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From war zones or scenes of natural disasters, news reporters often comment on the stench of decaying bodies. This characteristic malodour is made up of a complex mixture of volatile compounds that might be useful in forensic pathology, to establish the cause of death and the post-mortem interval. One of the vivid memories from on-the-spot reports in the days after the Asian tsunami is the image of news reporters with twisted faces describing the stench of death. With more than 280,000 people dead to date, and many more unaccounted for, this foul smell will be pervading the affected countries for weeks to come, especially in the remote areas that have not yet been accessed. For those on the front line who have experienced it, like rescue and aid workers as well as the survivors, there is no other smell like it. In the normal world, this characteristic smell is also well known to members of the police force, crime scene technicians, medical staff and forensic pathologists, as well as to some dogs. Its composition is the trigger used by tracker dogs to locate hidden bodies. The same odour is also recognised by insects that quickly colonise a body once it begins to decay. Now, Greek researchers have suggested that the odour can be used to determine the time since death and possibly help to establish the cause of death. Strange as it may seem, there does not seem to have been much research into the make up of the smell of decaying human bodies, possibly because the odours were presumed to be too low in concentration for measurement. However, A. Agapiou and M. Statheropoulos from the School of Chemical Engineering at the National Technical University of Athens (NTUA) and C. Spiliopoulou from the Department of Forensic Medicine and Toxicology at the University of Athens Medical School have proved otherwise. They analysed the volatile organic compounds (VOCs) evolving from two corpses by relatively simple methodology. First of all, they remind us that the VOCs that constitute the smell arise from the same sources in each human corpse. Carbohydrates in the body break down to give mainly oxygenated compounds (alcohols, aldehydes, ketones, acids, esters, ethers), proteins degrade to nitrogen, phosphorus and sulphur compounds, nucleic acids from nitrogen and phosphorus compounds and lipids decompose to nitrogen, phosphorus and oxygenated compounds and hydrocarbons. So, in theory, different decaying bodies should produce the same set of VOCs. In practice, however, such comparisons are rendered extremely difficult by the varying decomposition rate, which is influenced by many factors such as heat, humidity, the surrounding environment (air, water or soil), and attacks by bacteria, insects and animals. Nevertheless, Agapiou and his colleagues decided to compare the VOC profiles of two male corpses found in the sea near Samos in Greece. The ages were estimated at 30 and 40 years and examination of the internal organs revealed that one was more putrefied than the other. The corpses were stored in separate plastic body bags that were placed in metal cases and air-sealed with silicone resin in a wooden box. Apart from protecting against contamination during transport, sealing allowed the build up of VOCs within the bags. After transport to the lab, each body bag was pierced with two tubes linked to carbon dioxide and ammonia gas analysers and with a third tube linked to sorbent traps containing graphitised carbon black and carbon molecular sieves as adsorbents. About 5 L of gas were drawn through the traps. The adsorbed gases were analyzed by thermal desorption GC/MS and the components were identified from their retention times and mass spectra using a commercial database and an in-house database constructed from standard compounds. The results were described in Forensic Sci. Intl. 2005. A total of 86 substances were identified and quantified with the aid of internal standard compounds, 51 being found in both cases, ranging from 0.006 to 13.39 nmol/L. The more decomposed body had the greater number of different VOCs. The most abundant compounds were dimethyl disulphide, toluene, hexane, 1,2,4-trimethylbenzene, 2-propanone, 3-pentanone and 2-pentanone. The relatively high levels of toluene were unexpected, leading the authors to hint at the possibility of toluene poisoning of the victims. The high number of fatty acid esters found was explained in terms of saponification. Many hydrocarbons, aldehydes, ketones and alcohols were also detected. The two bodies were recovered from the sea, which may have affected the decomposition process, and they represent only one time point in the decomposition process. Nevertheless, the ability to detect and quantify so many VOCs in each case indicates a potential role for VOCs in post-mortem investigations. More studies on bodies decaying under different conditions should be conducted to determine the validity of the proposals. Related links:
Article by Steve Down |
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