Toxicology – Cadmium Fume Fever/Pneumonitis

Core concept

Acute inhalation of cadmium oxide fumes can initially resemble benign metal fume fever but may progress to severe chemical pneumonitis, noncardiogenic pulmonary edema, ARDS, and respiratory failure.

The characteristic progression is:

Cadmium fume inhalation → latent period → flu-like illness → cough/chest pain/dyspnea → chemical pneumonitis ± pulmonary edema

The key clinical warning is:

A patient may look relatively well immediately after exposure and deteriorate several hours later.

Symptoms commonly begin approximately 4–10 hours after exposure, while severe pulmonary injury can evolve over the following hours to days.

Sources and Uses

Cadmium oxide fumes are generated when cadmium-containing materials are heated.

Important exposure settings include:

• Welding cadmium-plated steel
• Flame cutting cadmium-coated metal
• Brazing
• Silver soldering
• Smelting
• Refining
• Cadmium-alloy production
• Battery manufacture
• Metal reclamation/recycling

OSHA specifically recognizes welding, cutting, brazing, and other work involving cadmium-containing materials as occupational exposure settings.

Cadmium oxide

Cadmium oxide fume is:

• Odorless
• Composed of very fine airborne particles
• Capable of producing significant toxicity before the worker recognizes substantial irritation

Therefore:

Absence of an obvious odor or severe immediate airway irritation does not exclude a dangerous exposure.

Cadmium Fume Fever vs Cadmium Pneumonitis

Metal fume fever-like phase

Early cadmium inhalation can produce:

• Fever
• Chills
• Myalgia
• Headache
• Malaise
• Cough

This may look identical to ordinary metal fume fever.

Cadmium pneumonitis

Unlike typical zinc-associated metal fume fever, which generally resolves spontaneously within approximately 48 hours:

Cadmium inhalation can progress to destructive pulmonary injury.

Patients with more intense cadmium exposure who fail to improve may develop:

Tracheobronchitis → chemical pneumonitis → pulmonary edema → ARDS

ATSDR specifically distinguishes the generally self-limited course of ordinary metal fume fever from cadmium pneumonitis, which may progress between approximately 8 hours and 7 days after exposure.

High-yield distinction

Ordinary metal fume fever → improves within ~24–48 h

Cadmium fume toxicity → worsening dyspnea/infiltrates/hypoxemia = chemical pneumonitis until proven otherwise

Pathophysiology

Cadmium oxide particles deposit in the respiratory tract and cause direct inflammatory and cytotoxic lung injury.

Mechanisms include:

• Oxidative stress
• Glutathione depletion
• Lipid peroxidation
• Inflammatory cytokine release
• Endothelial injury
• Alveolar epithelial injury

Severe pulmonary injury may produce:

• Tracheobronchial hyperemia
• Pulmonary edema
• Intra-alveolar hemorrhage
• Alveolar epithelial injury
• Small-vessel thrombosis
• Fibroblastic proliferation

The result is:

Capillary/alveolar injury → permeability edema → impaired gas exchange → hypoxemic respiratory failure

Toxic Exposure

There is no single airborne concentration that reliably predicts clinical outcome.

Severity depends on:

Concentration × duration of exposure

as well as:

• Particle characteristics
• Respiratory protection
• Ventilation
• Individual susceptibility

Historical human fatalities have occurred after exposures such as:

• Approximately 39 mg Cd/m³ for 20 minutes
• Approximately 40–50 mg/m³ for 1 hour
• Approximately 9 mg/m³ for several hours

These historical observations form part of the basis for the NIOSH IDLH of 9 mg/m³.

Thus, the older statement that 40 mg/m³ is lethal is too simplistic.

Clinical Features

Latent Period

The physical examination immediately after exposure may be normal.

Symptoms are characteristically delayed approximately:

4–10 hours

after significant inhalation.

This delay is a major diagnostic pitfall.

Early / Metal-Fume-Fever-Like Phase

Possible early manifestations include:

• Throat irritation
• Cough
• Headache
• Nausea
• Malaise
• Weakness
• Myalgia
• Chills
• Fever

Vital signs may show:

• Tachycardia
• Tachypnea
• Fever

At this stage the illness may appear deceptively benign.

Progressive Pulmonary Toxicity

Concerning manifestations include:

• Increasing cough
• Dyspnea
• Chest tightness
• Pleuritic chest pain
• Wheezing
• Crackles
• Hypoxemia
• Hemoptysis

Severe exposure may progress to:

• Tracheobronchitis
• Diffuse pulmonary infiltrates
• Noncardiogenic pulmonary edema
• Intra-alveolar hemorrhage
• ARDS
• Respiratory failure

Timing of deterioration

Pulmonary toxicity may continue evolving over:

Hours to several days

and patients who do not improve over the first 1–2 days deserve particular concern for cadmium chemical pneumonitis.

