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Occupational and Environmental Lung Disease

Chapter 300 | Part 7: Disorders of the Respiratory System · Part 7 – Respiratory Disorders · Chapter 300

Key Clinical Points

  1. Occupational and environmental lung diseases are often clinically indistinguishable from non-environmental origins; etiology is frequently multifactorial.
  2. Knowledge of exposure is critical for management, prognosis, and identifying legal/financial implications (e.g., cessation of exposure for occupational asthma or hypersensitivity pneumonitis).
  3. Asbestos-related diseases: 15–19 years latency for lung cancer; ≤1–2 years for mesothelioma.
  4. Acute silicosis presents with 'crazy paving' on HRCT (ground-glass opacities with thickened septa).
  5. Chronic silicosis features upper lobe nodules after 15–20 years and may present with 'eggshell' hilar calcification.
  6. Beryllium: Chronic Beryllium Disease (CBD) is distinguished from sarcoidosis by BeLPT results and noncaseating granulomas.
  7. Byssinosis: Characterized by 'Monday chest tightness' in cotton, flax, hemp, or jute workers; may progress to an obstructive pattern after >10 years of exposure.
  8. Farmer's lung: Hypersensitivity pneumonitis from moldy hay (thermophilic actinomycetes); presents with fever, chills, malaise, cough, and dyspnea 4–8 h after exposure.
  9. Particle size impact: <2.5 μm (fine-mode) deposit in lower airways; <0.1 μm (ultrafine) can enter systemic circulation; >10–15 μm do not pass the nose/throat.
  10. Tungsten carbide ('hard metal') contains cobalt and may cause giant cell interstitial pneumonitis or occupational asthma.
  11. In the US, drug-induced eosinophilic pneumonias are the most common cause of eosinophilic pulmonary infiltrates.
  12. Strongyloides stercoralis can lead to fatal hyperinfection syndrome in immunocompromised hosts.

DEFINITION & OVERVIEW

• General Characteristics: Difficulty of Diagnosis: Often indistinguishable from non-environmental origins; etiology may be multifactorial. Clinical Impact: Knowledge of exposure is critical for management (e.g., cessation), prognosis, and identifying legal/financial implications. Public Health: Identification allows for identifying other exposed individuals and recognizing new associations (e.g., nylon flock worker's lung, diacetyl-induced bronchiolitis obliterans, military burn pit-related constrictive bronchiolitis).

• Importance of Exposure History: Workplace Inquiry: Must include specific contaminants, visible dust, chemical odors, workspace size/ventilation, use of PPE, and coworker symptoms. Non-Work Sources: Hobbies, home characteristics, second-hand smoke, proximity to traffic or industrial facilities. Temporal Association: Link between work shift and symptom onset (e.g., Farmer's lung 4–8h post-exposure; Byssinosis 'Monday chest tightness').

EPIDEMIOLOGY

• Prevalence: Asthma/COPD: 15–20% of the burden of adult asthma and COPD is estimated to be due to occupational factors. Eosinophilic Infiltrates: Drug-induced eosinophilic pneumonias are the most common cause in the US. Parasitic Infections: Travel or immigration history may indicate parasite-associated disorders (e.g., Filariasis, Strongyloidiasis). Treatment: Tropical eosinophilia due to Wuchereria bancrofti or Wuchereria malayi is treated successfully with diethylcarbamazine.

ETIOLOGY & PATHOPHYSIOLOGY

• Physical/Chemical Properties of Inhaled Agents: Solubility: - Water-soluble (ammonia, SO_2) → upper/proximal airway irritation. - Less soluble (NO_2, phosgene) → bronchiolar/alveolar penetration → acute chemical pneumonitis. Particle Size Impact: - >10–15 μm → do not penetrate beyond nose and throat. - <2.5 μm (fine-mode) → dominate lower airway deposition. - <0.1 μm (ultrafine) → can enter systemic circulation. Complicated Silicosis: Defined by particles of 1 cm in diameter.

• Silicosis: Pathophysiology: Silica causes alveolar macrophage dysfunction → increased risk of infection (Mycobacterium tuberculosis, atypical mycobacteria, and fungi). Treatment Note: Patients with silicosis require longer treatment for latent tuberculosis. Immunological Effect: Silica acts as an immunoadjuvant → potential for autoimmune disorders (rheumatoid arthritis, scleroderma) and lung cancer. Other Silicates: Fuller's earth, kaolin, mica, diatomaceous earths, silica gel, soapstone, carbonate dusts, and cement dusts.

• Asbestosis: Latency: 15–19 years for lung cancer; ≤1–2 years for mesothelioma. Radiology: Pleural plaques (indicate exposure) and subpleural reticulation (Fig 3).

