Delhi’s unique experiment to curb air pollution by alternately allowing odd- and even-numbered cars on its roads has vital lessons for the rest of India. Bad air is the fifth leading cause of death across this land. Each year, six lakh people perish because of what we breathe in; thousands of children grow up with serious respiratory diseases. In the national capital, air quality is 10 times worse than the standards set by WHO. Similarly, in Pune air pollution has shot up by 35 per cent in the last five years. Five other cities—Patna, Lucknow, Agra, Raipur and Varanasi, the prime minister’s constituency—have pollution levels higher than what WHO prescribes. Twenty-three other cities, including Ahmedabad, Kanpur, Chennai and Bangalore are borderline cases. That makes the Delhi experiment—and its success—crucial, since we are dealing with a national emergency. Because so far, only Delhi has earnestly taken up damage control, and while it is a small step, that it has worked somewhat is encouraging.