Analysis of PM_2.5 Morphology, Composition and Health Risk in a Multi-Chair Dental Clinic

Particulate matter with aerodynamic diameter ≤ 2.5 μm (PM_2.5) at high concentrations in dental clinics poses significant health risks to healthcare professionals. However, the morphology and chemical composition of PM_2.5 in specific environments are not yet fully elucidated. In this study, we investigated the concentration, morphology, chemical composition, and health assessment of PM_2.5 collected in a multi-chair dental clinic in Shanghai, China. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were performed to observe the morphology and elemental composition of indoor and outdoor PM_2.5. Chemicals were measured for their concentrations using X-ray fluorescence spectrometry (XRF). In the dental clinic, the indoor PM_2.5 concentration ranged from 2.01 to 114.59 μg/m³, with a mean of 23.31 μg/m³, while the outdoor PM_2.5 concentration ranged from 2.88 to 157.4 μg/m³, with a mean of 30.98 μg/m³. Indoor particles showed more rough, irregular mineralization, which was confirmed as the dominant elements of Ca, P, Si, and zirconia (Zr) by EDS. The average concentrations of Ca, P, Cu, Sr, and Sb indoors were lower than those outdoors (p < 0.05). We also found that Cd, As, and Ni exceeded the annual limits of the Ambient Air Quality Standards of WHO. For the health assessment, the carcinogenic risks of Cd, As, and Cr were higher than the minimum acceptable level (1 × 10^-6), with values of 3.68 × 10^-5, 1.10 × 10,^-5 and 5.52 × 10^-6, respectively, and the non-carcinogenic risk of Cd was the highest, as illustrated by the Hazard Quotient of 2.04. These findings indicate that dental healthcare professionals may be exposed to PM_2.5 containing high concentrations of toxic metals and carcinogenic elements over the long term. This study highlights the importance of protective measures (e.g., the adoption of efficient air purification systems) to minimize the risk of particle inhalation for both patients and professionals.