The independent and joint effects of short-term exposure to ambient air pollutants on eczema in two cities of China.

This study aimed to explore individual and combined impacts of ambient PM2.5, PM10, NO2, SO2 and O3 on eczema outpatient visits and identify key pollutants, as the joint effects of multi-pollutant exposure on eczema remain unclear. We retrieved 879,356 daily eczema outpatient records from two Guangdong dermatology hospitals and matched daily air pollutant concentrations. Distributed lag nonlinear models assessed single pollutant effects, while quantile g-computation evaluated two four-pollutant mixtures. Every 10 µg/m³ rise in each pollutant significantly boosted eczema visits, with SO2 exerting the strongest individual effect (22.63%). Each quartile increase of the PM10-based mixture lifted visits by 4.14%, dominated by PM10 (49.46%), while the PM2.5-based mixture caused a 4.21% rise, mainly driven by SO2(38.12%) and NO2 (37.52%). Both mixtures induced 18 extra daily eczema visits. Air pollutant mixtures markedly aggravate eczema burdens, requiring targeted air quality governance to cut related medical demands.