Nanomaterials are highly diverse not only in chemical composition, but also in other materials characteristics such as size, shape, specific surface area, and surface state. While it has been pointed out that such features may affect their toxicity, it may not be realistic to undertake detailed assessment for all nanomaterials with diversity, and thus, a hazard assessment framework enabling risk management in the real-world is needed.
Consequently, to ensure the safety of diverse nanomaterials, the goals of the project are to develop rational and efficient methods for hazard assessment.
Specifically, as Figure below illustrates, a tiered approach to hazard assessment has been adopted which creates two tiers preceding inhalation toxicity testing, the gold standard for assessing hazard arising from respiratory exposure.
- Determination of whether the subject nanomaterials are deemed substantially equivalent to existing nanomaterials previously subject to hazard assessment (Tier 0).
- If not deemed substantially equivalent to the existing nanomaterials, implementation of intratracheal administration testing as toxicity screening (Tier 1).
Achievement of the goals requires development of low-cost, simple hazard assessment methods to acquire basic hazard information and the development and standardization of methods needed in toxicity testing and assessment. To this end, the following tasks were set in the research and development agenda.
- Development of methods for evaluating equivalence of nanomaterials
- Development of low-cost, simple hazard assessment methods to acquire basic hazard information; and
- Development of supporting methods for toxicity testing and assessment of nanomaterials
The project focuses on exposure through inhalation, which is the exposure route of greatest present concern, and designates “pulmonary inflammation and fibrosis” as its primary assessment endpoint.
All animal studies for this project were approved by each organization, and performed in accordance with the 3R Principles (Replacement, Reduction and Refinement).
Table below shows how each research and development item contributes to these tasks.