Hydrogen Sulfide Toxicity Clinical Presentation

Updated: Feb 25, 2022
  • Author: David Vearrier, MD, MPH; Chief Editor: Michael A Miller, MD  more...
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The presence of hydrogen sulfide usually is apparent because of the characteristic rotten egg smell. However, concentrations above 150 ppm may cause olfactory nerve paralysis so that the victim may have no warning of exposure. Similarly, continuous exposure to low concentrations of hydrogen sulfide result in olfactory fatigue and loss of the ability to smell or detect the gas even if it is still present in the environment.

Exposures can be subdivided into low-, high-, and very high-level categories. Low-level exposure often is more chronic in nature and usually is seen in industrial settings. Chronic low-level exposure of hydrogen sulfide results primarily in irritation to mucous membranes and the respiratory system. Other toxic effects are headaches, asthenia, bronchitis, pronounced deficits in balance and reaction time, dizziness, insomnia, and overpowering fatigue. [10]

High-level exposures of hydrogen sulfide result in more neurologic and pulmonary symptoms, as follows:

  • Cough
  • Dyspnea
  • Vertigo
  • Confusion
  • Nausea and vomiting
  • Possible loss of consciousness
  • Hemoptysis

Very high (> 1000 ppm) concentrations lead to the following manifestations:

  • Myocardial infarction
  • Sudden loss of consciousness ("knock down")
  • Seizure
  • Cardiopulmonary arrest

Physical Examination

Low-level exposure of hydrogen sulfide most often affects the mucous membranes and may show the following few physical signs:

  • Conjunctivitis "gas eye" (even at levels of only 4 ppm)
  • Pharyngitis
  • Green-gray line on gingiva
  • Wheezing

High-level exposure of hydrogen sulfide may manifest as follows:

Perform a secondary survey to rule out traumatic injuries. Historically, these have been found in about 10% of victims.