Companies battling lawsuits brought by people claiming injuries caused by exposure to asbestos or silica have long contended that they are the victims of fraud. The companies finally have evidence that their concerns may be real. Thousands of people who have said they were injured by one potentially lethal material are apparently double-dipping - now asserting separately that they were injured by the other. More than half the plaintiffs in a federal lawsuit in Texas seeking compensation for exposure to silica - used in making glass, paint, ceramics and other materials - previously filed claims against a trust set up...