In vitro bioanalytical assessment of aryl hydrocarbon and steroid receptor-mediated activities of primary and aged particulate emissions from residential pellet and logwood stoves

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) in ambient air. It also emits large quantities of volatile and semi-volatile organic compounds (VOCs and SVOCS), leading to the formation, via atmospheric oxidation processes, of secondary organic aerosols (SOA). Little is known about the comparative toxicity of the primary and aged (secondary) PM from this source. In this study, a battery of in vitro mechanism-based cellular bioassays was applied to assess the aryl hydrocarbon receptor (AhR), estrogen receptor (ER), and androgen receptor (AR)-mediated activities of primary and aged total suspended particulate (TSP) emissions from pellet and logwood stoves under nominal and reduced outputs. Emissions were aged using a potential aerosol mass-oxidation flow reactor (PAM-OFR) simulating day- and nighttime (only for logwood stove) oxidation processes. Logwood stove PM induced strong AhR-mediated and weak anti-androgenic activities, whereas pellet stove PM induced only weak AhR-mediated activities. Bioassay responses were strongly influenced by combustion conditions, with the highest responses observed under reduced outputs, consistent with the higher PM emission factors and poorer combustion quality. None of the PM emissions elicited measurable androgenic, estrogenic, or anti-estrogenic activities. After aging, biological activities generally decreased or remained comparable, reflecting the degradation or inactivation of active primary ligands and the formation of new bioactive compounds. Finally, targeted chemical analysis of 49 polycyclic aromatic hydrocarbons (PAHs), oxy-PAHs, and nitro-PAHs explained, depending on the sample, between 1 and 61% of the observed AhR-mediated activity. Overall, this work demonstrates the relevance of bioanalytical approaches to improve the assessment of the toxicological potential of complex atmospheric particulate mixtures beyond what can be explained by targeted chemical analysis alone.