Silicosis is the chronic fibrosing disease of the lungs produced by the prolonged and extensive exposure to free crystalline silica dust. When workers inhale crystalline silica (dust), the lung tissue reacts by developing fibrotic nodules and scarring around the trapped silica particles. This fibrotic condition of the lung is called silicosis. If the nodules grow too large, breathing becomes difficult and death may result. Silicosis victims are also at high risk of developing active tuberculosis. More than one million U.S. workers are exposed to crystalline silica, and each year hundreds of these workers die from silicosis. Silicosis treatment is very limited as there is no cure for the disease, but it is 100 percent preventable if employers, workers, and health professionals work together to reduce exposure.

Pneumoconiosis is the general term for lung disease caused by inhalation of mineral dust. Silicosis is a fibronodular lung disease caused by inhalation of dust containing crystalline silica (alpha-quartz or silicon dioxide), which is distributed widely, or its polymorphs (tridymite or cristobalite), which are distributed less widely.Silica-related diseases are associated only with crystalline-free silica. The most common examples of crystalline-free silica are beach or bank sands. A third form of free silica is fused silica which is produced by heating either the amorphous or crystalline forms. Other forms include cristobalite and tridymite. Workers exposed to silica dust are often exposed to asbestos as well and many will develop asbestos lung diseases including a rare lung disease called mesothelioma.