1. V.Hayward¹, K.Jones², J. Button 3, S.Lucas 4 M.Puchnarewicz 1 and D.W.Holt 1 1 Analytical Unit, St George’s, University of London, UK ² Health & Safety Laboratory, Derbyshire, UK 3 Forensic Science Service Ltd, Lambeth, London, UK 4 Dept of Histopathology, Guy’s & St Thomas’ NHS Foundation Trust, London, UK Introduction References Hydrogen sulphide (H 2 S) is a colourless gas which is produced and used in the chemical manufacturing industry; it can be also generated naturally by the putrefaction of organic substances. [1] In low concentrations it is characterised by the odour of rotten eggs, but as the concentration of the gas increases, the olfactory nerve is overwhelmed and the gas can no longer be sensed. Table 1. Human Health Effects of Hydrogen Sulphide at Various Concentrations [2] Hydrogen sulphide is unstable and rapidly metabolised in the body, one of the major metabolites is thiosulphate formed by the oxidation of sulphide. [3] Post-mortem reports after industrial accidents have shown blood thiosulphate concentrations of 25-120µmol/L and 18.47-20.48µmol/L. [3][4] In addition to accidental deaths, hydrogen sulphide has recently become a tool for suicide. The first trend of using hydrogen sulphide for this means was reported in Japan in 2008 [5] and there have been several cases highlighted in the United Kingdom (UK) in 2010. Instructions enabling individuals to create the deadly gas are readily available online. A simple method involves the mixing of a household chemical, such as drain cleaner, with a sulphur containing product, such as pesticide, in a confined space. [1] R.G.Hendrickson et al. Co-worker Fatalities From Hydrogen Sulfide. Amer J Indust Med. 2004 45:346- 350. [2] Adapted from M.Cush, Hydrogen Sulphide, Toxicological Overview. Health Protection Agency. 2009 1. [3] S.Kage et al. The Usefulness of Thiosulfate as an indicator of hydrogen sulfide poisoning: 3 Cases. Int J Legal Med 1997. 110:220-222 [4] Kage et al. Fatal and Nonfatal Posioning by Hydrogen Sulfide at an Industrial Waste Site. J Forensic Sci. 2002. 47(3):625-5 [5] K.C Wei et al. Suicide in Asia. Int Rev Psychiatry. 2008. Oct;20(5):434-40. [6] 2009/10 British Crime Survey, available online http://rds.homeoffice.gov.uk/rds/pdfs10/hosb1310.pdfhttp://rds.homeoffice.gov.uk/rds/pdfs10/hosb1310.pdf [7] B.Levine ed. Principles of Forensic Toxicology, 2 nd Edition. 2006 AACC Press, Washington Thiosulphate calibrators were prepared in blood and urine over a range of 0 to 500µmol/L. 200µL of calibrator/sample and 100µL of 10µM tribromobenzene were derivatised using pentafluorobenzyl bromide and extracted into 2mL 25mM iodine ethyl acetate solution and 1µL injected onto the GCMS system. A BP-5 equivalent GC column (30m x 0.32mm id, 1um film) was used with helium as the carrier gas. The oven was held at 100ºC for 2 minutes then ramped at 10 ºC /min. The ions monitored were m/z 426 for the thiosulphate and m/z 314 for tribromobenzene. Methodology Case study Conclusion On 20 th June 2010, Police were contacted by a friend concerned about the welfare of a 30 year old man who had not responded to telephone calls or email. Upon gaining entry to the property, a deceased male was discovered in the bathroom. In the bath were two tubs containing unknown substances and a bottle of an unknown liquid. Specialist units were called in due to the strong smell of ammonia and the presence of the unknown substances. They established that a lethal gas had been created by mixing a sulphur based product with battery acid. White powder, suspected to be cocaine, was also recovered from the house along with a signed suicide note. Neighbours reported that 5 days previously there had been a smell of ‘bad eggs’, which they had put down to faulty drains. At post-mortem a green discolouration to the brain was noted, which is consistent with hydrogen sulphide exposure. The pathologist reported that the heart did not exhibit the usual pathological features of chronic cocaine use, suggesting a one-off acute toxicity. This case is an example of death caused by combined toxicity, both the blood concentration of benzoylecgonine and thiosulphate were within fatal ranges. HM Coroner ruled that the deceased had taken his own life by creating the deadly gas and taking a cocaine overdose. Extensive toxicological screening also revealed the presence of ethanol, cannabis and olanzapine, but these were at low concentrations unlikely to have contributed to the death. Results Exposure via Inhlation Concentration 2 4 8 5 to 10 4 to 21 20 >100 >402 >502 Exposure via Inhlation Concentration 2 4 8 5 to 10 4 to 21 20 >100 >402 >502 Figure 4. Chromatograms of thiosulphate calibrator and samples. Figure 3. Benzoylecgonine Chromatogram relating to the case The Health and Safety Laboratory reported a blood thiosulphate concentration of 64µmol/L, which falls within fatal ranges. The urine concentration, of 2.7mmol/mol creatinine, was low but this would be expected if death had occurred soon after exposure. Urine concentrations in survivors have been reported between 12-50mmol/mol. A blood benzoylecgonine concentration greater than 15mg/L was detected. This is the highest concentration ever detected by the Forensic Toxicology Service and falls well within fatal ranges (table 2). Table 2. Fatality ranges in blood, taken from Baselt and supplied by the Health & Safety Laboratory Hydrogen Sulphide and Cocaine: Routine screening of blood and urine samples was carried out at the Forensic Toxicology Service; aliquots of these samples were sent to the Health and Safety laboratory for thiosulphate analysis. Figure 2. The Chemical Structure of Benzoylecgonine Figure 1. A Recent hydrogen sulphide suicide pact (20 Sep 10) In a case received by the Forensic Toxicology Service, hydrogen sulphide was seen in combination with high levels of cocaine. Cocaine is the second most abused illicit drug in the UK, behind cannabis, with an estimated 0.8 million adults reporting use of the drug in the last year. [6] The most common clinical symptoms of cocaine toxicity include central nervous system stimulation, ventricular arrhythmias, respiratory dysfunction and ultimately respiratory paralysis. Cocaine has an average half-life of 1 hour and is rapidly metabolised to benzoylecgonine, which appears in the plasma within 15 to 30 minutes of cocaine administration. [7] A Lethal Cocktail