IN THE EARLY HOURS OF 3 DECEMBER 1984, clouds of toxic gasses from a runaway chemical reaction started pouring out from a pesticide plant operated by the American multinational Union Carbide in Bhopal. The gasses, many heavier than the surrounding air, stayed close to the ground, and the wind took them southeast, smothering large swathes of the sleeping city. Bhopal was home to approximately 900,000 people at the time; over half a million were exposed to the toxins. By Union Carbide’s count, 3,828 people were killed that night, though other estimates place the number at no lower than eight thousand. The death toll to date is thought to stand at about 25,000. Over 120,000 people still suffer from disorders caused by the disaster, and by industrial pollution at the site, which now stands abandoned. This December marks thirty years since the gas leak, considered the worst industrial disaster in history.

Several officers of Union Carbide’s Indian subsidiary have since been tried and sentenced for their roles in the explosion, and numerous civil and criminal cases against Union Carbide—now owned by the Dow Chemical Company—are still pending before Indian courts. Warren Anderson, the chairman and CEO of Union Carbide at the time of the disaster, never answered charges filed against him; he died this September in the United States, which repeatedly denied requests by Indian officials for his extradition.

The disaster was extensively documented by reporters, photographers and television crews. The most iconic image of the tragedy remains the photojournalist Pablo Bartholomew’s shot, taken in the days after the explosion, of a dead child partly buried under rubble, its mouth half open as a living hand brushes dirt from its ashen face. Thousands of other disturbing images have emerged from Bhopal since, as photographers have documented the continuing social and physiological impacts of the disaster.