Excretion levels of urinary calcium and phosphorus among the inhabitants of Cd-polluted Kakehashi River basin of Japan.

Bone damage caused by exposure to cadmium (Cd) is often seen in Cd-polluted areas, and increased excretion of calcium (Ca) in urine is thought to be an important factor affecting bone damage. In order to clarify the significance of urinary Ca excretion in bone damage, we investigated the urinary excretion levels of Ca and phosphorus (P) of inhabitants of a Cd-polluted area and compared them to those of nonexposed subjects, and explored the possible association between urinary Ca or P and beta2-microglobulin (beta2-MG). The target subjects were 3164 inhabitants of the Cd-polluted Kakehashi River basin. Ca and Ca/P measurements were significantly higher in the Cd-polluted area than in the controls. In multiple-regression analysis, where either Ca or P was used as the criterion variable, and age, Cd, and beta2-MG were used as explanatory variables, there were positive associations between Ca and Cd and beta2-MG in both sexes. Therefore, the increased excretion level of Ca was the result of renal dysfunction. Bone damage is not thought to be caused by increased excretion of Ca alone because urinary excretion levels of Ca do not differ greatly between people with and without bone damage.