With some limited exceptions, drywall or sheet rock itself is not an asbestos-containing product. Health hazards from asbestos exposure came from handling and using asbestos-containing joint compound to finish the seams between sheets of drywall. Joint compound manufacturers used asbestos to keep the compound from cracking when it dried. Even though other materials were available to serve this same purpose, asbestos was the cheaper alternative. Joint compound manufacturers continued to incorporate asbestos into joint compound products well into the late 1970s, and these manufacturers failed to warn that it could cause deadly diseases, including mesothelioma and lung cancer.
Asbestos is hazardous to human health if it is respirable and in any form that it is dry and dusty and capable of entering the body through the mouth or nose. Joint compound is particularly dangerous in four steps of the drywall finishing process: (1) setup; (2) mixing; (3) sanding; and (4) clean up. A tremendous amount of dust is created as the joint compound moves from a dry form to its mixture with water. It also becomes airborne and creates dust when it is sanded and swept. Ready mix joint compound, which comes pre-mixed, is equally as dangerous as its dry counterpart during the sanding and clean-up phases.