A total of 81 compounds from highly-diverse chemical classes encompassing different structures, exposure levels and toxicological modes-of-action were selected. The compound library from a less sensitive and broad method only targeting endocrine-disrupting chemicals (EDCs) developed by Preind et al. (2019) was used as a foundation and subsequently expanded with the addition of genotoxic compounds, carcinogens, neurotoxins and other markers of exposure from various sources. Importantly, several human biotransformation products were also included to account for human phase I and phase II metabolism. The choice of chemicals was based on the toxicological potential (i.e. is the compound of relevance in a health context?), real-life exposure levels (i.e. does this compound occur in quantities feasible to be determined?), suitability of the instrumental platform (i.e. is retention via reversed-phase LC and ionization via ESI-MS sufficient for sensitive analysis?) and representativeness for each class of toxicants to guarantee thorough monitoring of multiple adverse exposures (i.e. does this compound usually occur alongside other relevant chemicals of the same chemical class?). The general sample preparation and LC-MS workflow are depicted in Figure a and b. The chemical classes included in the assay and the number of compounds is shown in Figure . For information on the chemicals and reagents that were used in this study, refer to the Supplementary Information and Supplementary Table .