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

ACUTE EFFECTS:

Acute effects of metals may affect any part of the respiratory tract from the nose (rhinitis), to large bronchi (tracheitis, bronchitis), to alveolar tissue (pneumonitis, for example, acute inflammation of the lung, or if severe, adult respiratory distress syndrome).

Acute effects may go on to cause chronic disease such as asthma, obstructive bronchiolitis or lung fibrosis.

Upper Respiratory Tract:

Nasal septal ulcers/perforation may occur on exposure to chromates or chromic acid. This exposure occurs in electroplating.

There was an outbreak of nasal perforations in Kwazulu-Natal electroplating plant a few years ago. [Colvin et al. S Afr Med J 1993; 83: 857-8 (letter)].

Chemical pneumonitis:

The best documented example is cadmium pneumonitis.

Cadmium is a metal which does not seem to be widely used (or at least documented) in South Africa, but it is described as a by-product of the lead and zinc industry, which are mined and smelted in South Africa. Cadmium is used in alloys and electroplating. The best known use is in nickel-cadmium batteries.

The two features emphasized by Nemery are first that cadmium fumes could be produced unknowingly in zinc or lead smelting or welding. Second, that there may be a delayed response to cadmium. These factors might make the attribution of the cause of the pneumonitis difficult.

Acute pneumonitis may be caused also by mercury vapours. (Note that mercury has an appreciable vapour pressure even if not heated).

Metal fume fever:

This is the most common of the acute effects of metals and occurs in workers exposed to fumes of zinc oxide, for example, in burning or welding galvanized iron. Other metallic oxides such as copper may be involved.

The condition is a short-lived flu-like illness with chills, headache and myalgia, typically with a normal chest x-ray and no lung function deficit. A leukocytosis may be found on the full blood count. Treatment is for myalgias and fever, and the illness is self-limiting within a day or two.

There is acquired tolerance as episodes typically occurs after a period of non-exposure on a Monday. Workers such as welders tend to become familiar with the syndrome and treat themselves without even reporting it.

It is uncertain whether there are long term effects.