Closer correlation of cadmium in urine than that of cadmium in blood with tubular dysfunction markers in urine among general women populations in Japan

The objectives of the present study are to investigate whether cadmium in blood (Cd-B) and cadmium in urine (Cd-U) correlate with each other irrespective of age among general populations and which one of Cd-B or Cd-U correlates more closely with three renal tubular dysfunction markers in urine of alpha(1)-microglobulin (alpha(1)-MG-U), beta(2)-microglobulin (beta(2)-MG-U) and N-acetyl-beta-d-glucosaminidase (NAG-U). Data on two exposure markers (Cd-B and Cd-U) and three effect markers (alpha(1)-MG-U, beta(2)-MG-U and NAG-U) were collected for 1,403 adult women in non-polluted areas all over Japan. Possible significance of correlation between the parameters and dependency on age was examined by simple and multiple regression analysis. Both Cd-B and Cd-U increased as a function of age. The two exposure markers correlated significantly with each other, and the Cd-U over Cd-B ratio also increased as a function of age. Although both Cd-B and Cd-U correlated significantly with the three effect markers, the correlation was closer for Cd-U than for Cd-B. Cd-U rather than Cd-B should be recommended as an exposure marker of choice in Cd biological monitoring of general populations. Effects of aging should be taken into account when evaluating study results.