Longitudinal monitoring of selected elements in blood of healthy young children

Which environmental sample type and statistical approach provides most information about metal exposure in young children from an urban setting?

Identification of sources and pathways is critical in minimizing exposure of young children to toxic materials. We monitored 108 children <5 years old 6-monthly for up to 5 years in a major urban setting. Samples (ñ7000) included interior handwipes (W1) and after exterior playing (W2), interior house dust (PD1) and day care dust (PD2) using petri dishes, exterior dust-fall accumulation, exterior dust sweepings, garden soil, blood and urine. Here we describe multi-element results to determine which sampling method and analysis of the data provide the most reliable indicators of metal exposure to young children. Samples were analysed by ICPMS for Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Ti, V and Zn. Pearson Correlations showed the highest number of significant correlations are for: W1 and W2, dust sweepings and soil. Mixed model analyses (MMA) for the blood levels as the dependent variable and environmental predictor variables showed the most consistent results were for W1, PD1 and sweepings. MMA to investigate the association between each metal (e.g. Ca) and the other 11 metals showed the largest numbers of significant relationships are for W1 and sweepings. Cluster analyses showed that the 'best' clusters in W1 and W2 are for Fe-Zn-Mg and Mn-Pb-Ni. For PD1 and PD2 the 'best' clusters were Fe-Zn-Mg, Cr-Ni-Ti, and Cu-Mn-Pb. Clusters for dust sweepings and soil are generally similar. Principal component analysis (PCA) loadings for W1 and PD1 accounted for >50% of the variance. Metals comprising loading 1 component for both sample types included Ca, Fe, Mg, and Mn. Overall cluster analyses provided more information than PCA loadings. In summary: The most suitable methods and analyses are MMA of W1 and sweepings, and cluster analyses of W1and PD1. Resuspension from outdoor surfaces and soils and deposition in the residences is a likely pathway for most metals.

The Reference Intervals of Whole Blood Copper, Zinc, Calcium, Magnesium, and Iron in Infants Under 1 Year Old

Trace elements are essential nutrients for the optimal growth, development, and health of infants, and the reference intervals (RIs) from these trace elements in the blood are very important for an accurate assessment of the status of the elements. In this study, blood samples from a total of 13,446 infants (7206 boys and 6240 girls) were used, and the copper (Cu), zinc (Zn), calcium (Ca), magnesium (Mg), and iron (Fe) in their blood were determined using atomic absorption spectrometry. After clearing the data and removing any outliers, the gender- and age-specific RIs obtained from the Cu, Zn, Ca, Mg, and Fe in the infants' blood were established according to the principles of the Clinical and Laboratory Standards Institute (CLSI) C28-A3. In the multivariable analysis, after making the relevant adjustments for the confounding factors, the age of the infants showed a significant positive correlation with the concentrations of Zn, Ca, Mg, and Fe found in the blood (p<0.01). Furthermore, there were obvious differences in the Cu, Zn, and Ca levels in the blood according to the gender of the infants (p<0.01). As infants are in the critical period of their growth and development, the gender- and age-specific RIs may provide helpful guidance for the nutritional status of the Cu, Zn, Ca, Mg, and Fe elements in the infants' blood.

Dietary zinc, calcium and nickel are associated with lower childhood blood lead levels

