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

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.

Higher rates of autism and attention deficit/hyperactivity disorder in American children: Are food quality issues impacting epigenetic inheritance?

In the United States, schools offer special education services to children who are diagnosed with a learning or neurodevelopmental disorder and have difficulty meeting their learning goals. Pediatricians may play a key role in helping children access special education services. The number of children ages 6-21 in the United States receiving special education services increased 10.4% from 2006 to 2021. Children receiving special education services under the autism category increased 242% during the same period. The demand for special education services for children under the developmental delay and other health impaired categories increased by 184% and 83% respectively. Although student enrollment in American schools has remained stable since 2006, the percentage distribution of children receiving special education services nearly tripled for the autism category and quadrupled for the developmental delay category by 2021. Allowable heavy metal residues remain persistent in the American food supply due to food ingredient manufacturing processes. Numerous clinical trial data indicate heavy metal exposures and poor diet are the primary epigenetic factors responsible for the autism and attention deficit hyperactivity disorder epidemics. Dietary heavy metal exposures, especially inorganic mercury and lead may impact gene behavior across generations. In 2021, the United States Congress found heavy metal residues problematic in the American food supply but took no legislative action. Mandatory health warning labels on select foods may be the only way to reduce dietary heavy metal exposures and improve child learning across generations.

Co-supplementation of Zinc and Calcium Suppresses Bio-absorption of Lead in Sprague Dawley Rats

Lead (Pb) is a widespread environmental toxicant and its toxicity causes huge health impacts. The present study was conducted to examine the protective role of zinc (Zn) and calcium (Ca) supplements against bio-absorption of Pb in blood and organs including the liver and kidney. Hence, Sprague Dawley rats were divided in to five groups. G₁ served as negative control and was provided with standard diet, G₂ as positive control receiving standard diet + PbAc (20 mg/kg BW), G₃ was provided with standard diet + PbAc (20 mg/kg BW) + ZnSO₄ (20 mg/kg BW), G₄ with standard diet + PbAc (20 mg/kg BW) + CaCO₃ (7.5 g/kg BW) whereas G₅ was fed on standard diet + PbAc (20 mg/kg BW) + ZnSO₄ (20 mg/kg BW) + CaCO₃ (7.5 g/kg BW). The salts were provided as solution, dissolved in 0.5 mL distilled water via orogastric tube. After 35 days, the overnight fasted rats were decapitated, and blood and organs were collected for analysis of levels of metals and liver and kidney function tests. The results depicted significant decrease in Pb concentration in blood and organs while increase in Zn and Ca absorption was observed as a result of Zn and Ca supplementation with Zn being better than Ca alone, specially however, combined effect of these supplements was more profound in improving liver and kidney stress biomarkers and maintained the normal architecture of renal and hepatic parenchyma. It was concluded that Zn and Ca co-supplementation hinder Pb absorption in blood, the liver, and kidney thus suggesting that their intake may protect from Pb toxicity.

Heavy Metal Concentrations in Malaysian Adults' Hair and Associated Variables in Bukit Mertajam, Penang, Malaysia

The presence of heavy metals in human hair is being tracked to predict health risk, forensics, and environmental monitoring. Heavy metals are typically non-biodegradable and have a lengthy half-life, allowing them to linger in humans and the environment for many years. Heavy metal exposure in hair has been attributed to multiple sources from the environment and food intake. In this study, copper (Cu), nickel (Ni), zinc (Zn), chromium (Cr), manganese (Mn), lead (Pb), and cadmium (Cd) levels were measured in the scalp hair of 50 individuals in Bukit Mertajam, Penang, Malaysia. In conjunction with sampling, subjects' age, gender, lifestyle, diet, and working environment were also obtained through the questionnaire. The Atomic Absorption Spectrometry (AAS) method was used to extract all the metals in the hair samples. The mean concentrations of heavy metals were found to be in the following order (unit of mg/kg): Cr > Zn > Pb > Ni > Cd > Cu. Manganese was detected below the limit of quantitation among the elements (< LOQ). All elements except Mn were higher and comparable to the previous studies' international limit values. Cadmium prevalence was substantially associated with age, smoking habit, dyed hair, and working environment in Pearson's correlation analysis (p ≤ 0.05). Zinc was also found to be related to the working environment. Some elements were observed to be statistically related between heavy metals, Cd/Zn, Cd/Ni, Cr/Ni, and Pb/Ni, whereas smoking habit/dyed hair and dyed hair/working environment were the associated factors for metal distribution that were statistically correlated (p ≤ 0.05). To recapitulate, this study found that the distribution of heavy metals in hair was influenced by associated factors and between heavy metals. It has been indicated that heavy metal exposure to humans is influenced by factors such as geographical location, lifestyle, and working environment.

