# Nanomaterial Databases: Data Sources for Promoting Design and Risk Assessment of Nanomaterials
## 3 Comparative Analysis of the Databases  
Although Nanowerk has the largest quantity of nanomaterials, considering that it mainly provides information about the vendors of commercial nanomaterials, and it does not have biological characterizations of the nanomaterials, we excluded it from our comparative analysis. Meanwhile, it is noteworthy that some databases share data with each other. For instance, some data in the NR database are from caNanoLab, NBI, and NIL. Similarly, the eNanoMapper database also has data from caNanoLab. In terms of the quantity of total nanomaterials, it was observed that the eNanoMapper, NR, and caNanoLab databases have more nanomaterials than the others. Each database has its own method of categorizing nanomaterials. Some databases just simply list each individual nanomaterial instead of grouping the nanomaterials. To make the comparative analysis of the databases clearer to researchers, we grouped the nanomaterials in each database into six categories based on their chemical composition: carbon-based nanomaterials, lipid-based nanomaterials, metal nanomaterials, metal oxide nanomaterials, polymeric nanomaterials, and semiconductor nanomaterials. The numbers of nanomaterials for the six categories in the seven databases were counted, and the results are listed in Table 2. The nanomaterials that could not be put into the six categories are listed as \"Other\" in Table 2. The comparative analysis revealed that caNanoLab, eNanoMapper, and NR not only contain large numbers of nanomaterials, but also cover all nanomaterial categoriesdefined in this paper. The other four smaller databases have no lipid nanomaterials and fewer polymer nanomaterials. In addition, structures of the nanomaterials with the same composition can be further categorized by their dimensionalities (nanomaterials without dimension information are not included) as illustrated in Figure 1. Most of the nanomaterials contained in these databases are nanoparticles and nanotubes. Among the nanomaterials with the six compositions shown in Table 2, lipid-based nanomaterials are included only in NR, caNanoLab, and eNanoMapper. All lipid-based nanomaterials collected in these databases are nanoparticles. All seven databases have semiconductor nanomaterials. All semiconductor nanomaterials in these databases are nanoparticles, except for NR, which has 21 nanotubes and more than 200 nanoparticles. NIL does not have metal oxide nanomaterials. All metal oxide-based nanomaterials collected in the other six databases are nanoparticles, except for NR, which has 26 nanotubes and more than 400 nanoparticles. No polymeric nanomaterials are included in NIL and NKB. Most of the polymeric nanomaterials contained in the four other databases are nanoparticles; only PubVINAS and NR have a few nanotubes of polymeric nanomaterials. The majority of the metal nanomaterials are nanoparticles and are included in all seven databases. NR, caNanoLab, NIL, and NBIK also have some metal-based nanotubes. Only NIL has a few nanofilms. The carbon-based nanomaterials cover all shapes as shown in Figure 2. However, only eNanoMapper and NR have all four types of shapes of carbon-based nanomaterials: nanoparticles, nanotubes, nanofilms, and nanocomposites. NKB and NBIK contain only carbon-based nanoparticles. NIL and caNanoLab include nanoparticles, nanotubes, and nanofilms, but not nanocomposites of carbon-based nanomaterials. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & **Carbon** & **Lipid** & **Metal** & **Metal Oxide** & **Polymer** & **Semiconductor** & **Other** \\ \hline caNanoLab & 78 & 97 & 143 & 272 & 528 & 73 & 192 \\ \hline eNanoMapper & 120 & 42 & 723 & 150 & 513 & 226 & 606 \\ \hline NR & 210 & 2 & 551 & 612 & 190 & 235 & 231 \\ \hline NBIK & 4 & 0 & 47 & 22 & 33 & 34 & 7 \\ \hline NIL & 17 & 0 & 15 & 13 & 0 & 25 & 18 \\ \hline NKB & 31 & 0 & 164 & 96 & 0 & 50 & 257 \\ \hline PubVINAS & 147 & 0 & 456 & 32 & 56 & 34 & 0 \\ \hline \end{tabular}
\end{table} 
Table 2: Nanomaterials in the seven databases.