BASIC INFORMATION ON RESPIRATORY FIBROGEN
What are Respiratory fibrogens?
The hazard of particulate matter is influenced by the toxicity and size and morphology of the particle. Figure below gives typical particle size ranges for particles from various sources.
The critical size of dust (and aerosol) particles is 0.5 to 7 μm, since these can become deposited in the respiratory bronchioles and alveoli.
If dust particles of specific chemicals, e.g. silica or the various grades of asbestos, are not cleared from the lungs then, over a period, scar tissue (collagen) may build up; this reduces the elasticity of the lungs and impairs breathing.
The characteristic disease is classified as pneumoconiosis. Common examples are silicosis, asbestosis, coal pneumoconiosis and talc pneumoconiosis.
An appreciation of the composition and morphology of the dust is important in the assessment of hazard.
Thus, among silica-containing compounds, crystalline silicates and amorphous silicas (silicon dioxide) are generally not considered fibrogenic, whereas free crystalline silica and certain fibrous silicates such as asbestos and talcs can cause disabling lung diseases.
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