A.J. Kennedy, M. Chappell, D. Edwards, W-S Shih, R. Patel, J. Brame, M. Brondum, S.A. Diamond, J. Coleman, A. Poda, J.A. Steevens
US Army Corps - Engineer Research and Development Center,
Keywords: nano-enabled, toxicology, environmental health and safety, testing framework
Summary:Most environmental health and safety (EHS) testing of engineered nanomaterials (ENMs) has focused on free particle hazard. Few comprehensive studies have investigated the release potential among structurally different nano-enabled technologies (NET) (freely dispersed, surface bound, composite) under relevant use scenarios , and release pathways throughout the NET life cycle (manufacturing, incorporation, disposal). Life cycle assessment (LCA) methods for conventional products and chemicals carries challenges with accurate representation in the life cycle inventory (LCI) and model uncertainty; inclusion of ENMs into the product LCI is expected to contribute additional uncertainty and regulatory scrutiny. For ENMs perceived as hazardous, capabilities to characterize and assess exposure and release from these materials must be enhanced and standardized . Available methods and tools need to be identified and integrated into a coherent repository. The work reported involves an approach integrating tools to first identify relevant release scenarios within the life cycle of a NET (CEA Conceptual Model Builder), followed by use of a tiered conceptual framework and testing process (NanoGRID, Figure 1)1, with modules for each life cycle compartment, to determine if ENMs need inclusion in the LCA inventory. To demonstrate, four NETs containing are conceptually evaluated. Two studied surface-bound technologies are printable inks used for electrical (Ag nanoparticles [NPs]) and sensing (carbon nanotubes [CNTs]) applications. Also considered are a self-cleaning concrete composite (TiO2) and a surface-bound anticorrosion paint (CNTs, ZnO, TiO2). While the AgNP ink did consist of NPs, release after printed circuit submersion (with and without UV weathering) resulted only in ion release (Figure 2a); this suggests AgNPs may be removed from the LCI. For the self-cleaning concrete, free TiO2 has not been detected thus far. However, abrasion and UV weathering of the composite under different pH rain simulations resulted in micron-sized cementitious material containing TiO2 that retained photocatalytic activity (Figure 2b); thus, a nano-aspect should be considered in the LCI or LCIA. Releases from the anticorrosion paint are most likely during product incorporation (worker exposure, waste discharge) and disposal (sand blasting). Release during abrasion had the typical profile of TiO2, likely from the pigment (Figure 2c). A comprehensive nanotechnology LCA approach is underway to fully evaluate the CNT sensor technology from cradle to grave. Integration of available tools for nanotechnology EHS testing and LCA at appropriate times, along with timely engagement of available methods, is the path forward for more expedient NET regulatory registrations and evaluations.