Relationship between environmental exposure to cadmium and bone metabolism in a non-polluted area of Japan.

Objectives: The purpose of this study was to investigate the effects of environmental low-grade cadmium exposure on bone in the population of a non-polluted area. We investigated the relationship between environmental cadmium exposure (via rice intake) and bone metabolism in middle-aged and elderly women living in a non-polluted area in Japan.

Methods: Four hundred and twenty-nine women over the age of 39 years (54.6 ± 9.1 years; arithmetic mean ± SD) participated in this study in 2003. We investigated blood and urine, and rice intake, and performed ultrasonic bone evaluation, and obtained individual information about the subjects' health. Multiple regression analysis was performed in the statistical analysis.

Results: The arithmetic mean of cadmium content in rice was 70.8 ± 44.7 μg/kg (AM ± SD). The geometric mean of daily cadmium intake (Cd intake) from rice calculated based on food consumption data was 9.12 μg/day (GSD 2.33). The geometric means of serum and urine cadmium concentrations were 1.57 μg/l (GSD 2.11) and 1.93 μg/g creatinine (cr.) (GSD 2.05), respectively. Multiple regression analysis showed positive correlations between (1) urinary free deoxypyridinoline (FDPD-U) and Cd intake (p < 0.05), (2) urinary cross-linked N-telopeptides of type I collagen (NTx-U) and Cd intake (p < 0.05), and (3) FDPD-U or NTx-U and cadmium concentration in urine (p < 0.01). No significant correlation between the parameters of ultrasonic bone evaluation and cadmium associated biomarkers was observed.

Conclusions: The results of the present study suggest the possibility of bone metabolic disorder induced by environmental low-grade cadmium exposure. With respect to osteoporosis, a long-term follow-up survey is required to assess the tolerable intake of cadmium in environmental exposure.