Variability of lead in urine and blood in healthy individuals

Cottage industry as a source of high exposure to lead: A biomonitoring study among people involved in manufacturing cookware from scrap metal

In low-income countries, a widespread but poorly studied type of cottage industry consists of melting scrap metal for making cookware. We assessed the exposure to lead (Pb) among artisanal workers, and their families, involved in manufacturing cookware from scrap metal. In a cross-sectional survey, we compared artisanal cookware manufacturing foundries with carpentry workshops (negative controls) and car battery repair workshops (positive controls), all located in residential areas, in Lubumbashi (DR Congo). We collected surface dust in the workspaces, and blood and urine samples among workers, as well as residents living in the cookware workshops. Trace elements were quantified in the samples by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In surface dust, median Pb concentrations were higher in cookware foundries (347 mg/kg) than in carpentries (234 mg/kg) but lower than in battery repair workshops (22,000 mg/kg). In workers making the cookware (n = 24), geometric mean (GM) Pb blood cencentration was 118 μg/L [interquartile range (IQR) 78.4-204], i.e. nearly twice as high as among carpenters [60.2 μg/L (44.4-84.7), n = 33], and half the concentration of battery repair workers [255 μg/L (197-362), n = 23]. Resident children from the cookware foundries, had higher urinary Pb [6.2 μg/g creatinine (2.3-19.3), n = 6] than adults [2.3 (2.2-2.5), n = 3]. Our investigation confirms the high Pb hazard linked to car battery repair and reveals a high exposure to Pb among artisanal cookware manufacturers and their families, especially children, in residential areas of a city in a low-income country.

Low-level exposure to lead and atherosclerosis in the carotid arteries: Results from the Swedish population-based cohort SCAPIS

BACKGROUND

Lead exposure is associated with cardiovascular disease. Atherosclerosis has been hypothesized to be one of the underlying mechanisms behind this association.

AIM

To investigate whether lead exposure is associated with an increased risk of atherosclerosis in the carotid arteries in a large Swedish population-based cohort.

METHODS

We performed a cross-sectional study using data from the population-based Swedish CardioPulmonary bioImage Study (SCAPIS), including 5622 middle-aged men and women, enrolled 2013-2018. Blood lead (B-Pb), measured by inductively coupled plasma mass spectrometry, was used as exposure biomarker. The presence of atherosclerotic plaque in the carotid arteries (yes/no), total plaque area (mm2) and the presence of large plaques (>25 mm2) were determined by ultrasonography. Associations between B-Pb and the different outcomes were analysed using Poisson and linear regression models, adjusted for potential confounders.

RESULTS

Atherosclerotic plaque was present in 57% of the individuals, for whom the median total plaque area was 16 mm2 (range: 0.2-222). The median B-Pb concentration was 14 μg/L (range: 0.75-203). After adjusting for potential confounders, individuals in the fourth quartile of B-Pb (Q4) had a prevalence ratio (PR) for plaque of 1.08 (95% CI: 1.01, 1.16) when compared with the first quartile (Q1). A 10 μg/L increase in B-Pb concentrations was associated with an increase of 0.92 mm2 (95% CI: 0.14, 1.71) in total plaque area. The PR for large plaque was 1.09 (95% CI: 0.84, 1.42 for Q4 vs Q1).

CONCLUSIONS

This study shows an association between B-Pb and atherosclerosis in the carotid arteries providing some support for the hypothesis that atherosclerosis is one of the mechanisms underlying the association between lead exposure and cardiovascular disease.

Genetic susceptibility to low-level lead exposure in men: Insights from ALAD polymorphisms

