Leobardo Segura Meza, 27, of Pacoima suffers from silicosis, an incurable lung disease that has been afflicting workers who cut and polish engineered stone high in crystalline silica. (Mel Melcon / ...

Inside the row of workshops in an industrial stretch of the Pacoima neighborhood in Los Angeles, men labored over hefty slabs of speckled stone, saws whining over the sounds of Spanish-language rock.