Selected Metal Concentration in Maternal and Cord Blood

Essential and non-essential elements deficiencies may lead to various birth complications. The aim of this paper was to determine calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), sodium (Na), phosphorus (P), lead (Pb), strontium (Sr), and zinc (Zn) concentrations in maternal blood and cord blood. Whole blood and cord blood samples collected from pregnant women (n = 136) were analyzed for the concentration of the elements by spectrophotometric atomic absorption in inductively coupled argon plasma (ICP-OES). The results showed that Ca, Pb, and Sr concentrations were similar in maternal and cord blood, while Fe and K levels were higher in cord blood than in maternal blood. The cord blood Cu, Na, and Zn concentrations were lower than those in maternal blood, suggesting transplacental transfer of these elements were limited. Moreover, checking the influence of studied elements on the anthropometric parameters of the newborns, we found that the highest number of associations was between Cu in cord blood. Due to the fact that the pregnant women were healthy, and the newborns were without any disorders, we suggest that the values obtained in our study are normal values of studied elements in whole blood and cord blood in patients from Poland.

Novel Application of Machine Learning Algorithms and Model-Agnostic Methods to Identify Factors Influencing Childhood Blood Lead Levels

Blood lead (Pb) poisoning remains a global concern, particularly for children in their early developmental years. Broken Hill is Australia's oldest operating silver-zinc-lead mine. In this study, we utilized recent advances in machine learning to assess multiple algorithms and identify the most optimal model for predicting childhood blood Pb levels (BLL) using Broken Hill children's (<5 years of age) data (n = 23,749) from 1991 to 2015, combined with demographic, socio-economic, and environmental influencing factors. We applied model-agnostic methods to interpret the most optimal model, investigating different environmental and human factors influencing childhood BLL. Algorithm assessment showed that stacked ensemble, a method for automatically and optimally combining multiple prediction algorithms, enhanced predictive performance by 1.1% with respect to mean absolute error (p < 0.01) and 2.6% for root-mean-squared error (p < 0.01) compared to the best performing constituent algorithm (random forest). By interpreting the model, the following information was acquired: children had higher BLL if they resided within 1.0 km to the central mine area or 1.37 km to the railroad; year of testing had the greatest interactive strength with all other factors; BLL increased faster in Aboriginal than in non-Aboriginal children at 9-10 and 12-18 months of age. This "stacked ensemble + model-agnostic interpretation" framework achieved both prediction accuracy and model interpretability, identifying previously unconnected variables associated with elevated childhood BLL, offering a marked advantage over previous works. Thus, this approach has a clear value and potential for application to other environmental health issues.

Plumbojarosite formation in contaminated soil to mitigate childhood exposure to lead, arsenic and antimony

In this study, a novel method for lead (Pb) immobilization was developed in contaminated soils using iron (III) (Fe³⁺) in conjunction with 0.05 M H₂SO₄. During method optimization, a range of microwave treatment times, solid to solution ratios, and Fe₂(SO₄)₃/H₂SO₄ concentrations were assessed using a mining/smelting impacted soil (BHK2, Pb: 3031 mg/kg), followed by treatment of additional Pb contaminated soils (PP, Pb: 1506 mg/kg, G10, Pb: 2454 mg/kg and SoFC-1, Pb: 6340 mg/kg) using the optimized method. Pb bioaccessibility was assessed using USEPA Method 1340, with Pb speciation determined by X-ray Absorption (XAS) spectroscopy. Treatment efficacy was also validated using an in vivo mouse assay, where Pb accumulation in femur, kidney and liver was assessed to confirm in vitro bioaccessibility outcomes. Results showed that Pb bioaccessibility could be reduced by 77.4-97.0% following treatment of soil with Fe₂(SO₄)₃ (0.4-1.0 M), H₂SO₄ (0.05 M) at 150 °C for 60 min in a closed microwave system. Results of bioavailability assessment demonstrated treatment effect ratio of 0.06-0.07 in femur, 0.06-0.27 in kidney and 0.06-0.11 in liver (bioavailability reduction between 73% and 93%). Formation of plumbojarosite in treated soils was confirmed by XAS analysis.

