Module 4: Metals And The Lung - Lecture (Continued)

INTERSTITIAL LUNG DISEASE:

Pneumoconiosis without fibrosis:

The most common form is siderosis, which manifests as diffuse symmetrical rounded nodules on the chest x-ray. In the absence of other risk factors, there may be no functional loss and the nodules may even fade with cessation of exposure.

Siderosis may occur in smelting, torch cutting, welding and grinding.

Mixed dust pneumoconiosis:

This is found where there is co-exposure to iron and silica, such as in iron foundries. The histology and chest x-ray are not typical of silicosis, showing a much less regular pattern of fibrosis. It has been suggested that the iron may interfere with the typical formation of silicotic whorls in the lung. This condition is not well documented, but the prognosis appears to be that of silicosis. Presumably there is an increased risk of tuberculosis.

Hard metal disease ("cobalt lung"):

Hard metal is a composite material composed mainly of cobalt and the compound tungsten carbide, with a small amount of titanium (Note: do not confuse with "heavy metals"). Also, known as artificial diamond, hard metal is used mainly for drilling and cutting tools (and thus used widely in the mining industry). The main exposures are in manufacturing of the material and in repair and sharpening drill heads, etc.

"Hard metal disease" proper is a pneumonitis whose most specific feature is multinucleated giant cells seen on histology or in lavage fluid. It appears that cobalt is the component that causes the disease and that an auto-immune response is involved.

Beryllium lung disease (granulomatous lung disease):

Beryllium exposure occurs in mining and refining and in "high tech" industries such as aeropace, electronics and computers, where it is used for its light weight, strength and other desirable properties, often in a copper alloy. Beryllium exposure has not been documented in South Africa, although it may occur as high tech industries develop.

This disease is notable in that it mimics sarcoidosis in almost every aspect, clinical, radiological, histological, immunological. (Sarcoidosis is a lung disease of unknown cause, characterized by the formation of granulomas in the lung. A granuloma is a solid grouping of inflammatory cells coming together in a lump or solid structure in the lung).

The one test that distinguishes beryllium lung disease from sarcoidosis is the lymphocyte transformation test. In this test lymphocytes from the blood or lavage fluid are incubated with beryllium salts in a test-tube and transformation (or proliferation) of the lymphocytes measured.

Aluminium pneumoniosis:

This is rare. It has been described in the smelting of bauxite ore from which the aluminium is extracted (Shaver’s Disease), in grinding (or "polishing") aluminium producing fine particles, in refinery workers and in welders.