Analysis of cyanide exposure status in fire-related deaths using a physiologically based pharmacokinetic model

Fire victims often inhale hydrogen cyanide (HCN) gas in addition to carbon monoxide. This study aimed to investigate the current prevalence of HCN inhalation among fire victims and assess the contribution of HCN as a toxic factor in fire-related deaths.

The study included 29 cases of fire-related deaths, where autopsies were conducted at the Department of Legal Medicine, Osaka University, from April 2014 to March 2020. No resuscitation was performed before death was confirmed and blood samples were obtained from both the left and right cardiac chambers. Blood cyanide concentrations were measured. Additionally, a physiologically based pharmacokinetic model, as described by Stamyr et al. (Arch Toxicol 89:1287-1296, 2015), was used to simulate the time course of blood concentration changes for different inhaled HCN concentrations. The inhaled HCN concentration and inhalation time that minimized the difference between the measured and simulated blood concentrations were calculated.

Cyanide was detected in the cardiac blood of 76.3% of cases. In all instances, left cardiac blood concentrations were higher than those in the right cardiac blood. The simulations using the physiologically based pharmacokinetic model revealed eight cases where the inhaled HCN concentration exceeded 5000 ppm, with an inhalation time of less than 0.5 min.

Many fire victims inhaled HCN gas, and in a few cases, it appears that death occurred rapidly after inhalation of high HCN concentrations. These findings suggest that the contribution of cyanide gas to fire-related deaths warrants closer examination.