Unprecedented Thermal Inversion Grips Tehran 

The Iranian capital Tehran is being choked by toxic smog as an uncharacteristically prolonged period of temperature inversion has trapped hazardous pollutants near ground. 
“The primary reason for Tehran’s air pollution this year is an overlong inversion, which is a completely natural phenomenon,” a senior official with Tehran Province’s Department of Environment, Zohreh Ebadati, was quoted as saying by ISNA.
Inversion is more likely to develop in winter when a layer of cold air at the surface is overlain by a layer of warmer air, keeping pollutants trapped in a bubble over the city.
Ebadati pointed out, “In the past years, inversion would not continue like this. It used to last only for a few days.”
Residents of the capital and the nearby city of Karaj have been struggling for a breath of clean air in the past weeks as the atmospheric mechanism, coupled with pollutants such as black carbon, nitrogen dioxide and particulate matter, caused a surge in respiratory problems. 
Air quality is gauged by a color-coded ranking system ranging from green to maroon. For five consecutive days, monitoring stations across Tehran have recorded Air Quality Index values in the 150-200 range, the red zone, which is unhealthy for all groups in the society.
High concentration levels of dangerous PM2.5 particles have risen past an average of 150 micrograms per cubic meter since Friday. 
The deadly particulate matter PM 2.5 has been linked to cardiovascular and respiratory diseases as the tiny particles can enter the bloodstream through the lungs. 

Managing the Crisis 

A lack of viable solutions has prompted the government to come up with adaptation policies such as the closure of schools and universities. 
All schools and universities in Tehran have switched to e-learning from Saturday in an attempt to minimize exposure to vulnerable groups and to cut car emissions. 
Provincial authorities also ordered government employees in Tehran Province to shift to remote work on Wednesday. 
A senior official with the Iran Meteorological Organization, Sadeq Ziayian, warned that AQI values could exceed 200 if airborne pollutants were not strictly controlled and there was no intervention by rain systems.  
“Everyone should avoid outdoor activities, not just sensitive groups,” he added. 
According to officials, the burning of substandard fuels is a major cause of the crisis and a ban on gas guzzlers in inversion conditions could help improve the quality of air in the short term.