Blood lead, nutrient intake, and renal function among type 2 diabetic patients

Lead (Pb) exposure has been reported to have nephrotoxicity. However, such an effect has not been well investigated in type 2 diabetes (T2D) patients, especially when taking into account the nutrition status of the patients. Therefore, we explore the association between blood lead levels (BLLs), dietary intake of nutrients, and impaired renal function among patients with T2D. We measured BLLs and biochemical parameters of renal injury in 780 patients. Dietary nutrients intake was assessed by a food frequency questionnaire in 420 of 780 participants. We found high BLLs were significantly associated with certain parameters of renal injury, and dietary intake of specific nutrients (mainly micronutrients) was associated with reduced BLLs at high percentile distribution of concentration. BLLs were also found to have moderation effects on the association between specific dietary nutrients and specific renal function parameters.

Stunting and lead: using causal mediation analysis to better understand how environmental lead exposure affects cognitive outcomes in children

BACKGROUND

Many children in Bangladesh experience poor nutritional status and environmental lead exposure, both of which are associated with lower scores on neurodevelopmental assessments. Recent studies have suggested that part of lead's adverse effects on neurodevelopment are caused in part by lead's effect on growth. New statistical methods are now available to evaluate potential causal pathways in observational studies. This study used a novel statistical method to test the hypothesis that stunting, a measure of linear growth related to poor nutrition, is a mediator and/or an effect modifier of the lead exposure's adverse effect on cognitive development.

METHODS

Participants were 734 children from a longitudinal birth cohort established in rural Bangladesh to study the health effects of prenatal and early childhood environmental metal exposures. Lead exposure was estimated using umbilical cord blood samples obtained at birth and blood obtained via venipuncture at age 20-40 months. Stunting was determined using the World Health Organization's standards. Neurodevelopment was assessed at age 20-40 months years using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). We evaluated the effect of lead on stunting and whether the effect of lead on cognitive scores is modified by stunting status in multivariable regression analyses. We then conducted a novel 4-way mediation analysis that allows for exposure-mediator interaction to assess how much of the effect of lead on cognitive scores is explained by the pathway through stunting (mediation) and how much is explained by the interaction between lead and stunt (effect modification).

RESULTS

Stunting was not a mediator of the effect of lead in our analyses. Results suggested effect modification by stunting. In an area of Bangladesh with lower lead exposures (median umbilical cord blood lead concentration, 1.7 μg/dL), stunting modified the relationship between prenatal blood lead concentrations and cognitive score at age 2-3 years. A 1-unit increase in natural log cord blood lead concentration in the presence of stunting was associated with a 2.1-unit decrease in cognitive scores (β = - 2.10, SE = 0.71, P = 0.003). This interaction was not found in a second study site where lead exposures were higher (median umbilical cord blood lead concentration, 6.1 μg/dL, β = - 0.45, SE = 0.49, P = 0.360).

CONCLUSIONS

We used a novel method of mediation analysis to test whether stunting mediated the adverse effect of prenatal lead exposure on cognitive outcomes in Bangladesh. While we did not find that stunting acted as mediator of lead's effect on cognitive development, we found significant effect modification by stunting. Our results suggest that children with stunting are more vulnerable to the adverse effects of low-level lead exposure.

Human biomonitoring of metals in sub-Arctic Dene communities of the Northwest Territories, Canada

