06.01.2004

Massive gas accident in Kainxian, China The end of the year 2003 has seen a tragic natural gas accident in Chuandongbei, Kaixian County, China. According to press reports 234* people were killed shortly after a gas field blowout released a cloud of toxic sulfurated compounds, most likely hydrogen sulphide. 290+ people, mostly children, were hospitalized in nearby hospitals for emergency care. More than 3,000 residents had typical symptoms (see below), and 41,000+ people were evacuated within a radius of 5km around the hot spot. No details have been reported, yet, how the blowout affected surrounding ecosystems. Hydrogen sulphide (H2S) [CAS RegNr 7783-06-4] is a colorless gas that is cytotoxic, irritating and neurotoxic. Its typical strong odour of rotten eggs has an odour threshold of 0.2ppt (= pars per trillion; 1 ppt = 1.416 ng/m3) but the odour will disappear at higher concentrations due to paralysis of the olfactory sense. The gas is soluble in water (4.0g/L at 20°C) and heavier than air. So it will creep along the floor. Small quantities of H2S are quite common in the environment, e.g. dissolved in mineral springs, bodies of water, waste water and above all in natural gases. H2S is produced during the decomposition of sulphurous protein amino acids due to the influence of putrifactive and sulphur bacteria, for example in marshes, standing water and sewage treatment plants. It is encountered in various production processes in industry such as in the manufacture of chemical fibres, or in coking plants and refineries. The hydrogen sulphide resulting from the purification of natural gas is generally processed immediately to form sulphur. Reaction with oxygen leads to acidic oxides that are toxic by themselves when inhaled. Human toxicity data indicate that 1.2-2.8mg/L of H2S in fresh air are immediately lethal after inhalation. At lower concentrations prolonged exposure times have also lead to death, e.g. 0.6mg/L for 30-60min. An inhalation of 0.1-0.15mg/L over several hours has been survived, but produced severe symptoms of toxicity. Inhaled or ingested H2S that is not lethal will be rapidly metabolized to sulphate and excreted in the urine. Typical symptoms of adverse H2S exposure of increasing strength are eye irritation, hyperpnoe, cough, nausea, bronchial catarrh, spasms and numbness, central respiratory failure due to paralysis, and finally coma and death. Environmental toxicity of H2S has been noted for terrestrial and aquatic organisms. For example, carps will die within 24h if the surrounding water contains 6.4+mg/L H2S. Plants are remarkably resistant. *   The former number of 191 deaths has officially been raised to 234 victims. 11:42:34 PM

A happy New Year 2004. And welcome again to the Toxicology Weblog. After a almost one year of silence I have now decided to revive this Weblog and will post regular headlines about toxicology-related events in Germany and elsewhere to provide a scientific background for the interested reader. The picture on the left is Leah's hand. <Thank you, Leah. > 7:35:44 PM