Chapter 100. Metal Fume Fever

Metal fume fever is an acute febrile illness associated with the inhalation of respirable particles (fume) of zinc oxide. Although metal fume fever has also been invoked as a generic effect of exposure to numerous other metal oxides (copper, cadmium, iron, magnesium, and manganese), there is little evidence to support this. Metal fume fever usually occurs in workplace settings involving welding, melting, or flame-cutting of galvanized metal (zinc-coated steel), or in brass foundry operations. Zinc chloride exposure may occur from smoke bombs; although it can cause severe lung injury, it does not cause metal fume fever.

1. Mechanism of toxicity. Metal fume fever results from inhalation of zinc oxide (neither ingestion nor parenteral administration induces this syndrome). The mechanism is uncertain but may be cytokine-mediated. It does not involve sensitization (it is not an allergy) and can occur with first exposure (in persons previously naïve to inhaled zinc oxide).

2. Toxic dose. The toxic dose is variable. Resistance to the condition develops after repeated days of exposure (tachyphylaxis) but wears off rapidly when exposure ceases. The ACGIH-recommended workplace exposure limit (TLV-TWA) for zinc oxide fumes is 5 mg/m3 as an 8-hour time-weighted average, which is intended to prevent metal fume fever in most exposed workers. The air level considered immediately dangerous to life or health (IDLH) is 500 mg/m3.

3. Clinical presentation

   1. Symptoms typically begin 4–8 hours after exposure with fever, malaise, myalgia, and headache. The white blood cell count may be elevated (12,000–16,000/mm3). The chest radiograph is usually normal. Typically, all symptoms resolve on their own within 24–36 hours.

   2. Rare asthmatic or allergic responses to zinc oxide fume have been reported. These responses are not part of the metal fume fever syndrome.

   3. Pulmonary infiltrates and hypoxemia are not consistent with pure metal fume fever. If present, this suggests possible heavy metal pneumonitis resulting from cadmium or other toxic inhalations (eg, phosgene and nitrogen oxides) associated with metal working, foundry operations, or welding.

4. Diagnosis. A history of welding, especially on galvanized metal, and typical symptoms and signs are sufficient to make the diagnosis.

   1. Specific levels. There are no specific tests to diagnose or exclude metal fume fever. Blood or urine zinc determinations do not have a role in clinical diagnosis of the syndrome.

   2. Other useful laboratory studies include CBC. Oximetry or arterial blood gases and chest radiography are used to exclude other disorders involving acute lung injury, if this is suspected.

5. Treatment

   1. Emergency and supportive measures

      1. Administer supplemental oxygen and give bronchodilators if there is wheezing and consider other diagnoses, such as an allergic response (See Bronchospasm). If hypoxemia or wheezing is present, consider other toxic inhalations (See Gases, Irritant).

      2. Provide symptomatic care (eg, acetaminophen or another antipyretic) as needed; symptoms are self-limited.

   2. Specific drugs and antidotes. There is no specific antidote.

   3. Decontamination is not necessary; by the time symptoms develop, the exposure has usually been over for several hours.

   4. Enhanced elimination. There is no role for these procedures.