Changes in the lead isotopic composition of blood, diet and air in Australia over a decade: globalization and implications for future isotopic studies

High precision blood lead radiogenic isotope signatures in a community exposed to Pb contaminated soils and implications for the current Pb exposure of the European population

Our study provides the most comprehensive dataset for high-precision radiogenic isotopes of lead (Pb) in blood for the western European population. It investigates their potential for elucidating the contribution of soil Pb to blood Pb using a human biomonitoring survey involving 81 adults and 4 children living in the urban area of Liège (Belgium). Soils in the area show moderate (median of 360 mg/kg) to high (95th percentile of 1000 mg/kg) Pb concentrations, due to former metal processing activities. Blood lead levels (BLL) measured in the study population are, on average, quantitatively consistent with a ∼ 20 % increase due to the exposure to Pb from soils, as estimated by a single-compartment biokinetic model. Consistently, its isotopic composition does not represent an endmember that fully accounts for the variability of Blood lead isotope (BLI) compositions measured in the study population. While some individuals show more thorogenic BLI ratios (relatively more enriched in 208Pb), which could be consistent with a greater exposure to local soils and/or by their country of birth, the BLI data mostly follow a trend roughly parallel to the European Standard Lead Pollution (ESLP) line, within the European leaded gasoline field, even two decades after the withdrawal of this source. Differences in BLI are probably associated with factors related to the presence of Pb in dwellings (pipes, paint) and drinking water distribution system, suggesting that the anthropogenic Pb in use, relevant to human exposure, may contain ore components of different origins, including the Australian Pb ore signature.

Distinguishing between Natural and Industrial Lead in Consumer Products and Other Environmental Matrices

California's Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65) was designed to protect the state's populace from exposures to toxic levels of chemicals in consumer products, including foods, by requiring businesses to warn the public about any of those hazards. There is, however, one qualification in the legislation, which is that warnings are not required if the source of that contamination is natural, as opposed to industrial. That qualification is especially problematic for lead because "natural" and "industrial" lead have a common origin and behave the same in the environment and industrial lead contamination has been pandemic for millennia. As a result of that historic and ongoing contamination, ambient lead levels in the biosphere may be orders of magnitude above natural levels, limiting comparisons of "natural" versus "industrial" lead concentrations in products. Further complicating those comparisons are reports of erroneously high measurements of lead concentrations in the biosphere as a result of sample contamination during collection, storage, and analysis. Some of those problems may be addressed with measurements of lead concentrations using rigorous trace metal clean techniques. These techniques often yield lead concentrations that are below the Act's maximum exposure in foods and non-foods of 0.5 μg/day, eliminating the need for a public alert. Those techniques have also been used to derive natural lead concentrations in a few organisms (marine fish, humans, rats, and dandelions), which range from 2- to 100-fold below ambient levels. However, extrapolating from those few determinations to establish natural lead levels in other organisms is complicated and often inappropriate. Complementary stable lead isotopic composition measurements have also been used to estimate the percent of natural and industrial lead in some consumer products, including foods, wine, and dietary supplements. These measurements, however, require the isotopic compositions of both the "natural" and "industrial" lead end members, which may be poorly defined. In addition, the global market has further complicated identification of the "industrial" lead end member, because lead contamination of foods can occur during production, harvesting, storage, shipping, processing, and packaging, which can happen in different locales within a country, different countries, and even different continents.

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

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.

Urinary lead in relation to combustion-derived air pollution in urban environments. A longitudinal study of an international panel

BACKGROUND

Urinary lead (Pb) is generally considered to have limited use in biomonitoring environmental exposure to lead. Carbon load in airway macrophages (AM BC) is an internal marker to assess long-term exposure to combustion-derived aerosol particles. In urban environments, atmospheric Pb and black carbon may have common sources. We aimed to study the temporal change of urinary Pb (U-Pb) when exposure to outdoor air pollution changes, and the relationship between U-Pb and AM BC.

