NEW DELHI (Reuters) – India’s top court on Wednesday upheld the ban on use of petroleum coke in and around New Delhi as the country battles to clean the air in its capital, one of the world’s most polluted cities.

India is the world’s biggest consumer of petroleum coke – a dirtier alternative to coal composed mainly of carbon – which emits 11 percent more greenhouse gases than coal, according to the Carnegie–Tsinghua Center for Global Policy. Burning it also emits several times more sulphur dioxide, which causes lung diseases and acid rain.

“Keeping in view the fact that pollution is increasing, we are not lifting the ban on use of petcoke and furnace oil in these industrial units in three states,” a top court bench headed by Justice Madan Bhimrao Lokur said in its order, referring to polluting units.

The ban, which covers the states of Rajasthan, Uttar Pradesh and Haryana, came into effect on Nov. 1.

Record levels of smog earlier this month in New Delhi and other major centers have piled pressure on the government to tackle a growing public heath crisis.

Sulphur-heavy petcoke and other cheap, highly polluting fuels such as furnace oil are widely used by cement factories, dyeing units, paper mills, brick kilns and ceramics businesses.

India’s annual demand for the fuel, which is more energy efficient than coal, has nearly doubled over the past four years to more than 27 million tonnes.

Indian health ministry data shows that respiratory issues killed about 10 people per day in the year ended March 2017 in the National Capital Region – a rapidly urbanizing and polluted area around New Delhi that is a third the size of New York state, but houses 2.5 times more people.

The continued ban on the sale and use of petcoke could hit the country’s small and medium scale industries, which employ millions of workers and operate on thin margins.