Hydrogen Sulfide Toxicity

Updated: Feb 25, 2022
  • Author: David Vearrier, MD, MPH; Chief Editor: Michael A Miller, MD  more...
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Practice Essentials

Hydrogen sulfide (H2S) is a colorless, flammable gas that has strong odor of rotten eggs. H2S poisoning is a rarity, mainly observed in industrial settings. However, the deliberate mixture of household chemicals to create hydrogen sulfide is increasingly used as means of committing suicide, and these cases pose a potential risk for first responders. Emergency physicians must be aware of the presentation and management of hydrogen sulfide poisoning because rapid identification and treatment is essential for recovery.



Significant hydrogen sulfide poisoning usually occurs by inhalation. Local irritant effects, along with arrest of cellular respiration, may follow. Hydrogen sulfide forms a complex bond to the ferric moiety causing inhibition of mitochondrial cytochrome oxidase (iron-containing protein), thereby arresting aerobic metabolism in an effect similar to cyanide toxicity. Very high lipid solubility allows it to penetrate easily through biologic membranes.

As a cellular poison, hydrogen sulfide affects all organs, particularly the CNS and pulmonary system. The spectrum of illness depends on the concentration and duration of exposure, with concentration being more important than duration. [1] High concentrations (>700 ppm or >975 mg/m3) have the potential to cause sudden death, theoretically due to hydrogen sulfide’s effect on the brainstem respiratory center.



Hydrogen sulfide most often is encountered as a byproduct of the petroleum, viscose rayon, rubber, and mining industries. [1] The petroleum industry is responsible for most cases of hydrogen sulfide toxicity in North America. Organic decomposition of sulfur compounds in sewers, barns, liquid manure pits, ships' holds, and sulfur springs also produces hydrogen sulfide. In nature, hydrogen sulfide can be found in caves, sulfur springs, underground deposits of natural gas, or as result of volcanic eruptions.

The use of hydrogen sulfide as a means of committing suicide became a trend in Japan in 2007. [2] In these cases, bath sulfur was mixed with toilet bowl cleaner to produce the gas. Subsequently, the practice spread to the United States—facilitated by Internet sites providing instructions on the technique—and its use appears to be increasing. [2, 3, 4]

In these cases, hydrogen sulfide is created by mixing household chemicals (eg, an acidic detergent such as a toilet bowl cleaner, which acts as a proton donor, and a sulfur source such as a pesticide or bath salts), leading to the terms detergent suicide and chemical suicide. These are mixed in an enclosed space, such as a closet or an automobile, and despite the fact that suicide victims often place warning signs on closet doors or car windows, rescue workers and others entering the space have been affected. [3]



In the United States from 1999 to 2007, 45 deaths from hydrogen sulfide exposure occurred, all of them unintentional. [2] In occupationally-related hydrogen sulfide deaths, 25% of fatalities usually involve rescuers, professionals, or bystanders. [5]

Since 2008, approximately 2000 people in Japan have committed suicide by inhaling hydrogen sulfide. [6] In the United States, use of hydrogen sulfide for suicide reportedly resulted in 2 deaths in 2008, 10 in 2009, and 18 in 2010; however, the incidence is probably underreported. [2] In addition to deaths, at least 80% of hydrogen sulfide suicides “have resulted in injuries to police officers, firefighters, emergency workers or civilians exposed to the gas.” [6]

In 2019, 761 single exposures to hydrogen sulfide exposure were reported to Poison Control Centers in the United States. Major outcomes occurred in nine cases, along with one death. [7]  In 2020, 622 single exposures to hydrogen sulfide exposure were reported to Poison Control Centers in the United States. Major outcomes occurred in 16 cases and death in 6 cases, one of which was a suicide. [8]



Low-level exposures to hydrogen sulfide usually produce local eye and mucous membrane irritation, while high-level exposures rapidly produce fatal systemic toxicity. [9] Exposures of 700-800 ppm or greater can cause loss of consciousness and cardiopulmonary arrest. Complications include the following:

  • Acute respiratory distress syndrome
  • Acute myocardial infarction
  • Delayed neuropsychiatric sequelae

Occurrence of long-term neurologic sequelae from hydrogen sulfide exposure is unknown but appears to be linked to longer sublethal exposures. Paradoxically, high-concentration exposures of hydrogen sulfide may have no long-term effects.