Air pollution in Delhi can't become a political battle, the Supreme Court said today, stressing that the choking air quality is responsible for the "murder of people's health". The court said the burning of crop residue in neighbouring states Punjab, Haryana, Uttar Pradesh and Rajasthan is a key factor behind the massive spike in Delhi's air pollution every winter. It asked the state governments to take steps to stop stubble burning. "We want it stopped. We don't know how you do it, it's your job. But it must be stopped. Something has to be done immediately," the court told the Punjab government lawyer.