IN the Mumbai kindergarten my son went to, the children never had to clean up after themselves; that was the servants’ job. So I really liked the school my son attended when we moved back to Brooklyn, where the teachers made the children tidy up at the end of the day. “Cleanup time, cleanup time!” my 6-year-old sang, joyfully gathering his scraps. It’s a wonderful American tradition: you always clean up the mess you made.

This is the 25th anniversary of the Bhopal gas disaster, an epic mess that started one night when a pesticide plant owned by the American chemical giant Union Carbide leaked a cloud of poisonous gas. Before the sun rose, almost 4,000 human beings capable of love and anguish sank to their knees and did not get up. Half a million more fell ill, many with severely damaged lungs and eyes.

An additional 15,000 people have since died from the aftereffects, and 10 to 30 people are said to die every month from exposure to the hundreds of tons of toxic waste left over in the former factory. But amazingly, the site still has not been cleaned up, because Dow Chemical, which since acquired Union Carbide, refuses to accept any responsibility. The groundwater is contaminated; children of the survivors suffer from genetic abnormalities; and the victims have long since run out of their measly compensation and are begging on the streets.

I have traveled to Bhopal and seen the post-apocalyptic devastation, seen the sick, seen the factory. Methyl isocyanate is a deadly chemical used to kill insects. The night that 40 tons of it wafted out of the factory is, for the survivors, a fulcrum in time, marking the before and after in their lives. They still talk about “the gas” as if it were an organism they know well  how it killed buffalo and pigs, but spared chickens; how it traveled toward Jahangirabad and Hamidia Road, while ignoring other parts of the city; how it clung to the wet earth in some places but hovered at waist level in others; how it blackened all the leaves of a peepul tree; how they could watch it move down the other side of the road, like a rain cloud seen from a sunny spot.