METHODS

A panel of 50 young healthy adults [mean (SD) 26.7 (5.2) years], including 17 long-term (>1 year) residents in Leuven, Belgium (BE), 15 and 18 newcomers (arrived <3 weeks) from low- and middle-income countries (LMIC) and high-income countries (HIC), respectively, underwent 8 repeated measurements at 6 weeks intervals. In urine spot samples obtained at 5 time points (T1, T2, T4, T6, T8), 24 trace elements were quantified by inductively coupled plasma-mass spectrometry. At each time point, AM BC was quantified as the median surface of black inclusions (in μm²) by means of image analysis of 25 macrophages obtained by induced sputum. Changes in urinary metal concentrations (with and without creatinine correction) and the relationship between U-Pb and AM BC were estimated using linear mixed models adjusted for covariates and potential confounders.

RESULTS

Only U-Pb differed between groups and exhibited significant time trends. Participants from the LMIC group had significantly higher initial U-Pb (1.18 μg/g creat) than the HIC group (0.44 μg/g creat) and BE group (0.45 μg/g creat). In the LMIC group, U-Pb decreased significantly with time by 0.061 μg/g creatinine per 30 days [95% confidence interval (CI): 0.034, 0.088]. U-Pb remained unchanged in the other two groups. An increase in AM BC of 1 μm² was associated with an increase in U-Pb of 0.369 μg/g creat (95% CI: 0.145, 0.593).

CONCLUSION

This panel study demonstrates that U-Pb may be a valid alternative to blood Pb for biomonitoring changes in exposure to lead, at least at group level. In addition, we identified a positive association between U-Pb and AM BC, a biomarker of exposure to traffic-related air pollution, suggesting the existence of common sources of Pb and black carbon in urban environments.

Concerns about Quadrupole ICP-MS Lead Isotopic Data and Interpretations in the Environment and Health Fields

There has been a massive increase in recent years of the use of lead (Pb) isotopes in attempts to better understand sources and pathways of Pb in the environment and in man or experimental animals. Unfortunately, there have been many cases where the quality of the isotopic data, especially that obtained by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS), are questionable, resulting in questionable identification of potential sources, which, in turn, impacts study interpretation and conclusions. We present several cases where the isotopic data have compromised interpretation because of the use of only the major isotopes ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁷Pb/²⁰⁶Pb, or their graphing in other combinations. We also present some examples comparing high precision data from thermal ionization (TIMS) or multi-collector plasma mass spectrometry (MC-ICP-MS) to illustrate the deficiency in the Q-ICP-MS data. In addition, we present cases where Pb isotopic ratios measured on Q-ICP-MS are virtually impossible for terrestrial samples. We also evaluate the Pb isotopic data for rat studies, which had concluded that Pb isotopic fractionation occurs between different organs and suggest that this notion of biological fractionation of Pb as an explanation for isotopic differences is not valid. Overall, the brief review of these case studies shows that Q-ICP-MS as commonly practiced is not a suitable technique for precise and accurate Pb isotopic analysis in the environment and health fields.

Estimates of potential childhood lead exposure from contaminated soil using the US EPA IEUBK Model in Sydney, Australia

Surface soils in portions of the Sydney (New South Wales, Australia) urban area are contaminated with lead (Pb) primarily from past use of Pb in gasoline, the deterioration of exterior lead-based paints, and industrial activities. Surface soil samples (n=341) were collected from a depth of 0-2.5cm at a density of approximately one sample per square kilometre within the Sydney estuary catchment and analysed for lead. The bioaccessibility of soil Pb was analysed in 18 samples. The blood lead level (BLL) of a hypothetical 24 month old child was predicted at soil sampling sites in residential and open land use using the United States Environmental Protection Agency (US EPA) Integrated Exposure Uptake and Biokinetic (IEUBK) model. Other environmental exposures used the Australian National Environmental Protection Measure (NEPM) default values. The IEUBK model predicted a geometric mean BLL of 2.0±2.1µg/dL using measured soil lead bioavailability measurements (bioavailability =34%) and 2.4±2.8µg/dL using the Australian NEPM default assumption (bioavailability =50%). Assuming children were present and residing at the sampling locations, the IEUBK model incorporating soil Pb bioavailability predicted that 5.6% of the children at the sampling locations could potentially have BLLs exceeding 5µg/dL and 2.1% potentially could have BLLs exceeding 10µg/dL. These estimations are consistent with BLLs previously measured in children in Sydney.

