To increase the knowledge and understanding of the development of new in vitro test methods, validation is crucial for the evaluation of chemical substances and mixtures such as PPPs as it can facilitate the acceptance of further in vitro toxicity data in the NZ and in the EU. The use of new in vitro test methods, for assessing the risks related to chemical mixtures such as PPPs, will minimize the human health risks due to chemical exposure since in vitro test methods can provide better understanding of the mechanisms for a chemical substance and thus help categorize its effect in the evaluation of mixtures. However, due to the limited applicability domain of available in vitro methods, evaluation of the data should be carefully made by using a WoE approach. Further development and validation of suitable in vitro methods is needed for it to be used in regulatory risk assessment of PPPs.