The genetic susceptibility to low-level lead (Pb) exposure in general populations has been poorly investigated and is limited to the single nucleotide polymorphism (SNP) rs1800435 in the delta-aminolevulinic acid dehydratase gene (ALAD). This study explored associations between ten selected ALAD SNPs with Pb concentrations in blood (BPb) and urine (UPb) among 281 men aged 18-49 years from Slovenia, including 20 individuals residing in a Pb-contaminated area. The geometric mean (range) of BPb and UPb were 19.6 (3.86-84.7) μg/L and 0.69 (0.09-3.82) μg/L SG, respectively. The possible genetic influence was assessed by examining SNP haplotypes, individual SNPs, and the combination of two SNPs using multiple linear regression analyses. While no significant associations were found for haplotypes, the presence of variant alleles of rs1800435 and rs1805312 resulted in an 11% and 13% decrease in BPb, respectively, while the presence of variant allele of rs1139488 (homozygous only) exhibited significant 20% increase in BPb, respectively. Additionally, variant allele of rs1800435 resulted in lower UPb. Individual SNPs in the model explained only around 1 additional percentage point of BPb variability. In contrast, combination analyses identified six combinations of two SNPs, which significantly explained 3-22 additional percentage points of BPb variability, with the highest explanatory power observed for the rs1800435-rs1139488 and rs1139488-rs1805313 combinations. Moreover, excluding participants from the Pb-contaminated area indicated that exposure level influenced SNPs-Pb associations. Our results confirm the importance of the ALAD gene in Pb kinetics even at low exposure levels. Additionally, we demonstrated that identifying individuals with specific combinations of ALAD SNPs explained a larger part of Pb variability, suggesting that these combinations, pending confirmation in other populations and further evaluation through mechanistic studies, may serve as superior susceptibility biomarker in Pb exposure compared to individual SNPs.

Prenatal Metal Exposures and Child Social Responsiveness Scale Scores in 2 Prospective Studies

Background

Prenatal exposure to metals is hypothesized to be associated with child autism. We aim to investigate the joint and individual effects of prenatal exposure to urine metals including lead (Pb), mercury (Hg), manganese (Mn), and selenium (Se) on child Social Responsiveness Scale (SRS) scores.

Methods

We used data from 2 cohorts enriched for likelihood of autism spectrum disorder (ASD): Early Autism Risk Longitudinal Investigation (EARLI) and the Markers of Autism Risk in Babies-Learning Early Signs (MARBLES) studies. Metal concentrations were measured in urine collected during pregnancy. We used Bayesian Kernel Machine Regression and linear regression models to investigate both joint and independent associations of metals with SRS Z-scores in each cohort. We adjusted for maternal age at delivery, interpregnancy interval, maternal education, child race/ethnicity, child sex, and/or study site.

Results

The final analytic sample consisted of 251 mother-child pairs. When Pb, Hg, Se, and Mn were at their 75th percentiles, there was a 0.03 increase (95% credible interval [CI]: -0.11, 0.17) in EARLI and 0.07 decrease (95% CI: -0.29, 0.15) in MARBLES in childhood SRS Z-scores, compared to when all 4 metals were at their 50th percentiles. In both cohorts, increasing concentrations of Pb were associated with increasing values of SRS Z-scores, fixing the other metals to their 50th percentiles. However, all the 95% credible intervals contained the null.

Conclusions

There were no clear monotonic associations between the overall prenatal metal mixture in pregnancy and childhood SRS Z-scores at 36 months. There were also no clear associations between individual metals within this mixture and childhood SRS Z-scores at 36 months. The overall effects of the metal mixture and the individual effects of each metal within this mixture on offspring SRS Z-scores might be heterogeneous across child sex and cohort. Further studies with larger sample sizes are warranted.

Assessing lead exposure in U.S. pregnant women using biological and residential measurements

There is strong scientific evidence for multiple pathways of human exposure to lead (Pb) in residential settings, particularly for young children; however, less is known about maternal exposure during pregnancy and children's exposure during early lifestages. A robust, multi-faceted secondary analysis was conducted using data collected by the National Institute of Child Health and Human Development in the 2009-2014 National Children's Study Vanguard Studies. Descriptive statistics summarized Pb concentrations of maternal blood, maternal urine, and house dust vacuum samples collected during pregnancy and residence surface wipes collected both during pregnancy and six months post-partum. The maternal blood Pb level geometric mean was 0.44 μg/dL (n = 426), with no women having values ≥ 5 μg/dL; creatinine-adjusted maternal urinary Pb geometric mean was 0.43 μg/g (n = 366). These blood and urine concentrations are similar to those observed for females in the general U.S. population in the National Health and Nutrition Examination Survey 2010-2011 cycle. A modest correlation between maternal blood Pb and surface wipe measurements during pregnancy was observed (Spearman r = 0.35, p < 0.0001). Surface wipe Pb loadings obtained in mother's homes during pregnancy (n = 640) and from areas where children spent the most time at roughly 6 months of age (n = 99) ranged from 0.02 to 71.8 ng/cm2, with geometric means of 0.47 and 0.49 ng/cm2, respectively, which were relatively low compared to other national studies. Survey responses of demographic, lifestyle, and residence characteristics were assessed for associations with blood concentration and surface wipe loading. Demographic (e.g., race/ethnicity, income, education, marital status) and housing characteristics (e.g., year home built, paint condition, own or rent home, attached garage) were associated with both maternal blood and surface wipe loadings during pregnancy. The availability of residential environmental media and extensive survey data provided enhanced understanding of Pb exposure during pregnancy and early life.

