Silicosis

Occupational medicine

Silicosis is a chronic diffuse interstitial fibronodular lung disease caused by long-term inhalation of dust containing free silica.

For silicosis to develop, it requires a long time high-dose exposure to silica. Silica is a natural mineral that represents the major component of most rocks and soils. Silica (silicon dioxide, SiO2) is formed of two atoms of oxygen and one of silicon (Si). It occurs in several crystalline forms (more or less biologically able to cause silicosis) and also amorphous non-crystalline forms (glass - nonfibrogenic).

Exposure to silica dust occurs in numerous industries, occupations and environments, mainly in occupations associated with removal of stones, processing stones or sand, abrasive use of silica or sand, production of fine silica powder or utilization of sand or silica powder.
In order to diagnose silicosis, an occupational medicine physician will consider the history of sufficient exposure to silica and the chest radiograph showing small opacities consistent with the disease, excluding other concomitant similar illnesses.

The clinical signs are not characteristic, often auscultation is quite normal despite advanced silicosis. In an advanced stage of silicosis, the patient presents a pattern of mixed obstruction and reduction in lung volumes. The massive, progressive fibrosis will lead to severe restriction, loss of pulmonary compliance and hypoxemia.

The chest radiograph is required to show the characteristic abnormalities of small rounded opacities diffusely scattered mostly in the upper lobes and enlargement of hilar and mediastinal lymph nodes with peripheral calcification (so-called eggshell calcification).

At this time, there is no specific standard therapy for silicosis, although many strategies have been proposed and tried.

The prevention of workplace silica exposure plays the central part in silicosis management and a variety of measures to control and reduce silica exposure have been developed, by reducing respirable silica in the air and isolating workers from air with high content silica dust.

Reference for this article: G. S. Davis - "Silicosis", chapter in D.J. Hendrick, P.Sherwood Burge, W.S.Beckett, A.Churg - "Occupational Disorders of the Lung", WB Saunders, Harcourt Publishers Limited, 2002