The air in the Iranian capital of Tehran has gotten so hazardous, the government is now canceling school, banning outdoor sports, and urging all who can to stay inside.

Tehran's air quality index hovered around 159 on Wednesday — which is more than three times the World Health Organization's advised maximum of between 0 and 50. Iranian media reported that in an area in northeastern Tehran, the index rose as high as 238. With pollution that bad, WHO advises that people in Tehran avoid breathing outside air unless they absolutely have to.

The crisis is nothing new. For the past 18 days pollution levels in Iran's capital city have been dangerously high, forcing many to wear masks or avoid going outdoors. And for the past six years, the air quality in Iran has gotten worse. This is largely because US sanctions against Iran have limited its supply of refined fuel, forcing the country to burn low-quality diesel. Tehran authorities reported last year that 270 people die daily of respiratory disease, heart trouble, and other pollution-related sicknesses.

The crisis is not limited to the capital city. The semi-official Iranian Student News Agency reported on Wednesday that state meteorologists are now predicting that pollution could cause acid rain in Isfahan, Iran's third largest city.

Earlier this year, VICE News spoke to Sepideh, a nurse the southwestern city of Ahwaz, who reported dangerously high pollution levels there as well. According to WHO, Ahwaz is the most polluted city on earth.

"During the winter we deal with thousands of elderly patients with heart and respiratory problems from the pollution, and asthma cases in children are also rising," Sepideh said last January. "The situation has become much worse since Iran started producing so much domestic gasoline. You can even smell it is different than before."

Emissions from vehicles contribute roughly 80 percent of the air pollution in Iran. A combination of overcrowded roads, low fuel quality, and poor emission standards has created perfect storm, plunging Tehran into a toxic cloud of exhaust and fumes.

David Michel, a non-resident fellow at the Stimson Center, singles out lax vehicle requirements as a major cause for the crisis.

"The roadways in Tehran have the capacity for less than a million cars, but there are more are 3.5 to four million cars in the city now," he explained. "The stock of cars is older and doesn't have the emission control technologies that you'll find in the US or other Western countries."

Though an official up-to-date tally of the cost of pollution is hard to come by, in 2012 Iran's Health Ministry estimated that poor air quality contributed to the premature deaths of 4,500 people in Tehran and about 80,000 across the nation.

On Wednesday, President Hassan Rouhani emerged from a cabinet meeting pledging to do something about the crisis. His cabinet had made "urgent and short-term decisions" to address dangerous air pollution, Rouhani told the Iranian media after meeting with his top advisors, though he did to elaborate on any specific policies adopted.

Just last month, Ayatollah Ali Khamenei, Iran's supreme leader, issued a 15-point list of policy suggestions on how the government should confront what's become an environmental crisis. He directed Rouhani to develop policies that would criminalize pollution and promote green energy industries.

As the pollution crisis intensifies, members of the country's political class are pointing fingers at each other, with different branches of government blaming others for the filthy air.

A clean air bill is currently being considered by Iran's parliament, the Majlis, but it has been stalled for nearly two years. Over 100 parliamentarians penned a letter to Rouhani on Monday urging him to take action. The head of Iran's environmental protection organization, the well-known reform politician Massoumeh Ebtekar, then fired back at parliament on Wednesday, telling state news agencies that conservative Majlis speaker Ali Larijani should speed up parliamentary review of clean air laws.

"I called on the speaker to put the clean air bill on the Majlis' agenda as a priority," she said. "Unfortunately, it has yet to be reviewed."

Mohammad Bagher Ghalibaf, the conservative mayor of Tehran, criticized others for "politicizing" the issue.

"We understand the issue of air pollution," he told reporters on Wednesday. "There is no lack of laws to resolve it; our problem is the implementation of the laws."

That view seemed to contradict Ebtekar, who blamed the pollution on a lack of specific emissions standards.

"One factor that intensifies air pollution is that the first emission test of newly-manufactured cars is carried out only five years after the purchase of the car," she said on Wednesday. "This interval is too long."

As the politicians bickered, daily life in Tehran ground to a halt. Iran's premier soccer league postponed two games over the weekend, and certain parts of the city were closed to cars. Vehicles with plates ending in an odd number are not allowed to drive on Saturday, Monday, and Wednesday; cars with even-numbered plates are banned on Sunday, Tuesday, and Thursday.

City officials also ordered most schools to shut their doors.