<P> Researchers analyzing the event have focused likely blame on pollutants from the zinc plant, whose emissions had killed almost all vegetation within a half - mile radius of the plant . Dr. Devra L. Davis, director of the Center for Environmental Oncology at the University of Pittsburgh Cancer Institute, has pointed to autopsy results showing fluorine levels in victims in the lethal range, as much as 20 times higher than normal . Fluorine gas generated in the zinc smelting process became trapped by the stagnant air and was the primary cause of the deaths . Further research was conducted by Mary Amdur about the effects of the smog; she was pressured to withdraw publication of these results but refused to be bowed . </P> <P> Preliminary results of a study performed by Dr. Clarence A. Mills of the University of Cincinnati and released in December 1948 showed that thousands more Donora residents could have been killed if the smog had lasted any longer than it had . </P> <P> Lawsuits were filed against U.S. Steel, which never acknowledged responsibility for the incident, calling it "an act of God". While the steel company did not accept blame, it reached a settlement in 1951 in which it paid about $235,000, which was stretched over the 80 victims who had participated in the lawsuit, leaving them little after legal expenses were factored in . Representatives of American Steel and Wire settled the more than $4.6 million claimed in 130 damage suits at about 5% of what had been sought, noting that the company was prepared to show at trial that the smog had been caused by a "freak weather condition" that trapped over Donora "all of the smog coming from the homes, railroads, the steamboats, and the exhaust from automobiles, as well as the effluents from its plants ." U.S. Steel closed both plants by 1966 . </P> <P> By 1949, a year after the disaster, the total value of the predominantly residential property in Donora had declined by nearly 10% . </P>

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