Investigation of the relationship between low environmental exposure to metals and bone mineral density, bone resorption and renal function.

Environmental exposure to metals has been linked to adverse health outcomes. Exposure to cadmium has been associated with decreased bone density, an increased risk of osteoporotic fracture and possible renal dysfunction. Older women are a group at risk of renal and bone density impacts and exposure to metals may be an important risk factor for these health outcomes. This study was a cross sectional study of 77 women aged 50 years and above examining the relationship between metals exposure and renal and bone health. Urinary and blood metals concentrations, plasma creatinine, iron, ferritin and transferrin were measured in these subjects. Bone biomarkers assessed included the pyridinium crosslinks, pyridinoline and deoxypyridinoline measured by ELISA. Renal function was assessed using eGFR and KIM-1. Whole body, hip and lumbar spine bone mineral density was assessed using DEXA. Blood and urinary metals concentrations were generally low in the subjects, with a median urinary cadmium concentration of 0.26 μg/g creatinine (range <0.065-1.03 μg/g). Urinary cadmium was found to be a significant predictor of bone mineral density at whole body, lumber spine, total hip and femoral neck, with increasing urinary Cd concentrations associated with decreased bone density. Urinary cadmium and aluminium concentrations were positively correlated with bone resorption whilst blood zinc and mercury concentrations were negatively correlated. Urinary aluminium was positively correlated with KIM-1 concentrations, a marker of early kidney damage, however blood zinc concentrations were significantly negatively correlated with this biomarker. This study provides additional support for low cadmium exposure being of concern for the health of older women. Further investigation into the role of exposure to other metals on bone and renal health is warranted.