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.

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.

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.

He studied environmental and occupation health at Rutgers University.