Toxicology – Metal Fume Fever

Definition

Metal fume fever is an acute, self-limited inhalational illness caused by breathing freshly generated metal oxide fumes, classically during welding, cutting, brazing, smelting, or heating galvanized metal.

The classic cause is zinc oxide, particularly from welding galvanized steel.

Other implicated metal fumes include oxides of:

• Copper
• Magnesium
• Aluminum
• Manganese
• Iron
• Nickel
• Chromium

Historical names include welder’s fever, zinc shakes, brass chills, and Monday fever.

Pathophysiology

Heating metals can generate very small respirable metal oxide particles that penetrate deeply into the lungs.

The current understanding emphasizes an acute inflammatory response in the respiratory tract, with activation of alveolar macrophages and release of inflammatory cytokines.

This produces a transient systemic influenza-like syndrome.

Metal fume fever is therefore primarily an inflammatory response rather than a classic allergic reaction or systemic heavy-metal poisoning.

Important Distinction: Cadmium

Cadmium fume inhalation is not simply ordinary metal fume fever.

Cadmium can cause severe delayed:

• Chemical pneumonitis
• Noncardiogenic pulmonary edema
• ARDS
• Respiratory failure
• Systemic toxicity

Therefore, the specific metal involved must be identified whenever possible.

Occupational Exposures

Common settings include:

• Welding
• Cutting galvanized steel
• Brazing
• Soldering
• Metal smelting
• Foundry work
• Metal reclamation/recycling
• Grinding or fabrication
• Furnace operations

Exposure frequently occurs when adequate local exhaust ventilation or respiratory protection is absent.

Onset

Symptoms typically begin several hours after exposure, commonly about 4–12 hours later.

Because of this delay, a worker may feel well during the exposure and become ill later that evening.

Clinical Features

The illness resembles an acute viral syndrome.

Common symptoms include:

• Fever
• Chills
• Malaise
• Fatigue
• Headache
• Myalgia
• Arthralgia
• Weakness
• Sweating

Respiratory symptoms may include:

• Dry cough
• Chest tightness
• Dyspnea
• Sore throat
• Wheezing
• Pleuritic chest discomfort

A metallic or unusual taste may occur shortly after exposure.

Monday Fever

Repeated exposure can produce temporary tolerance or tachyphylaxis.

Workers may experience:

• Strong symptoms after returning to work following several exposure-free days
• Diminishing symptoms with repeated exposure during the week
• Recurrence after another exposure-free interval

This phenomenon produced the historical term “Monday morning fever.”

Importantly, temporary tolerance does not mean that continued inhalation of welding fumes is safe.

Physical Examination

Findings may include:

• Fever
• Tachycardia
• Tachypnea
• Diaphoresis

Pulmonary examination may be:

• Normal
• Mildly abnormal with wheezing or crackles

Marked hypoxemia, severe respiratory distress, or substantial abnormal lung findings should prompt investigation for a more serious inhalational injury rather than uncomplicated metal fume fever.

Diagnosis

Diagnosis is primarily clinical.

The most important diagnostic clue is:

Recent metal-fume exposure + delayed influenza-like illness + spontaneous improvement after removal from exposure

A careful occupational history is therefore essential.

Ask about:

• Welding or cutting
• Galvanized metal
• Type of metal/alloy
• Coatings on the metal
• Ventilation
• Confined-space exposure
• Other workers with similar symptoms
• Potential exposure to cadmium or other highly toxic metals

Laboratory Findings

No laboratory test specifically confirms metal fume fever.

Possible nonspecific findings include:

• Leukocytosis
• Mild inflammatory abnormalities

Serum or urine metal concentrations are generally not useful for diagnosing uncomplicated metal fume fever.

Targeted metal testing may be appropriate when a specific toxic metal exposure is suspected.

Chest Radiograph

Chest radiography is usually normal in uncomplicated metal fume fever.

A radiograph may be appropriate when there is:

• Significant dyspnea
• Hypoxemia
• Persistent respiratory symptoms
• Abnormal lung examination
• Concern for pneumonitis or pulmonary edema

Substantial infiltrates should raise concern for an alternative or more severe inhalational injury.

