Comprehensive GC×GC-MS-based Non-Target Screening to Unveil Chemical Profiles of Indoor Dust from Seven European Countries

People spend most of their time indoors, where dust serves both as an important reservoir of organic chemicals released from building materials, consumer products, activities, and outdoor sources, and as a significant human exposure pathway, particularly through inadvertent dust ingestion. Previous studies have primarily focused on targeted analysis or limited suspect screening of selected contaminant classes, providing only a partial characterization of the chemical complexity of dust. This study – as a part of the INQUIRE project – aimed to comprehensively characterize the lipophilic organic chemical composition of indoor dust collected from households in seven European countries using comprehensive two-dimensional gas chromatography‒mass spectrometry (GC×GC-MS) and an advanced non-target screening (NTS) workflow. Indoor dust samples from 174 households were analyzed using novel data processing workflows that enabled comprehensive feature extraction, alignment, and annotation. Over 2300 anthropogenic and naturally occurring compounds were tentatively identified and classified according to their functional uses using multiple complementary chemical databases. (Semi-)quantitative concentration estimates revealed pronounced differences in chemical composition among countries and identified distinct national chemical fingerprints. Country-specific signature compounds included organophosphates, plasticizers, personal care product ingredients, pharmaceuticals, pesticides, fragrances, and naturally derived compounds, reflecting differences in consumer product use, building materials, lifestyle, and environmental conditions across the examined countries. The inclusion of natural compounds alongside anthropogenic contaminants provided a more comprehensive characterization of indoor dust than has been reported in previous large-scale studies. The risk from dust ingestion exposure was estimated via hazard quotient (HQ) and cancer risk (CR) calculations. No median HQs exceeded 1 and CRs exceeded 10 ^− 6 only in a small subset of households for several polycyclic aromatic hydrocarbons and dyes. This work represents one of the most comprehensive NTS studies of organic contaminants in European indoor dust to date. The results demonstrate the complexity of indoor dust chemistry and highlight the value of combining comprehensive chromatographic separation and advanced data processing for large-scale environmental screening. Although no median HQs exceeded 1, the assessment considering only dust ingestion likely underestimates overall exposure. CRs exceeding 10 ^− 6 indicate that dust ingestion may contribute to non-negligible lifetime cancer risk in some indoor environments. The generated dataset substantially expands current knowledge of chemicals present in indoor dust and provides a foundation for future studies investigating exposure sources and the compounds contributing to biological activity and potential health effects within the INQUIRE project.