Mathematical models are available to assess and estimate the exposure and uptake of substances in consumer products. Calculations are performed with a computer program called CONSEXPO. Since the huge number of consumer products does not allow exposure models and parameter values to be determined for every product separately, a limited number of main categories containing similar products are defined. Examples are paint, pesticides, cosmetics and floor covering. The information on each main category is described in a fact sheet. This particular fact sheet deals with the use of children.s toys, classifying the ways in which children can be exposed and defining the different exposure categories. One or several representative examples are given for each of the 17 exposure categories defined. Default models were chosen for these examples to determine the exposure to, and the uptake of, substances from the toys. The default parameter values were also filled in. On the basis of these representative defaults for the examples chosen, the default values for an exposure route of any type of toy can be derived. Because some parameters depend on the type of toy, these should still be filled in for every type of toy. It appears that suitable models for every exposure category are available, allowing us to describe the exposure reliably. In our analysis, it was in most cases impossible to fill in all default-parameter values reliably enough to soundly estimate the exposure and the uptake of substances from the toys.
The crucial parameter, for which we have too little information for a sound estimate, is usually the factor that describes the migration of the substance under investigation from the product. The substance-dependent migration parameter referred to here will depend on the migrating substance and on the material from which it migrates. Empirically determining this parameter is the best way of arriving at a sound exposure estimate. This migration parameter is not known for mouthing, skin contact with solid products and eye contact for almost all substance/material combinations.
CONSEXPO does not only have the capacity to calculate the amount of substance taken up on the basis of contact, exposure and uptake models, but it can also do the reverse. If the amount taken up is known (e.g. the maximum amount which may be taken up, as defined in a standard), CONSEXPO can back-calculate and therefore calculate one of the other parameters. If the amount that a child can take up is known for a particular type of toy, CONSEXPO can calculate the associated migration factor as long as all the other parameters are known.