Research and development item: ① “Development of methods for evaluating equivalence of nanomaterials”

As for conventional chemical substances, it is considered possible to share hazard testing results among substances having the same chemical formula even when their producers or production methods are different. As for nanomaterials, on the other hand, it may be considered that the hazard of materials having the same chemical formula depends on their physical chemical properties such as sizes and shapes. There is concern that unrealistic requirements, under this premise, such as hazard testing for each production lot of materials would impede the development and application of nanomaterials.

To ensure the safety of nanomaterials effectively and efficiently, it is needed not to perform hazard tests for every materials having the same chemical formula produced by different producers or methods but to perform systematic hazard assessment focusing on the similarity of their physical chemical properties such as sizes and shapes. For this, the development of equivalence criteria is considered effective. Here, the equivalence criteria are variation ranges of physical chemical properties of a material, within which the hazard of the material is thought not to be changed. While it is considered difficult to develop equivalence criteria only through the analysis of existing hazard testing data, performing a large number of inhalation toxicity tests to study the dependency of toxicity on physical chemical properties is not realistic due to the cost and technical difficulties involved.

Accordingly, we are developing equivalence criteria by illuminating the dependency of toxicokinetics and biological responses on physical chemical properties of nanomaterials through systematic intratracheal administration testing on nanomaterials with different physical chemical properties.