Institut national de l’environnement industriel et des risques (Ineris), Unité d’expertise toxicologique des substances chimiques, Direction des risques chroniques, Parc technologique ALATA, BP2, 60550 Verneuil-en-Halatte, France
The prevention of atmospheric release of dangerous chemical compounds requires risk managers to identify acute toxicity threshold values to help them study toxic risks during the risk assessment process. This process is necessary for decreasing risk potential, preparing emergency plans and regulating land use around chemical plants. This article presents the methodological choices made by the French institute for industrial environment and risks (Ineris) in deriving acute toxicity threshold values and draws attention to the uncertainties generated during this process and the related calculation of effect distances. Threshold values are determined by 1% and 5% lethal concentrations. This study shows that the uncertainty related to lethal concentrations can cause substantial variability (> 60%) in these effect distances.