50 Human Hazard Assessment of Nanomaterials: Supporting Risk Decision Making Through Interlaboratory Trial Data

The prevalent application of engineered nanomaterials (ENMs) has led to an extensive effort to develop tools facilitating their risk assessment and management. This interlaboratory trial (encompassing two laboratories) sought to investigate the genotoxic impact of ENMs using the hypoxanthine phosphoribosyltransferase (HPRT) forward mutation assay and in vitro cytokinesis-blocked micronucleus (CBMN) assay, utilising harmonised protocols. In the CBMN assay, human lymphoblast (TK6) cells were exposed to zinc oxide (ZnO), titanium dioxide (TiO2) and tungsten carbide-cobalt (WC/Co) for 24-hours after which 1000 binucleated cells were scored for micronuclei (n=2). For the HPRT assay, TK6 and mouse fibroblast (V79) cells were exposed to ZnO, TiO2, WC/Co, CuO and Nanocyl-CNTs for 24-hours after which 600 wells were scored for point mutations (n=2). Significant cytotoxicity and micronuclei frequency was reported following ZnO exposure (20µg/ml). Significant micronuclei induction was reported following WC/Co exposures (2-fold over control, 100µg/ml). No significant mutagenicity was detected with ZnO or TiO2; both laboratories observed significant cytotoxicity following exposure to ZnO (20µg/ml; 37% reduction in cell viability). In the second interlaboratory trial CuO induced significant cytotoxicity (36% reduction in viability: 0.5µg/ml), and a 32-fold increase in mutagenicity. The Nanocyl induced a 6-fold increase in mutagenicity. The data generated here has shown good statistical concordance between laboratories and has highlighted a promising route forward in supporting risk decision making for ENMs. The authors would like to acknowledge this research has received funding from the European Union’s Horizon 2020 research and innovation program for the RiskGONE project, grant agreement #814425.