Metal Fume Fever

Metal fume fever is a self-limiting, influenza-like illness that follows inhalation of freshly generated metal oxide fumes. Zinc oxide is the commonest cause, from welding or cutting galvanized steel, brass casting and zinc smelting. Copper, magnesium, aluminum, iron and manganese fumes can cause it too. Cadmium and mercury are different and cause severe, delayed chemical pneumonitis.

Exposure to fumes of particles under 1 micrometer, which reach the alveoli, is needed. Zinc fume concentrations over 5 mg/m3 can cause disease. It is called "Monday morning fever" because tolerance develops over several days of exposure, is lost after a few days away and is regained quickly.

Mechanism: fine particles in the alveoli induce release of inflammatory cytokines (TNF alpha, IL-6 and IL-8) and neutrophil influx, which cause systemic symptoms and transient lung inflammation. It is not an allergic reaction, and requires no prior sensitization. Symptoms start 3 to 10 hours after exposure and resolve within 24 to 48 hours without sequelae. Complications are rare, but include a mistaken diagnosis of infection and unnecessary admission, and progression to pneumonitis when the fume is cadmium or the exposure is massive.

• Metallic or sweet taste, dry throat, cough and chest tightness, starting during or after work
• Fever of 38 to 40 degrees Celsius, chills and rigors, headache, malaise, myalgia and nausea, with onset 3 to 10 hours after exposure
• Mild tachycardia and tachypnea, and clear or mildly abnormal chest examination
• Leukocytosis, with resolution in 24 to 48 hours
• Red flags: dyspnea, hypoxemia, hemoptysis, abnormal chest radiograph and symptoms lasting over 48 hours, which suggest cadmium pneumonitis or another cause

1. Clinical diagnosis from the exposure history (welding or heating galvanized or zinc-containing metal), the time course and the natural recovery.
2. Chest radiograph: normal in most patients, or minor transient changes. A normal film does not exclude early cadmium pneumonitis.
3. Blood tests: white cell count (12 to 25 × 10^9/L, with neutrophilia), C-reactive protein, creatinine and liver tests. Urine zinc is raised after exposure but is not required.
4. Oxygen saturation and spirometry: possible mild restriction and reduced diffusing capacity, which recover.
5. Cadmium exposure: blood and urine cadmium and a repeat chest radiograph at 24 hours when cadmium is possible.
6. Exclusion of other causes: infection (influenza, pneumonia), polymer fume fever from heated polytetrafluoroethylene, organic dust toxic syndrome and hypersensitivity pneumonitis.

Differentials: influenza and other viral illness, pneumonia, polymer fume fever, organic dust toxic syndrome, cadmium pneumonitis and hypersensitivity pneumonitis.

1. Remove from exposure and rest.
2. Antipyretic and analgesic: paracetamol 1 g orally every 6 hours (maximum 4 g a day), or ibuprofen 400 mg orally every 8 hours with food. Children 15 mg/kg of paracetamol every 6 hours.
3. Fluids: oral fluids 2 to 3 L over 24 hours.
4. Bronchospasm: salbutamol 2.5 mg nebulized or 4 puffs of 100 micrograms by spacer as needed.
5. No antibiotics or corticosteroids are needed, as the illness is non-infectious and self-limited.
6. Suspected cadmium or massive exposure: observe in hospital for at least 24 to 36 hours, with oxygen for hypoxemia, repeat chest radiograph at 24 hours, and treat pneumonitis if it appears (oxygen, ventilatory support, and prednisolone 40 mg orally once daily for 5 days when severe).
7. Prevention:
   • Remove zinc coating from the weld area (grinding with appropriate protection) before welding.
   • Local exhaust ventilation and general ventilation, and welding in open or ventilated areas.
   • Respiratory protection with a powered air-purifying respirator or a P3 particulate filter, and avoiding head position in the fume plume.
   • Use of alternative techniques such as cold cutting or non-galvanized material when practical.
8. Education: workers should know that symptoms may follow work by several hours, should not be mistaken for influenza, and should lead to review of fume controls.

No follow-up is needed if recovery is complete within 48 hours. Review workplace exposure after a cluster of cases, and counsel workers to seek care if cough or dyspnea persists.