Irritant Gas Exposure

Basics

Description

  • An irritant is any noncorrosive substance that on immediate, prolonged, or repeated contact with respiratory mucosa will induce a local inflammatory reaction
  • Respiratory irritants are inhaled as gases, fumes, particles, or liquid aerosols
  • Inhaled irritants:
    • Pulmonary toxicity is determined primarily by their water solubility
  • Inhalation accidents frequently involve a mixture of irritant gases, simple asphyxiants, and chemical asphyxiants:
    • Carbon monoxide
    • Hydrogen cyanide
    • Hydrogen sulfide
    • Oxides of nitrogen
    • Carbon dioxide
  • Risk factors include exposure to potential irritants:
    • Occupational
    • Leisure
    • Intentional
    • Accidental
  • Pathophysiology:
    • Cellular injury through interaction with respiratory mucosal water with subsequent formation of acids, alkalis, and free radicals

Etiology

  • Settings:
    • Industrial: Chemical manufacturing, mining, plastics, and petroleum industries
    • Home: Improper use or storage of cleaning chemicals
    • Fires: Combustion yields toxic gases
    • Civil disturbance: Riot control agents
  • Immediate onset of upper airway inflammation with highly water-soluble irritant gases or with aerodynamic diameter >5 mm:
    • Ammonia (fertilizers, refrigerants, dyes, plastics, synthetic fibers, cleaning agents):
      • Immediate symptoms range from mild edema and erythema to full-thickness burns and airway obstruction
    • Sulfur dioxide (fumigants used on produce, bleaching, tanning, brewing, wine making, combustion of coal, and smelting of sulfide-containing ores):
      • Combines with water, forming sulfuric acid
    • Hydrogen chloride (formed during combustion of chlorinated hydrocarbons such as polyvinyl chloride):
      • Combines with water, forming hydrochloric acid
    • Chloramine (generated when ammonia and bleach are mixed):
      • When exposed to moist surfaces, releases hypochlorous acid
    • Acrolein (production of plastics, pharmaceuticals, synthetic fibers; formed during combustion of petroleum products, cellulose, wood, paper):
      • May cause protein damage via free radical production and sulfhydryl binding
    • Ethylene oxide (sterilant, production of glycols):
      • Alkylating agent. Hypersensitivity possible
    • Formaldehyde (production of plywood, particle board, insulation; combustion product of gas stoves and heaters):
      • Combines with water to form sulfuric acid and formic acid
    • Hydrogen fluoride (combustion of fluorinated hydrocarbons, petroleum, and semiconductor industries):
      • Depletes calcium stores, resulting in cell death
    • Riot-control agents (capsaicin [OC], chlorobenzylidene malononitrile [CS], and chloroacetophenone [CN]):
      • Lacrimation agents, which cause temporary ocular discomfort
      • Respiratory mucosa irritation possible at high concentrations and enclosed spaces
  • Latent period of minutes to hours before onset of symptoms with irritant gases of intermediate water solubility or aerodynamic diameter of 1–5 mm:
    • Chlorine (product of chlorinated chemicals; bleaching agent):
      • Upper and lower airway damage after reacting with water to form hydrochloric and hypochlorous acids
    • Hydrogen sulfide (sewage/organic matter decay, petroleum industry):
      • Irritant at low concentrations (∼50–500 ppm), chemical asphyxiant at high concentrations (>∼500 ppm)
      • Reacts with respiratory secretions forming sodium sulfide, a caustic. Results in upper and lower airway damage
  • Delayed onset of symptoms up to 24 hr after inhalation with irritant gases of poor water solubility or aerodynamic diameter <1 mm (with little or no warning of exposure):
    • Oxides of nitrogen produced:
      • In manufacture of dyes and fertilizers
      • By electric arc welding and gas blowing
      • By fermentation of nitrogen-rich silage (silo-filler's disease)
      • In combustion of nitrocellulose and polyamides
    • Phosgene/carbonyl chloride (arc welding and pesticide production: Combustion of chlorinated hydrocarbons and solvents)
    • Ozone (produced during arc welding)
    • Metal phosphides (react with water to form phosphine gas)
    • Metal pneumonitis:
      • Cadmium oxide (smelting, welding, and electroplating) – delayed pulmonary fibrosis possible
      • Zinc oxide (welding, galvanization) – metal fume fever possible
      • Mercury vapor (heating, vacuuming)

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