• Coal Worker's Pneumoconiosis (CWP): Simple CWP: Small, rounded opacities (similar to silicosis); usually no impairment. Seen in ~10% of all coal miners; up to 50% of anthracite miners with >20 years of work. Complicated CWP: Nodules ≥1 cm in diameter → potential for PMF and mortality. Caplan Syndrome: Combination of pneumoconiotic nodules and seropositive rheumatoid arthritis.

• Beryllium: Clinical Presentation: Chronic granulomatous disease similar to sarcoidosis. Differentiation: BeLPT (beryllium lymphocyte proliferation test) → identifies specific cell-mediated immune response (measured by radiolabeled thymidine uptake). Genetics: Susceptibility linked to HLA-DP alleles.

• Tungsten Carbide ('Hard Metal'): Composition: Contains cobalt. Clinical Manifestation: Giant cell interstitial pneumonitis or occupational asthma.

• Organic Dusts: Byssinosis: Exposure to cotton, flax, hemp, or jute → 'Monday chest tightness' and FEV1 drop during work shift. After >10 years of exposure, more likely to show an obstructive pattern. Farmer's Lung: Moldy hay (thermophilic actinomycetes) → hypersensitivity pneumonitis; 4–8h post-exposure; no wheezing.

• Toxic Chemicals: Acid Anhydrides: Respiratory irritation; chronic exposure leads to asthma/bronchitis. Acroline: Mucous membrane irritant; can cause bronchiectasis. Cadmium: Acute respiratory distress (ARDS); chronic → COPD. Halides & Acid Salts: Potential for pulmonary edema or reduced FVC. Isocyanates: Can lead to bronchiolitis obliterans in 2–6 weeks. Ozone: Risk of new-onset asthma in children; delayed onset of bronchiolitis. Sulfur Dioxide: Bronchospasm (especially in asthmatics).

DIAGNOSTIC APPROACH

  1. Exposure History:
  2. Identify specific contaminants, visible dust, and chemical odors.
  3. Assess workspace size/ventilation and use of PPE.
  4. Evaluate temporal association (e.g., 4–8h for Farmer's lung; 'Monday chest tightness' for Byssinosis).
  5. Clinical Correlation:
  6. Match symptoms with work shifts to differentiate from non-environmental causes.
  7. Specific Testing:
  8. BeLPT: To differentiate Chronic Beryllium Disease from sarcoidosis.
  9. Pulmonary Function Tests: Monitor FEV1 during work shifts in cotton dust exposure.
  10. Imaging:
  11. CXR/HRCT: Identify 'crazy paving' (acute silicosis), pleural plaques (asbestosis), or upper lobe nodules (chronic silicosis).

MANAGEMENT & TREATMENT

  1. Exposure Mitigation:
  2. Cessation of exposure → primary management for occupational asthma and hypersensitivity pneumonitis.
  3. Environmental Controls (Byssinosis):
  4. Exhaust hoods, increased ventilation, and wetting procedures to reduce dust.
  5. PPE required during specific operations.
  6. Medical Intervention:
  7. Whole-lung lavage → used in acute silicosis for symptomatic relief and to slow progression.
  8. Workplace Safety:
  9. Move workers with persistent symptoms or reduced lung function to lower-risk areas.

KEY PEARLS & HIGH-YIELD POINTS

• Asbestos Latency: 15–19 years for cancer; ≤1–2 years for mesothelioma. Silicosis Differentiation: - Acute: 'Crazy paving' (Fig 1). - Chronic: Upper lobe nodules, 'eggshell' hilar nodes (Fig 4). Beryllium vs. Sarcoidosis: - Key differentiator is the BeLPT. Tungsten Carbide: - Contains cobalt → potential for giant cell interstitial pneumonitis. Particle Size Rule: - >10–15 μm → stop at nose/throat. - <2.5 μm (fine) → lower airways. - <0.1 μm (ultrafine) → systemic circulation. Byssinosis: - 'Monday chest tightness' in cotton/flax/hemp/jute workers. Farmer's Lung: - 4–8h post-exposure; no wheezing; caused by moldy hay (thermophilic actinomycetes).

Reference Tables

TABLE 299-4 Infectious Causes of Pulmonary Eosinophilia Löffler Syndrome Ascaris Hookworm Schistosomiasis Heavy…

Harrison's 22e, p.2234

  • Löffler Syndrome
  • Ascaris
    Hookworm
    Schistosomiasis
  • Heavy Parasite Burden
  • Strongyloidiasis
  • Direct Pulmonary Penetration
  • Paragonimiasis
    Visceral larval migrans
  • Immunologic Response to Organisms in Lungs
  • Filariasis
    Dirofilariasis
  • Cystic Disease
  • Echinococcus
    Cysticercosis
  • Other Nonparasitic
  • Coccidioidomycosis
    Basidiobolomycosis
    Paracoccidioidomycosis
    Tuberculosis

TABLE 300-1 Categories of Occupational Exposure and Associated Respiratory Conditions