A human biomonitoring project investigating environmental exposures to metals from hair, blood and urine samples was implemented in the Northwest Territories, Canada, between January 2016 and March 2018. This study reports the metal biomarker levels from nine Dene communities located in the Dehcho and Sahtú regions to identify contaminants of interest. Levels of metals in the urine (n = 198), blood (n = 276) and hair (n = 443) samples were generally similar to those seen in other biomonitoring studies in Canada, but lead levels in blood (GM = 16 μg/L; 95th percentile = 71 μg/L) and urine (GM = 0.59 μg/L, 0.69 μg/g of creatinine; 95th percentile = 4.2 μg/L, 4.0 μg/g of creatinine) were higher than those observed in the Canadian Health Measure Survey (CHMS, cycles 2 and 5). Hair mercury (but not blood mercury) appeared higher than observed in participants from the CHMS cycle 5. The vast majority of participants had biomarker levels below the biomonitoring guidance values established for mercury and lead. Based on a comparative analysis of biomarker statistics relative to a nationally-representative survey, metals and essential trace elements of particular interest for follow-up research include: lead, manganese, mercury, and selenium. This project provided baseline biomarker levels in participating regions, which is essential to track changes in the future, and identify the contaminants to prioritize for further investigation of exposure determinants.

A 25-year record of childhood blood lead exposure and its relationship to environmental sources

Broken Hill, the oldest silver (Ag)-zinc (Zn)-lead (Pb) mining community in Australia, has a legacy and ongoing problem of environmental Pb exposure that was identified as early as 1893. To reduce Pb exposure risks, identifying potential exposure pathways and related factors is a critical first step. This study examined blood lead (PbB) levels of children ≤60 months old (n = 24,106 samples), along with Pb concentrations in corresponding soil (n = 10,160 samples), petri-dish dust (n = 106 houses) and ceiling dust (n = 80 houses) over a 25-year period from 1991 to 2015. Regression analysis was used to examine the relationships between environmental Pb sources and children's blood lead (PbB) outcomes. Analysis of the dataset showed Aboriginal children in Broken Hill had a geometric mean PbB of 7.4 μg/dL (95% CI: 6.7-7.4) being significantly higher (p < 0.01) than non-Aboriginal children (PbB 6.2 μg/dL, 95% CI: 6.2-6.3) for all years between 1991 and 2015. Children at the age of 24-36 months had a higher PbB compared with other age groups. Higher PbB levels were also statistically associated with lower socio-economic status and children living in houses built before 1940 (p < 0.01). Blood Pb was also significantly correlated with both soil Pb and indoor petri-dish dust Pb loadings, confirming that these are important pathways for exposure in Broken Hill. A 100 mg/kg increase in soil Pb was associated with a 0.12 μg/dL increase in childhood PbB. In addition, PbB concentrations increased with indoor petri-dish dust Pb loadings (i.e., 0.08 μg/dL per 100 μg/m²/30 days). The 25-year data show that the risk of exposure at ≥ 10 μg/dL was seemingly unavoidable irrespective of residential address (i.e., children of all ages presenting with a ≥10 μg/dL across the whole city area). In terms of moving forward and mitigating harmful early-life Pb exposures, all children aged 24-36 months should be prioritised for feasible and effective intervention practices. Primary intervention must focus on mitigating contemporary ongoing dust emissions from the mining operations and the associated mine-lease areas along with household soil remediation, to help prevent recontamination of homes. Additional practices of dust cleaning using wet mopping and wiping techniques, vacuuming of carpets and furnishings, ongoing monitoring of children and household dust remain important but short-lived abatement strategies. Overall, the key goal should be to eliminate risk by removing contamination in the wider environment as well as in individual homes.

Screening for Elevated Blood Lead Levels and Related Risk Factors among Thai Children Residing in a Fishing Community

The present study explored environmental and behavioral factors associated with elevated blood lead (Pb) levels in 311 children (151 girls and 160 boys), aged 3–7 years, who lived in a coastal fishing community of the Pakpoon Municipality, Nakhon Si Thammarat, Thailand. The geometric mean for blood Pb was 2.81 µg/dL, ranging between 0.03 and 26.40 µg/dL. The percentage of high blood Pb levels, defined as blood Pb ≥ 5 µg/dL, was 10.0% in boys and 13.9% in girls. Parental occupation in producing fishing nets with lead weights was associated with a marked increase in the prevalence odds ratio (POR) for high blood Pb (POR 17.54, 95%; CI: 7.093, 43.390; p < 0.001), while milk consumption was associated with 61% reduction in the POR for high blood Pb (POR 0.393, 95%; CI: 0.166, 0.931; p = 0.034). High blood Pb was associated with an increased risk for abnormal growth (POR 2.042, 95%; CI: 0.999, 4.174; p = 0.050). In contrast, milk consumption was associated with a 43% reduction in POR for abnormal growth (POR 0.573, 95%; CI: 0.337, 0.976; p = 0.040). After adjustment for age, the mean (standard error of mean, SE) values for blood Pb were 6.22 (0.50) μg/dL in boys and 6.72 (0.49) μg/dL in girls of parents with an occupation in making fishing nets with lead weights. These mean blood Pb values were respectively 2.3 and 2.5 times higher than similarly aged boys and girls of parents with other occupations. These data are essential for setting surveillance and programmes to prevent toxic Pb exposure, especially in children of coastal fishing communities in southern Thailand.

