Categorization of ENM toxicity based on expression of lncRNAs involved in regulation of DNA damage and repair response. In (A), the frequency distribution of DE lncRNA transcripts across the various engineered nanomaterial (ENM) exposures is shown. The highest number of these regulatory lncRNAs were identified as differentially expressed in CuO exposures, with the exception of CuO-PEG (red font), followed by all MWCNT plus TiO2p-NH2/PEG (black font). A few to none of these lncRNAs were differentially expressed in all TiO2r exposures, CuO-PEG, and TiO2p-Core/COOH (gray font). A heatmap of the hierarchical clustering that is based on the average relative (Z-score) expression of these lncRNAs across all sample groups is shown in (B). Clusters of the sample groups that ranks the relative toxicity of the ENM in very much the same way as seen in (A). That is, from zero (unexposed)/low (gray box) to mid toxicity (black box) and then high toxicity (red box) ENM.