Conclusion

When performing any safety assessment, the first step is generally to perform a screening type exposure assessment to establish a margin of safety. Should the established margin of safety prove inadequate, the next step is to perform a more refined exposure assessment. A number of possible refinements are available, such as improving habits and practices data, refining concentration data, and the inclusion of presence probabilities. Bringing such refinements into an assessment has varying impacts and requires a probabilistic modelling framework in order to do so. In this specific example of triclosan in cosmetics and personal care products, it can be seen that the greatest refinements result from better habits and practices data with product co-use, and the use of presence probabilities. The refinement of concentration values has less impact on predicted exposure, which makes sense in light of the fact that refinement in concentration is directly proportional to the resulting exposure, whereas refining product co-use and the frequency of occurrence can reduce the estimated exposure by several orders of magnitude. In addition, for this example the higher tier 2 aggregate exposure assessment was similar to or lower than the maximal exposure predicted for a single use in the Tier 1 assessment.