Nation IN BRIEF : INDIANA : Officials Puzzled Over Missing PCBs

Environmental Protection Agency officials say they’re stumped by the disappearance of PCBs from a hazardous waste site that once had high concentrations of the cancer-causing substance. Polychlorinated biphenyls, once used as insulators in electrical transformers, were banned by the federal government in the 1970s. They have not been known to break down in the environment and have been considered nearly impossible to destroy. But officials say an oil refinery site in Westville, Ind., that once contained more than triple the concentration of PCBs allowed by law now appears free of the contaminants. Officials said the leading theory is that high heat and low moisture during a long drought in 1988 combined to disintegrate the contaminants.