Source identification of lead exposure by lead isotopic measurement in human nails and hair

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The lead isotopic ratio of human hair or nails is expected to be a useful means for discriminating the source of lead exposure to human body by comparison with that of environmental samples. It is difficult to collect human tissue. Scalp hair and nails are easy to collect with minimal hazard to human. In this study we investigated the isotopic measurement by LA/ICP-MS and evaluated the possibility for identifying the source of human lead by lead isotopic ratio. Laser system consists of a pulsed Nd : YAG laser, which is coupled to the ICP-MS. A measured value of the lead isotopic ratio of the sample was normalized by the certified value of that of the NIST standard reference material 981 lead. As a first step standard reference material BCR 397 Human Hair was used as a measurement sample by pressed into a form of pellet and mounted on the double sided tape(called tape sample). The isotopic measurements of pellet sample were capable greater precision than tape sample. The isotopic measurement of scalp hair was carried out above method after pre-treatment. It is necessary to wash the hair prior to analysis. Scalp hair was washed with different solvents in sequence : acetone three times of water - acetone. The washed samples were dried with warm air, and ashed at 2000C for lh. BCR standard human hair sample and scalp hair sample also were measured by ICP-MS for sample solution after high pressure oxygen combustion. The differences in lead isotopic ratios of scalp hair collected from some women lived in adjoining area measured of this study cannot be regarded as significant. But we can discriminate between isotopic ratio and that reported in reference literature collected foreign area.