Simple silicosis is the most common type of silicosis; it develops after at least 5 to 10 years of exposure to silica dust. Patients with simple silicosis are identified by abnormal opacities on chest x-ray, and they are usually asymptomatic. Pulmonary function studies are usually normal. [LaDou, p. 378-80] [Harber, p. 380] In a surveillance program of 5 states from 1994 to 2000, the CDC identified nine cases of silicosis among dental laboratory technicians. Cases of silicosis are now much less common in developed countries, but continue to be reported among sandblasters and hard rock drillers. Rom, p. 366-7] Medical surveillance examinations are recommended for workers exposed to silica dust at concentrations that are unknown or >0.05 mg/m3. [PMID 16404216
] "Silicosis deaths decreased nearly 6-fold from 1,065 in 1968 to 178 in 1998;" [See Hyperlink] Since 1995, about 30 deaths per year from silicosis have been reported among those of working age. [PMID 18626906
] ". . . we identified no clear threshold effect for cumulative exposure but for intensity of exposure. This finding is consistent with toxicologic considerations. Alveolar clearance mechanisms are assumed to operate on the instantaneously deposited amount of dust in the lungs. Thus, if there is a threshold effect caused by a clearance mechanism, it should be related to intensity of exposure and not to cumulative exposure." [PMID 24504246
] See "Silicosis, complicated" and "Silicosis, acute." See "Silica, crystalline."