Financial Tribune- Tehran's air quality, which deteriorated on Saturday following a short respite on Friday, is expected to last until Monday morning.

Despite wind speed picking up, it will not be enough to have an impact until at least Sunday evening, ISNA reported, quoting the Tehran Air Quality Control Company.

Tehran's air quality index was 139 on Saturday, meaning sensitive groups (children, the elderly, pregnant women and people suffering from cardiovascular and respiratory diseases) should stay indoors. Every year with the drop in temperature in winter, a phenomenon known as temperature inversion occurs during which cold air underpins warm air at higher altitude, leading to the entrapment of air pollutants in the city, which causes heavy smog.