Lead in the Japanese living environment

Lead has long been known to be a neurotoxic heavy metal, particularly in the context of occupational health. However, its adverse effect on the cognitive development of children at lower exposure levels has only recently received attention. Although the exposure level of contemporary Japanese children is among the lowest in the world, it is desirable to reduce exposure as much as reasonably possible due to the absence of a threshold of exposure for adverse effects. In this review, information on lead levels in milieus of our proximate environment, such as the atmosphere, drinking water, soil, house dust, diet and others, of contemporary Japan was compiled with the aim of updating our knowledge on lead distribution. Monitoring data demonstrates that lead concentrations in the atmosphere and lead intake from food consumption have decreased substantially from the 1970s. Lead was hardly detectable in tap water in a recent nation-wide monitoring survey. To the contrary, elevated lead concentrations were detected in surface soil and house dust in one of the studies on daily exposure to lead from all potential sources, and both of these sources were regarded by the authors as significant contributors of lead exposure to general Japanese children. A similar study indicated that diet is the sole major source of lead for Japanese children. A significant difference was present in the estimated dietary lead intake levels in different studies, resulting in significant discrepancies in the current knowledge on lead in our environment. Further studies are warranted to identify the major source(s) of lead exposure in Japanese children in order to establish an effective countermeasure to reduce lead exposure to children.