Individual risks

A (cumulative) risk assessment aims to characterise the health impact due to one or multiple substances present in food causing one or more health effects. The health impact is characterized by a distribution of individual risks: exposures and hazard characterizations are compared at the chosen level (external or internal) via margins of exposure (MOE) or hazard indices (HI = 1/MOE). Hazard characterisations are included as single values or in a probabilistic way.

The aim is to specify the probability that a random individual from a defined (sub)population will have an exposure high enough to cause a particular health effect of a predefined magnitude, the critical effect size. The exposure level that results in exactly that critical effect in a particular person is that person’s individual critical hazard dose. Individuals in a population typically show variation, both in their individual exposure and in their hazard characterization. Both the variation in exposure and the variation in hazard characterization are quantified in the form of probability distributions. Assuming independence between both distributions, they are combined by Monte Carlo methods.

The proportion of the MOE distribution below unity is the probability of critical exposure (\(\mathit{PoCE}\)) in the particular (sub)population. Uncertainties involved in the overall risk assessment (i.e., both regarding exposure and effect assessment) are quantified using Monte Carlo and bootstrap methods. This results in an uncertainty distribution for any statistic of interest, such as the probability of critical exposure (\(\mathit{PoCE}\)).

In Figure 71, margin of exposures for a number of substances are shown. As shown, the distinction between variability (grey bars, 90% probability) and uncertainty (whiskers) is retained. This is discussed in van der Voet and Slob (2007) and van der Voet et al. (2009).

Figure 71 Individual margin of exposure (MOE) plot for multiple substances.

In Figure 72, hazards versus exposures are plotted for the same substances.

Figure 72 Hazard vs. exposure plot for multiple substances. 95% bivariate confidence areas for target hazard dose distribution and exposure distribution. Inner ellipses express variability, outer ellipses uncertainty.