Tracing fetal and childhood exposure to lead using isotope analysis of deciduous teeth

We report progress in using the isotopic composition and concentration of Pb in the dentine and enamel of deciduous teeth to provide a high resolution time frame of exposure to Pb during fetal development and early childhood. Isotope measurements (total Pb and (208)Pb/(206)Pb, (207)Pb/(206)Pb ratios) were acquired by laser ablation inductively coupled mass spectrometry at contiguous 100 micron intervals across thin sections of the teeth; from the outer enamel surface to the pulp cavity. Teeth samples (n=10) were selected from two cohorts of children, aged 5-8 years, living in NE England. By integrating the isotope data with histological analysis of the teeth, using the daily incremental lines in dentine, we were able to assign true estimated ages to each ablation point (first 2-3 years for molars, first 1-2 years for incisors+pre-natal growth). Significant differences were observed in the isotope composition and concentration of Pb between children, reflecting differences in the timing and sources of exposure during early childhood. Those born in 2000, after the withdrawal of leaded petrol in 1999, have the lowest dentine Pb levels (<0.2µgPb/g) with (208)Pb/(206)Pb (mean ±2σ: 2.126-2.079) (208)Pb/(206)Pb (mean ±2σ: 0.879-0.856) ratios that correlate very closely with modern day Western European industrial aerosols (PM10, PM2.5) suggesting that diffuse airborne pollution was probably the primary source and exposure pathway. Legacy lead, if present, is insignificant. For those born in 1997, dentine lead levels are typically higher (>0.4µgPb/g) with (208)Pb/(206)Pb (mean ±2σ: 2.145-2.117) (208)Pb/(206)Pb (mean ±2σ: 0.898-0.882) ratios that can be modelled as a binary mix between industrial aerosols and leaded petrol emissions. Short duration, high intensity exposure events (1-2 months) were readily identified, together with evidence that dentine provides a good proxy for childhood changes in the isotope composition of blood Pb. Our pilot study confirms that laser ablation Pb isotope analysis of deciduous teeth, when carried out in conjunction with histological analysis, permits a reconstruction of the timing, duration and source of exposure to Pb during early childhood. With further development, this approach has the potential to study larger cohorts and appraise environments where the levels of exposure to Pb are much higher.

Isotopic ratio based source apportionment of children's blood lead around coking plant area

Lead exposure in the environment is a major hazard affecting human health, particularly for children. The blood lead levels in the local children living around the largest coking area in China were measured, and the source of blood lead and the main pathways of lead exposure were investigated based on lead isotopic ratios ((207)Pb/(206)Pb and (208)Pb/(206)Pb) in blood and in a variety of media, including food, airborne particulate matter, soil, dust and drinking water. The children's blood lead level was 5.25 (1.59 to 34.36 as range) μg dL(-1), lower than the threshold in the current criteria of China defined by the US Centers for Disease Control (10 μg dL(-1)). The isotopic ratios in the blood were 2.111±0.018 for (208)Pb/(206)Pb and 0.864±0.005 for (207)Pb/(206)Pb, similar to those of vegetables, wheat, drinking water, airborne particulate matter, but different from those of vehicle emission and soil/dust, suggesting that the formers were the main pathway of lead exposure among the children. The exposure pathway analysis based on the isotopic ratios and the human health risk assessment showed that dietary intake of food and drinking water contributed 93.67% of total exposed lead. The study further indicated that the coal used in the coking plant is the dominant pollution source of lead in children's blood.

