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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