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In his final days, Luis G. Alvarez, a former New York City police detective, told family members that he was imagining himself walking and walking and walking. They asked him where.

“I’m on the pile,” Mr. Alvarez replied.

Shorthand for ground zero after the terror attacks of Sept. 11, 2001, the pile was where thousands of victims were buried in rubble. His time there would come to define Mr. Alvarez’s police career and transform him physically, likely causing the cancer that whittled his stocky frame to bone. He became the face — a grimly urgent one — of others like him in an emotional address to members of Congress last month.