• Case reports highlight that hydrogen sulphide toxicity in working environments calls for tox investigation 
• Scene investigation and autopsy assists next of kin in claiming insurance, compensation and benefits in accidental workplace hydrogen sulphide exposure deaths 

BY Ruwan Laknath Jayakody  Since toxicological investigation is vital when there is a suspicion of hydrogen sulphide (H2S) toxicity, scene investigation together with the autopsy assists in addressing possible issues which could arise in cases of hydrogen sulphide toxicity, in particular in the working environment.  This was noted in a research article based on case reports titled “Hydrogen sulphide toxicity: Two case reports” which was authored by K.R. Munasinghe, M.A. Rascon and J. Diaze (all three attached to the Office of the Medical Examiner and Forensic Laboratory in El Paso, Texas, the US) and A.N. Vadysinghe (attached to the Peradeniya University’s Medical Sciences Faculty’s Forensic Medicine Department) and published in the Sri Lanka Journal of Forensic Medicine, Science and Law 9 (2) in December 2018.  Hydrogen sulphide inhalation is, as Munasinghe et al. explained, not a rare presentation in the routine forensic practice as the majority of such cases are accidental (“Dung lung: A report of toxic exposure to liquid manure” by L.N. Osbern and R.O. Crapo, “A fatal disaster case based on exposure to hydrogen sulphide – An estimation of the hydrogen sulphide concentration at the scene” by K. Kimura, M. Hasegawa, K. Matsubara, C. Maseda, M. Kagawa, S. Takahashi and K.I. Tanabe, “The usefulness of thiosulfate [an ion] as an indicator of hydrogen sulphide poisoning: Three cases” by S. Kage, K. Takekawa, K. Kurosaki, T. Imamura and K. Kudo, and “A fatality caused by the accidental production of hydrogen sulphide” by A.K. Chaturvedi, D.R. Smith and D.V. Canfield) and rarely intentional (“Death from hydrogen sulphide fumes” by C. Winek, W. Collom and C. Wecht, “Suicidal poisoning due to hydrogen sulphide produced by mixing a liquid bath essence containing sulphur and a toilet bowl cleaner containing hydrochloric acid” by K. Kobayashi and H. Fukushima, and “An autopsy case of death due to hydrogen sulphide poisoning” by K. Hatake, Y. Morimura, R. Kudo, A. Ishitani, M. Kusatani, A. Fukudome and S. Kasuda).  Hydrogen sulphide is a colourless gas with the smell of rotten eggs, commonly generated through the degradation of protein-based waste. It is, as J.S. Schneider, E.H. Tobe, P.D. Mozley Junior, L. Barniskis and T.I. Lidsky’s “Persistent cognitive and motor deficits following acute hydrogen sulphide poisoning” noted, also identified in sewers and is therefore commonly known as the sewer’s gas, and is, per the National Institute of Occupational Safety and Health’s Criteria for a Recommended Standard Occupational Exposure to Hydrogen Sulphide and “Provisional advisory levels for hydrogen sulphide” by T. Marshall, D. Dorman, D. Gardner and F. Adeshina, flammable at ambient temperature, while pressure acts as an irritant and causes asphyxiation.  Hence, Munasinghe et al. presented two fatal cases of hydrogen sulphide toxicity where the toxicological analysis played a vital role in addressing important medico legal issues.  First case  A previously healthy 40-year-old male was working in a water treatment plant which was almost closed. His body was recovered hours later, submerged in spilled sewage. The body was refrigerated until autopsy. The post-mortem examination revealed early stage putrefaction including a foul odour, the swelling of the body, the marbling and the peeling of the epidermis and greenish colour skin (hypostasis where there is an accumulation of fluid or blood in the lower parts of the body or organs under the influence of gravity, as occurs in cases of poor circulation or after death). The upper and lower airways showed a small amount of dark coloured semi solid substance with the retention of patency (the condition of being open or unobstructed) of the air passage. A mild frothy fluid was noted on the cut surface of the lungs. The brain was greenish in colour but otherwise normal. The other organs were normal macroscopically and microscopically except for early putrefactive changes. Femoral (a large artery in the thigh and the main arterial supply to the thigh and leg) blood was positive for thiosulfate.  Second case  A 34-year-old male working in a water treatment plant was trapped in a closed space due to the sudden spillage of sewage. He died prior to initiating resuscitation. He was an adult of average build. There was no evidence of putrefaction or the greenish discolouration of the skin (the skin colour was therefore normal). The respiratory passages were normal with no evidence of sewage within. The cut surface of the lungs showed a mild frothy fluid. Mild atherosclerosis (thickening or hardening of the arteries caused by a buildup of plaque in the inner lining of an artery) of the left coronary (relating to or denoting the arteries which surround and supply the heart) and mild fatty changes in the liver were noted. Other organs appeared normal, macroscopically and microscopically. The toxicology revealed the presence of thiosulfate.  