Association between urinary metal exposure and vital capacity in Chinese university students

Metal pollution is a global public health concern. Previous studies have focused on single metals in occupational or child populations, with limited longitudinal evidence in university students and insufficient evaluation of vital capacity (VC) as an early lung damage marker. This study aimed to assess the longitudinal associations between urinary multi-metal exposure and VC in Chinese university students, exploring potential effects of mixed metal exposure on VC. Baseline urinary metals and longitudinal VC data from 2762 university students (mean follow-up 2.86 years) were analyzed, with statistical models adjusted for key demographic, lifestyle, and socioeconomic factors such as age, sex, BMI, smoking status, and physical activity. Key metals associated with VC were identified using Elastic Net and Weighted Quantile Sum (WQS) regression models, and Bayesian Kernel Machine Regression (BKMR). WQS and BKMR assessed mixed-metal effects on baseline and final VC, while linear mixed-effects models (LMM) evaluated single and combined metal impacts on longitudinal VC. Nonlinear relationships were explored using restricted cubic splines (RCS). Sensitivity analyses excluded values below detection limits; multiple comparisons were adjusted by FDR ( P ≤ 0.05). Fourteen key metals were identified. Multi-metal exposure was associated with VC decline (WQS β = −72.85 mL, 95% CI −75.13 to −0.99, P = 0.006). Cadmium (Cd), copper (Cu), and thallium (Tl) were main contributors, with Cd showing persistent negative effects. LMM indicated significant negative associations for Cd, Cu, Tl, antimony (Sb), and arsenic (As). High-exposure groups consistently exhibited lower VC over follow-up. Multi-metal exposure may impair VC among university students, with cadmium emerging as a primary risk factor, underscoring its public health relevance and potential long-term implications for lung function in young populations. These findings highlight the need for enhanced environmental monitoring, longitudinal lung function surveillance, and early targeted preventive strategies. • A 3-year cohort of 2762 Chinese university students measured urinary metals and vital capacity (VC). • Fourteen metals were linked to VC, with Cd, Cu, and Tl showing strongest effects. • Cd showed consistent inverse associations with VC and the most stable effects over follow-up. • Multi-metal exposure may impair VC in university students, supporting prevention.