Authorities in Iran’s capital Tehran and suburbs will close educational institutions two days a week as air pollution has reached a dangerous level in winter.

Tehran province governor’s office announced on Tuesday that measures were necessary to reduce pollution and protect citizens by closing all educational institutions and limiting commercial activities on Wednesdays and Thursdays each week.

Air pollution is a persistent problem in large Iranian cities, especially in cold and hot weather when more electricity is used and power stations resort to using heavy dirty diesel fuels because of natural gas shortages. Last winter, power plants had to be shut down prompting power cuts that led to some protests. The situation is expected to get worse in January and February.

Iran has the world’s second largest natural gas reserves, but consumption is much higher than in other countries while production remains flat due to lack of investment and new technologies.

Authorities have also banned operations of polluting industrial plants for two days a week and will clamp down on vehicles without a clean bill of health. Many private and large vehicles in Iran are old, using outdated technology as the government strictly limits imports of modern vehicles to support local manufacturing.