Urinary cadmium excretion is correlated with calcaneal bone mass in Japanese women living in an urban area

Nine hundred eight women aged 40–88 years living in a non-Cd-polluted area in Japan were analyzed for urinary cadmium (Cd), N-acetyl-β- -glucosaminidase (NAG) activity, β2-microglobulin (B2MG) concentration, and for the stiffness index (STIFF) of calcaneal bone using an ultrasound method. The urinary Cd in the subjects, with a mean and range of 2.87 and 0.25–11.4 μg/g creatinine, respectively, showed a significant correlation with NAG but not with B2MG. STIFF was significantly inversely correlated with urinary Cd, and the association remained significant after adjusting for age, body weight, and menstrual status, suggesting a significant effect of Cd on the bone loss in these subjects without signs of Cd-induced kidney damage. A two-fold increase in urinary Cd was accompanied by a decrease in STIFF corresponding to a 1.7-year rise in age. These results emphasize the need for reassessment of the significance of Cd exposure in the general Japanese population.