A suspect and non-target approach to unveil the chemical fingerprint of a multi-environment indoor dust.

Indoor dust accumulates hundreds of chemicals that may pose a risk to human health. This work extensively characterized Persistent Organic Pollutants (POPs) and emerging contaminants in indoor dust from residential, occupational, and educational settings. A combined suspect and non-target screening (SS/NTS) workflow using gas chromatography quadrupole time-of-flight mass spectrometry was developed to explore the occurrence of 269 suspect contaminants identified or annotated with confidence levels 1-3. A high number of compounds were detected per sample (26-159) with widespread presence of synthetic chemicals and polymer-derived compounds such as classic and alternative plasticizers, antioxidants, flame retardants, or rubber-related additives. Among the latter, this study provides the first evidence of 6PPD and other tire-wear related additives in Spanish indoor dust from conventional settings, highlighting the potential infiltration of outdoor-derived particles. Homes exhibited the highest chemical complexity and chemical burden in terms of number of compounds and individual normalized instrumental responses (NIRs), characterized by antioxidants such as tris(2,4-di-tert-butylphenyl) phosphate (AO168═O). In educational environments, although the number of contaminants was lower, the results revealed a higher prevalence of phthalates and alternative plasticizers (e.g. 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate, TXIB). Statistical characterization further characterized that polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were key markers in residential and occupational buildings, while certain personal care products and plastic-related compounds predominated in educational settings. Overall, this study establishes qualitative indoor-dust chemical fingerprints through a multi-tiered screening framework to support potential source identification and contaminant prioritization across diverse exposure-relevant indoor media.