The 7 deadly sins of hydrogen sulfide (H2S)

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Mass Extinction and Hydrogen Sulfide

You may not know much about hydrogen sulfide (H2S) but you are certainly familiar with its existence. It is the chemical compound that gives the foul odour of rotten eggs. Although the smell may not necessarily kill you, H2S can certainly cause human death. In fact, H2S has big four elements that you do not want to come across: it is flammable and explosive, it is poisonous, and it is corrosive. Given this, there are several documented cases where H2S has caused harm and even death. Below we list 7 examples of these deadly sins.


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  1. The Permian-Triassic Mass Extinction

This extinction event was the biggest of all of the mass extinction events, killing an estimated 90% of all species on Earth. Some scientists believe that hydrogen sulfide had a direct hand in causing the catastrophe (Kump et al 2005). Towards the end of the Permian the oceans had become anoxic and sulphate reducing bacteria caused a build-up of H2S in the oceans. Upwelling of the H2S from lower depths in the ocean to surface waters caused H2S to then enter the atmosphere. The amount of H2S was so great that atmospheric H2S levels reached toxic levels leading to the direct poisoning of terrestrial plants and animals. H2S also interacted with ozone, effectively eliminating the ozone layer, and causing massive doses of UV-B radiation to reach the Earth’s surface. This influx of UV-B radiation would have killed off many species at the time.

Other scientists have questioned this scenario (e.g. Lamarque et al 2007) citing the residence time of H2S (about 10 days) in the atmosphere would be too short to cause such a widespread and prolonged extinction event. But if it indeed did occur, then H2S significantly shaped the direction of evolution and biodiversity leading to the world we have today.



Kump et al (2005). Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia. Geology, 33, 397-400.

Lamarque et al (2007). Role of hydrogen sulfide in a Permian-Triassic boundary ozone collapse. Geophysical Research Letters, 34, L02801.


more information

The Permo-Triassic mass extinction and its aftermath


Mass Extinction and Hydrogen Sulfide

The species depicted in this image, trilobites, succumbed to the massive extinction event at the end of the Permian period. Image copied with permission, Witze 2015. Image source:



  1. H2S Leads to Mass Fish Kills

Mass fish kill events occur across many rivers and estuaries in all parts of the world. In New South Wales, it is estimated that on average there are 40 mass fish kill events per year (DPI NSW 2011). The causes can be numerous and complex and hydrogen sulfide has been implicated in some events.

Hydrogen sulfide can build in sediments at the bottom of rivers, lakes lagoons and billabongs. These H2S enriched sediments build due to anoxic conditions that arise from poor decomposition. When left undisturbed, such sediments do not cause any issues and many microbial species have adapted to the H2S enriched environment. Microprofiling studies with H2S microsensors often demonstrate that, over a depth of only a few millimetres, sediments can move from highly enriched in oxygen to a completely oxygen depleted state and a rapid increase in H2S.

H2S in Sediment Biogeochemistry

An example of an oxygen and hydrogen sulfide microprofile with measurements commencing in water (-1000um), moving through the diffusive boundary layer (DBL), and into sediment (0 to 2000um). As values of oxygen reach zero, there is an increase in the amount of H2S in the sediment. Image source: Unisense.


When these sediments are disturbed, due to bioactivity or large scale events such as a storm, H2S is released into the water column leading to a depletion of dissolved oxygen. Subsequently, a mass fish kill event can occur and such a process has been implicated in mass kill fish events in Delaware, United States (Luther III et al 2004).

But it is not all bad news for fish if H2S is present in water in high concentrations. In cave ecosystems in Mexico, the Cave Molly (Poecilia mexicana) dominates areas where there is high H2S concentrations. The diversity of the fish community in such caves is heavily reduced with the Cave Molly often dominating these communities. Scientists believe that the Cave Molly is one of the only examples where a vertebrate species, of any kind, can actually tolerate a high H2S environment (Tobler et al 2006).



DPI NSW (2011).

Luther III et al (2004). The Roles of Anoxia, H2S, and Storm Events in Fish Kills of Dead-end Canals of Delaware Inland Bays. Estuaries, 27, 551-560.

Tobler et al (2006). Life on the edge: hydrogen sulfide and the fish communities of a Mexican cave and surrounding waters. Extremophiles, 10, 577-585.



  1. World War One and Chemical Warfare

Chemical warfare and World War One are synonymous but long before this a form of chemical warfare, involving hydrogen sulfide, was used in Bohemia. Around 600 years ago, in 1422, a castle belonging to King Charles IV was under siege. Around 2000 kegs were filled with the filth and rank of the streets and sewers of Prague and hurled into the besieged castle. The occupants were not only overwhelmed by the stench and prospect of having to clean such a mess, but they also exhibited symptoms linked with H2S intoxication (Gupta 2015).

