Air pollution in Tehran has left 4,460 people dead in a year, an Iranian health official said in reports Sunday, with another sounding the alarm over high dose of carcinogens in domestically-made petrol.

Hassan Aqajani, an adviser to the health minister, made the announcement on state television, and said the Tehran residents died in a year-long period since March 2011.

High air pollution is a constant woe for the eight million residents in Tehran. It forced the city's closure on Saturday, the second time in a month.

"In recent days, the number of patients who have visited Tehran hospitals with heart problems has increased by 30 percent," Aqajani said.

Tehran's pollution is mainly blamed on bumper-to-bumper traffic in a city wedged between two mountains which trap fumes. But major Iranian cities also struggle with pollution on a seasonal basis.

Pollution is also exacerbated by increasing reliance on domestic production of petrol of a lower grade, and therefore more polluting, a byproduct of Western sanctions on Iran's fuel imports.

Youssef Rashidi, director of Tehran's air quality monitoring services, on Sunday warned carcinogens in Iranian-made petrol is higher than international standards.

"Based on Euro 4 standard the amount of carcinogens in petrol should be less than one percent but the level of our domestically-produced petrol is between two and three percent," Rashidi said in remarks reported by Bahar daily.

The level of sulfur in the petrol is three times higher than the standard, he said.

Iran produces around 60 million litres of petrol on a daily basis, corresponding roughly to its national consumption, according to figures from the oil ministry.

Officials have promised to increase the production of higher grade petrol with Euro 4 and 5 standards, used in European countries, from nine million litres per day to around 25 million by March 2013.