Silica occurs in both crystalline and amorphous forms. Quartz is the most common crystalline form, and it causes most cases of silicosis. [Harber, p. 373] Exposure to crystalline silica (alpha-quartz and cristobalite) is associated with lung fibrosis (silicosis) and increased risk of lung cancer. [ACGIH] Classic silicosis is caused by low to moderate silica exposure for 20 years or more. Disabling complications include tuberculosis and progressive massive fibrosis. Diagnosis is made by 1.) history of sufficient exposure; 2.) x-ray findings of silicosis; and 3.) absence of miliary tuberculosis and fungal infections. Open lung biopsy is usually not necessary. [Rom, p. 371] "The possible association of silica and glomerulonephritis is suggested by animal studies, case-control studies, and multiple case reports."[LaDou, p. 422] "Overall the evidence is still too sparse to be summarized as conclusive, but it seems very probable that silica causes kidney disease." [
PMID 15940719] Silica-associated kidney disease was not detected in a study of 4 million death certificates of US workers for the period from 1982 to 1995. [
PMID 12554850] While the studies of cohorts exposed to silica found elevated SMRs for renal disease, no clear evidence of a dose-response relationship emerged." [
PMID 28409224] "Low grade silicosis cannot be excluded in workers with normal chest radiographs (ILO 0/0). In relatively highly exposed construction workers, a sevenfold increased risk of simple (nodular) silicosis was found. Emphysema on HRCT was associated with current or former smokers, but not with exposure, and contributed to reduced diffusion capacity. Airflow limitation was mainly determined by current smoking and was not associated with simple (nodular) silicosis." [Reference #2] See "Respirable crystalline silica exposure-response evaluation of silicosis morbidity and lung cancer mortality in the German porcelain industry cohort." [
PMID 21346639] "The absence of an excess mortality from lung cancer does not support the hypothesis of an association between silica exposure and the development of lung cancer, in the absence of silicosis." [
PMID 28691999] See "Silicosis, simple."