Other Organ Toxicity

Although the lungs dominate acute inhalational poisoning, sufficiently large absorbed doses can also cause:

Renal

• Proximal tubular injury
• Acute kidney injury

Hepatic

• Elevated aminotransferases
• Hepatocellular injury

These are much less characteristic than the pulmonary syndrome but should be considered after substantial exposure.

Diagnosis

Diagnosis is primarily based on:

Compatible occupational exposure + delayed respiratory/flu-like syndrome

A careful occupational history is often more useful than an individual laboratory test.

Ask specifically about:

• What metal was being welded/cut
• Whether it was cadmium plated
• Solder composition
• Duration of work
• Confined-space exposure
• Ventilation
• Respirator use
• Whether coworkers are symptomatic

Material safety documentation or analysis of the metal/fume source can be valuable.

Differential Diagnosis

Other toxic inhalations

Consider:

• Phosgene
• Nitrogen dioxide
• Zinc oxide metal fume fever
• Copper fumes
• Other metal fumes
• Chlorine
• Smoke inhalation

Medical

Consider:

• Influenza or other viral illness
• Pneumonia
• Pulmonary embolism
• Acute heart failure
• Other causes of ARDS

Key diagnostic clue

A welder or metalworker who develops:

Delayed fever + cough + progressive dyspnea after heating cadmium-plated metal

should be considered to have cadmium fume toxicity until adequately evaluated.

Investigations

Pulse Oximetry

Perform in all symptomatic patients.

However:

Normal early oxygen saturation does not exclude evolving pneumonitis.

Serial measurements are more useful than a single initial value.

Chest Radiograph

Obtain for:

• Dyspnea
• Hypoxemia
• Persistent cough
• Chest pain
• Abnormal lung examination

The initial radiograph may be normal early despite significant exposure.

Later findings may include:

• Diffuse infiltrates
• Pulmonary edema
• ARDS pattern

Blood Gas

Consider ABG or VBG when there is:

• Respiratory distress
• Hypoxemia
• Suspected hypercapnia
• Severe systemic illness

Laboratory Tests

For moderate/severe exposure consider:

• CBC
• Electrolytes
• BUN
• Creatinine
• Urinalysis
• Liver enzymes

Blood Cadmium

Blood cadmium may help confirm recent significant exposure, but it should not determine acute pulmonary management.

A single blood cadmium level:

• Does not reliably predict severity
• Does not exclude toxicity when low
• Should not delay treatment

The older threshold of >5 μg/L should therefore not be treated as a definitive acute poisoning cutoff.

Urinary Cadmium

Urinary cadmium is more useful for assessing cumulative occupational body burden than for determining the immediate severity of acute pneumonitis.

It is not an emergency bedside test.

Urinary β₂-Microglobulin

β₂-microglobulin is useful mainly as a marker of:

Chronic proximal tubular cadmium injury

It is not a primary diagnostic test for acute cadmium fume pneumonitis.

This corrects the emphasis in the older source.

Treatment

1. Remove From Exposure

Immediately:

• Stop welding/cutting
• Move the patient to uncontaminated air
• Remove contaminated clothing if necessary

Rescuers must avoid entering a contaminated environment without appropriate respiratory protection.

2. Oxygen

Give supplemental oxygen for:

• Hypoxemia
• Respiratory distress
• Significant pulmonary toxicity

There is no need to automatically administer “100% oxygen” to every asymptomatic patient; oxygen should be titrated according to clinical need.

The mainstay of serious inhalational cadmium treatment remains:

• Oxygen
• Supportive care
• Mechanical ventilation when required

3. Bronchospasm

If bronchospasm occurs:

Inhaled β₂-agonist bronchodilators may be used.

For example:

• Albuterol/salbutamol

Treat according to the patient’s clinical bronchospasm rather than routinely administering bronchodilators to everyone.

4. Pulmonary Edema / ARDS

Severe cadmium pneumonitis is treated similarly to other causes of acute lung injury.

Management may include:

• Supplemental oxygen
• High-flow oxygen when appropriate
• Noninvasive support in carefully selected patients
• Endotracheal intubation for respiratory failure
• Lung-protective mechanical ventilation
• Appropriate PEEP
• Conservative fluid strategy once shock has resolved

ATSDR identifies oxygen and mechanical ventilation as central treatments in severe acute inhalational cadmium toxicity.

