High cadmium and low lead exposure of children in Japan.

Background: Cadmium (Cd) is a wide-spread environmental pollutant with insidious toxicity to kidneys, and children are considered to be a high-risk group. Lead (Pb) is suspected to induce retardation in mental development in children. Daily foods are an important source of both Cd and Pb exposure for general population. Nevertheless, data on dietary exposure of children to Cd and Pb are still scarce in Japan.
Objectives: This study was initiated to clarify the extent of exposure of children to Cd. Exposure to Pb, another environmental pollutant element, was also studied in combination.
Methods: Twenty-four-hour food duplicates and the first morning urine samples were collected from 296 children (159 boys and 137 girls at the ages of 3-6 years) in 15 kindergartens in Miyagi prefecture on the Pacific coast in north-east Japan; no environmental pollution with Cd has been known in the prefecture. Cd, Pb and iron in food duplicates and Cd in urine were analyzed by inductively coupled plasma-mass spectrometry. α(1)-Microglobulin (α(1)-MG) in urine was measured by the latex method. Log-normal distributions were confirmed for these analytes.
Results: The geometric mean (GM) values for dietary intake of Cd and Pb were 11.8 and 2.28 μg/day, or 4.20 and 0.84 μg/kg body weight/week, respectively, for total children studied. No significant difference was detected in dietary Cd and Pb intake between boys and girls of the same age (except for Pb on a μg/day basis at 6 years) as well as of all ages in combination. Trends of increase in Cd and Pb intake were observed parallel to age when calculated on a daily intake basis, but the trends disappeared after correction for body weight. No age-dependent increase was observed in α(1)-MG, despite there was an age-dependent increase in Cd.
Conclusions: The dietary intake of Cd and Pb for children studied were 4.20 and 0.84 μg/kg body weight/week, respectively. International comparison of the present results with values reported in literature suggested that exposure of children in Japan was higher with regard to Cd, and lower regarding Pb, reproducing the observation in adult Japanese populations. For better health of children, efforts may be necessary to reduce high dietary exposure to Cd.