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Chemical Pneumonitis

Clinical Subject Page

Chemical Pneumonitis

Chemical pneumonitis is an acute or chronic inflammatory injury of the lungs caused by inhalation or aspiration of irritating or toxic substances.

Also called

Aspiration pneumonitis — when caused by aspiration of gastric contents

ICD-10

J68.0

Specialty

Pulmonology

Onset

Acute & Chronic

Reviewed

July 2026

On This Page

Overview

Chemical substances can directly damage the:

  • Airways
  • Alveoli
  • Lung interstitium

The injury causes:

Chemical exposure → Direct lung tissue damage → Inflammation → Edema → Impaired gas exchange and leading to Chemical Pneumonitis

Severe cases may progress to acute respiratory failure or acute respiratory distress syndrome (ARDS).

Etiology & Risk Factors

Common Causes of Chemical Pneumonitis

Aspiration of Gastric Contents

  • Vomiting
  • Reduced consciousness
  • General anesthesia
  • Seizures

Inhaled Gases and Fumes

  • Chlorine gas
  • Ammonia
  • Nitrogen dioxide
  • Sulfur dioxide
  • Smoke

Hydrocarbons

  • Gasoline
  • Kerosene
  • Petroleum products

Other Chemical Exposures

  • Cleaning products
  • Industrial chemicals
  • Pesticides
  • Solvents

Risk Factors For Chemical Pneumonitis

  • Occupational chemical exposure
  • Fire or smoke exposure
  • Poorly ventilated environments
  • Reduced consciousness
  • Dysphagia
  • Vomiting
  • Seizures
  • General anesthesia
  • Substance intoxication

Important Note

Chemical pneumonitis is caused by direct tissue injury and is not initially a bacterial infection.

Pathophysiology

Inhalation or aspiration of toxic substance
⬇
Direct injury to airway and alveolar cells
⬇
Inflammatory response
⬇
Increased capillary permeability
⬇
Pulmonary edema + Alveolar damage
⬇
Impaired ventilation and gas exchange
⬇
Hypoxemia
⬇
Severe injury → ARDS and respiratory failure

Key Concept

The severity of Chemical pneumonitis depends on the type, concentration, duration, and amount of chemical exposure.

Clinical Presentation

  • Symptoms

    • Sudden cough
    • Dyspnea
    • Chest tightness
    • Burning sensation in the chest
    • Wheezing
    • Choking
    • Chest pain

    After Aspiration

    May include:

    • Sudden coughing
    • Respiratory distress
    • Hypoxemia
    • Fever

    Signs

    • Tachypnea
    • Tachycardia
    • Reduced oxygen saturation
    • Wheezing
    • Crackles

    Severe Disease

    • Cyanosis
    • Severe hypoxemia
    • Altered mental status
    • Respiratory failure

History Taking

  • Ask about:

    • What substance was involved?
    • Was it inhaled or aspirated?
    • When did the exposure occur?
    • How long was the exposure?
    • Was the exposure in an enclosed space?
    • Cough or choking?
    • Shortness of breath?
    • Chest pain or tightness?
    • Vomiting or aspiration?
    • Loss of consciousness?

Physical Examination

Look for:

  • Respiratory distress
  • Tachypnea
  • Tachycardia
  • Cyanosis
  • Reduced oxygen saturation

Chest Examination

Look for:

  • Wheezing
  • Crackles
  • Reduced air entry

Upper Airway Examination

Look for:

  • Facial burns
  • Soot around the mouth or nose
  • Hoarseness
  • Stridor
  • Oropharyngeal burns

Investigations of Chemical pneumonitis

  • Pulse Oximetry

    Assess oxygen saturation.

    Arterial Blood Gas

    Consider in:

    • Significant hypoxemia
    • Respiratory distress
    • Severe exposure

    Chest X-ray

    May show:

    • Pulmonary infiltrates
    • Pulmonary edema
    • Diffuse bilateral opacities

    Important Note

    The initial chest X-ray may be normal despite significant lung injury.

    CT Chest

    Consider when:

    • Diagnosis is uncertain
    • Symptoms are severe
    • Complications are suspected

    Additional Tests

    Depending on the exposure:

    • CBC
    • Electrolytes
    • Renal function
    • ECG
    • Carboxyhemoglobin after smoke exposure
    • Methemoglobin level for specific toxic exposures

Types of Pneumonias

CAP vs HAP vs Chemical Pneumonitis · Overview

Community-Acquired
Pneumonia (CAP)
Outside hospital or <48h of admission
Hospital-Acquired
Pneumonia (HAP)
≥48h after hospital admission
Chemical
Pneumonitis
Non-infectious lung injury
Definition
Lung infection acquired outside hospital or within 48h of admission, in a non-healthcare resident
Lung infection developing ≥48 hours after hospital admission, including ventilator-associated pneumonia (VAP)
Non-infectious lung injury from inhalation or aspiration of chemical irritants — no bacteria involved initially
Common causes
S. pneumoniae H. influenzae Atypicals
Mycoplasma, Chlamydophila, Legionella — especially in younger patients. Viruses (influenza, COVID-19) increasingly common.
Gram-negative bacilli P. aeruginosa MRSA
Klebsiella, Acinetobacter, Enterobacter. Often multidrug-resistant (MDR) organisms.
Gastric acid Toxic gases Hydrocarbons
Aspiration of gastric contents (Mendelson's syndrome), smoke inhalation, chemical fumes, petroleum products.
Typical patient
Any age. Risk ↑ with: age >65, smoking, COPD, asplenia, immunosuppression, alcoholism
ICU patients, ventilated patients, post-surgery, prolonged hospitalisation, immunocompromised
Reduced consciousness (anaesthesia, seizures, alcohol intoxication), GERD, dysphagia, occupational chemical exposure
Onset
Acute — hours to days; fever, productive cough, pleuritic chest pain
Variable — often more insidious; may be masked by underlying illness or sedation in ICU
Rapid — symptoms within 1–6 hours of exposure; acute dyspnea, cough, bronchospasm

