Hydrogen Sulfide Toxicity

Excerpt

Hydrogen sulfide is a highly flammable, colorless, and toxic gas found naturally in sewage, swamps, manure gas, hot springs, geysers, and volcanoes. The toxic gas is found in the oil and gas industries and is used in food processing, paper mills, and tanneries. In addition, it is found in some homemade cleaning mixtures that are occasionally employed in suicide attempts.

Hydrogen sulfide poisoning occurs through inhalation. Low-level exposure typically produces mucous membrane and skin irritation, whereas high-level exposure produces fatal toxicity. Hydrogen sulfide gas has a characteristic odor of rotten eggs; however, due to the olfactory paralysis that occurs with exposure, this scent often dissipates, leading to a false sense of safety. Toxicity manifests with sudden unconsciousness, which can be fatal if the victim is not promptly removed from the environment of exposure. Other clinical manifestations of toxicity include conjunctivitis, pulmonary edema, seizures, and cardiopulmonary arrest. Toxicity is due to the inhibition of cellular respiration at cytochrome c oxidase, also known as Complex IV. The generation of free radicals also induces cellular damage and apoptosis. There is no known antidote for toxicity, and treatment is mainly supportive. Although it is still unclear if chronic low-level exposures produce pulmonary effects, there is evidence linking such exposures to neurotoxicity and delayed neurological issues.