Bone Mineral Density in Population Long-Term Exposed to Rare Earth Elements from a Mining Area of China

This study aims to investigate the effects of individuals' exposure to rare earth elements (REEs) on bone metabolism. Adopting the inductively coupled plasma mass spectrometry, we measured REEs and eight other elements (Ca, Fe, Cu, Na, K, Zn, Mg, and P) in the hair of 53 miners exposed to REEs from Baiyunebo and 57 healthy farmers as the control group. Furthermore, bone mineral density (BMD) in both groups was assessed by dual-energy X-ray absorptiometry. Analysis of variance showed that the concentrations of La, Ce, Pr, Nd, Tb, Ho, Tm, and Yb in male hair of exposed group were significantly higher compared with the control group, whereas the concentrations of Ca and Fe in exposed group were significantly lower; the results of female hair, except for Ce, Tb, Ho, Tm, and Yb, were consistent with male hair. Student's t test showed that the BMD of exposed males at lumbar vertebrae, femoral neck, greater trochanter, and intertrochanter was significantly lower than that of controls, and exposed females reported lower BMD values at lumbar vertebrae and femoral neck. Multiple linear regression analysis showed that concentrations of differential REEs were inversely related to BMD in males, and concentrations of Ca and Fe were positively related to BMD both in males and females. Our study suggests that long-term environmental and occupational exposure leads to REE accumulation, and a low level of iron and calcium due to the competitive binding of REEs, which together induce bone metabolism disorders, and further reduce BMD.