Aggregation over multiple available hazard characterisations

In some scenarios, for a given substance and effect, multiple hazard characterisations are available e.g. different studies yield different NOAEL s. In such cases, a single hazard characterisation should be derived from the available candidates.

In a conservative approach, choose the lowest hazard characterisation ($\mathrm{HC}$) of the available hazard characterisations. I.e.,

$$\mathrm{HC}=\underset{i=1,\dots ,n}{min}{\mathrm{HC}}_i$$

Alternatively, the candidates are aggregated into a new “average” hazard characterisation. For this, the harmonic mean, also used for obtaining central value estimates in the imputation of missing hazard characterisations, is a suitable approach.

$$\mathrm{HC}={\left(\sum _i^n\frac{1}{{\mathrm{HC}}_i}\right)}^{-1}$$