Source Identification Analysis of Lead in the Blood of Japanese Children by Stable Isotope Analysis

Abstract

Considering the negative effect of lead (Pb) on children’s neurodevelopment, Pb exposure should be minimized to the lowest extent possible, though the blood Pb (BPb) concentrations in Japanese children are among the lowest in the world. To identify the sources of Pb in blood, isotope ratios (IRs: 207Pb/206Pb and 208Pb/206Pb) of Pb (PbIR) in whole blood from eight Japanese children were measured by multi-collector ICP mass spectrometry. Further, samples of house dust, soil, duplicate diet, and tobacco, collected from home environments, were also measured and were compared with PbIR of blood case by case. The relative contribution of Pb in the home environment to BPb were estimated by linear programming (finding an optimal solution which satisfy the combination of IRs and intakes from various sources) when appropriate. Source apportionment for three children could be estimated, and contributions of diet, soil, and house dust were 19–34%, 0–55%, and 20–76%, respectively. PbIR for the remaining five children also suggested that non-dietary sources also contributed to Pb exposure, though quantitative contributions could not be estimated. Non-dietary sources such as soil, house dust, and passive tobacco smoke are also important contributors to Pb exposure for Japanese children based on PbIR results.

The Use of Pb Isotope Ratios to Determine Environmental Sources of High Blood Pb Concentrations in Children: A Feasibility Study in Georgia

“…This provides a strong indication that the Pb from dust and spices made a significant contribution to the Pb in the blood. This finding is in agreement with other studies where an association with household dust and blood Pb has been suggested [ 19 , 20 , 21 , 22 , 24 ]. The Pb isotope data showed that it was not always the environmental samples with the highest total Pb concentrations that were the likely main contributory sources of blood Pb.…”

“…Here, we define sources as being isotopically indistinguishable if their isotope ratios are within the analytical uncertainty (calculated as twice the standard error of the mean) of the measurement. If there is a significant contribution of Pb in the blood from a number of sources, the Pb isotope signature of the blood shall be some intermediate of these and determined by their relative contributions [ 21 , 44 ].…”

“…In addition to blood samples from the child being taken during the visit, environmental samples of soil, spices, milk, water, household dust, flour (maize and wheat), paint, and toys were taken where available, being potential sources of Pb exposure for the child, and the parent/guardian gave informed consent. The types of environmental samples that were included in this study were selected based on them being reasonable potential sources of Pb, either from the published literature and/or informed by data and information from the Georgian National Food Agency and the Georgian Environment Agency [ 21 , 27 , 28 , 29 ].…”

“…In a recent study, similar to the one presented here, by Becker et al [ 19 ], Pb isotope ratios were used to determine that the environmental sources of Pb in five children from Kansas City with BLCs > 5 µg dL −1 included household dust, soil, turmeric, and paint. Other studies by Gulson et al [ 20 ] and Takagi et al [ 21 , 22 ] that used Pb isotope ratios to identify the most likely dominant sources of Pb in the blood of children in Australia and Japan, respectively, also found a strong link with household dust. In a study by Forsyth et al [ 23 ], the blood of 45 pregnant women from a rural area of Bangladesh was analysed and found to be most isotopically similar to that of turmeric, which had elevated levels of Pb and Cr, and indicated that the dominant source of Pb found in blood was from the adulterant spices with lead chromate.…”

Commentary on the Risk Assessment of Lead by the Food Safety Commission of Japan

“…Lead exposure from other sources, such as house dust, soil, and toys, in Japan was estimated using the results of previous studies [27][28][29] . Some studies have indicated that exposure from non-dietary sources might be important in children 30,31) ; however, the estimated values of the contribution of non-dietary sources to the overall lead exposure were highly variable depending on the studies and thus no representative value could be derived. The use of different analytical methods for measuring lead concentrations in environmental media and the estimation of lead intake values by applying different ingestion rates were thought to be the source of variance.…”