Fig. 1
The characteristics of the two fundamental MAF classes (MAFfactor and MAFceiling). The original (arbitrary) mixture comprises 3 chemicals, being present with a risk quotient (RQ) of 0.66, 0.33 and 0.33, i.e., 66%, 33% and 33% of the carrying capacity of the exposed entity (a human body (DNEL) or an ecosystem (PNEC), symbolized by the open box). For this mixture, “safe use” is demonstrated for each individual chemical. However, the RQ sum is 1.33, i.e., the mixture overburdens the exposed entity with 133% of its carrying capacity. Two different classes of MAF can be applied to estimate by how much the overall exposure needs to be reduced. MAFfactor applies an identical factor (1.3. in the example) to every substance in the mixture in order to ensure that 100% capacity is not exceeded. In contrast, MAFceiling establishes a new maximum acceptable single substance RQ of 1/3 = 0.33, which affects only 1 of the 3 mixture components (the first chemical, whose RQ exceed a value of 1/MAFceiling). This makes the RQ values of the MAF-adjusted mixture more similar to each other