Association between Urinary Metal Exposure and Child Growth and Development with Dietary Modification Effects

Objective To investigate the association between mixed exposure to six urinary metals (aluminum, chromium, iron, zinc, barium, thallium) and growth indicators in children aged 0–9 years, and to evaluate the modifying effects of dietary factors and physical activity on the metal‑growth association.

Methods This cross‑sectional study was based on the National Nine‑Province Child and Adolescent Cohort, including 10,235 children aged 0–9 years. Urinary metal concentrations were measured by ICP‑MS, and height‑for‑age (HAZ), weight‑for‑age (WAZ), and BMI‑for‑age (BAZ) Z‑scores were calculated. Linear regression and restricted cubic spline (RCS) were used to assess single‑metal effects and non‑linear associations; WQS, Qgcomp, and BKMR models were applied to evaluate mixed exposure effects; the CVEK model and additive interaction analysis were used to examine modification by dietary factors and physical activity.

Results After adjusting for confounders, Tl was significantly negatively associated with HAZ, WAZ, and BAZ; Zn was significantly negatively associated with WAZ and BAZ; Ba was significantly positively associated with BAZ (allP<0.01), while Al, Cr, and Fe showed no statistically significant associations. In mixed exposure models, Tl and Zn were the major negative contributors. RCS revealed non‑linear associations for Zn, Tl, Al, and Cr with at least one growth indicator (P<0.05). CVEK models indicated significant modification effects of dietary factors such as milk, freshwater fish/shrimp, cod liver oil, and zinc supplements on metal effects (P<0.05). Additive interaction analysis showed a synergistic effect of zinc supplements combined with summer physical activity on Al‑HAZ (RERI=0.18) and Al‑WAZ (RERI=0.16), and an antagonistic effect of freshwater fish/shrimp combined with summer physical activity on Ba‑BAZ (RERI=‑0.28).

Conclusion Mixed metal exposure in childhood was negatively associated with growth, with Zn and Tl as major contributing metals. Dietary nutrition and physical activity can modify the effects of metals on growth, providing preliminary evidence for comprehensive intervention strategies in children from high‑risk areas.