For over a decade, workers at the Conwed factory in Cloquet, Minn., claim they unknowingly risked their health, causing some to develop lung abnormalities, while others lost their lives. Conwed, formerly known as the Wood Conversion Co., used asbestos in the production of its Lo-Tone mineral board and ceiling tile products, potentially exposing about 6,000 workers to the hazardous ingredient.