The Pb isotopic record of historical to modern human lead exposure

Human teeth and bones incorporate trace amounts of lead (Pb) from the local environment during growth and remodeling. Anthropogenic activities have caused changes in the natural Pb isotopic background since historical times and this is reflected in the Pb isotopes of historical European teeth. Lead mining and use increased exponentially during the last century and the isotopic compositions of modern human teeth reflect the modern anthropogenic Pb. USA teeth show the most radiogenic Pb and Australian teeth show the least radiogenic Pb, a result of different Pb ores used in the two regions. During the last century the Australian Pb was exported to Europe, Asia, South America, and Africa, resulting in swamping of the local environmental Pb signal by the imported Pb. As a result, the modern human teeth in Europe show a significant drop to lower isotopic values compared with historical times. Similarly, modern human teeth in other regions of the world show similar Pb isotopic ratios to modern European teeth reflecting the Pb imports. The specific pattern of human Pb exposure allows us to use the Pb isotopic signal recorded in the skeleton as a geo-referencing tool. As historical European teeth show a distinct Pb signal, we can identify early European skeletal remains in the New World and likely elsewhere. In modern forensic investigations we can discriminate to some extent Eastern Europeans from Western and Northern Europeans. Australians can be identified to some extent in any region in the world, although there is some overlap with Western European individuals. Lead isotopes can be used to easily identify foreigners in the USA, as modern USA teeth are distinct from any other region of the world. By analogy, USA individuals can be identified virtually in any other region of the world.

Identification of lead sources in residential environments: Sydney Australia

Interior and exterior dust, soil and paint were analysed at five brick urban Sydney homes over 15 months to evaluate temporal variations and discriminate sources of lead (Pb) exposure. Exterior dust gauge Pb loading rates (μg/m(2)/28 days), interior vacuum dust Pb concentrations (mg/kg) and interior petri-dish Pb loading rates (μg/m(2)/28 days), were correlated positively with soil Pb concentrations. Exterior dust gauge Pb loading rates and interior vacuum dust Pb concentrations peaked in the summer. Lead isotope and Pb speciation (XAS) were analysed in soil and vacuum dust samples from three of the five houses that had elevated Pb concentrations. Results show that the source of interior dust lead was primarily from soil in two of the three houses and from soil and Pb paint in the third home. IEUBK child blood Pb modelling predicts that children's blood Pb levels could exceed 5 μg/dL in two of the five houses.

Surface dust wipes are the best predictors of blood leads in young children with elevated blood lead levels

BACKGROUND

As part of the only national survey of lead in Australian children, which was undertaken in 1996, lead isotopic and lead concentration measurements were obtained from children from 24 dwellings whose blood lead levels were ≥15 µg/dL in an attempt to determine the source(s) of their elevated blood lead. Comparisons were made with data for six children with lower blood lead levels (<10 µg/dL).

METHODS

Thermal ionisation and isotope dilution mass spectrometry were used to determine high precision lead isotopic ratios (208Pb/206pb, 207Pb/206Pb and 206Pb/204Pb) and lead concentrations in blood, dust from floor wipes, soil, drinking water and paint (where available). Evaluation of associations between blood and the environmental samples was based on the analysis of individual cases, and Pearson correlations and multiple regression analyses based on the whole dataset.

