Changes in the critical value for BMDLs

Based on the comments of users of the rapid exposure assessment tools, it can be concluded that many persons have difficulties with the Margin of Exposure as a means to test whether a consumers exposure is to be considered "safe" or nor. The EFSA guidance documents on that topic are very clear with regard to the evaluation of genotoxic carcinogens, but less informative with regard to the other chemicals. In some EFSA Opinions the Margin of Exposure is evaluated by means of a critical value of 100 in stead of 10,000. Based on that observation it can be concluded that one can use the Margin of Exposure for all chemicals without a HBGV (e.g. also for chemicals of which a HBGV is withdrawn, like lead). As EFSA is referring to a BMDL10 of experimental animals, one can however wonder how to evaluate a BMDL05 or BMDL01 of animal studies, or BMDLs derived from epidemiological (human) studies.

As there is no guidance on the use of other BMDLs it was decided to develop an alternative approach for the evaluation of a Margin of Exposure for this portal. Following the EFSA approach with an evaluation limit of 10,000 for genotoxic carcinogens, and 100 for non-genotoxic chemicals, and an analysis of the current approach of Safety Factors to take into account differences between species and differences in toxicokinetics and toxicodynamics, it is possible to derive alternative evaluation factors for the different types of BMDLs. The alternative approach is now included in EAST and EAST 2. The procedure for the search of chemicals is slighlty changed, and the results now show the genotoxic properties, and the critical value for the MoE. A similar kind of update of XI and ImproRisk is foreseen in the forthcoming revision.