Tehran's Air Quality Control Unit said on Tuesday the Pollutant Standard Index (PSI) - a standard measurement incorporating carbon monoxide, dust and other pollutants - has hovered around the "very unhealthy" level of 160 for several days.
Such alerts are becoming increasingly common, with increased traffic causing the sprawling city's air to be deemed unhealthy for at least 100 days of the year. This week the situation is worse due to a total lack of wind.
"But you cannot just blame nature," Elmira Parto, a Tehran pollution official, told AFP. "It is the cars that are the problem."
Many of the two million plus vehicles in the city of 10 million are more than 20 years old and consume cheap subsidised petrol at an alarming rate. Private car ownership has also exploded, with the public transport system failing to provide adequate coverage.
The government has proposed various steps to resolve the problem, such as phasing out the old cars and restricting vehicle use on certain days of the week - but so far none have been effectively applied.
"There's a huge demand for pain killers and anti-histamines at the moment. People are suffering from chronic headaches, allergies and nose irritation"
"There's a huge demand for pain killers and anti-histamines at the moment. People are suffering from chronic headaches, allergies and nose irritation," said Mahsa Vosouqi, a local pharmacist.
Anti-asthmatic inhalers and face masks, manufactured locally and on open sale in most chemists, have also been selling out.
And Tehran's Darabad hospital, which specialises in respiratory ailments, said the number of visiting outpatients has tripled in recent days.
According to a recent study, each resident of Tehran - now considered one of the world's most polluted cities - inhales an estimated 7.1 to 9.3kg of dust every year.