Integration of time as a description parameter in risk characterisation: Application to methyl mercury

Within the food risk assessment procedure, the characterisation of the risk consists in the comparison of the dietary exposure with a health based guidance value established in a previous step. One of the identified weaknesses of this comparison is that the time is not considered in the description. m of this paper is to describe the dietary exposure as a dynamic process determined by the accumulation phenomenon due to successive dietary intakes and by the pharmacokinetics ruling the elimination process in between intakes. Such a process belong to the category of piecewise deterministic Markov processes, which are widely used in a large variety of applications in insurance risk or in operations research, ranging from queuing systems to inventory/storage models. puts of the Kinetic Dietary Exposure Model are the probability distributions governing intakes and inter-intake times, as well as the half-life of the contaminant in the human body. In this paper, an application to methyl mercury is considered, with exponential distributions for both the intakes and the inter-intake times, fitted from the French national consumption survey INCA, and a fixed half-life of 6 weeks for the elimination process. Within this framework, the process settles to a steady-state after approximately 5 years. A “Kinetic Tolerable Intake” (KTI), derived from the “Provisional Tolerable Weekly Intake” (PTWI) of 1.6 μg/kg bw, is set to 14.6 μg/kg and the probability of exceeding this threshold in the long run in the French adult female population is 1.22 E−15.