Hydrogen sulfide is a colorless, flammable gas that smells like rotten eggs at low concentration levels in the air. It is commonly known as sewer gas, stink damp, and manure gas. At high concentration levels, it has a sickening sweet odor. At extremely high levels, a person can lose their ability to smell the gas and become unaware of its presence. This condition, known as olfactory fatigue, can also occur when people have been exposed to hydrogen sulfide for a longer period of time. Hydrogen sulfide is heavier than air, so it can build up in low-lying areas and enclosed spaces.
In the environment, hydrogen sulfide is produced from the bacterial breakdown or decomposition of dead plant and animal matter, especially when there is a lack of oxygen. It occurs in unrefined natural gas and petroleum, volcanic gases, sulfur deposits, hot springs, and swamps. Beaches with large amounts of decaying seaweed and mudflats with trapped organic material below the sediment can produce hydrogen sulfide. Hydrogen sulfide also occurs naturally in the human body and is produced by human and animal wastes.
Hydrogen sulfide is used in preparation of other sulfur chemical compounds and can be a byproduct of industrial activities such as pulp and paper mills, manufacturing rayon, food processing, tanneries and fur processing, and oil and natural gas refineries. Hydrogen sulfide's chemical formula is H2S.
Hydrogen sulfide is both an irritant and a chemical asphyxiant (it will take the place of oxygen so there is not enough for someone to breathe). Some people are able to detect it at very low concentrations while others may not smell it. Some people have greater sensitivities than others to the potential effects. Low concentrations may irritate the eyes, nose, throat, and respiratory system. Asthmatics may experience difficulty in breathing. Moderate concentrations can cause more severe eye and respiratory irritation, headache, dizziness, nausea, and vomiting. Brief exposures to high concentrations of hydrogen sulfide can cause loss of consciousness, coma, and possible death.
In most cases, a person who is exposed to hydrogen sulfide will make a full recovery within hours to a few weeks - it depends upon the individual and the level of exposure. In some individuals, there have been permanent or long-term effects such as headaches, poor attention span, poor memory, and poor coordination. Long-term, low level exposure to hydrogen sulfide may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness.
Content Source: Environmental Toxicology Program