Toxicology – Hydrogen Sulfide Poisoning

Source

Hydrogen sulfide is a toxic gas produced during the breakdown of organic material. It may accumulate in sewers, manure pits, petroleum facilities, paper mills, and other poorly ventilated confined spaces. Because it is heavier than air, it can collect in low-lying areas.

Typical Presentation

Workers in a confined space may suddenly collapse after exposure to hydrogen sulfide. Rescuers who enter without proper respiratory protection can also become rapidly incapacitated.

Clinical Features

Lower-level exposure mainly causes mucous membrane and respiratory irritation, including:

• Runny nose
• Tearing
• Red or irritated eyes
• Headache
• Nausea and vomiting
• Dizziness
• Confusion

More severe exposure can produce:

• Sudden loss of consciousness
• Respiratory failure
• Cardiac dysrhythmias
• Coma
• Death
• Delayed pulmonary edema

Mechanism of Action

Hydrogen sulfide inhibits cytochrome oxidase, disrupting cellular oxygen utilization in a manner similar to cyanide. It also directly irritates the eyes and respiratory tract. At high concentrations, it can cause extremely rapid CNS depression and collapse.

Although hydrogen sulfide has a characteristic rotten-egg odor, prolonged or intense exposure can impair the sense of smell, making odor an unreliable warning sign.

Management

Treatment is mainly supportive:

• Immediate removal from the contaminated environment by appropriately protected rescuers
• Airway and respiratory support
• High-concentration oxygen
• Continuous cardiac monitoring
• Treatment of dysrhythmias and other complications as needed

Specialized therapies such as hyperbaric oxygen or hydroxocobalamin have been considered in severe cases, but supportive resuscitation remains the mainstay of treatment.

Key Points

• Hydrogen sulfide is especially dangerous in confined spaces.
• High concentrations can cause sudden collapse with little warning.
• The rotten-egg smell cannot be relied upon because olfactory fatigue may occur.
• Delayed pulmonary complications can develop even after the initial exposure.