Cadmium and tubular dysfunction marker levels in urine of residents in non-polluted areas with natural abundance of cadmium in Japan.

OBJECTIVES

Literature survey has suggested that cadmium (Cd) in the general environment is more abundant in the northern part of the coast on the sea of Japan. The present survey was initiated to examine if the exposure to Cd in the area has been higher than other parts of Japan, and if so, the higher exposure has been associated with tubular dysfunction among the local residents.

METHODS

In three prefectures of Akita, Yamagata and Ishikawa in the region, adult women (about 700 subjects per prefecture) were invited to participate in the survey. Each of the participants provided informed consents, offered spot urine samples and filled questionnaires (on age etc.). The urine samples were analyzed for Cd, alpha(1)-microglobulin (alpha(1)-MG), beta(2)-microglobulin (beta(2)-MG) and N-acetyl-beta-D: -glucosaminidase, together with creatinine and specific gravity. The results were combined with published data on two other prefectures of Niigata and Toyama (both in the area), as well as Japan as a whole (all Japan-A excluding Niigata prefecture, which was studied separately in the present study), and subjected to analysis for possible difference from all Japan-A in terms of the levels of internal Cd burden, and prevalence of beta(2)-MG-uria.

RESULTS

Geometric means (GMs) for urinary Cd in the five prefectures were in a range from a low of 1.20 to a high of 2.65 microg/l, being higher than the GM (0.99 microg/l) for all Japan-A. GMs for alpha(1)-MG (2.15-2.80 mg/l) and beta(2)-MG (99-107 microg/l) were only slightly higher or even lower than all Japan-A values depending on the prefectures. Elevation in the prevalence of beta(2)-MG-uria was significant in Akita prefecture, but the elevation in beta(2)-MG was not associated with elevation in Cd in urine. Literature survey on general population Cd epidemiology showed that Cd, alpha(1)-MG and beta(2)-MG levels in urine of the residents in the five prefectures were within the levels reported for non-polluted areas, and such was also the case for prevalence of beta(2)-MG-uria.

CONCLUSIONS

In an over-all evaluation, no clear-cut evidence was available for increased prevalence of Cd exposure-associated renal tubular dysfunction among general populations in the five prefectures in the northern part on the coast of Sea of Japan than in other prefectures in Japan, despite moderate elevation in urinary Cd levels.