Effects of metallic components in ambient PM₂.₅ on pediatric respiratory diseases in Shijiazhuang

Considerable attention has been paid to the short-term association between ambient PM 2.5 exposure and children’s respiratory health, yet evidence on individual and combined exposure to its metal components remains limited, especially in typical industrial cities. Based on daily data on pediatric respiratory outpatient visits, concentrations of 12 PM₂.₅-bound metals, and meteorological variables in Shijiazhuang from 2020 to 2023, a generalized additive model was used to assess short-term lag effects of individual metals, and a quantile g-computation model was applied to evaluate the joint effect of metal mixtures. Stratified analyses were further performed by sex and age. A variety of metal elements are significantly correlated with the increased risk of children’s respiratory outpatient visits. Lead (Pb) and zinc (Zn) showed the strongest effects: at lag0-7 days, each interquartile range increment in Pb and Zn concentrations corresponded to increases of 13.188%(95%CI: 9.157%-17.369%) and 9.685%(95%CI: 5.612%-13.915%) in total visits, respectively. Pb had the strongest effect on acute upper respiratory infections (excess risk = 24.510%).Stratified analyses showed no statistically significant differences in metal associations between boys and girls, whereas Zn showed a statistically significant difference between the two age groups, with a stronger association among children aged 7–14 years. Combined exposure to eight metals was associated with a 1.041-fold(95%CI: 1.023–1.059) increase in outpatient risk per decile increase, with Pb and Cr contributing the highest weights. The combined exposure to multiple metals in ambient PM 2.5 was significantly associated with an increased number of pediatric respiratory outpatient visits in Shijiazhuang, with variations by disease subtype, sex, and age. Priority should be given to reducing Pb and Cr emissions and developing differentiated health protection strategies for school-aged children and girls.