1 Department of Food Science and Agricultural Chemistry, McGill University, 21111 Lakeshore, Ste-Anne-de-Bellevue, Quebec, H9X 3V9, Canada.
2 Armand-Frappier Santé Biotechnologie Research Centre, Institut National de la Recherche Scientifique, 531 boulevard des Prairies, Laval, Quebec, H7V 1B7, Canada.
3 Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke O, Montreal, Quebec, H4B 1R6, Canada.
4 Brock-Niagara Validation, Prototyping and Manufacturing Institute, Brock University, St. Catharines, L2S 3A1, Ontario, Canada.
5 Department of Physical & Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, M1C 1A4, Ontario, Canada.
6 Sherbrooke University, Department of Applied Geomatics, Sherbrooke, QC, Canada.
7 Department of Food Science and Agricultural Chemistry, McGill University, 21111 Lakeshore, Ste-Anne-de-Bellevue, Quebec, H9X 3V9, Canada. Electronic address: stephane.bayen@mcgill.ca.

Air pollution is closely associated with increased lung cancer incidence and mortality. Because many semi-volatile industrial chemicals, pesticides and combustion by-products are endocrine-disrupting or genotoxic, their mixtures in outdoor urban air, even at trace levels, could have cumulative effects. However, evidence for the impact of outdoor air pollution on human health remains limited, partly because its composition is poorly characterized. Non-targeted analysis (NTA) based on the combination of liquid (LC) and gas (GC) chromatographic separation with high resolution mass spectrometry (MS), allows for the comprehensive analysis of contaminants in environmental samples. Here, we present the first application of an NTA approach using both LC- and GC-MS to characterize the chemical mixture in outdoor urban air by analyzing forty passive samplers deployed for 82 days during summer 2021 across the Island of Montreal, Canada. The confirmed 25 molecular features included nitrophenols, pesticides/repellents, plasticizers, organophosphorus compounds, organohalogen compounds, other industrial chemicals, and natural products. Triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, n-octyl-pyrrolidone, quinoline n-oxide, 4-hydroxy-acetophenone, citric acid, 2-phenyl acetamide, and hexachloroethane were detected for the very first time in the atmosphere. Previously reported in atmospheric particles, 4-nitrophenol, 2,4-dinitrophenol, tri- and tetraethylene glycol, nonanoic acid, diethylene glycol dibenzoate, caprolactam, phenylacrylic acid, pinonic acid and triphenylphosphine oxide were also detected in the outdoor atmospheric gas phase. The spatial grouping of data between residential and public areas emphasizes the impact of anthropogenic activities on atmospheric vapor composition. This study facilitates the assessment of airborne exposure to chemical mixtures and its effects on human health.