Hydrogen sulphide poisoning: blood sulphide concentration and changes in haem metabolism.

Hydrogen sulphide is still a potential hazard in several occupations"2 and especially in sulphate pulp mills (P Jappinen, academic dissertation) and oil refineries. Blood sulphide may be used as an indicator of an excessive human hydrogen sulphide exposure. Fatal hydrogen sulphide concentrations are known.34 Blood sulphide concentrations have been determined before by ion selective electrodes combined with Conway microdiffusion cells but only high concentrations, 1 70-375 mg/l, in fatal cases could be detected by this method.4 Recently, the method using ion selective electrodes has been improved by preconcentration oftrapped sulphide in sodium hydroxide solution.5 This new application allows blood sulphide determinations at low concentrations and it is thus suitable also for non-fatal hydrogen sulphide poisonings. Although decreased activities ofhaem synthesising enzymes, especially delta-aminolaevulinic acid synthase (ALA-S) and haem synthase (Haem-S) have been reported to occur in workers exposed to hydrogen sulphide and methyl mercaptan,6 it has been difficult to assess the severity of hydrogen sulphide poisoning in non-fatal cases. The aim ofthe present work was to evaluate the usefulness of blood sulphide concentrations and activities of haem synthesising enzymes in this respect.