Harrison's 22e, p.2236

OCCUPATIONAL EXPOSURES NATURE OF RESPIRATORY RESPONSES COMMENT
Inorganic Dusts
Asbestos: mining, processing, construction, ship repair Fibrosis (asbestosis), pleural disease, cancer,
mesothelioma		 Virtually all new mining and construction with
asbestos done in developing countries
Silica: mining, stone cutting, sandblasting, quarrying,
artificial stone manufacture and installation		 Fibrosis (silicosis), progressive massive fibrosis
(PMF), cancer, tuberculosis, chronic obstructive
pulmonary disease (COPD)		 Improved protection in United States; persistent risk in
developing countries
Coal dust: mining Fibrosis (coal worker’s pneumoconiosis),
PMF, COPD		 Risk persists in certain areas of United States,
increasing in countries where new mines open
Beryllium: processing alloys for nuclear power and
weapons, aerospace, and electronics		 Acute pneumonitis (rare), chronic granulomatous
disease, lung cancer (highly suspect)		 Risk in high-tech industries persists
Other metals: aluminum, chromium, cobalt, nickel, titanium,
tungsten carbide, or “hard metal” (contains cobalt)		 Wide variety of conditions from acute
pneumonitis to lung cancer and asthma		 New diseases appear with new process development
Organic Dusts
Byssinosis (an asthma-like syndrome), chronic
bronchitis, COPD
Asthma, chronic bronchitis, COPD
Hypersensitivity pneumonitis (farmer’s lung),
asthma, chronic bronchitis
Asthma, chronic bronchitis, COPD,
hypersensitivity pneumonitis, pneumoconiosis,
and cancer

TABLE 300-2 Selected Common Toxic Chemical Agents That Affect the Lung AGENT(S) Acid anhydrides Acid fumes: H SO , HNO

Harrison's 22e, p.2239

AGENT(S) SELECTED EXPOSURES ACUTE EFFECTS FROM HIGH OR
ACCIDENTAL EXPOSURE		 CHRONIC EFFECTS FROM
RELATIVELY LOW EXPOSURE
Acid anhydrides Manufacture of resin esters, polyester resins,
thermoactivated adhesives		 Nasal irritation, cough Asthma, chronic bronchitis,
hypersensitivity pneumonitis
Manufacture of fertilizers, chlorinated organic compounds,
dyes, explosives, rubber products, metal etching, plastics		 Mucous membrane irritation, followed by
chemical pneumonitis 2–3 days later
Acrolein and other
aldehydes		 By-product of burning plastics, woods, tobacco smoke Mucous membrane irritant, decrease in lung
function		 Upper respiratory tract irritation
Refrigeration; petroleum refining; manufacture of fertilizers,
explosives, plastics, and other chemicals		 Same as for acid fumes, but bronchiectasis
also has been reported
Cadmium fumes Smelting, soldering, battery production Mucous membrane irritant, acute respiratory
distress syndrome (ARDS)		 Chronic obstructive pulmonary
disease (COPD)
Manufacture of resins, leathers, rubber, metals, and woods;
laboratory workers, embalmers; emission from urethane
foam insulation		 Same as for acid fumes
Halides and acid
salts (Cl, Br, F)		 Bleaching in pulp, paper, textile industry; manufacture
of chemical compounds; synthetic rubber, plastics,
disinfectant, rocket fuel, gasoline		 Mucous membrane irritation, pulmonary
edema; possible reduced forced vital
capacity (FVC) 1–2 years after exposure		 Upper respiratory tract irritation,
epistaxis, tracheobronchitis
By-product of many industrial processes, oil, other
petroleum processes and storage		 Increase in respiratory rate followed by
respiratory arrest, lactic acidosis, pulmonary
edema, death
Isocyanates (TDI,
HDI, MDI)		 Production of polyurethane foams, plastics, adhesives,
surface coatings		 Mucous membrane irritation, dyspnea,
cough, wheeze, pulmonary edema		 Upper respiratory tract irritation,
cough, asthma, hypersensitivity
pneumonitis, reduced lung function
Silage, metal etching, explosives, rocket fuels, welding,
by-product of burning fossil fuels		 Cough, dyspnea, pulmonary edema may
be delayed 4–12 h; possible result from
acute exposure: bronchiolitis obliterans in
2–6 weeks
Ozone Arc welding, flour bleaching, deodorizing, emissions from
copying equipment, photochemical air pollutant		 Mucous membrane irritant, reduced
pulmonary function transiently in children
and adults, asthma exacerbation		 Excess cardiopulmonary mortality
rates, increased risk for new-onset
asthma in children
Organic compound, metallurgy, volatilization of chlorine-
containing compounds		 Delayed onset of bronchiolitis and pulmonary
edema
Sulfur dioxide Manufacture of sulfuric acid, bleaches, coating of
nonferrous metals, food processing, refrigerant, burning of
fossil fuels, wood pulp industry		 Mucous membrane irritant, epistaxis,
bronchospasm (especially in people with
asthma)		 Chronic bronchitis