SILICOSIS

SILICOSIS

• Is a chronic diffuse interstitial lung disease caused by fibronodular long-term inhalation of dust containing free silica crystalline
• Dry mineral particles of respirable, size 0.1 to 10 µm aerodynamic diameter, usually complexed with oxygen to form silica (SiO2)
• Silica (SiO2) occurs in crystalline forms and in amorphous forms
• Among crystalline polymorphs, quartz (the most abundant) and is the form usually assosiate with human disease
• Cristobalite and trydimite are less common but are more biologically active on equal weight basis and can cause disease appropriate exposure
• Stishovite and coesite appear to be less toxic

TRYDIMITE

• Formula: SiO 2
• System: Triclinic
• Colour: Colourless, white
• Vitreous Lustre:
• Hardness: 6½-7
• Name: From the Greek "Tridymos", triplet, alluding to its common twinning as trillings.
• Polymorphn of: Coesite, Quartz, Cristobalite, Stishovite

 The surface properties of the particles "appears to be critical in conferring the biological properties of crystalline silica

SILICOSIS

• May be associated with chronic indolent tuberculosis (silicotuberculosis) in:

hard rock miner, coal miners, granite workers, and other industrial workers.

• Increased risk for development of lung cancer.

Silica potentiates the growth of m. Tuberculosis in macrophage cultures in vitro, but the organism also grows in such cell culture without the addition of dust. Macrophage recovered from human workers exposed to silica and from animal models to demonstrate normal silicosis phagocytosis and killing of recurrent pyogenic bacteria. It is possible that the immune-inflammatory responses that characterize silicosis create locations in which cell agregate, and that these cells are particularly susceptible to infection by Mycobacteria. Respond well to conventional antituberculosis therapy. Reactivation following an apparent cure is common in silicotuberculosis. For these reason many expers recommended multidrug treatment of silicotuberculosis.

Health Effects Of Silica Exposure Relateds To Silicosis:

1. Chronic nodular silicosis

first recognized as a radiographic abnormality (Eggshell calcification of the hilar nodes)

2. the PMF (Progressive Massive Fibrosis)

produce severe restriction, loss of pulmonary compliance, hypoxemia

3. Accelerated silicosis

relatively rare but can developed in 2 to 5 years.

4. Acute silicosis

rapidly progressive dyspnea and respiratory insuffisiency.

Chronic Nodular Silicosis

SILICOSIS – EGGSHELL CALSIFICATION

SILICOSIS

Bronchoalveolar Lavage

• Increased number of alveolar macrophage, IL-1, fibronectine
• Macrophage, lymphocytes, neutrophils, fibroblasts, mast cells, alveolar epithelium

CT-scan of the thorax

Silicosis in a 56-year-old man

who worked for 25 years as

a stonecutter.