Toxicological Profiling of Select Canadian Domestic Substances List (DSL) Nanomaterials

Health Canada (HC) will provide samples of commercially available metal-oxide nanoparticles to the Contractor, spanning a broad range of characteristics under one Chemical Abstract Service Registry Numbers (CASRN) or chemical grouping for in vitro toxicity testing. The particles will comprise different size ranges, different primary particle shapes, and different particle coatings. The contractor will conduct both single-parameter cytotoxicity testing (MTS assay, and ATP assay) and multiple mechanistic assays for markers of oxidative stress on all nanomaterials supplied to determine whether differences in nanoparticle phys-chem properties lead to different potencies or effects within the same CASRN. Many chemical substances currently in commerce in Canada (i.e., those listed on the DSL) also exist at the nanoscale (i.e., have a particle diameter between 1 and 100 nm); however, their nanoscale forms have not yet been evaluated for their potential risks to human health or the environment. As such, HC and Environment and Climate Change Canada (ECCC) are addressing nanoscale forms of substances on the DSL as a part of the third phase of the Chemicals Management Plan (2016-2021). Given the large number of nanomaterials that exist, each of which may also exist in several forms (e.g., shapes, sizes, agglomeration states etc.), HC and ECCC are faced with challenges in appropriately concluding on the risk posed by these substances. It is unclear, however, how best to fill existing data gaps for nanoforms given the uncertainty regarding effects of a nanomaterial’s physical-chemical properties on its toxicity. Even nanomaterials that are described by a single CAS RN (e.g., titanium dioxide, CAS RN 13463-67-7) may exist in several forms (i.e., sizes, surface modifications, charge etc.), each of which may differ in toxicity and thus potential human health risk. In order to better inform strategies for their eventual risk assessment, HC is investigating the relationship between the physical-chemical properties of various metal-oxide nanoparticles and the outcomes of in vitro toxicological tests. The information from the test data obtained through this contract will be used directly in nanomaterial risk assessments and will also allow evaluators at HC to determine whether particular physical and/or chemical properties of nanomaterials made of the same core substance are drivers of toxicity. Conclusive evidence showing which properties of real-world nanomaterials are important triggers of cellular toxicity will allow for refinement of tools and approaches HC evaluators are able to use for assessment of risk of nanomaterials on the DSL. The contractor will be required to receive and appropriately store samples of commercially available metal-oxide nanoparticles. All equipment and approaches applied to the toxicity screening of samples must be validated for its application to nanomaterials. Sample physical and chemical properties will need to be characterized to a degree required for appropriate dosing of cell cultures. Toxicological profiling will be undertaken using two (2) cell lines, ideally a macrophage-derived cell line and a pulmonary epithelial-derived cell line to best approximate pulmonary exposures, with multiple dose levels and multiple time points in order to capture contrasting effects. The Contractor must perform at least two (2) varied cytotoxicity assays to determine cellular viability and at least two (2) assays assessing the effect of the nanoparticles on cellular oxidative stress response. Complete analysis of the data will be presented in the form of technical reports.