CAP vs HAP vs Chemical Pneumonitis · Management & Prognosis

Community-Acquired
Pneumonia (CAP)
Outside hospital or <48h of admission
Hospital-Acquired
Pneumonia (HAP)
≥48h after hospital admission
Chemical
Pneumonitis
Non-infectious lung injury
Severity score
CURB-65 — score 0–5; guides home vs hospital vs ICU disposition
CPIS score — Clinical Pulmonary Infection Score; uses temperature, WBC, secretions, oxygenation, CXR
PaO₂/FiO₂ ratio — severity of hypoxia; ARDS criteria if <300 with bilateral infiltrates
Treatment
Mild: Amoxicillin 500mg TDS oral
Moderate: Amoxicillin + Clarithromycin
Severe: Co-amoxiclav IV + Clarithromycin IV
Duration: 5–7 days (severe: 7–10)
Broad-spectrum IV: Pip-tazo or Meropenem
+ MRSA cover (Vancomycin / Linezolid) if risk factors
Duration: 7–8 days. De-escalate based on cultures.
Supportive: O₂, bronchodilators, NIV/intubation if needed
Corticosteroids — consider in severe cases
Antibiotics NOT given initially — add only if secondary bacterial infection develops
Remove source of exposure. Decontamination if skin/oral contact.
Prognosis
Generally good with treatment. 30-day mortality: ~5–14% (hospitalised). Full recovery expected in most; elderly & severe cases higher mortality.
Worse prognosis than CAP. 30-day mortality: ~20–50%. MDR organisms, ICU stay, and underlying disease worsen outcomes.
Variable — depends on agent and severity. Mild cases resolve in 24–72h. Severe cases may progress to ARDS with mortality >30%.

CAP vs HAP vs Chemical Pneumonitis · Key Differentiating Points

Key differentiating points
CAP — think typical vs atypical
Typical (S. pneumoniae): sudden onset, high fever, single lobe, productive cough
Atypical (Mycoplasma, Legionella): gradual onset, dry cough, bilateral, younger patient
Always use CURB-65 to guide admission decision
HAP — think resistant organisms
Always cover MDR Gram-negatives and Pseudomonas — standard CAP antibiotics are NOT adequate
VAP (ventilator-associated) = HAP developing ≥48h after intubation
Prevention: head-of-bed elevation 30–45°, oral chlorhexidine, early mobilisation, VAP bundles
Chemical pneumonitis — no antibiotics initially
No fever in early hours — fever = infection, not aspiration itself
Mendelson's syndrome = aspiration of sterile gastric acid — bilateral infiltrates, rapid onset
Start antibiotics only if no improvement by 48–72h or cultures become positive
Home / Home / Clinical Cases / Respiratory System Clinical Cases / Chemical Pneumonitis

Related Topics

Management of Chemical Pneumonitis

  • Immediate Management Fro Chemical Pneumonitis

    • Remove the patient from further exposure
    • Ensure a safe environment
    • Assess airway, breathing, and circulation
    • Provide oxygen when needed

    Supportive Treatment

    • Oxygen therapy
    • Bronchodilators for bronchospasm
    • Mechanical ventilation if respiratory failure develops

    Aspiration Pneumonitis

    • Supportive care is the main treatment
    • Monitor respiratory status closely

    Antibiotics For Chemical Pneumonitis

    • Not routinely indicated for uncomplicated chemical or aspiration pneumonitis
    • Consider only when secondary bacterial infection is suspected

    Corticosteroids

    • Not routinely recommended
    • May be considered only in selected specific chemical exposures

    Severe Chemical Pneumonitis

    May require:

    • ICU admission
    • High-flow oxygen
    • Mechanical ventilation
    • ARDS management

Complications of Chemical Pneumonitis

  • Acute respiratory failure
  • Acute respiratory distress syndrome (ARDS)
  • Pulmonary edema
  • Secondary bacterial pneumonia
  • Bronchospasm
  • Airway injury
  • Pulmonary fibrosis
  • Death

Prognosis of Chemical Pneumonitis

  • Prognosis depends on:
    • Type of chemical
    • Amount of exposure
    • Duration of exposure
    • Severity of initial lung injury
    • Development of ARDS
  • Mild cases may recover completely.
  • Severe exposure may cause prolonged respiratory failure.
  • Some patients develop chronic lung disease or pulmonary fibrosis.
  • Early removal from exposure and appropriate supportive care improve outcomes.

Key Points / Clinical Pearls of Chemical Pneumonitis

  • Chemical pneumonitis is caused by direct chemical injury to the lungs.
  • It is not initially a bacterial infection.
  • Aspiration of gastric contents is an important cause.
  • Symptoms may be immediate or delayed.
  • The initial chest X-ray may be normal.
  • Treatment is mainly supportive.
  • Antibiotics are not routinely required unless secondary infection is suspected.
  • Corticosteroids are not routinely recommended.
  • Severe cases may progress to ARDS and respiratory failure.