The Occupational Safety and Health Administration (OSHA) is in final preparations for a hazard communication related to a Occupational Exposure to Crystalline Silica. This rule will basically set standards for exposure to silica dust during blasting (and other operations) in confined work spaces. Inhalation of silica is generally considered to increase the risk of silicosis.
According the OSHA, in 2005 “silicosis was identified on 161 death certificates as an underlying or contributing cause of death. Exposure to crystalline silica has also been associated with an increased risk of developing tuberculosis and other nonmalignant respiratory diseases, as well as renal and autoimmune diseases.” The need for the exposure standard is the standardize monitoring, training for use with silica and compliance.
Of course, in an abrasive blasting environment the best way to avoid the hazards of silicosis is to use media that do not contain crystalline silica such as Crushed Glass Grit.