Reliability of low mass toenail samples as biomarkers of chronic metal exposure

BACKGROUND

Toenails are a promising matrix for chronic metal exposure assessment, but there are currently no standard methods for collection and analysis. Questions remain about sample mass requirements and the extent to which metals measured in this matrix are representative of chronic body burden.

OBJECTIVE

This study proposes a method to maximize sample conservation for toenail metals analysis using inductively coupled plasma mass spectrometry (ICP-MS). We demonstrate the reliability of an ~25 mg toenail sample (typically 1-2 clippings) for metals analysis and evaluate the intra-individual variability of multiple metals in this matrix over time in men from the Gulf Long-term Follow-up (GuLF) Study.

METHODS

Toenail samples from 123 GuLF Study participants were collected at two visits 3 years apart and analyzed for 18 elements using ICP-MS. Participants with samples exceeding 200 mg at the first visit (n = 29) were selected for triplicate sub-sample analysis. Kendall's coefficient of concordance (W) was used to assess sub-sample reliability and Spearman's correlation coefficients (ρ) were used to evaluate fluctuations in elemental concentrations over time.

RESULTS

Results were not reported for Cd, Co, Mo, Sb, and V (detected in <60% of the samples). There was strong agreement among triplicate samples (Kendall's W: 0.72 (Cu)-0.90 (Cu)) across all elements evaluated, moderate correlations of elemental concentrations (Spearman's ρ: 0.21-0.42) over 3 years for As, Ca, Cr, Fe, Pb, Mn, and Zn, and strong correlations (>0.50) for Se, Cu, and Hg.

IMPACT STATEMENT

This toenail reliability study found that a low-mass (~25 mg) toenail sample (1-2 clippings) is suitable for the determination of most elements using ICP-MS and helps to increase the analytical capacity of limited toenail biospecimens collected in cohort studies. The results highlight differences in the suitability of toenails for chronic metal exposure assessment by element and underscore the need to consider intra-person variability, especially when comparing results across studies. We also provide recommendations for analytical standardization and the partitioning of the total collected toenail sample into multiple analytic sub-samples for future studies using toenail biospecimen for multiple assays.

Quantitative analysis of the minimum days of dietary survey to estimate dietary pesticide exposure: Implications for dietary pesticide sampling strategy

Populations are exposed to pesticides through diet on a daily basis. However, there is no research guiding how to evaluate dietary pesticide exposure, and researchers used 1-day, 3-days, 7-days or even longer dietary survey to evaluate without any consensus. It is important for dietary pesticide evaluation to identify the minimum survey days. To increase knowledge of this, a data combination was applied between a two-wave consecutive repeated-measures study in Baoding City and the Fifth China Total Diet Study. Further policy consistency on pesticides were evaluated to explain its credibility. We computed the sensitivity and specificity to evaluate how well different days of dietary survey classify participants with high exposure, and calculated the minimum days required to estimate the participant-specific mean at different acceptable error range. With 1 day of dietary survey, the classification sensitivity was low (<0.6) for total HCH, endosulfan, chlordane, cyhalothrin, allethrin, and prallethrin; that for the other pesticides was high sensitivity (≥0.6). Sensitivity increased as the number of days increased, and the maximum marginal sensitivity increase (≥0.039) occurred from 1 to 2 days for all pesticides except phenothrin, whose maximum marginal sensitivity increase (0.042) occurred from 2 to 3 days. The specificity increased gradually from 0.8 to 0.9 from 1 to 7 days. Under the acceptable error range of 0.5%, 3-28 days were required for participant-specific mean estimation and 1-7 days were required when acceptable error range was shrunk in 1%. Only 1 day was enough if 5% error range was acceptable. In conclusion, 3 days in the study period was cost-effective to distinguish high exposure group, and it rose to 7 when estimating participant-specific mean from a conservative perspective. This study can serve as a reference to determine the minimum survey days for epidemiological studies employing dietary surveys.

