Swedish forensic data 1992-2009 suggest hydrogen cyanide as an important cause of death in fire victims

Between 60 and 80% of all deaths related to fire are attributed to toxic fumes. Carbon monoxide (CO) is commonly thought to be the major cause. However, hydrogen cyanide (HCN) is also formed. Still, the exact contribution of HCN to fire-related fatalities is unknown. The aim of the study was to investigate the impact of HCN in relation to CO as a cause of death in fire victims. Data on carboxyhemoglobin (COHb) and blood cyanide from deceased fire victims in the period 1992-2009 were collected from two Swedish nationwide forensic databases (ToxBase and RattsBase). The databases contain data on COHb and/or cyanide from 2303 fire victims, whereof 816 on both COHb and cyanide. Nonparametric statistical tests were used. Seventeen percent of the victims had lethal or life-threatening blood cyanide levels (>1 mu g/g) and 32% had lethal COHb levels (>50% COHb). Over 31% had cyanide levels above 0.5 mu g/g, an indication of significant HCN exposure. The percentages may be underestimates, as cyanide is quickly eliminated in blood also after death. Our results support the notion that HCN contributes more to the cause of death among fire victims than previously thought.