The Indian government ordered diesel generators and a power plant in Delhi to be shut down on Tuesday as air quality in the capital deteriorated ahead of the Hindu festival of lights, when a night of firecrackers sends pollution levels rocketing.

Under a plan that imposes anti-pollution measures when air quality drops below a certain level, the Environment Pollution (Prevention and Control) Authority (EPCA) also ordered some brick kilns to close and the burning of rubbish to stop.

With Delhi’s air already in the “very poor and severe” category, the measures will stay in place until March to prevent pollution levels from rising.

Many richer residents of Delhi have diesel generators as a back-up during regular power supply disruptions.

Emergency services like hospitals will not be forced to shut down their generators.

“Delhi has a long way to go before it can lay claim to having reasonably clean and breathable air,” Sunita Narain, an EPCA member and director general of the Centre for Science and Environment, a Delhi-based thinktank, said in a statement.

Air pollution in Delhi has become a major public policy issue in recent years as residents wake up to the life-threatening implications of breathing air frequently ranked among the world’s most toxic.

Indian courts have taken up much of the role in trying to clean the air, although enforcement of the various bans and restrictions has proven difficult.

Last week the Supreme Court temporarily banned the sale of firecrackers in and around Delhi ahead of Diwali, the Hindu festival of lights, as it looks to prevent a repeat of severe air pollution that forced school closures last year.

Diwali falls on October 19 this year.

Last November, about a million children were forced to stay home from school and thousands of workers reported sick as New Delhi struggled with its worst pollution for nearly 20 years.

Vehicle emissions and dust from construction sites were the factors blamed for that spike, besides firecrackers and crop burnings.

India and China together accounted for more than half of the 4.2 million deaths attributable to air pollution worldwide in 2015, a study by the US-based Health Effects Institute showed.

The closure of Delhi’s Badarpur thermal power plant is one of the actions required when the air quality turns very poor by the government’s Graded Response Action Plan (GRAP), which came into force in January.

Power plants in neighboring states will also be monitored for pollution levels.