Independent and combined associations of multiple-heavy-metal exposure with lung function: a population-based study in US children

Previous research has found relationships between some single metals and lung function parameters. However, the role of simultaneous multi-metal exposure is poorly understood. The crucial period throughout childhood, when people are most susceptible to environmental dangers, has also been largely ignored. The study aimed to evaluate the joint and individual associations of 12 selected urinary metals with pediatric lung function measures using multi-pollutant approaches. A total of 1227 children aged 6-17 years from the National Health and Nutrition Examination Survey database of the 2007-2012 cycles were used. The metal exposure indicators were 12 urine metals adjusted for urine creatinine, including arsenic (As), barium (Ba), cadmium (Cd), cesium (Cs), cobalt (Co), mercury (Hg), molybdenum (Mo), lead (Pb), antimony (Sb), thallium (Tl), tungsten (Tu), and uranium (Ur). The outcomes of interest were lung function indices, including the 1st second of a forceful exhalation (FEV₁), forced vital capacity (FVC), forced expiratory flow between 25 and 7% of vital capacity (FEF_25-75%), and peak expiratory flow (PEF). Multivariate linear regression, quantile g-computation (QG-C), and Bayesian kernel machine regression models (BKMR) were adopted. A significantly negative overall effect of metal mixtures on FEV₁ (β = - 161.70, 95% CI - 218.12, - 105.27; p < 0.001), FVC (β = - 182.69, 95% CI - 246.33, - 119.06; p < 0.001), FEF_25-75% (β = - 178.86 (95% CI - 274.47, - 83.26; p < 0.001), and PEF (β = - 424.17, 95% CI - 556.55, - 291.80; p < 0.001) was observed. Pb had the largest negative contribution to the negative associations, with posterior inclusion probabilities (PIPs) of 1 for FEV₁, FVC, and FEF_25-75%, and 0.9966 for PEF. And Pb's relationship with lung function metrics showed to be nonlinear, with an approximate "L" shape. Potential interactions between Pb and Cd in lung function decline were observed. Ba was positively associated with lung function metrics. Metal mixtures were negatively associated with pediatric lung function. Pb might be a crucial element. Our findings highlight the need for prioritizing children's environmental health to protect them from later respiratory disorders and to guide future research into the toxic mechanisms of metal-mediated lung function injury in the pediatric population.

Subacute Exposure to Low Pb Doses Promotes Oxidative Stress in the Kidneys and Copper Disturbances in the Liver of Male Rats

Recent data indicate that lead (Pb) can induce adverse effects even at low exposure levels. Moreover, the corresponding mechanisms of low Pb toxicity have not been well identified. In the liver and the kidneys, Pb was found to induce various toxic mechanisms leading to organ physiological disruption. Therefore, the purpose of the study was to simulate low-dose Pb exposure in an animal model with the aim of assessing oxidative status and essential element levels as the main mechanism of Pb toxicity in the liver and kidneys. Furthermore, dose-response modelling was performed in order to determine the benchmark dose (BMD). Forty-two male Wistar rats were divided into seven groups: one control group, and six groups treated for 28 days with 0.1, 0.5, 1, 3, 7, and 15 mg Pb/kg b.w./day, respectively. Oxidative status parameters (superoxide dismutase activity (SOD), superoxide anion radical (O₂^-), malondialdehyde (MDA), total sulfhydryl groups (SHG), and advanced oxidation protein products (AOPP)) and Pb, copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) levels were measured. Lowering Cu levels (BMD: 2.7 ng/kg b.w./day), raising AOPP levels (BMD: 0.25 µg/kg b.w./day) in the liver, and inhibiting SOD (BMD: 1.3 ng/kg b.w./day) in the kidneys appear to be the main mechanisms of Pb toxicity. The lowest BMD was derived for a decrease in Cu levels in liver, indicating that this effect is the most sensitive.

