Hydrogen sulfide

For an alternative meaning for H₂S, see H2S radar.

The chemical compound hydrogen sulfide (Hydrogen sulphide in British English) H₂S is the gas that causes the unpleasant smell of rotten eggs. It can result from bacterial breakdown of sulfur-containing proteins and is responsible for much of the foul odor of feces and flatulence and for the decay smells in swamps.

The gas is highly toxic and can kill or seriously injure sewer workers.

Hydrogen sulfide occurs naturally in crude petroleum, natural gas, volcanic gases, and hot springs. Hydrogen sulfide can also result from industrial activities, such as food processing, sewage treatment, coke ovens, paper mills, tanneries, and petroleum refineries..

It is an acidic gas which reacts with alkali and metals such as silver. This is the reason why silver jewelry turns black when exposed to polluted atmosphere for a long duration. The silver sulfide resulting from the reaction is black in colour.

Chemically, hydrogen sulfide is similar to water (H₂O) since oxygen and sulfur occur in the same periodic table group.

Health effects

Hydrogen sulfide is considered a broad-spectrum poison, meaning it can poison several different systems in the body. Breathing high levels of hydrogen sulfide may paralyze the olfactory nerve (making it impossible to smell the gas) and can cause death within just a few breaths. There could be loss of consciousness after one or more breaths.

Exposure to lower concentrations can result in eye irritation, a sore throat and cough, shortness of breath, and fluid in the lungs. These symptoms usually go away in a few weeks. Long-term, low-level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness.

Animal studies showed that pigs that ate food containing hydrogen sulfide had diarrhea after a few days and weight loss after about 105 days.

Hibernation

In 2005, Mark Roth and other scientists from the University of Washington and the Fred Hutchinson Cancer Research Center in Seattle demonstrated that mice can be put into a state of suspended animation by applying a low dosage of Hydrogen sulfide (80 ppm H₂S) in the air. Such a hibernation is normally observed in toads. The heartbeat of the animals sank from 120 to 10 beats per minute and their temperature fell from 37 degrees Celsius to 11 degrees Celsius. The mammals survived this procedure for 6 hours and showed no negative health consequences. Mice don't hibernate in nature but they can fall into a state called clinical torpor when food shortage occurs. Animals and humans produce Hydrogen sulfide in their body by metabolism. Some researchers assume that the gas regulates the metabolism activity and the body temperature. This discovery seems to confirm these theories.

Weblinks

• BBC about suspended animation by H2S