Permanent Scarring of The Lungs by Silica

Silicosis is permanent scarring of the lungs caused by inhaling silica (quartz) dust. It is the oldest known occupational lung disease and develops in people who have inhaled silica dust for many years. Silica is the main constituent of sand, so exposure is common among metal miners, sandstone and granite cutters, foundry workers, and potters. Usually symptoms appear only after 20 to 30 years of exposure to the dust. However, in occupations such as sand blasting, tunneling and manufacturing abrasive soaps, in which high levels of silica dust are produced, symptoms may appear in less than 10 years.

When inhaled the silica dust passed into the lungs, and scavenger cells such as macrophages engulf it.

Enzymes released by the scavenger cells cause the lung tissue to scar. At first the scarred area are tiny round lumps (simple nodular silicosis); but eventually they may aggregate into large masses (conglomerate silicosis (These scarred areas can transfer oxygen into the blood normally The lungs become less flexible, and breathing takes more effort.

Essentials of Diagnosis :

i) History of exposure to dust containing silicon dioxide (e.g. hardrock, mining, sand-blasting).

ii) Characteristic X-ray changes : Bilateral nodules, fibrosis, hilar lymphadenopathy.

iii) Recurrent respiratory infections.

iv) It may be noted that tuberculosis is a common complication.

General considerations :

The pneumoconiosis are chronic fibrotic pulmonary diseases caused by inhalation of inorganic occupational dusts. Free silica (silicon dioxide) is by far the most common offender. Prolonged exposure is usually required. Immunoglobulins of type II (cytotoxic) class (Ig G and IgM) have been demonstrated in silicotic tissue, and it appears that further study of the immunologic mechanism will clarify the pathogenesis of this unusual disease.

Symptoms and sings : Symptoms may be absent or may consist only of unusual susceptibility to upper respiratory tract infections, "bronchitis" and "pneumonia". Dyspnoea on exertion is the most common presenting complaint. It may progress slowly for years. Cough usually develops and is dry initially but later becomes productive, frequently with blood-streaked sputum. Severe, and occasionally, fatal haemoptysis may occur. Physical findings may be absent in patients with advanced silicosis.

Laboratory findings : Sputum studies for acid fast bacilli are indicated to rule out silicutuberculosis. Lung biopsy is occasionally indicated to establish the diagnosis for compensation purpose.

X-ray finding : Chest X-rays are not diagnostic but often strongly suggest the diagnosis. Abnormalities are usually bilateral symmetric, and predominant in the inner midlung fields. Small nodules tend to be of uniform size and density.

Enlargement of the hilar nodes is a relatively early finding. Peripheral calcification of the nodes, giving and "eggshell" appearance may occur later. Fibrosis is manifested by five linear markings and reticulation. Coalescence of nodules produces larger densities. Associated emphysema gives an X-ray picture of increased rediolucency, often quite striking at the lung bases.

Treatment : Silicosis can't be cured. However, if a person with an early stage of the illness stops being exposed to silica, the progression of slicosis may stop.

A person who has difficulty in breathing may benefit from the treatments used for chronic obstructive pulmonary disease, such as drug therapy to keep the airways open and free of secretions.

Because people with silicosis have a high risk of developing tuberculosis, they should have regular check ups that include a tuberculosis skin test.

Prevention : Controlling the dust in the work place can help prevent silicosis. When dust can't be controlled, as may be true in the sandblasting industry, workers should wear, hoods that supply clean external air or masks that completely filter out the tiny particles.

Such protection may not be available to all people working in a dusty area (for example, painters and welders), so whenever possible, abrasive's other than sand should be used.

Workers exposed to silica dust should have regular chest X-rays every 6 months for sand blusters and every 20 to 5 years for other works, so that problem can be detected early. If the X-rays show silicosis, a doctor will probably advise the worker to avoid continued exposure to silica.

Prognosis : Gradually progressive dyspnoea may be present for years. The development of complications, especially tuberculosis, markedly worsens prognosis.

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