Metal fume fever

Metal Fume Fever has been known by a variety of names over the years, including: Monday Fever, brass chills, foundry fever, welder's ague, and smelter chills. It's a result, as many of the names suggest, of exposure to fumes from heated metal. Zinc vapors are usually responsible, but Metal Fume Fever can also be caused by copper, iron, and other metals.

What we're talking about here is an industrial disease, an occupational hazard. The most commonly affected people are shipbuilders or other people who weld metals in relatively enclosed spaces. Arc welding of galvanized steel is particularly troublesome.

Approximately 1500 to 2000 case of metal fume fever are reported yearly in the United States. There are probably a lot more cases than that. Some sources estimate that as many as 40 percent of welders over the age of 30 have suffered from metal fume fever at some point during their careers. However, incidences have been decreasing over the last fifty years, mostly due to awareness of the importance of proper ventilation.

Symptoms

The symptoms of metal fume fever usually begin within 4 to 8 hours after exposure, and are nonspecific. Patients normally complain of a sweet or metallic taste in the mouth, which distorts the taste of food and cigarettes. Fever, chills, nausea, headache, fatigue, muscle aches, and joint pains are also common. Patients often report a dry or irritated throat, which may lead to hoarseness and coughing. These symptoms usually resolve on their own within 24 to 48 hours, resembling a viral condition. 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 and blood plasma 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 metal fume fever consists of bedrest, and symptomatic therapy (e.g. aspirin for headaches) as indicated.

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 bronchitis, pneumonia, pulmonary edema, nasal cancer and even bone damage.

Prevention

Prevention of metal fume fever in workers who are at potential risk 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.