On Monday, Iranian President Masoud Pezeshkian said the government was forced to burn mazut, a highly polluting fuel, to prevent interruptions to household gas supplies this year.

"We were not supposed to burn mazut at all, and we announced this. But then we got stuck. If we hadn't used it, we would have had to cut off gas supplies to households, because our consumption is many times higher than in other countries. We were forced to," Pezeshkian said in a speech broadcast on state TV.

"In order to stop these problems from happening next year, we've started to create plans," he added, without providing further details.

Iran, one of the largest oil producers in the world, has faced a severe gasoline shortage since last summer. That shortage has prompted refineries to bulk out the fuel's volume with other substances, like mazut.

In November 2024, the government issued a decree ordering an increase in household gas tariffs and authorizing provinces to use mazut in all power plants and industries.

Despite repeated promises since to phase out the use of the highly polluting fuel oil in power plants, several reports suggest the practice has not stopped.

Tehran has also implemented rolling power cuts for residential and commercial areas this winter due to a severe shortage of natural gas, the primary fuel source for the country's power plants. The government initially presented the rolling blackouts as a necessary measure to avoid using mazut or diesel.

According to a 2023 report by Radio Farda, official Oil Ministry reports showed that the country intensified its use of mazut in December 2022 to 38.5 million liters per day, a 22 percent increase, and 42 million liters per day in January 2023.

Mazut, the non-standard gasoline contains harmful additives and has significantly contributed to the air pollution crisis in the country.

In 2023, UN special rapporteur on human rights and the environment David Boyd called on Iran to halt the practice, declaring it a human rights violation.

"Iran is burning mazut, one of the dirtiest fuels, to generate electricity. This produces massive volumes of toxic air pollution, which poisons millions of people in Iran, violating their human rights, including the right to a healthy environment. Iran must stop burning mazut!," the post on X read.

The use of the low-grade fuel mazut by power plants in Iran has been linked to severe harm to public health and even fatalities, with Iranians frequently expressing frustration over the worsening air quality and pollution in many cities.