Differential Diagnosis

Important alternatives include:

• Viral respiratory infection
• Bacterial pneumonia
• COVID-19 or influenza
• Chemical pneumonitis
• Occupational asthma
• Hypersensitivity pneumonitis
• Polymer fume fever
• Chlorine or other irritant-gas exposure
• Nitrogen dioxide exposure
• Pulmonary embolism
• Sepsis

Particularly important occupational toxic exposures include:

• Cadmium fumes
• Nickel carbonyl
• Other severe metal or combustion-product exposures

Metal Fume Fever vs. Cadmium Pneumonitis

Metal fume fever

• Influenza-like illness
• Usually begins several hours after exposure
• Chest radiograph usually normal
• Usually resolves within 1–2 days
• Serious pulmonary injury is unusual

Cadmium fume toxicity

• Can initially resemble metal fume fever
• May progress to severe respiratory symptoms
• Chemical pneumonitis/pulmonary edema may develop
• Can cause systemic toxicity
• Potentially life-threatening

Failure to distinguish these conditions is an important diagnostic pitfall.

Management

There is no specific antidote for uncomplicated metal fume fever.

Treatment is primarily:

• Termination of exposure
• Rest
• Adequate hydration
• Symptomatic treatment of fever and pain
• Oxygen when hypoxemia is present

Most patients improve rapidly once exposure stops.

Bronchospasm

If clinically significant bronchospasm occurs, an inhaled beta₂-agonist bronchodilator may be used.

The source recommends routine systemic corticosteroids for bronchospasm, but corticosteroids are not routinely required for uncomplicated metal fume fever.

They may be considered when a separate condition such as significant reactive airway disease or another inflammatory pulmonary process is present.

Antibiotics

Prophylactic antibiotics have no established role in uncomplicated metal fume fever because this is not a bacterial infection.

Antibiotics should be used only when there is evidence of a bacterial infectious process.

Decontamination

The most important intervention is removal from further inhalational exposure.

If clothing or skin is significantly contaminated with metal-containing dust:

• Remove contaminated clothing.
• Wash exposed skin.

Extensive decontamination is generally unnecessary after isolated inhalation of metal fumes when there is no ongoing surface contamination.

Prognosis

Uncomplicated metal fume fever has an excellent prognosis.

Typical course:

Exposure → latent period of several hours → influenza-like symptoms → improvement within approximately 24–48 hours

Persistent or worsening symptoms should prompt reconsideration of the diagnosis.

Warning Signs

Features inconsistent with simple metal fume fever include:

• Progressive dyspnea
• Significant hypoxemia
• Hemoptysis
• Persistent high fever
• Pulmonary infiltrates
• Pulmonary edema
• Severe chest pain
• Neurologic abnormalities
• Renal or hepatic injury
• Symptoms lasting substantially beyond the expected course

These findings should raise concern for cadmium toxicity, chemical pneumonitis, infection, or another serious exposure.

Prevention

Prevention is central because recurrence follows re-exposure.

Occupational measures include:

• Adequate local exhaust ventilation
• Appropriate respiratory protection
• Identification of metal composition and surface coatings
• Avoidance of welding in poorly ventilated or confined spaces without proper controls
• Occupational-health assessment after recurrent episodes

Repeated episodes should not simply be accepted as an unavoidable consequence of welding.

Key Points

• Metal fume fever is an acute, self-limited inflammatory illness following inhalation of metal oxide fumes.
• Zinc oxide from welding galvanized steel is the classic cause.
• Symptoms typically appear several hours after exposure and resemble influenza.
• Common manifestations are fever, chills, myalgia, headache, fatigue, cough, and chest tightness.
• Repeated exposure can produce temporary tolerance, explaining the term “Monday fever.”
• Diagnosis is primarily based on a careful occupational exposure history.
• Chest radiography is usually normal in uncomplicated disease.
• Serum or urine metal measurements are usually unnecessary for straightforward metal fume fever.
• Treatment is primarily removal from exposure and supportive care.
• Antibiotics and systemic corticosteroids are not routinely indicated for uncomplicated disease.
• Symptoms usually resolve within 24–48 hours.
• Cadmium fume pneumonitis must not be mistaken for benign metal fume fever, because cadmium inhalation can cause severe delayed lung injury and respiratory failure.