Researchers are closing in on exactly what it is that cadaver dogs are sniffing for when they’re deployed. That uniquely human “smell of death” may be created when a combination of compounds, called esters, is released by a decomposing body, according to findings published in PLoS ONE this week.
When we and other animals decompose, a wide spectrum of volatile organic compounds (VOCs) is emitted into the environment. Previous work to characterize that smell had already identified a variety of compounds, but a specific marker for human decomposition hadn't been isolated.
So, University of Leuven’s Elien Rosier and colleagues examined the compounds that were released over the course of six months from the decomposing remains of six humans and 26 animals: rabbits, mice, moles, frogs, chicks, robins, a woodpecker, warbler, sparrow, song thrush, sturgeon, turtle, and of course, a pig. Pig remains are often used as human analogues because of we have similar hair coverage, weight, fat to muscle ratio, gut fauna and biochemistry. Organs from the human and pig remains were also removed and analyzed separately.
Because decomposition can be influenced by environmental factors ranging from temperature and humidity to soil type, the team placed the remains into glass jars in a lab environment at room temperature. The metal screw caps on the jars weren’t airtight in order to let oxygen enter, and they had a hole in them that made it possible for the researchers to periodically sample the headspace.
The team identified 452 compounds, and a specific combination of eight compounds distinguished human and pig remains from other animal remains. Furthermore, the researchers managed to separate the pig remains from human remains based on five esters – compounds found in fat and oils. If you’re curious, they are: 3-methylbutyl pentanoate, 3-methylbutyl 3-methylbutyrate, 3-methylbutyl 2-methylbutyrate, butyl pentanoate and propyl hexanoate.
Future work in the field with full bodies will be needed to corroborate these results. Having human specific markers could help better train cadaver dogs, making them more efficient and faster at locating bodies. Also, it might be possible to develop a portable device sensitive enough to locate human remains.