Avoid fluid overload

This is principally a permeability lung injury, not a disorder requiring aggressive fluid administration unless the patient is genuinely hypovolemic or shocked.

Excessive fluid may worsen pulmonary edema.

Corticosteroids

Older recommendation

The older source recommends:

Methylprednisolone 1 g IV

based on anecdotal experience.

Current interpretation

There is no established high-quality evidence that corticosteroids prevent cadmium-induced pulmonary edema or improve outcomes.

Therefore:

Routine high-dose corticosteroid therapy is not recommended as established treatment for cadmium pneumonitis.

If steroids are considered in an unusual severe case, this should be individualized with:

• Medical toxicology
• Pulmonary/critical-care consultation

rather than given automatically.

The core treatment remains supportive respiratory care.

Antibiotics

Cadmium pneumonitis is a chemical, not bacterial, pneumonitis.

Therefore:

Do not give prophylactic antibiotics.

Antibiotics are indicated only when there is evidence of:

• Secondary bacterial pneumonia
• Another documented infectious process

Antidote

There is no specific antidote for cadmium fume poisoning.

Chelation

Routine chelation is not recommended

The historical suggestion that early CaNa₂EDTA might improve acute cadmium inhalation is not supported by adequate clinical evidence.

Modern ATSDR guidance states that:

Chelation has no established role in cadmium poisoning.

Chelators may mobilize cadmium and potentially increase delivery to the kidney.

Therefore:

Do not routinely administer CaNa₂EDTA for cadmium fume pneumonitis.

Dimercaprol

Dimercaprol (BAL) should not be used for cadmium toxicity because cadmium-chelator complexes can worsen renal injury.

The absence of a proven chelator is an important difference from poisoning by metals such as arsenic or mercury.

Hemodialysis

Hemodialysis is not effective for removing established cadmium body burden because absorbed cadmium becomes strongly protein- and tissue-bound.

Dialysis should therefore not be used simply to treat the cadmium exposure.

It remains appropriate for conventional complications of severe acute kidney injury, such as:

• Refractory hyperkalemia
• Severe metabolic acidosis
• Fluid overload
• Uremia

Skin and Eye Exposure

If particulate contamination also occurred:

Skin

• Remove contaminated clothing
• Wash thoroughly with soap and water

Eyes

• Irrigate copiously with water or saline

This prevents continued local exposure but does not alter cadmium already deposited in the lungs.

Monitoring

Respiratory

Monitor:

• Respiratory rate
• Work of breathing
• Pulse oximetry
• Serial lung examination

For significant exposure consider:

• Serial chest imaging
• Blood gases
• Continuous cardiac/respiratory monitoring

Renal

After substantial exposure monitor:

• Creatinine
• Electrolytes
• Urine output
• Urinalysis

Hepatic

Consider serial liver tests after substantial systemic exposure.

Observation

The historical fixed rule of:

“12 hours and normal pulmonary function tests = discharge”

should not be applied rigidly.

Because clinically significant symptoms are frequently delayed 4–10 hours, observation after a meaningful exposure should extend through the expected latent period and be individualized according to:

• Exposure magnitude
• Confined-space exposure
• Respiratory protection
• Symptoms
• Examination
• Oxygenation
• Imaging

A patient with a credible substantial exposure should not be discharged simply because the initial examination and chest radiograph are normal.

Admission

Hospital admission is appropriate for:

• Dyspnea
• Persistent cough after substantial exposure
• Chest pain
• Hypoxemia
• Hemoptysis
• Bronchospasm
• Abnormal chest imaging
• Pulmonary edema
• Significant systemic toxicity
• Acute kidney or hepatic injury

Patients with:

• Progressive hypoxemia
• Pulmonary edema
• ARDS
• Respiratory fatigue

require ICU-level care.

Pulmonary Function Testing

PFTs are not required emergently in every exposed patient.

They may be useful for:

• Persistent respiratory symptoms
• Occupational evaluation
• Long-term follow-up after significant pneumonitis

Acute testing should never delay treatment of respiratory distress.

Prognosis

Mild exposure

Patients with a mild metal-fume-fever-like syndrome may recover completely.

Severe pneumonitis

Severe disease may progress over several days and can result in:

• Prolonged respiratory failure
• ARDS
• Pulmonary fibrosis
• Persistent restrictive impairment
• Death

Historical reports documented substantial mortality among patients who developed severe pulmonary edema, but the older statement that approximately 20% of all cadmium fume cases are fatal should not be generalized to contemporary exposures. Severe high-dose occupational exposures are now uncommon.