The potential mitigation of elevated blood lead (PbB) levels with nutrient intake remains debatable. A comprehensive review by Kordas (2017) concluded that careful examination of the links between nutrition (nutritional status, nutrients, diet) and lead (Pb) exposure revealed limited and tenuous evidence. We have measured 20 elements including calcium (Ca), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), nickel (Ni), zinc (Zn), and Pb from 6-day duplicate diets of 108 young children over a 5-year period and expressed these as intakes per body weight. Bivariate analyses showed a weak positive association between the Pb content in the diets of the participants and the level of Pb in their blood, as might be expected. Weak, but negative, associations occurred between the other elements in the diet and PbB. The associations for Ca, Mg, Ni and Zn were statistically significant for both subject-based (between subjects) and within-subject effects: that is, as the levels of elements in diet increased, the PbB level decreased. The largest percentage of variance of PbB in the context of the bivariate model accounted for was 4.23% for Zn, followed by Ca (3.91%) and Fe (2.20%). Supplementary analyses indicated that the between- and within-subject effects did not vary with the age at which participants entered the study, or with the levels of elements at their first measurement. A multivariable analysis using Weighted Quantile Sum Regressions showed that a weighted composite comprised of all the dietary elements had a significant association with PbB when adjusted for Pb in the diet and other covariates and also when adjusted for Pb in house dust; the latter was found to have the strongest association with PbB in earlier analyses. The highest weights were for Ca (0.29), Ni (0.27) and Zn (0.22); these results are generally consistent with those from the mixed model analyses.

Tracing natural and industrial contamination and lead isotopic compositions in an Australian native bee species

This study investigates trace element concentrations (arsenic (As), manganese (Mn), lead (Pb) and zinc (Zn)) and Pb isotopic compositions in an Australian native bee species, Tetragonula carbonaria, and its products of honey and wax. Co-located soil and dust samples were simultaneously analysed with the objective of determining if the bees or their products had potential application as a proxy for monitoring environmental contamination. The most significant relationships were found between Pb concentrations in honey (r = 0.814, p = 0.014) and wax (r = 0.883, p = 0.004) and those in co-located dust samples. In addition, Zn concentrations in honey and soil were significantly associated (r = 0.709, p = 0.049). Lead isotopic compositions of native bee products collected from background sites adjacent to Sydney national parks (²⁰⁶Pb/²⁰⁷Pb = 1.144, ²⁰⁸Pb/²⁰⁷Pb = 2.437) corresponded to local geogenic rock and soil values (²⁰⁶Pb/²⁰⁷Pb = 1.123-1.176, ²⁰⁸Pb/²⁰⁷Pb = 2.413-2.500). By contrast, inner Sydney metropolitan samples, including native bees and wax (²⁰⁶Pb/²⁰⁷Pb = 1.072-1.121, ²⁰⁸Pb/²⁰⁷Pb = 2.348-2.409), co-located soil and dust (²⁰⁶Pb/²⁰⁷Pb = 1.090-1.122, ²⁰⁸Pb/²⁰⁷Pb = 2.368-2.403), corresponded most closely to aerosols collected during the period of leaded petrol use (²⁰⁶Pb/²⁰⁷Pb = 1.067-1.148, ²⁰⁸Pb/²⁰⁷Pb = 2.341-2.410). A large range of Pb isotopic compositions in beehive samples suggests that other legacy sources, such as Pb-based paints and industrials, may have also contributed to Pb contamination in beehive samples. Native bee data were compared to corresponding samples from the more common European honey bee (Apis mellifera). Although Pb isotopic compositions were similar in both species, significant differences in trace element concentrations were evident across the trace element suite, the bees and their products. The statistical association between T. carbonaria and co-located environmental contaminant concentrations were stronger than those in European honey bees, which may be attributable to its smaller foraging distance (0.3-0.7 km versus 5-9 km, respectively). This implies that T. carbonaria may be more suitable for assessing small spatial scale variations of trace element concentrations than European honey bees.

Evaluating the efficacy of playground washing to reduce environmental metal exposures

Washing and wet mopping is often advocated as a remedial treatment to limit exposure to lead dust. Here, surface and pre- and post-play wipes were measured to ascertain dust metal exposures (arsenic, cadmium, copper, lead and zinc) following play routines at four playgrounds in the smelter city of Port Pirie, South Australia, which are washed regularly. Although post-play hand wipe metals were 55.9% (95% CI: -0.78, -0.34) lower on wash days, loadings increased ∼5.1% (95% CI: 1.2, 11.7) per hour after washing. Despite washing, post-play hand lead exceeded a conservative value of 800 μg/m(2) within 24 h or sooner, with loadings increasing in proximity to the smelter. Post-play lead loadings were always >1000 μg/m(2) at the playground closest to smelter. Playground washing results in short-lived exposure reduction and effective treatment requires elimination of smelter emissions.

