The sample extraction protocol for metabolomics/exposomics was adapted from Moschet et al. and Dubocq et al. . Briefly, 50 mg of each dust sample was extracted using acetonitrile (ACN): methanol (MeOH) (1:1, v/v). The extract was evaporated (Labconco CentriVap, -4 °C, 24-48 h), reconstituted using 0.1 % formic acid (FA) in MilliQ water and MeOH (90:10, v/v), and filtered (Phenex-RC 4 mm syringe filter, 0.2 µm). Ten internal standards were used to check the instrument performance (see Table ). Extraction blanks and quality control (QC) samples (Figure ) were prepared following the guidelines from Broadhurst et al. . A standard mix of 170 polar compounds (50 µM) was used to serve as reference standards later (see Table for full listing). Further details are given in the Supplementary Material (SM), section S1.1.1.