(A) Sinus MC gating from control and toxin-exposed tissue. (B) Granulocyte percentage of CD45⁺ leukocytes for individual control (n = 10) and exposed (n = 13) subjects. Data are presented as mean ± SEM; Student’s t test. (C) Tissue toluidine blue staining. Red arrows indicate MCs. Scale bars = 60 μm; original magnification, ×40. (D) Sinus tissue bulk RNA-seq from control (n = 10) and exposed (n = 10) subjects. GSEA of enriched pathways and violin plots of key MC transcripts with adjusted P values shown. (E) H&E- or toluidine blue–stained sections of mouse sinonasal respiratory epithelium after 4 weeks of exposure to ALT, CPC, or a combination. Red arrows indicate MCs. Scale bars = 20 μm. (F) Total and Integrin B7⁺ MCs in mouse sinonasal tissue over 8 weeks. Data are presented as mean ± SEM for n = 4 mice per time point. Mixed-effects model (restricted maximum likelihood) and Tukey’s multiple-comparison test at indicated time points (*P < 0.05, **P < 0.01). (G) Representative flow plots of Integrin β7 and ST2 MCs.