Lack of correlation between cadmium level in local brown rice and renal failure mortality among the residents: a nation-wide analysis in Japan.

OBJECTIVES: Cadmium is a ubiquitous hazardous element with nephro-toxicity after long-term exposure. The present study was initiated to examine possible effects of dietary cadmium (Cd) intake on health of local residents across Japan. For this purpose, Cd in locally harvested brown rice (Cd-BR) was taken as the parameter of Cd exposure, and two measures of mortality, i.e., standardized mortality ratio (SMR) and age-adjusted renal insufficiency mortality rate (AARIMR) were employed as parameters of over-all health effects including effects on kidney.
METHODS: Japan consists of 47 prefectures. Data on Cd in 37,250 brown rice samples harvested in 1997-1998 in the 47 prefectures were made available from the Ministry of Agriculture, Forestry and Fisheries, Japan. SMR and AARIMR data (for the year 2000) by two genders in the 47 prefectures were cited from publications of the Ministry of Health, Labour and Welfare, Japan. Possible correlation of Cd in brown rice (Cd-BR) with SMR and AARIMR was examined by Poisson regression analysis.
RESULTS: The geometric mean (GM) Cd-BR for Japan as a whole was 0.040 mg/kg with a geometric standard deviation (GSD) of 2.72. Prefectural GM values varied from a low of <0.01 mg/kg to a high of 0.089 mg/kg. Nevertheless, SMR (in a range of 89.9-119.5 for men and 87.1-111.7 for women) did not correlate with Cd-BR significantly. AARIMR (in a range of 5.3-11.9 and 3.2-8.4 for men and women, respectively) tended to decrease as a function of increasing Cd-BR both in men and women, although the correlation was insignificant in both genders.
CONCLUSIONS: No evidence was obtained in the present analysis to suggest that either mortality as a whole or the mortality due to renal failure is affected by dietary intake of Cd in rice.