The study was to investigate the effect of co-exposure to rare earth elements (REEs) and lead on children's intelligence, and whether there is a certain interactive effect of exposure.
Exposure to REEs and lead was assessed by analysing the scalp hair samples of children aged 6-16 years who lived in a rare earth mining area, by atomic absorption spectrometry. Intelligence was assessed using Raven's Standard Progressive Matrices. Bayesian Structural Equations were built to explore different patterns of associations between REEs and lead explore and children's intelligence, and the best-fitted one was selected for the most reasonable explanation according to DIC and BIC. In our best-fitted model, which did not contain any interactive item between REEs and lead, age had the greatest effect on IQ with a path coefficient of 0.339. Then came hair lead (-0.166), showing a negative effect on intelligence development. Impact of light REEs and heavy REEs were similar (-0.044 and -0.043, respectively).
Both light and heavy REEs, as well as lead in hair had negative effect on intelligence of children aged 6 to 16-years-old,, but interactive effect was not found. Future studies with improved methodologies and focus on mechanisms are expected.