Metals in PM2.5 Linked to More Pediatric Respiratory Visits

Children in Shijiazhuang experienced more respiratory outpatient visits when concentrations of several metals carried by ambient fine particulate matter increased, according to a four-year observational study using daily pediatric visits, PM₂.₅ measurements and weather data from 2020 to 2023. Lead and zinc showed the strongest individual associations with total visits, while a mixture of eight metals was linked to a higher estimated outpatient risk. The results identify specific metallic components of PM₂.₅ as potential contributors to pediatric respiratory burden, but they do not establish that the metals caused the additional visits.

The researchers analyzed daily pediatric respiratory outpatient visits alongside daily concentrations of 12 PM₂.₅-bound metals and meteorological variables in Shijiazhuang. A generalized additive model was used to estimate short-term lagged associations for each metal, and a quantile g-computation model assessed the joint association of metal mixtures with outpatient visits. The models were also used to examine whether associations differed by sex and age.

The individual-metal analysis considered exposure over lags from zero to seven days, allowing the researchers to assess associations across the days surrounding changes in measured concentrations. Several metal elements were significantly associated with increased pediatric respiratory outpatient visits. For the total number of visits, an interquartile-range increase in lead concentration corresponded to a 13.188% increase, with a 95% confidence interval of 9.157% to 17.369%.

Zinc had the next-largest reported association: an interquartile-range increase corresponded to a 9.685% increase in total visits, with a 95% confidence interval of 5.612% to 13.915%. Lead showed the strongest association with acute upper respiratory infections, with an estimated excess risk of 24.510%. These estimates describe statistical associations in the study data and include uncertainty expressed through the reported confidence intervals; the study did not test whether the associations were causal.

The mixture analysis found that combined exposure to eight metals was associated with a 1.041-fold increase in outpatient risk for each decile increase in combined exposure, corresponding to an estimated 4.1% increase. The 95% confidence interval for the fold estimate was 1.023 to 1.059. Lead and chromium contributed the highest weights to this combined association.

The researchers found no statistically significant differences in metal associations between boys and girls. Zinc, however, differed significantly between the two age groups examined, with a stronger association among children aged 7 to 14 years. Thus, the age-stratified results suggest that the relationship between zinc and outpatient visits may differ across age groups, whereas the sex-stratified analysis did not detect statistically significant modification.

Because the study was observational and focused on daily ambient PM₂.₅ exposure and pediatric respiratory outpatient visits in one city over four years, its estimates are subject to the limitations of this design. The findings therefore support the conclusion that metallic components of PM₂.₅ are associated with increased pediatric respiratory outpatient visits in Shijiazhuang, with lead, zinc and chromium emerging as particularly relevant components. The authors’ conclusion calls for priority to be given to reducing lead and chromium emissions and for differentiated health-protection strategies for school-aged children and girls, while the reported evidence itself concerns short-term associations rather than proof of causal effects.

Subject of Research: Short-term associations between PM₂.₅-bound metals and pediatric respiratory outpatient visits in Shijiazhuang

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

Article References: Du, X., Xu, N., Guan, M., Zhang, X., Chen, S., Tian, Z., Wu, L., Xu, M., & Chen, F. (2026). Effects of metallic components in ambient PM₂.₅ on pediatric respiratory diseases in Shijiazhuang. BMC Public Health. https://doi.org/10.1186/s12889-026-29760-5

Image Credits: AI Generated

DOI: 10.1186/s12889-026-29760-5

Keywords: PM₂.₅, metallic components, pediatric respiratory health, outpatient visits, lead exposure, zinc exposure, chromium, air pollution, Shijiazhuang, Effects, metallic, components