"Human Health Risk Assessment of Lead in Japan Based on the Blood Lead Levels" 

Norihiro Kobayashi, Kikuo Yoshida, Junko Nakanishi 

National Institute of Advanced Industrial Science and Technology

The 11th International Congress of Toxicology (Montreal 2007/7/15)

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Abstract

Human health risks of lead were assessed in Japan based on the blood lead levels obtained from both a monitoring of actual blood lead levels and the estimation using a biokinetic model for humans (IEUBK model). The population selected for human health risk assessment of lead was children living in Japan. The endpoint of “effects on the central nervous system” was selected for risk assessment with the reference value of 10 μg/dL of blood lead level. In this study, the blood lead level of 10 μg/dL was defined as the concern level. In the population monitored, the geometric mean and the geometric standard deviation of the blood lead levels were 1.4 µg/dL and 1.6, respectively. Based on the distribution of the blood lead levels, the probability that blood lead levels exceed the concern level was estimated to be less than 0.01%. Using IEUBK model, the geometric mean of blood lead levels and the exceeding probability in the whole population of the Japanese children were estimated to be 2.3 μg/dL and 0.08%, respectively. International agencies conducting risk assessments including U.S.EPA and WHO established the standard level for environmental lead, aiming that the percentage of children whose blood lead levels exceed 10 μg/dL ranges 1 to 5%. The probabilities obtained from both a monitoring and the IEUBK model estimation were 1 order of magnitude lower than this standard. From these results, it is judged that the estimated risks are not in the level which warrants any action for risk reduction in Japan.

Keywords

lead, blood, risk assessment, biomonitoring, IEUBK model