Dynamics of Lead Bioavailability and Speciation in Indoor Dust and X-ray Spectroscopic Investigation of the Link between Ingestion and Inhalation Pathways

Lead (Pb) exposure from household dust is a major childhood health concern because of its adverse impact on cognitive development. This study investigated the absorption kinetics of Pb from indoor dust following a single dose instillation into C57BL/6 mice. Blood Pb concentration (PbB) was assessed over 24 h, and the dynamics of particles in the lung and gastro-intestinal (GI) tract were visualized using X-ray fluorescence (XRF) microscopy. The influence of mineralogy on Pb absorption and particle retention was investigated using X-ray absorption near-edge structure spectroscopy. A rapid rise in PbB was observed between 0.25 and 4 h after instillation, peaking at 8 h and slowly declining during a period of 24 h. Following clearance from the lungs, Pb particles were detected in the stomach and small intestine at 4 and 8 h, respectively. Analysis of Pb mineralogy in the residual particles in tissues at 8 h showed that mineral-sorbed Pb and Pb-phosphates dominated the lung, while organic-bound Pb and galena were the main phases in the small intestines. This is the first study to visualize Pb dynamics in the lung and GI tract using XRF microscopy and link the inhalation and ingestion pathways for metal exposure assessment from dust.

Relationship between Pb relative bioavailability and bioaccessibility in phosphate amended soil: Uncertainty associated with predicting Pb immobilization efficacy using in vitro assays

In this study, an in vitro in vivo correlation (IVIVC) between Pb in vitro bioaccessibility (IVBA) and relative bioavailability (RBA) was explored to determine whether the efficacy of Pb immobilization in phosphate amended soils could be predicted using an in vitro approach. Mining/smelting impacted soil from Broken Hill, Australia (582-3536 mg/kg of Pb in the <250 μm soil particle fraction) was amended with Phosphoric Acid (PA), Mono Ammonium Phosphate (MAP) or Triple Super Phosphate (TSP) at Pb:P molar ratios of 1:1-1:5. Pb speciation in pre- and post-treated soil was assessed using X-ray Absorption Spectroscopy (XAS), Pb IVBA was measured using the Solubility Bioaccessibility Research Consortium (SBRC) assay (gastric and intestinal phases), and Pb RBA was determined in mice using blood Pb concentration as the bioavailability endpoint. XAS analysis revealed a 3.75-6.00 fold increase in the weighted % of Pb phosphates in soil containing >1000 mg/kg Pb while treatment effect ratios of 0.89-0.99 (SBRC-G), 0.09-0.71 (SBRC-I) and 0.27-0.80 (RBA) were observed in PA amended soil (Pb:P = 1:5). Although significant (p < 0.05) correlation were obtained between Pb RBA and IVBA (%) determined using SBRC-G (r = 0.64) and SBRC-I (r = 0.67), the strengths of the relationships were weak (r2 = 0.41-0.45). This research highlights the complexities associated with the prediction of Pb RBA in phosphate amended soil.

Potential dietary factors for reducing lead burden of Chinese preschool children

Dietary approaches to treat children's low lead exposure are implemented routinely in China, while evidence for the effect could not be provided until now. The aim of this study was to examine the relationship between diets including nutrition supplementation and blood lead level of preschool children of China. In total, 17,859 preschool children from 14 cities were recruited, and their social-demography, living environment, and dietary intakes were collected, and capillary blood sample was tested for lead concentration. The average blood lead concentration was 34.5 μg/L, and after adjusting children's social-demography factors, the consumption of milk or dairy production, fruits, and calcium supplementation had negative dose-response relationships with blood lead level. Conversely, intake of iron-rich food and supplementation was not associated. Further studies are needed to prove the causal relationships.