Lawyers who are veterans of the wave of asbestos litigation have begun to file more and more lawsuits contending that their clients are suffering from exposure to silica. But while the lawyers say they are zeroing in on another potentially lethal substance, their opponents counter that there is no medical crisis...Silica — for the most part, highly purified quartz — is used to make glass, fiberglass, paints and ceramics, as well as in foundry casting. [refers to lawsuits against U.S. Silica, Bechtel, Ingersoll Rand, Lockheed Martin]