Occupational Lethal Asphyxiation by Toxic Gas in Unconfined Spaces: Hydrogen Sulphide Poisoning

After attending this presentation, attendees will better understand specific aspects of Hydrogen Sulphide poisoning, an important cause of work-related death.The goal of this presentation is to recount the story of the deaths of two men who, while working in a truck tank which transported leachate, were poisoned by H2S in an open air. Introduction: Hydrogen sulphide (H2S) is a toxic gas generated by non-specific and anaerobic bacterial reduction of sulphates and sulphur-containing organic compounds at the temperature >20°C. Severe or fatal H2S intoxications are very uncommon in locations which lack the characteristics of confined spaces. The case reports an accidental death of two workers during the hatch opening on a truck-tank filled of leachate water. The first worker (P.R.) was hit by a massive gas flow therefore he fell on the tank. A fellow worker (L.F.), rushed to his aid, but also lost consciousness and rushed to the ground. Environmental toxicological analyses were carried out on the air outside the tank with both closed and open porthole, inside the tank at various depths, on liquid samples of the tank, and during the collection of the leachate. Toxicological and chemical-physical analyses (pH, etc.) were also carried out on leachate samples. Air monitoring was performed at 2 hours, 20 days and 70 days after the incident using Gastec Color Dosimeter Tubes. Elemental analysis, Gas chromatography/Mass-spectrometry (GC/MS) analysis and potentiometric titration was performed on leachate samples. Toxicological analyses on biological samples were carried out about 2 months after the autopsy. Thiosulfate (H2S metabolite) was quantified using a GC/MS technique after derivatization with pentafluorobenzyl bromide. These environmental findings were confirmed by toxicological analyses on biological samples through the measurement of thiosulfate,4.5 mg/ml for the first worker and 1.21 mg/l for the second one. Despite the possible loss of H2S from the tank during rescue operations even at the time elapsed from the accident (seventy days), there was still a lethal concentration of the gas 750 ppm.The two workers were wrapped by a H2S bubble gas leaked from truck-tank; therefore it is occurred a unconfined space gas death. Prolonged inhalation of this concentration causes sudden loss of cosciousness that can lead to fatal respiratory paralysis if rescue operations are not rapid. These enviromental findings were confirmed by toxicological analyses through the measurement of thiosulfate, which is one of the main H2S metabolites