Dust containing crystalline silica is highly fibrogenic. It is far more dangerous than coal dust. A worker with 30 g of coal dust in his lungs may be asymptomatic and perfectly well whereas only 3 g of silicon dust in a worker's lung may cause extensive fulminating fibrosis, respiratory failure and death.
- silicosis is caused by inhalation and deposition of large amounts of crystalline silica over time (1)
- when silica dust is inhaled, the particles deposit within the distal airways
- macrophages ingest these particles and initiate an inflammatory response by releasing proinflammatory molecules such as tumor necrosis factor, interleukin-1, and other cytokines - this inflammatory response often leads to the formation of nodular lesions and tissue fibrosis
Silicotic nodules have concentric whorls or densely arranged collagen fibres with a variable amount of hyaline change
- silicosis is characterized by fibrotic nodules with concentrically arranged collagen fibers, central hyalinization, and fibrotic lesions
Macrophages and alveoli may also contain silica.
The heaviest infiltration of silica in alveoli is seen in the most proximal alveoli that open off the respiratory bronchioles.
Notes (3):
- in the health context, silica usually refers to respirable crystalline silica dust, respirable dust being the fine particles, usually invisible to the naked eye and mostly smaller than 7 microns in diameter
Reference:
- Sato T et al. Silicosis and lung cancer: current perspectives. Lung Cancer: Targets and Therapy 2018; 9: 91-101.
- Leung CC et al.Silicosis. Lancet 2012; 379 (9830): 2008-2018.
- Rees D, Murray J. Silica, silicosis and tuberculosis.Int J Tuberc Lung Dis 2007;11(5):474-484