Int. J. Environ. Res. Public Health 2009, 6 1005 international HapMap for Japanese. According to this data set, the major allele frequency of ALAD (ALAD1) was 0.92 and the minor allele frequency (MAF) for ALAD (ALAD2) was 0.08. Although our study population is the non-occupationally lead exposed subjects, the frequency of MAF was very similar to that of the general Japanese population according to the International HapMap Project data, as well as the study of Sakai et al. [26] that reported on an high occupational lead exposed subject. Thus our study not only confirmed the allele and genotype frequencies of ALAD2 even in the non-occupationally lead exposed free living Japanese population, but also the ALAD2 allele was rare in Japanese population. It seems to be concluded that the ALAD2 allele is rare in Asian populations including a Taiwanese population [15,21]. This finding may at least partly provide support for a explanation about that why the blood lead levels in the general population with environmental exposure to lead level are lower in Japan and other Asian countries when compared with the European countries [27]. Figure 1. Histogram of blood lead in all non-occupationally lead exposed participants. Vertical axis showed number of subjects divided by 10 individual each. Longitudinal axis showed concentration of blood lead (g/dl). Vertical bar (light blue) showed GG genotype of ALAD gene, and vertical bar (dark blue) showed GC genotype of ALAD gene. 0 1 2 3 4 5 Lead in blood (g/dl) 6 7 8 9 Table 2 shows the concentration of biomarkers for lead exposure, in non-occupationally lead exposed subjects. There were no significant differences for serum and urinary ALA, and ZnPP between the subjects with GG and GC genotype. The hematopoietic system is one of the target organs in lead poisoning. One of the most important mechanisms of lead toxicity is its effect on enzymes in the heme biosynthetic pathway. The enzyme in the biosynthetic pathway of heme in which the effects of lead are Subject Number 40 30 20 10 0 GG GC