Bhola, 36, worked at a construction site in Delhi—the kind of job that didn’t ask much of a résumé but took a toll on his lungs. The air he breathed on a routine workday was thick with particulate matter—PM2.5 and PM10, to be precise. The city, a place where smog rises with the sun and hangs low till dusk, had claimed another victim. He died of a heart stroke. Doctors pointed to the usual culprits—prolonged exposure to dirty air, the kind that creeps in quietly and stays. The kind that kills early and often. Millions more have died in much the same way, in a country of 1.46 billion where air pollution continues to be both an open secret and a silent killer.