[en] Health risk of populations dwelling in the hospital has been a global concern, but has not been adequately examined. PM_2.5 and PM₁ samples were collected in two indoor locations (outpatient department and inpatient department) and one outdoor location (courtyard) of the hospital in Shanghai. The concentrations of size-fractionated trace metals and the morphology of single particles were determined to accurately assess the health risk for populations in the hospital. The results indicated that the mean concentrations of PM_2.5 and PM₁ were in the order of outpatient department > courtyard > inpatient department. The mean concentrations of PM₁ decreased with floors (first floor: 78.0 μg/m³, second floor: 64.1 μg/m³, fourth floor: 48.4 μg/m³). However, the mean PM_2.5 concentrations were in the order of first floor (124.0 μg/m³) > fourth floor (91.4 μg/m³) > second floor (90.6 μg/m³), which was likely associated with the number of patients. The PM_2.5 and PM₁ concentrations have begun to increase rapidly from 9:00 am and decreased after 15:00 pm in the first floor, whereas they remain relatively stable in the second and fourth floor. The abundance of Mg, Ca, Al and K in the fine particles and coarse particles were both higher than other elements for all floors. The concentrations of trace metals (e.g., Zn, Ba, Fe, Mn, Cr, Ca, Ti, Na, and K) except Mg and Al in the coarse particles (> 2.5 μm) decreased with floors, whereas Zn, Ba, Fe, and Cr in the fine particles (< 2.5 μm) displayed opposite variation. Trace metals in the first floor were mainly concentrated in the > 2.5 μm and 1–2.5 μm, whereas they chiefly peaked at 0.25–0.5 μm and below 0.25 μm in the second and fourth floor. Single particles analysis showed that mineral particles, soot, and Fe-rich particles were mainly concentrated in the first floor, indicating the impacts of walking of patients, traffic emissions, and food cooking, respectively. Sulfate particles were internally mixed with soot, fly ash and Fe-rich particles in the second floor, which suggested that these sulfate particles probably underwent aging processes during the atmospheric long-range transport. In the fourth floor, fly ash, sulfate particles, Zn-rich particles, and biogenic particles were identified under the transmission electron microscopy (TEM). Higher abundance of sulfates and absence of chlorate hinted existence of heterogeneous reactions during long-range transport with the Cl⁻ replaced by SO₄²⁻. The index of average daily intake (ADI), hazard quotient (HQ), and carcinogenic risks (CR) indicated that Cr pose carcinogenic risks to the surrounding populations, while non-carcinogenic risks of Mn, Zn, and Cr were not remarkable. - Graphical abstract: Mineral particles, soot, and Fe-rich particles were mainly concentrated in the first floor, indicating the impacts of walking of patients, traffic emissions, and food cooking. Sulfate particles were internally mixed with soot, fly ash and Fe-rich particles in the second floors, which suggested that these sulfate particles probably underwent aging processes during atmospheric long-range transport. In the fourth floor, fly ash, sulfate particles, Zn-rich particles, and biogenic particles were identified under the TEM. - Highlights: • The mean concentrations of PM₁ and PM_2.5 decreased with floors as a whole. • Trace metals in the first floor were mainly concentrated in the coarse particles. • Minerals, soot, fly ash, sulfate, biogenic particles, Fe-rich and Zn particles were observed in the hospital.