Lead isotopic compositions of environmental certified reference materials for an inter-laboratory comparison of lead isotope analysis.

Lead isotope ratios, viz. 207Pb/206Pb and 208Pb/206Pb, of the commercially available certified reference materials (CRMs) issued in Japan are presented with an objective to provide a data set, which will be useful for the quality assurance of analytical procedures, instrumental performance and method validation of the laboratories involved in environmental lead isotope ratio analysis. The analytical method used in the present study was inductively coupled plasma quadrupole mass spectrometry (ICPQMS) preceded by acid digestion and with/without chemical separation of lead from the matrix. The precision of the measurements in terms of the relative standard deviation (RSD) of triplicated analyses was 0.19% and 0.14%, for 207Pb/20Pb and 208Pb/206Pb, respectively. The trueness of lead isotope ratio measurements of the present study was tested with a few CRMs, which have been analyzed by other analytical methods and reported in various literature. The lead isotopic ratios of 18 environmental matrix CRMs (including 6 CRMs analyzed for our method validation) are presented and the distribution of their ratios is briefly discussed.

[Relationship between fetal lead exposure and birth weight--evaluation using deciduous incisor enamel].

OBJECTIVE: The purpose of this study was to examine the relationship between fetal lead exposure and birth weight, using deciduous incisor enamel as a biomarker and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for analysis of lead. METHODS: We asked dental clinics (n=11) and kindergartens (n=11), mainly in the Tokyo metropolitan area and Miyagi Prefecture, and parents to enroll donors of exfoliate deciduous incisors. Donors who consented to this study voluntarily sent deciduous incisors and questionnaires to the authors between March and October, 2003. The Pb/Ca ratios of inner enamel samples were determined by LA-ICP-MS. The relationship between the lead-to-calcium ratio in the enamel and the birth weight was evaluated by stepwise multiple linear regression analysis. RESULTS: One hundred forty-one subjects (male, 72; female, 69) were enrolled in this study. The mean Pb/Ca ratio in the enamel was as low as 0.24 mg-Pb/kg-Ca (SD=0.17). Stepwise multiple linear regression analysis extracted the following maternal variables with a positive coefficient with birth weight: gestational age (p < 0.01), weight gain during pregnancy (p < 0.01), prepregnancy BMI (body mass index, p < 0.01), and parity (p < 0.05). Lead concentration in the enamel was significantly negatively associated with birth weight (p < 0.05). CONCLUSIONS: Our study indicated that lead concentration in the enamel was inversely related to birth weight. This association was found in a population of which the mean blood lead level was estimated to be as low as about 1 microg/dl. We concluded that in utero low lead exposure decreased birth weight, within the normal range of birth weight.

Analysis of lead in tooth enamel by laser ablation-inductively coupled plasma-mass spectrometry.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine the Pb/Ca ratios in the enamel of deciduous incisors, a biomarker of in utero Pb exposure, using pelletized bone certified reference materials (CRMs) as calibrants. The detection limit for Pb by LA-ICP-MS was 11 microg kg(-1) demonstrating an adequate sensitivity for Pb in the teeth of unexposed individuals (0.1-10 mg kg(-1)). The precision for the Pb/Ca ratios in NIST SRM 1486 Bone Meal was 3.4%. The correlation between Pb/Ca ratios obtained by LA-ICP-MS and those obtained by a digestion method was highly significant. We found one point calibration by a CRM was applicable for the quantification of Pb in tooth enamel. This method will be valuable for the assessment of in utero Pb exposure levels.