Chemical warfare is considered a cowardly way to conduct war and is largely banned today. In the middle of World War One, however, both the Germans and the Allies were desperate for any advantage and chemical warfare was used over a number of years. In 1916, the British Army used H2S as a chemical agent in warfare on two occasions. H2S is not a particularly potent or useful chemical warfare gas, but as other gases were in short supply it was used on these occasions (Gupta 2015).



Gupta (2015). Handbook of Toxicology of Chemical Warfare Agents. Academic Press.



  1. A Wave of Japanese Suicides

In late April and early May, Japan enters a holiday season called Golden Week. It is a time when a number of public holidays coincide, but it is also a time when there is a spike in suicides. Japan has a terrible record of suicides numbering over 30,000 per year. Around 2008, a new and worrying trend emerged involving household chemicals, easily purchased at supermarkets, being used to create a hydrogen sulfide gas for suicides.

The concoction not only kills the intended person, but it can also affect rescuers or innocent by-standers. In northern Japan, 350 neighbours needed to be evacuated from their residence as one of the occupants had committed suicide using a H2S gas, and several floors of the Peninsula Hotel in Tokyo also needed to be evacuated following the suicide of a guest.


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ABC News Health Article on Japanese Suicides



  1. An X-Files scene, Denver City, Texas, 1975

At 5.15am on a Sunday morning, in February 1975, a police officer received a phone call from a frantic Mrs Patton. In the call, she told the police officer that she and her family were about to be killed by some leaking gas. The police officer raced to Mrs Patton’s home and about half a mile from the Patton home they noticed a ute veered off into a ditch on the side of the road. Slumped over the wheel was the former high school sporting hero, Steve Sparger. When the police officer arrived at the house there were dead chickens, rabbits, dogs, cats and even a coyote littered around the yard in a wide kill zone. Inside of the house, the furniture was overturned in signs of a frantic attempt to escape an unseen danger. The police officer found a car outside containing seven dead people. Another man was found on the ground nearby. In all, nine people, most from the Patton family, had died due to hydrogen sulfide intoxication.

The source of the H2S was from a nearby oil field. A newly introduced practice, at the time, would inject a concoction of 96% carbon dioxide and 4% hydrogen sulfide into underground reservoirs in order to put oil under pressure and force it into wells. If there is a leak during such a practice, it can lead to deadly consequences.


more information

Howard Swindle, “The Deadly Smell of Success”. Texas Monthly, June 1975. June 1975. Retrieved December 14, 2010.

Special Report in EENEWS on H2S and Oil Fields


H2S Fracking Gas

In response to H2S gas leaks in oil fields near urban areas, the initial response is to install signs warning locals of potential dangers. Image source: 



  1. The Potential Dangers of Manure

Manure is great fertiliser for your garden and agricultural operations can produce large quantities of manure. In particular, where animals are concentrated, such as in swine (pork) production, manure can accumulate in large quantities in pits. Inevitably, where there is sewage or manure there is hydrogen sulfide – giving its other common name of sewer gas. Small amounts of H2S are given off in these manure pits and long term exposure can lead to agricultural lung diseases such as asthma, tracheobronchitis, silo-filler’s disease and pulmonary edema. The most significant issue, however, can occur when the manure pits are cleaned. During such events, the release of H2S can be as high as 1000ppm, well above the 10ppm safety level recommended by USA’s OSHA. Therefore swine farmers need to be extra vigilant during their operations.


more information

Kirkhorn and Garry (2000). Agricultural lung diseases. Environmental Health Perspective, 108 (suppl 4), 705-712.



  1. A Foul Smell in a Thailand Mall

When you head down to a newly built mall, the last thing you would want is to shop for a new top or shoes with the smell of rotten eggs. But this is what shoppers in Thailand experienced in middle of 2014 following the opening of Siam Square One. Shoppers, business owners and staff all complained of the smell and there were even incidents of breathing difficulties. Management initially denied there was any problem, but after H2S was measured in the basement basin in the order of 83ppm the issue could no longer be ignored. Values above 10ppm are considered unsafe for humans and, in a newly built, modern shopping mall, values should actually be zero!

Further investigations found that the waste water treatment facility in the basement had failed or was not properly functioning. Engineers solved the problem by installing in a new waste water treatment system and slowly treating the large volume of water over several months. Fortunately, there were no reported deaths but a range of jewellery and coins were highly corroded.


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Thailand Mall Hydrogen Sulfide Leak

The Siam Square One Mall, Thailand. Image source: Siam Square One.