TEHRAN, Iran — Already battered by international threats against their nation’s nuclear program, sanctions and a broken economy, Iranians living here in the capital are now trying to cope with what has become an annual pollution peril: a yellowish haze that engulfs Tehran this time of year.

For nearly a week, officials here and in other large cities have been calling on residents to remain indoors or avoid downtown areas, saying that with air pollution at such high levels, venturing outside could be tantamount to “suicide,” state radio reported Saturday.

On Sunday, government offices, schools, universities and banks reopened after a government-ordered shutdown for five days to help ease the chronic pollution. Tehran’s normally bustling streets were largely deserted.

Residents who dare to go outside cover their mouths and noses with scarves or surgical masks, but their eyes tear up and their throats sting from the mist of pollutants, which a report by the municipality of Tehran says is made up of a mixture of particles containing lead, sulfur dioxins and benzene.

“It feels as if even God has turned against us,” Azadeh, a 32-year-old artist, said on a recent day as she looked out a window in her apartment that often offers a clear view of Tehran, a sprawling city that is home to millions.

The haze of pollution occurs every year when cold air and windless days trap fumes belched out by millions of cars and hundreds of old factories between the peaks of the majestic Alborz mountain range, which embraces Tehran like a crescent moon.

Iran is prominently represented in the World Health Organization’s 2011 report on air quality and health, with three of its provincial towns among the organization’s list of the world’s 10 most-polluted cities. The report says Tehran has roughly four times as many polluting particles per cubic meter as Los Angeles. Many cities known for their poor air quality, like Mexico City, Shanghai and Bangkok, are all cleaner than Tehran.

But since 2010, when American sanctions on Iranian imports of refined gasoline began to bite, the situation has grown worse, according to the report by the municipality of Tehran.

Faced with possible fuel shortages, Iran surprised outsiders by quickly making up for the loss of imports by producing its own brew of gas. While the emergency fuel kept vehicles running, experts warned it was creating much more pollution.

The pollution caused by the use of the emergency fuel concoction has been a taboo subject here, as officials try to portray each measure to counter the economic sanctions as a success.

On state television, several officials have denied that the haze has anything to do with the locally produced gas.

Meanwhile, the government has imposed strict traffic regulations in Tehran, Isfahan and other major population centers. An odd-even traffic-control plan based on the last digit of vehicle license plates keeps about half of the approximately 3.5 million cars in Tehran off the streets on a daily basis.