New York ? A retired 34-year-old New York City police detective who spent hundreds of hours searching for Sept. 11 victims at ground zero died Thursday of a respiratory disease related to the cleanup, union officials said.

James Zadroga is believed to be the first emergency responder to die as a result of exposure to World Trade Center dust and debris, said Michael Palladino, president of the Detectives’ Endowment Assn.

Zadroga had developed black lung disease and mercury on the brain as a result of working at ground zero, Palladino said. Palladino said Zadroga had worked up to 16 hours a day in rescue and recovery efforts the first month after the Sept. 11, 2001, collapse of the trade center towers.

He developed shortness of breath and other respiratory problems in the months after the attacks, and retired on disability in 2004.