Metal fume fever

Metal fume fever is illness caused primarily by exposure to certain metal fumes. Chemicals such as zinc oxide (ZnO) or magnesium oxide (MgO), often cause this through breathing fumes created by heating or welding certain metals, such as galvanized steel. Cadmium, present in silver brazing flux can, in extreme cases, cause loss of consciousness within a matter of minutes.

Symptoms
The symptoms are nonspecific but are generally flu-like including fever, chills, nausea, headache, fatigue, muscle aches, and joint pains. A sweet or metallic taste in the mouth which distorts the taste of food and cigarettes is also normally reported along with a dry or irritated throat which may lead to hoarseness. Symptoms may also include a burning sensation in the body, shock, no urine output, collapse, convulsions, shortness of breath, yellow eyes or yellow skin, rash, vomiting, watery or bloody diarrhea or low blood pressure, which require prompt medical attention. Milder flu-like symptoms will normally disappear within 24 to 48 hours, and someone suffering from metal fume fever will usually feel well enough to return to work the next day, despite the fact that they may still be feeling a little bit under the weather. It often takes 4 days to fully recover.

Cause
The exact cause of metal fume fever is not known. The most plausible theory involves an immune reaction which occurs when inhaled metal oxide fumes injure the cells lining the airways. This is thought to modify proteins in the lung. The modified proteins are then absorbed into the bloodstream, where they act as allergens.

Diagnosis
Physical examination findings vary among persons exposed, depending largely upon the stage in the course of the syndrome during which examination occurs. Patients may present with wheezing or crackles in the lungs. They may also have an increased white blood cell count, and urine, blood plasma and skin zinc levels may (unsurprisingly) be elevated. Chest X-ray findings are generally unremarkable.

Diagnosis of metal fume fever can be difficult, as the complaints are nonspecific and resemble a number of other common illnesses. When respiratory symptoms are prominent, metal fume fever may be confused with acute bronchitis. The diagnosis is based primarily upon a history of exposure to metal oxide fumes.

An interesting feature of metal fume fever involves rapid adaptation to the development of the syndrome following repeated metal oxide exposure. Workers with a history of recurrent metal fume fever often develop a tolerance to the fumes. This tolerance, however, is transient, and only persists through the work week. After a weekend hiatus, the tolerance has usually disappeared. This phenomenon of tolerance is what led to the name "Monday Fever".

Treatment
Treatment of mild metal fume fever consists of bedrest, and symptomatic therapy (e.g. aspirin for headaches) as indicated. Milk is highly regarded by experienced welders and technical training institutions as effective treatment for absorbing the metals that accumulate in the body. It is best to drink milk before the onset of symptoms.

Prognosis
The symptoms of metal fume fever are usually self-limiting, and dissipate rapidly upon removal from the source of metal fumes. Depending on the metals involved, repeated exposure can lead to longer term illnesses such as asthma, "metal fume fever, airway irritation, lung function changes, susceptibility to pulmonary infection, and a possible increase in the incidence of lung cancer", bronchitis, pneumonia, pulmonary edema, nasal cancer and even bone damage.

Prevention
Prevention of metal fume fever in workers who are at potential risk (such as welders) involves avoidance of direct contact with potentially toxic fumes, improved engineering controls (exhaust ventilation systems), personal protective equipment (respirators), and education of workers regarding the features of the syndrome itself and proactive measures which can be taken to prevent its development.