Slice of a lung affected by<unk>  When small silica dust particles are inhaled, they can embed themselves deeply into the tiny alveolar sacs and ducts in the lungs, where oxygen and carbon dioxide gases are exchanged. There, the lungs cannot clear out the dust by mucus or coughing. When fine particles of crystalline silica dust are deposited in the lungs, macrophages that ingest the dust particles will set off an inflammatory response by releasing tumor necrosis factors, interleukin-1, leukotriene B4 and other cytokines. In turn, these stimulate fibroblasts to proliferate and produce collagen around the silica particle, thus resulting in fibrosis and the formation of the nodular lesions. The inflammatory effects of crystalline silica are apparently mediated by the NLRP3 inflammasome. Characteristic lung tissue pathology in nodular<unk>  consists of fibrotic nodules with concentric "onion-skinned" arrangement of collagen fibers, central hyalinization, and a cellular peripheral zone, with lightly birefringent particles seen under polarized light. The silicotic nodule represents a specific tissue response to crystalline silica. In acute<unk> , microscopic pathology shows a periodic acid-Schiff positive alveolar exudate (alveolar lipoproteinosis) and a cellular infiltrate of the alveolar walls. Silica Silicon (Si) is the second most common element in the Earth's crust (oxygen is the most common). The compound silica, also known as silicon dioxide (SiO2), is formed from silicon and oxygen atoms. Since oxygen and silicon make up about 75% of the Earth's crust, the compound silica is quite common. It is found in many rocks, such as granite, sandstone, gneiss and slate, and in some metallic ores. Silica can be a main component of sand. It can also be in soil, mortar, plaster, and shingles. The cutting, breaking, crushing, drilling, grinding, or abrasive blasting of these materials may produce fine to ultra fine airborne silica dust. Silica occurs in 3 forms: crystalline, microcrystalline (or cryptocrystalline) and amorphous (non-crystalline). "Free" silica is composed of pure silicon dioxide, not combined with other elements, whereas silicates (e.g., talc, asbestos, and mica) are SiO2 combined with an appreciable portion of cations. * Crystalline silica exists in 7 different forms (polymorphs), depending upon the temperature of formation. The main 3 polymorphs are quartz, cristobalite, and tridymite. Quartz is the second most common mineral in the world (next to feldspar). * Microcrystalline silica consists of minute quartz crystals bonded together with amorphous silica. Examples include flint and chert. * Amorphous silica consists of kieselgur (diatomite), from the skeletons of diatoms, and vitreous silica, produced by heating and then rapid cooling of crystalline silica. Amorphous silica is less toxic than crystalline, but not biologically inert, and diatomite, when heated, can convert to tridymite or cristobalite. Silica flour is nearly pure SiO2 finely ground. Silica flour has been used as a polisher or buffer, as well as paint extender, abrasive, and filler for cosmetics. Silica flour has been associated with all types of<unk> , including acute<unk> .<unk>  is due to deposition of fine respirable dust (less than 10 micrometers in diameter) containing crystalline silicon dioxide in the form of alpha-quartz, cristobalite, or tridymite.
Silicosis
Asbestosis
Coalworker's pneumoconiosis
Beryllium granuloma
Asbestos-related diseases
Occupational asthma
Pneumoconiosis
Organic dust toxic syndrome