Persistent pulmonary-function abnormalities have been documented years after severe cadmium pneumonitis.

Long-Term Follow-Up

After significant pneumonitis consider follow-up with:

• Pulmonary function testing
• Respiratory symptom assessment
• Occupational medicine evaluation

Because significant systemic cadmium absorption may also affect the kidneys, follow:

• Creatinine
• Urinalysis
• Occupational cadmium biomarkers when appropriate

Return to cadmium exposure should occur only after occupational safety review and adequate exposure controls.

Occupational Standards

OSHA PEL

Current OSHA permissible exposure limit for cadmium:

5 μg/m³ (0.005 mg/m³) as an 8-hour TWA

OSHA Action Level

2.5 μg/m³ (0.0025 mg/m³) as an 8-hour TWA

NIOSH

NIOSH treats cadmium as an occupational carcinogen and recommends reducing exposure to the lowest feasible concentration.

NIOSH IDLH

For cadmium fume:

9 mg Cd/m³

The difference between these values is important:

OSHA PEL = routine occupational limit

IDLH = immediately dangerous exposure

Prevention

Cadmium fume poisoning is largely preventable.

Important controls include:

• Identifying cadmium-containing metals before heating
• Local exhaust ventilation
• Appropriate respiratory protection
• Avoiding welding/cutting cadmium materials in poorly ventilated spaces
• Occupational air monitoring
• Worker education

Personal protective equipment must complement rather than replace appropriate engineering controls.

Important Pitfalls

1. Calling it ordinary metal fume fever

Early symptoms may be identical.

But:

Worsening after 24–48 h strongly suggests cadmium pneumonitis rather than uncomplicated metal fume fever.

2. Being reassured by an initially normal examination

Cadmium pulmonary toxicity is characteristically delayed.

Symptoms often begin 4–10 hours later.

3. Being reassured by an initially normal chest X-ray

Radiographic pulmonary edema may lag behind the exposure and early symptoms.

Clinical monitoring is essential.

4. Waiting for a cadmium concentration

Blood and urine cadmium testing can support exposure assessment but:

Treatment should never wait for the level.

5. Treating β₂-microglobulin as an acute pneumonitis marker

It is mainly a biomarker of renal tubular injury/chronic cadmium exposure.

6. Giving prophylactic antibiotics

Cadmium pneumonitis is initially a chemical lung injury.

7. Routinely giving megadose steroids

The older recommendation for 1 g methylprednisolone is based on anecdotal experience and is not established evidence-based therapy.

8. Routinely giving EDTA

Modern toxicology does not recommend routine chelation for cadmium poisoning.

9. Assuming dialysis removes cadmium

Dialysis treats complications of renal failure but does not effectively remove tissue-bound cadmium.

10. Using the old workplace limits

Current OSHA PEL:

0.005 mg/m³

Current NIOSH IDLH:

9 mg/m³

High-Yield Toxicology Pearls

Cadmium fume = delayed toxic lung injury

Think:

Welder + cadmium-plated metal + delayed fever/cough → watch for pneumonitis

Key points:

• Cadmium oxide fumes are produced by welding, cutting, brazing, and heating cadmium-containing metals
• Cadmium oxide is odorless
• Initial examination may be normal
• Symptoms typically begin after a 4–10-hour latent period
• Early symptoms can mimic metal fume fever
• Ordinary metal fume fever usually resolves within ~48 hours
• Cadmium toxicity may instead progress to chemical pneumonitis
• Severe toxicity → noncardiogenic pulmonary edema/ARDS
• Main treatment: supportive respiratory care
• Oxygen for hypoxemia
• Bronchodilators for bronchospasm
• Severe cases require lung-protective mechanical ventilation + PEEP
• No specific antidote
• Routine EDTA chelation is not recommended
• Routine high-dose corticosteroids are not established therapy
• Antibiotics only for documented secondary infection
• Blood/urine cadmium concentrations support diagnosis but do not determine acute treatment
• β₂-microglobulin is primarily a renal/chronic exposure biomarker
• Do not rely on a fixed 12-hour discharge rule after substantial exposure
• OSHA PEL: 5 μg/m³ over 8 hours
• OSHA action level: 2.5 μg/m³
• NIOSH IDLH: 9 mg/m³
• Persistent restrictive pulmonary impairment can follow severe pneumonitis
• The most important clinical pearl:

A “metal fume fever” syndrome that worsens rather than improves should prompt urgent reassessment for cadmium pneumonitis.