NEW YORK (CBSNewYork) — A prominent scientist who studied the health effects of the material found after 9/11 has died.

Paul Lioy died Wednesday after collapsing at Newark Liberty Airport. The cause of his death has not been determined, his wife told The New York Times.

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Lioy was 68.

He was an environmental scientist who studied the dust at Ground Zero, WCBS 880’s Peter Haskell reported. Lioy determined a link between that material and responders’ illnesses.

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He spoke about his findings in an interview with the 9/11 Museum.

“So you had the cement, the fibers and the high pH, all which can contribute to irritation,” he said.

Lioy compared the toxic material to Drano.

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He studied environmental and occupation health at Rutgers University.