Impact of metals exposure on lung function and serum club cell secretory protein among schoolchildren: A mixture and mediation analysis

Particulate matter (PM) and its harmful components are significant contributors to respiratory diseases and impaired lung function, especially in children. Club cell secretory protein (CC16) is a maker of lung epithelium or club cell injuries. To date, the relationship between metals related with PM and CC16 and lung function impairment has been overlooked in children. We enrolled 603 schoolchildren exposed to different levels of PM in China. We found per doubling increase, urinary thallium, and iron was associated with a 3.42 % (95 % CI: 0.01, 6.72) and 3.09 % (95 % CI: 0.55, 5.56) decrease of serum CC16, respectively, whereas urinary cadmium was associated with a 4.74 % (95 % CI: 1.29, 8.31) increase of serum CC16. The Bayesian kernel machine regression (BKMR) model confirmed these associations and showed a potential synergistic interaction between thallium and cadmium. Urinary metal mixtures were associated with lower CC16 when they were below the 35th percentile compared with their median. Serum CC16 mediated 11.47 % (95 % CI: 0.06, 45.00) of the association between urinary thallium and FEV