silicosis (sĭlĭkōˈsĭs) [key], occupational disease of the lungs caused by inhalation of free silica (quartz) dust over a prolonged period of time. Free silica is dispersed in the air and inhaled by workers engaged in the mining of lead, hard coal, and gold, in cutting sandstone and granite, in sandblasting, and in the manufacture of silica abrasives. The irritative action of the silica in the lung results in the formation of nodular lesions; these may coalesce and form massive areas of fibrous tissue. In advanced cases patients experience difficult breathing, coughing with sputum, chest pain, and a tendency to develop tuberculosis or repeated attacks of pneumonia. Once fibrosis has developed there is no cure, and treatment is directed at the management of symptoms. Preventive measures adopted in industries where the hazard of silicosis exists have greatly reduced its incidence.