CHAPTER 2-100: METAL FUME FEVER

INTRODUCTION

Metal fume fever is an acute febrile illness caused by the inhalation of respirable particles (fume) of zinc oxide. Although metal fume fever is 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 (although some of those metals can cause acute lung injury). Metal fume fever usually occurs in workplace settings involving welding, melting, or flame-cutting galvanized metal (zinc-coated steel), or in brass foundry operations. Zinc chloride from smoke bombs can cause severe lung injury, but does not cause metal fume fever.

MECHANISM OF TOXICITY

Metal fume fever results from inhalation of zinc oxide (neither ingestion nor parenteral administration induces this syndrome, although other toxicity may result from those routes of exposure). 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).

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 2 mg/m³ as an 8-hour time-weighted average with a short-term exposure limit (STEL) of 10 mg/m³, which is intended to prevent metal fume fever in most exposed workers. Welding on galvanized metal without appropriate ventilation easily can exceed these limits. The air level considered immediately dangerous to life or health (IDLH) is 500 mg/m³.

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.

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 manifested as acute lung injury, if this is suspected.

TREATMENT

1. Emergency and supportive measures

   1. Administer supplemental oxygen ...