Miners carried asbestos home on their clothes; vermiculite used to cover school running tracks in Libby; and some residents used vermiculite as mulch in their home gardens.
The company and its one-time heads were accused of knowingly endangered the lives of mine workers and other residents of Libby, and ignoring warnings by state agencies to clean up the vermiculite mining operation. They were also accused of Clean Air Act violations and obstruction of government efforts to address problems in Libby.
W.R. Grace released a statement saying the company was "gratified" with the verdict.
"We always believed that Grace and its former executives had acted properly and that a jury would come to the same conclusion when confronted with the evidence," the statement said.
Charges against two executives were dropped during the trial at the request of prosecutors. The jury then acquitted Henry Eschenbach, Jack Wolter and Robert Bettacchi.
"I'm grateful and happy to go home," said Wolter, who is retired and lives in Palm Desert, Calif.
Gayla Benefield of Libby, who suffers health effects from asbestos exposure and lost both parents to asbestos-related lung diseases, said she doesn't know what the next step will be.
"They have gotten away with murder. That's all I can say," she said.
Another defendant in the case, Grace in-house lawyer O. Mario Favorito, was scheduled for trial in September. Grace also faces civil cases in which hundreds of Libby residents seek compensation for health problems.
The company knew about the health hazards of asbestos, but covered it up "so they could continue making money as well as avoid liability," Assistant U.S. Attorney Kris McLean said during Wednesday's closing arguments.
