Sadly, the effort to update OSHA's silica dust regulation, first issued in 1971, is not done more than 15 years after this campaign began. Each year, more than 250 American workers die with silicosis. Silicosis is an incurable lung disease caused by inhalation of dust that contains free crystalline silica. Overexposure to dust that contains microscopic particles of crystalline silica can cause scar tissue to form in the lungs, which reduces the lungs ability to extract oxygen from the air we breathe. Inhalation of crystalline silica, the second most common mineral in the earth's crust, can lead to chronic, accelerated or acute silicosis and is associated with bronchitis and tuberculosis. Some studies also indicate an association with lung cancer. Those who remove paint and rust from buildings, bridges, tanks and other surfaces; clean foundry castings; mine through rock; crush stone or work with clay; etch or frost glass; and work in construction are among those at risk of overexposure to crystalline silica. The earliest recorded cases of silicosis date back to the first century A.D. In the mid 1930s, labor secretary Frances Perkins launched a nationwide effort to tackle the problem of silicosis.