Australia's leading public health body delays action on the revision of the public health goal for blood lead exposures

Globally, childhood blood lead levels have fallen precipitously in developed countries since the 1970s following action by international bodies such as the WHO and Food and Agricultural Organization (FAO) of the United Nations. These reductions have been affected by the activities of national agencies such as the US EPA and US Centers for Disease Control and Prevention in the establishment of air lead and blood lead standards, the introduction of legislation to remove lead from petrol, paint and consumer products and tighter restrictions on lead emissions. The outcome of recent major international reviews of research into the effects of low-level lead exposures (e.g. by WHO, USA health and environmental agencies, German and Canadian health bodies) has resulted in recommendations to reduce and eliminate lead exposures. By contrast, Australian policy responses to the incontrovertible evidence that adverse neurocognitive and behavioural effects that occur at levels well below the current national goal of 10μg/dL have stalled. The delayed response by Australia occurs at a time when blood lead levels in two of Australia's three primary lead mining and smelting cities: Port Pirie, South Australia and Broken Hill, New South Wales, are rising. In the third city, Mount Isa, Queensland, there is still no systematic, annual testing of childhood blood lead values. This is despite the fact that Mount Isa has the highest lead (and other toxic metals such as cadmium and arsenic) emissions to the environment (120tonnes of lead in 2011/12) from any single point source in Australia. It is clear that both state and national policy approaches to the ongoing risks of lead exposure need to be revised urgently and in line with contemporary international standards. Recommended changes should include a new lower blood lead intervention level of no more than 5μg/dL, with a national goal for all children under 5years of age to have a blood lead level of below 1μg/dL by 2020. In order to achieve any new lower exposure goals other relevant lead standards including air, dust, soil and water must also be revised downwards.

Current role of ICP–MS in clinical toxicology and forensic toxicology: a metallic profile

As metal/metalloid exposure is inevitable owing to its omnipresence, it may exert toxicity in humans. Recent advances in metal/metalloid analysis have been made moving from flame atomic absorption spectrometry and electrothermal atomic absorption spectrometry to the multi-elemental inductively coupled plasma (ICP) techniques as ICP atomic emission spectrometry and ICP–MS. ICP–MS has now emerged as a major technique in inorganic analytical chemistry owing to its flexibility, high sensitivity and good reproducibility. This in depth review explores the ICP–MS metallic profile in human toxicology. It is now routinely used and of great importance, in clinical toxicology and forensic toxicology to explore biological matrices, specifically whole blood, plasma, urine, hair, nail, biopsy samples and tissues.

Pathways of Pb and Mn observed in a 5-year longitudinal investigation in young children and environmental measures from an urban setting

We monitored 108 children ≤5 years on a 6-month basis for up to 5 years in a major urban setting. Samples (n ∼ 7000) included blood, urine, handwipes (interior, and after exterior playing), 6-day duplicate diet, drinking water, interior house and day care dust-fall accumulation using petri dishes, exterior dust-fall accumulation, exterior dust sweepings, paint, soil and urban air. The geometric mean blood Pb (PbB) was 2.1 μg/dL and blood Mn (MnB) was 10.0 μg/L. Following a path modelling approach, mixed model analyses for a fully adjusted model showed the strongest associations for PbB were with interior house dust and soil; for MnB there were no significant associations with any predictors. Predictor variables only explained 9% of the variance for Pb and 0.7% for Mn. Relationships between environmental measures and PbB in children are not straightforward; soil and dust sweepings contribute only about 1/5th of the amounts to PbB found in other studies.

