A.J. Kennedy, J. Brame, M. Wood, T. Rycroft, A. Poda, S. Diamond, M. Chappell, W-S Shih, V. Panchal
US Army Engineer Research and Development Center,
Keywords: nano, advanced, material, health and safety, testing strategy
Summary:The novel properties of advanced materials (AdMs), including nanomaterials (NMs), offer opportunities to improve conventional materials and create new material applications. However, these same properties may place AdMs into a high risk prioritization category within the reformed Toxic Substances Control Act, now called the Lautenberg Chemical Safety Act (CSA). As with NMs, the lack of specific Environmental Health and Safety (EHS) methods may delay regulatory decisions and commercialization of AdMs. The CSA seeks timely decisions on new substances by streamlining of the decision process using tiered testing strategies. We published a tiered testing strategy (Figure 1) for NM-enabled products, since few comprehensive strategies were available. The tiered strategy was previously demonstrated using a nano-silver enabled printable electrical circuit that illuminated the ambiguity of size-only definitions since the hazard profile of the circuit was related to the released dissolved fraction. In this presentation, the tiered testing and documentation process is demonstrated using a self-cleaning TiO2 cement, a nitrocellulose-based combustible case material and a nanotube-containing temperature and humidity sensor. Results prompted a transition of scope from a primary focus on “nano” size (1-100 nm definition ) to AdMs, defined as “materials that are intentionally engineered to exhibit novel or enhanced properties that confer superior performance relative to conventional materials; as a result of their unique characteristics and properties, AdMs have a highly uncertain environmental health and safety risk profile. In the case studies, different release tests were considered for each AdM-enabled product. Results indicated that the process and an associated tool NanoGRID were effective at prioritizing a large number of testing possibilities to a more feasible number of relevant tests based upon defined parameters (relevance, worst case scenario, time, cost). A dichotomous key was employed to identify each enabled product as a NM, AdM or conventional material, thus facilitating the prioritization process. The TiO2 self-cleaning cement test was established (Figure 2A) and had enhanced photo-oxidative properties but the released material had a short persistence (hours) in surface water and low hazard; however, the presence of UV-light dramatically increased TiO2 toxicity. The combustible casing was defined as an AdM due to its improved hydrophobic property but no intentional nano-dimensionality. Release testing was established (Figure 2) and identified little to no particle emissions or hazard, with effects occurring only for the combusted residue. Finally, a release testing strategy was developed for the nanotube sensor to assess its release potential based on intended use.