RESULTS AND DISCUSSION

The correlations showed an association for isotopic ratios in blood and wipes (r=0.52, 95% CI 0.19-0.74), blood and soil (r=0.33, 95% CI -0.05-0.62), and blood and paint (r=0.56, 95% CI 0.09-0.83). The regression analyses indicated that the only statistically significant relationship for blood isotopic ratios was with dust wipes (B=0.65, 95% CI 0.35-0.95); there were no significant associations for lead concentrations in blood and environmental samples. There is a strong isotopic correlation of soils and house dust (r=0.53, 95% CI 0.20-0.75) indicative of a common source(s) for lead in soil and house dust. In contrast, as with the regression analyses, no such association is present for bulk lead concentrations (r=-0.003, 95% CI -0.37-0.36), the most common approach employed in source investigations. In evaluation of the isotopic results on a case by case basis, the strongest associations were for dust wipes and blood.

Environmental lead pollution threatens the children living in the Pearl River Delta region, China

INTRODUCTION AND PURPOSE

The objective of this study is to determine children's blood lead levels and identify sources of lead exposure. Childhood lead exposure constitutes a major pediatric health problem today in China. A blood lead screening survey program for children in the age group of 2-12 years residing in Pearl River Delta region, south of China, was carried out from Dec 2007 to Jan 2008.

METHODS

Blood lead levels and lead isotope ratios of a total of 761 participants were assessed by inductively coupled plasma mass spectroscopy. Measurements of urban environmental samples for source identification of children lead exposure were also performed.

RESULTS AND CONCLUSIONS

The geometric mean value of the children's blood lead levels was 57.05 μg/L, and 9.6% of them were higher than 100 μg/L. The blood lead levels were still much higher than those in developed countries. Based on the data of environmental lead source inventories, lead isotopic tracing revealed that there is about 6.7% past used gasoline Pb embedded in Shenzhen residential dust and about 15.6% in Guangzhou dust, respectively.

Lead isotopes reveal different sources of lead in balsamic and other vinegars

Fifty-eight brands of balsamic vinegars were analyzed for lead concentrations and isotopic compositions ((204)Pb, (206)Pb, (207)Pb, and (208)Pb) to test the findings of a previous study indicating relatively high levels of lead contamination in some of those vinegars--more than two thirds (70%) of them exceeded California's State Maximum Level (34 μg/L) based on consumption rates ≥0.5 μg Pb per day. The lead isotopic fingerprints of all those vinegars with high lead concentrations were then found to be primarily anthropogenic. This isotopic analysis unquestionably reveals multiple contamination sources including atmospheric pollutant Pb and an unidentified contamination source, likely occurring after grape harvest. Organically grown grape vinegars display the same Pb content and isotopic signatures as other vinegars. This implies that pesticides might not be a significant source of pollutant Pb in vinegars. A significant post-harvest contamination would be inherited from chemicals added during production and/or material used during transport, processing or storage of these vinegars. This is consistent with the highest Pb levels being found in aged vinegars (112±112 μg/L) in contrast to other vinegars (41.6±28.9 μg/L) suggesting contamination during storage. It is, therefore, projected that lead levels in most vinegars, especially aged balsamic and wine vinegars, will decrease with improvements in their manufacture and storage processes consequential to recent concerns of elevated levels of lead in some vinegars.

Exposures to lead

The Pacific Basin Consortium for Environment and Health hosted a workshop on Exposures to Lead. Speakers from Australia and the United States of America addressed current research knowledge on lead exposures and health effects in children, risk assessment and communication issues in dealing with lead exposure sources, different methods for assessing exposure, and the variety of scenarios where lead still remains a pollutant of concern. Mining continues to be a source of lead for many communities, and approaches to reducing exposures in these settings present particular challenges. A Perth Declaration for the Global Reduction of Childhood Lead Exposure was signed by participants of the meeting and is aimed at increasing attention to the need to continue to assess lead in the environment and to develop strategies to reduce lead in the environment and exposure by communities.

