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article imageThe unique smell of human death — What makes it different?

By Karen Graham     Sep 26, 2015 in Science
The smell of death, particularly human death, is singularly unique. The smell of a human decomposing is sort of a fruity assault on the olfactory organs, and distinguishes it from all other animals.
While the subject of human death may seem to be ghoulish, in fact, the study of the chemical compounds that make that smell is important to understanding the decomposition process in not just human beings, but in all creatures.
Everyone is aware of what cadaver dogs are used for. We have seen them on our television screens, searching the rubble of the World Trade Center, the aftermath of earthquakes in Nepal and China, and more recently, in the charred remains of homes devastated by the wildfires in California.
Indiana Bones  aka Indy  is the Los Angeles County Coroners Department first cadaver dog. With his t...
Indiana Bones, aka Indy, is the Los Angeles County Coroners Department first cadaver dog. With his trainer, Investigator Renee Grand Prix, Indy is dispatched to crime scenes where he sniffs out evidence.
John Vande Wege
So how do the dogs know what a human being smells like in death? What compounds are used in training these highly-specialized canines? For over ten years, scientists have been researching the "smell of death."
It started in 2004 when a University of Tennessee research station called the Body Farm released a paper on the gasses released during late decomposition. Another study done at the same time came out of Greece, where researchers looked at the gasses released in the early stages of decomposition.
The smell of human death isolated
In 2010, analytical chemist, Eva Cuypers and her forensic toxicology lab at the University of Leuven in Belgium was approached by the Belgian Disaster Victim Identification Team. They needed help in finding the best way to train cadaver dogs in picking out the smell of human death.
Cuypers' team went to work, separating the tissues and organs of six human cadavers and 26 different animals. The samples were put into jars in a laboratory closet. The screw-capped jars, which let in a small amount of air, had stoppered holes on the top. This allowed lab assistants to periodically take samples of the gasses released by the samples.
Cuypers included a pig as one of the 26 samples used in the study because pigs have a great similarity to humans. They carry the same microbes in their intestines, they have the same percentage of body fat, and even similar hair to people. The one thing that has not been studied was their decomposition compared to human decomposition.
The research team was able to identify 452 distinct chemical compounds released by all the samples, human, and animal. Eight of those were specific to humans and pigs, and five esters were unique to humans.
Pigs and humans share biological similarities  and are often used in studies of decomposition.
Pigs and humans share biological similarities, and are often used in studies of decomposition.
YouTube
Specifically, human corpses emit a unique five-chemical cocktail — comprised of 3-methylbutyl pentanoate, 3-methylbutyl 3-methylbutyrate, 3-methylbutyl 2-methylbutyrate, butyl pentanoate and propyl hexanoate — that separates them from the rest of the animal kingdom.
Lead author of the study, Elien Rosier, a forensic toxicologist at the University of Leuven in Belgium, said their work could even lead to the use of portable devices in finding human remains. She also pointed out that the decomposition gasses change over time as the body degrades. She said that during the early stages, distinct sulfurous compounds are given off, but they eventually disappear.
Speaking to the journal Science, Dr Cuypers said: "The next step in our research is to see whether the same compounds are found in buried, full decomposing bodies in the field and to see whether dogs trained on the mixture respond more specific[ally] to human decomposing bodies."
But it is now possible that one day, the smell of human death could be bottled for use as an aid in training cadaver dogs. Of course, some ghoulish people might think the bottled product could be used at Halloween parties to give some added ambiance to the spooky surroundings.
This interesting study, "The Search for a Volatile Human Specific Marker in the Decomposition Process," was published in the journal PLOS One September 16, 2015.
More about smell of death, chemical cocktail, esters, Cadaver dogs, pigs and humans
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