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 (\(\operatorname{HC}\)) of the available hazard characterisations. I.e.,

\[\operatorname{HC} = \min_{i=1,\ldots,n} \operatorname{HC}_i\]

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.

\[\operatorname{HC} = \left( \sum_{i}^{n} \frac{1}{\operatorname{HC}_i} \right) ^{-1}\]