Air pollution or particulate matter is a phenomenon that arises from the combination of particulate matter and dust with urban pollutants and is caused by climate change, drying of wetlands, drought, and construction of dams.
The average air pollution index in Tehran is currently 177 units and in an unhealthy condition for all groups. On April 9, Tehran’s air pollution ranked at a record 491 and was rated as the most polluted city in the world. In the category of air pollution conditions, the index is defined as 150 to 200 unhealthy, 200 to 300 very unhealthy, and 300 and above dangerous.