Insights into the health status of the general population living near an electroplating industry zone: metal elevations and renal impairment

A cross-sectional study was conducted in 2016 in Zhejiang Province, China, to evaluate the body burdens of metals and metalloids associated with renal dysfunction in populations living near electroplating industries. We recruited 236 subjects and performed physical examinations, determined the blood and urinary levels of arsenic (As), cadmium (Cd), chromium (Cr), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), and selenium (Se) by an inductively coupled plasma mass spectrometer (ICP-MS), and measured three renal impairment biomarkers, namely nacetyl-β-_D-glucosaminidase (NAG), retinol-binding protein (RBP), and β₂-microglobulin (BMG). The proportion of abnormal nasal symptoms in the exposure group (10.1%) was much higher than in the control group (0; p < 0.05). The blood and urinary levels of As, Cd, and Se in the exposure group were significantly higher than those in the control group (p < 0.05). The blood levels of Mn and Pb, as well as the urinary levels of Cr and Ni, were significantly higher in the exposure group than in the control group (p < 0.05). The exposure group demonstrated higher levels of NAG, RBP, and BMG than the control group (0.51 vs. 0.14 mg/g creatinine, 12.79 vs. 9.26 IU/g creatinine, and 1.39 vs. 0.78 mg/g creatinine, respectively; p < 0.05). Urinary BMG was positively correlated with urinary Cd levels (r = 0.223, p < 0.05), while urinary RBP was correlated with blood Cd levels (r = 0.151, p < 0.05) and urinary Cd, Cr, Ni, and Se levels (r = 0.220, 0.303, 0.162, and 0.306, respectively; p < 0.05). In conclusion, our study indicated that a population living in the vicinity of electroplating industries had high body burdens of certain metals and metalloids associated with non-negligible renal dysfunction.

Contribution and Effects of PM2.5-Bound Lead to the Cardiovascular Risk of Workers in a Non-Ferrous Metal Smelting Area Considering Chemical Speciation and Bioavailability

Lead is known to have toxic effects on the cardiovascular system. Owing to its high concentration, transmission range, and absorption efficiency in organisms, inhalation of fine particulate matter (PM2.5)-bound lead (PM2.5-Pb) may cause significant cardiovascular damage. However, the contribution and adverse effects of PM2.5-Pb on workers and residents in non-ferrous metal smelting areas are not fully understood. In this work, the concentration and chemical speciation of PM2.5-Pb were analyzed to determine its pollution characteristics at a typical non-ferrous metal smelting site. A panel study conducted among factory workers revealed that PM2.5-Pb exposure makes an important contribution to the human absorption of Pb. Although the chemical speciation of PM2.5-Pb suggested poor water solubility, a high bioavailability was observed in mice (tissue average value: 50.1%, range: 31.1-71.1%) subjected to inhalation exposure for 8 weeks. Based on the bioavailability data, the relationship between PM2.5-Pb exposure and cardiovascular damage was evaluated in animal simulation experiments. Finally, a damage threshold and cardiovascular-specific risk assessment model were established for the non-ferrous metal smelting area. Our project not only accurately estimates the risk of PM2.5-bound heavy metals on the cardiovascular system but also offers a scientific basis for future prevention and therapy of PM2.5-Pb-related diseases.

Occupational exposure to metals among battery recyclers in France: Biomonitoring and external dose measurements

In battery-recycling facilities, exposure to trace elements may occur through inhalation of contaminated dust or vapor emanating from the treatment processes. Exposure of battery-recycling workers to lead has been quite well covered in the literature. In contrast, we lack data on exposure to other elements contained in batteries. The aim of this study was to characterize the exposure of French battery recyclers to multiple elements using biomonitoring and airborne measurements. Eighty-six workers participated in the study. Inhalable metal concentrations were determined for personal airborne samples, and total exposure was determined from pre-shift and post-shift urine samples collected during the working week. In both types of sample, a total of 33 trace elements were measured using inductively coupled plasma mass spectrometry. Results showed battery recyclers to be mostly exposed to Cd, Co, Cr, Li, Mn, Ni, and Pb. Administrative and sorting workers were exposed at lower levels than maintenance, treatment, and dismantling workers. Cd, Co, Li, Mn, and Ni were detected at high levels in air samples, especially near the treatment facilities, with airborne cadmium levels of up to 79.4 µg/m³. Urinary sample analysis indicated exposure to Cd and Co, with levels measured at up to 27.6 and 3.34 µg/g of creatinine, respectively. Concentrations were compared to data reported for e-waste recycling companies. The data presented provide valuable information on exposure to trace elements for workers involved in battery-recycling. They also highlight the need to improve both collective and individual protective measures, which were not sufficient in the participating companies.