Import LiverTox IDs and toxicity ratings

[gtsueng]

Livertox is an NCBI Bookshelf public domain resource for livertoxicity that primarily consists of unstructured text and lacks identifiers. A Wikidata property has already been created for LiverTox IDs which will be mapped via Mix N Match.

Once mapped, we can import the livertox toxicity ratings of various drugs/chemicals. A property proposal for livertox toxicity ratings is currently under discussion.