Fig. 1

PubChem Compound Table of Contents (TOC) Tree (2 Nov. 2020) from the PubChem Classification Browser [34]. The contents (and categories) are updated regularly. Left: the top 22 categories (of the current total 524) are shown (default view). Yellow shading indicates the seven categories used in PubChemLite tier0 (“environmental” selection), the purple shading indicates the additional category used for PubChemLite tier1 (“exposomics”); red shading indicates the two categories that were added into the final PubChemLite exposomics selection. Right: Expansion of the “Agrochemical Information” and “Use and Manufacturing” sections as examples of sub-categories