Independent analysis of time-varying hydrogen cyanide gas exposures on rats using toxic load-based modelling

The US Defence Threat Reduction Agency (DTRA) sponsored a two-year set of experiments, conducted in 2012 and 2013, that were designed and executed by the US Army's Edgewood Chemical and Biological Center (ECBC) and the Naval Medical Research Unit Dayton (NAMRU-D) to explore time-varying inhalation exposures of hydrogen cyanide gas on rats. Our analysis, detailed in a separate paper, finds that a single set of fitted parameters for the toxic load model (i.e., the toxic load exponent n, probit slope m, and median lethal exposure TL50) cannot accurately model the single exposure experimental data across the experiments' full range of time from 2.3 to 30 minutes but can on the longer timescales of 10 to 30 minutes. However, none of the toxic load models that we considered fits the experimental data for the novel, time-varying exposures well, with the average concentration and Griffiths-Megson models providing the least inaccurate casualty predictions.