Past, present, and future of environmental specimen banks

Environmental specimen banks are an essential part of the infrastructure of environmental sciences. They have various functions: (1) evaluation of governmental environmental policy-making and regulations; (2) a resource for animal health evaluation; (3) research tools to investigate time trends in ecosystems; (4) detection of newly emerging chemicals in the time trends; (5) validations of computer models for environmental phenomena; (6) source identification of contaminants; (7) a tool for food safety; (8) evaluation of genetic selection pressure due to environmental changes. In this review paper, we present a detailed description of the Kyoto University Human Specimen Bank (history, protocol and questionnaires) and provide brief outlines of other representative environmental specimen banks. We then review two illustrative cases in which environmental specimen banks have unveiled insidious contaminations of polybrominated diphenyl ethers and perfluorooctanoic acids. Finally, we give a perspective of new functions for environmental specimen banks in the next 20 years.

Use and abuse of Pb-isotope fingerprinting technique and GIS mapping data to assess lead in environmental studies

The danger to health, especially of young children, from lead-bearing particulates in the surface environment is still a valid concern. Given the multifaceted uses of lead today as well as historically, the sources of lead must be investigated to distinguish the etiology of lead contamination on the environment. The lead isotope finger printing technique based on isotopic ratio analyses (IRA) is one of the methods used commonly for provenancing lead sources in environmental studies throughout the world. This technique, however, has some inherited shortcomings. Therefore, caution must be used in the interpretation of the results, as this technique can lead to overestimations as well as underestimations of the true source etiology/apportionment of lead in specific environments. This paper illustrates this with some examples. Data on geographical information systems (GIS) mapping in urban regions are also presented in this paper.

The Fremantle lead study part 2

AIM

A 1993 study of blood lead levels (BLLs) in pre-schoolers living in Fremantle showed 25% had BLLs >or= 10 microg/dL. This study compares the 1993 BLLs with a sample of contemporary Fremantle pre-schoolers.

METHODS

Pre-schoolers (0-5 years) living in the Fremantle area were recruited from hospital and community settings during 2005. As in the 1993 study, guardians completed a questionnaire concerning demographic, environmental and behavioural variables. BLLs were determined by the same method used in 1993. Statistical analysis compared the 1993 and 2005 samples according to demographic variables and dichotomised BLL. Multivariate linear regression was used to control for confounding variables, and linear regression was used to identify risk factors in the 2005 sample.

RESULTS

Community (40) and hospital (60) participants provided blood and completed questionnaires; none had BLLs >or=10 microg/dL. Compared with the 1993 sample, 2005 participants were younger, fewer were aboriginal, more had occupied their homes for over 6 months and more had a habit of putting soil in their mouths. After controlling for these variables, the geometric mean BLL in 2005 remained significantly lower than the 1993 value (1.83 and 6.82 microg/dL respectively). As in 1993, aboriginality, presence of participants during home renovation, occupancy of home less than 6 months and living <200 m from a main road were associated with higher mean BLLs.

CONCLUSIONS

The reassuring decline in the mean BLL between the1993 and 2005 samples is likely associated with the phasing out of leaded petrol. Future research should concentrate on monitoring groups at higher risk.

Stable lead isotopes in environmental health with emphasis on human investigations

There has been widespread use of stable lead isotopes in the earth sciences for more than 40 years focussed on the origin and age of rocks and minerals with lesser application in environmental investigations where the emphasis has been directed typically to the source of lead in environmental media such as air, water and soils. In contrast, the number of environmental health investigations focussed on humans (and primates) is limited in spite of the demonstrated utility of the approach in pioneering studies in the early 1970's. This paper reviews the status of lead isotopes in human investigations especially over the past 2 decades, the period over which most activity has taken place. Following a brief introduction to the method, examples are provided illustrating the use of lead isotopes in a wide spectrum of activities including sources and pathways of lead in diverse environments from urban to mining communities, various applications associated with pregnancy, the contribution of bone lead to blood lead including in the elderly, the half-life of lead in blood, and lead in bones and other media. A brief outline of critical research on non-human primates is also given. The lead isotope method is a powerful technique for tracing lead and could be employed more widely in human investigations.