The cause of death in both cases was confirmed as hydrogen sulphide gas toxicity. The manner of death was concluded as accidental. Hydrogen sulphide is, as the “Oxidation of sodium sulphide by rat liver, lungs and kidney” by T.C. Bartholomew, G.M. Powell, K.S. Dodgson and C.G. Curtis, “A critical review of the literature on hydrogen sulphide toxicity” by R.O. Beauchamp, J.S. Bus, J.A. Popp, C.J. Boreiko, D.A. Andjelkovich and P. Leber, and “A simple screening test for sulphite oxidase deficiency: Detection of urinary thiosulfate by a modification of Sorbo's method (a colourimetric method for the determination of thiosulfate)” by V.E. Shih, M.M. Carney and R. Mandell noted, extremely unstable and rapidly converts to its main metabolite – thiosulfate, which remains stable in the body. Therefore, the level of thiosulfate is considered a reliable marker for hydrogen sulphide poisoning, per Kage et al., and S. Kage’s “Usefulness of thiosulfate as an indicator of hydrogen sulphide poisoning in forensic toxicological examination: A study with animal experiments”.  That said, thiosulfate, according to the “Determination of sulphide, thiosulfate and polysulphides in biological materials for diagnosis of sulphide poisoning” by S. Kage, K. Kudo and N. Ikeda, “Reversed phase ion pair liquid chromatographic procedure with electrochemical detection for the analysis of urinary thiosulphate” by B. Kagedal, M. Kallberg, J. Martensson and B. Sorbo, and the “Determination of thiosulfate in human urine and plasma by high performance liquid chromatography with a dual electrochemical detector” by T. Kawanishi, T. Togawa, A. Ishigami, S. Tanabe and T. Imanari, is naturally present in very low levels in blood and urine even in healthy individuals.  In both the local cases, the blood levels of thiosulfate were however above the toxic level (per Osbern and Crapo, Kimura et al., Winek et al., B.H. McAnalley, W.T. Lowry, R.D. Oliver and J.C. Garriott’s “Determination of inorganic sulphide and cyanide in blood using specific ion electrodes: Application to the investigation of hydrogen sulphide and cyanide poisoning” and K. Maebashi, K. Iwadate, K. Sakai, A. Takatsu, K. Fukui, M. Aoyagi, E. Ochiai and T. Nagai’s “Toxicological analysis of 17 autopsy cases of hydrogen sulphide poisoning resulting from the inhalation of intentionally generated hydrogen sulphide gas”) and was sufficient to cause death.  Hydrogen sulphide is produced naturally during putrefaction, per T. Nagata, S. Kage, K. Kimura, K. Kudo and N. Noda’s “Sulphide concentrations in post-mortem mammalian tissues”. Maebashi et al. noted the absorption of hydrogen sulphide via the skin if the body is exposed to a high concentration of hydrogen sulphide; but in the instant cases, there was no major influence on the concentration in the blood levels which showed a very high level of toxicity.  As R.P. Smith and R.E. Gosselin’s “Hydrogen sulphide poisoning” explained, the mechanism of action of hydrogen sulphide involves the prevention of oxygen utilisation at the cellular level. Low and moderate exposure to hydrogen sulphide causes local tissue irritation with cyanosis (a bluish purple hue to the skin which indicates that there may be decreased oxygen attached to the red blood cells in the bloodstream and may in turn suggest a problem with the lungs or the heart), coma and rapid death in severe exposure (per the National Institute for Occupational Safety and Health, J.W. Peters’s “Hydrogen sulphide poisoning in a hospital setting”, L. Adelson and I. Sunshine’s “Fatal hydrogen sulphide intoxication: Report of three cases occurring in a sewer” and J.W. Snyder, E.F. Safir, G.P. Summerville and R.A. Middleberg’s “Occupational fatality and persistent neurological sequelae after mass exposure to hydrogen sulphide”).  Minimal local reaction due to hydrogen sulphide in the two local victims indicated that the victims were exposed to a high level of hydrogen sulphide, according to Munasinghe et al. The mild frothy fluid seen on the cut sections of the lungs in both the deceased indicates the possibility of asphyxia due to rapid exposure to high concentrations than local irritation which occurs in low and moderate exposure (L.D. Knight and S.E. Presnell’s “Death by sewer gas: Case report of a double fatality and review of the literature”, D.S. Gabbay, F.D. Roos and J. Perrone’s “20 foot fall averts fatality from massive hydrogen sulphide exposure” and S. Tanaka, S. Fujimoto, Y. Tamagaki, K. Wakayama, K. Shimada and J. Yoshikawa’s “Bronchial [the larger air passages of the lungs, including those that lead from the trachea/windpipe to the lungs and those within the lungs] injury and pulmonary [pertaining to the lungs] edema [swelling caused by excess fluid trapped in the body's tissues] caused by hydrogen sulphide poisoning”).  On the other hand, the greenish discolouration of the skin as seen in one of the local cases is a recognised feature of hydrogen sulphide poisoning (S. Kage, S. Ito, T. Kishida, K. Kudo and N. Ikeda’s “A fatal case of hydrogen sulphide poisoning in a geothermal power plant”, T.H. Milby and R.C. Baselt’s “Hydrogen sulphide poisoning: Clarification of some controversial issues” and M. Ago, K. Ago and M. Ogata’s “Two fatalities by hydrogen sulphide poisoning: Variation of pathological and toxicological findings”). Moreover, per Adelson and Sunshine, greenish discolouration was seen in the brain at autopsy in the same case.  Therefore, the findings at the scene investigation and the autopsy leading to the conclusion that the manner was accidental in both the instances, in turn assists Munasinghe et al. elaborated, the next of kin when claiming insurance, compensation or any other benefits.