Lead concentrations in whole blood (BPb) of Japanese children were measured to obtain insight into the sources of variation and to estimate health risk.

Blood samples were taken from 352 children (aged 1–14 years) at pediatric clinics/hospitals in 3 regions of Japan (Tokyo, Shizuoka, and Osaka) during 2005–2006 (Shizuoka only) and 2008–2010 (3 regions), and BPb was measured by inductively coupled plasma mass spectrometry after acid digestion.

Geometric mean BPb of the 352 children was 1.07 μg/dL, among the lowest in the world. Based on this result, the probability of exceeding BPb 10 μg/dL, the action level proposed by the US Centers for Disease Control and Prevention , in general Japanese children was estimated to be negligible. There was a significant negative correlation between BPb and age, while sex difference was not significant. BPb was significantly lower in subjects in Tokyo than in the other two regions. Age-adjusted mean BPb was significantly higher in children with a family member who smoked in their presence than in those who did not have such a family member, indicating that passive smoking had a significant effect on BPb.

Health risk of lead exposure is minimal in Japanese children. To lower the exposure level further, reduction of passive smoking is suggested as one of the effective measures.