosols have many sources from both natural and anthropogenic activities. These include naturally occurring aerosols from windblown dust and episodic activities such as forest žres/agricultural burning (mostly anthropogenic). Increasing human factors such as combustion from automobiles and industries and emissions from power plants also contribute. Apart from direct emissions, PM is also produced by other processes such as gas-to-particle conversion in the atmosphere.
