Air pollution killed more Indians last year than any other risk factor, and Delhi is among the most polluted cities in the country. But the burden is unequally shared. Children from poor families in Delhi spend more of their lives outdoors. Their families are more likely to use wood-burning stoves, which create soot. They can't afford the air filters that have become ubiquitous in middle-class homes. And often, they don't even think much about air pollution, because they face more pressing threats, like running out of food. Joshua Apte, a pollution scientist at the University of California, Berkeley, helped with The New York Times study's research design, showing that pollution can shave years off a child's life.