Analysis for threshold levels of cadmium in urine that induce tubular dysfunction among women in non-polluted areas in Japan.
OBJECTIVE
To examine if there is a threshold in urinary cadmium concentration that induces elevation in urinary microglobulins.


METHODS
The database developed in a previous field survey (Ezaki et al. 2002) was employed. In the survey conducted in 2000 and 2001, more than 10,000 middle-aged women (with no occupational exposure to Cd) in ten prefectures all over Japan gave morning spot urine samples, which were analyzed for cadmium (Cd-U), calcium (Ca-U), magnesium (Mg-U), zinc (Zn-U), alpha(1)- and beta(2)-microglobulins (alpha(1)- and beta(2)-MG-U), and creatinine (cr). The urinary analyte concentrations were corrected for cr concentration (to be expressed as, e.g., Cd-Ucr), and the data thus obtained were subjected to statistical evaluation. The largest geometric mean (GM) for Cd-Ucr among the ten prefecture was 3.2 microg Cd/g cr, and the maximum Cd-Ucr observed among the women studied was 20.9 microg Cd/g cr.


RESULTS
Both alpha(1)-MG-Ucr and beta(2)-MG-Ucr increased as a function of the increase in Cd-Ucr among all the women and also in sub-populations of narrow age ranges (i.e., 41-50 and 51-60 years), with no apparent threshold Cd-Ucr. Comparison of the cases exceeding cut-off alpha(1)-MG-Ucr and beta(2)-MG-Ucr levels also indicated a Cd dose-dependent increase in the prevalence, similarly without a threshold Cd-Ucr. In addition, such findings were essentially reproducible when elevation in alpha(1)-MG-Ucr and beta(2)-MG-Ucr levels was examined with the three essential elements, especially with Ca-Ucr and Mg-Ucr, although less clearly with Zn-Ucr. The observations as a whole suggest a possibility that the dose-dependent increases in alpha(1)-MG-Ucr and beta(2)-MG-Ucr with no apparent threshold for element concentration is not specific to Cd-Ucr but common to other elements.


CONCLUSIONS
No threshold Cd-Ucr was detected in relation to the increases in alpha(1)-MG-Ucr and beta(2)-MG-Ucr. The element dose-dependent increases in the two MGs with no threshold in the element concentration might be not limited to Cd, but common to other elements. Further studies are apparently necessary.
Ezaki
T
T
Kyoto Industrial Health Association, 67 Nishinokyo-Kitatsuboicho, Nakagyo-ku, Kyoto 604-8472, Japan.
Tsukahara
T
T
Moriguchi
J
J
Furuki
K
K
Fukui
Y
Y
Ukai
H
H
Okamoto
S
S
Sakurai
H
H
Honda
S
S
Ikeda
M
M
D000328:Adult; D000368:Aged; D002104:Cadmium / Q000494:pharmacology / Q000652:urine*; D002105:Cadmium Poisoning / Q000652:urine*; D002118:Calcium / Q000652:urine; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D007564:Japan; D007674:Kidney Diseases / Q000139:chemically induced* / Q000652:urine*; D007684:Kidney Tubules / Q000187:drug effects; D008274:Magnesium / Q000652:urine; D008875:Middle Aged; D015032:Zinc / Q000652:urine
D002104:Cadmium; D008274:Magnesium; D015032:Zinc; D002118:Calcium