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.

Update on a Pharmacokinetic-Centric Alternative Tier II Program for MMT-Part I: Program Implementation and Lessons Learned

Concerns have been raised regarding environmental manganese exposure since high exposures have been associated with neurological disorders. The USA Environmental Protection Agency most recent human health risk assessment of inhaled manganese conducted in 1993 identified specific areas of uncertainty regarding manganese pharmacokinetics. This led to the development of a test rule under the USA Clean Air Act that required the generation of pharmacokinetic information on the inorganic manganese combustion products of the organometallic fuel additive methylcyclopentadienyl manganese tricarbonyl (MMT). The Alternative Tier 2 testing program for MMT, described in this paper, has yielded substantial pharmacokinetic data and has enabled the generation of physiologically based pharmacokinetic (PBPK) models for manganese. These models are capable of predicting tissue manganese concentrations across a variety of dose routes, levels, and durations while accounting for factors such as age, gender, and reproductive status, enabling the consideration of tissue dosimetry in future risk assessments.

δ-Aminolevulinic acid dehydratase single nucleotide polymorphism 2 and peptide transporter 2*2 haplotype may differentially mediate lead exposure in male children

Child low-level lead (Pb) exposure is an unresolved public health problem and an unaddressed child health disparity. Particularly in cases of low-level exposure, source removal can be impossible to accomplish, and the only practical strategy for reducing risk may be primary prevention. Genetic biomarkers of increased neurotoxic risk could help to identify small subgroups of children for early intervention. Previous studies have suggested that, by way of a distinct mechanism, δ-aminolevulinic acid dehydratase single nucleotide polymorphism 2 (ALAD(2)) and/or peptide transporter 2*2 haplotype (hPEPT2*2) increase Pb blood burden in children. Studies have not yet examined whether sex mediates the effects of genotype on blood Pb burden. Also, previous studies have not included blood iron (Fe) level in their analyses. Blood and cheek cell samples were obtained from 306 minority children, ages 5.1 to 12.9 years. (208)Pb and (56)Fe levels were determined with inductively coupled plasma-mass spectrometry. General linear model analyses were used to examine differences in Pb blood burden by genotype and sex while controlling for blood Fe level. The sample geometric mean Pb level was 2.75 μg/dl. Pb blood burden was differentially higher in ALAD(2) heterozygous boys and hPEPT2*2 homozygous boys. These results suggest that the effect of ALAD(2) and hPEPT2*2 on Pb blood burden may be sexually dimorphic. ALAD(2) and hPEPT2*2 may be novel biomarkers of health and mental health risks in male children exposed to low levels of Pb.

Blood lead level and its relationship to certain essential elements in the children aged 0 to 14 years from Beijing, China

OBJECTIVE

To investigate blood lead level and its relationship to copper, zinc, calcium, magnesium and iron in the children aged 0 to 14 years old from Beijing, China.

METHODS

We classified 3181 children into one of the four groups: Group A (n=783, <1 year old); Group B (n=1538, 1-3 years old); Group C (n=443, 3-7 years old); and, Group D (n=417, 7-14 years old). All these metal elements were determined by atomic absorption spectrometry.

RESULTS

The blood lead level was 0.207±0.105 μmol/L. There was a significant gender difference for zinc (P<0.05) in Group C, and there was also a significant gender difference for copper (P<0.05) and lead (P<0.05) in Group D. Controlling for gender and age, we observed that there was a negative correlation of lead with zinc (r=-0.052, P<0.01), magnesium (r=-0.042, P<0.05) and iron (r=-0.031, P<0.05), respectively. Furthermore, in the children aged 1-7 years old, we also found there was a negative linear correlation of lead with zinc, magnesium and iron, respectively (P<0.01).

CONCLUSION

Blood lead level in children from Beijing was markedly decreased. And deficiency of zinc, magnesium and iron is related to the elevated blood lead level in the children aged 1-7 years.