The epidemiology of lead toxicity in adults: measuring dose and consideration of other methodologic issues

Highly sensitive and highly selective lead ion electrochemical sensor based on zn/cu-btc-nh2 bimetallic MOFs with nano-reticulated reinforcing microstructure

Identifying ultra-trace amounts of divalent lead ions (Pb2+) with high response and selectivity, continues to be a pressing issue in identifying environmental pollutants and preventing health complications. This paper details how the in-situ electrodeposited Zn/Cu-BTC-NH2 metal-organic frameworks (MOFs) boosts Pb2+ concentration for amino adsorption and facilitates ion transfer between Cu element and Pb2+. The modified coating of the glassy carbon electrode (GCE) exhibits a unique nano-reticulated structure loaded with octahedron particles, the nano-reticulated structure ensures the structural strength of the modified electrode layer, while the loaded octahedral particles enhancing electrocatalytic activity. The ultra-trace detection of Pb2+ at concentrations below μg·L-1 is accomplished by using the square wave anodic stripping voltammetry (SWASV) method, the fabricated Zn/Cu-BTC-NH2 modified electrode signifies a detection threshold of 0.021 μg L-1 and a clearly ascending linear interval prior to the rise in Pb2+ concentration to 120 μg L-1. The reported electrochemical method for the precise identification of Pb2+ in water-based solutions offers a practical approach for modifying MOFs materials and detecting heavy metal ions.

Associations of a toenail metal mixture with attention and memory in the Gulf long-term follow-up (GuLF) study

BACKGROUND

Research on metal-associated neurodegeneration has largely focused on single metals. Since metal exposures typically co-occur as combinations of both toxic and essential elements, a mixtures framework is important for identifying risk and protective factors. This study examined associations between toenail levels of an eight-metal mixture and attention and memory in men living in US Gulf states.

METHODS

We measured toenail concentrations of toxic (arsenic, chromium, lead, and mercury) and essential (copper, manganese, selenium, and zinc) metals in 413 non-smoking men (23-69 years, 46 % Black) from the Gulf Long-Term Follow-Up (GuLF) Study. Sustained attention and working memory were assessed at the time of toenail sample collection using the continuous performance test (CPT) and digit span test (DST), respectively. Associations between toenail metal concentrations and performance on neurobehavioral tests were characterized using co-pollutant adjusted general linear models and Bayesian Kernel Machine Regression.

RESULTS

Adjusting for other metals, one interquartile range (IQR) increase in toenail chromium was associated with a 0.19 (95 % CI: -0.31, -0.07) point reduction in CPT D Prime score (poorer ability to discriminate test signals from noise). One IQR increase in toenail manganese was associated with a 0.20 (95 % CI, -0.41, 0.01) point reduction on the DST Reverse Count (fewer numbers recalled). Attention deficits were greater among Black participants compared to White participants for the same increase in toenail chromium concentrations. No evidence of synergistic interaction between metals or adverse effect of the overall metal mixture was observed for either outcome.

CONCLUSIONS

Our findings support existing studies of manganese-related memory deficits and are some of the first to show chromium related attention deficits in adults. Longitudinal study of cognitive decline is needed to verify chromium findings. Research into social and chemical co-exposures is also needed to explain racial differences in metal-associated neurobehavioral deficits observed in this study.

Improving prediction of linear regression models by integrating external information from heterogeneous populations: James-Stein estimators

We consider the setting where (1) an internal study builds a linear regression model for prediction based on individual-level data, (2) some external studies have fitted similar linear regression models that use only subsets of the covariates and provide coefficient estimates for the reduced models without individual-level data, and (3) there is heterogeneity across these study populations. The goal is to integrate the external model summary information into fitting the internal model to improve prediction accuracy. We adapt the James-Stein shrinkage method to propose estimators that are no worse and are oftentimes better in the prediction mean squared error after information integration, regardless of the degree of study population heterogeneity. We conduct comprehensive simulation studies to investigate the numerical performance of the proposed estimators. We also apply the method to enhance a prediction model for patella bone lead level in terms of blood lead level and other covariates by integrating summary information from published literature.

Estimating effects of longitudinal and cumulative exposure to PFAS mixtures on early adolescent body composition

Few methods have been used to characterize repeatedly measured biomarkers of chemical mixtures. We applied latent profile analysis (LPA) to serum concentrations of 4 perfluoroalkyl and polyfluoroalkyl substances (PFAS) measured at 4 time points from gestation to age 12 years. We evaluated the relationships between profiles and z scores of height, body mass index, fat mass index, and lean body mass index at age 12 years (n = 218). We compared LPA findings with an alternative approach for cumulative PFAS mixtures using g-computation to estimate the effect of simultaneously increasing the area under the receiver operating characteristic curve (AUC) for all PFAS. We identified 2 profiles: a higher PFAS profile (35% of sample) and a lower PFAS profile (relative to each other), based on their average PFAS concentrations at all time points. The higher PFAS profile had generally lower z scores for all outcomes, with somewhat larger effects for males, though all 95% CIs crossed the null. For example, the higher PFAS profile was associated with a 0.50-unit lower (β = -0.50; 95% CI, -1.07 to 0.08) BMI z score among males but not among females (β = 0.04; 95% CI, -0.45 to 0.54). We observed similar patterns with AUCs. We found that a higher childhood PFAS profile and higher cumulative PFAS mixtures may be associated with altered growth in early adolescence. This article is part of a Special Collection on Environmental Epidemiology.

Lead exposure across the life course and age at death

BACKGROUND

Lead (Pb) exposure has been associated with an increased risk of all-cause mortality, even at low levels. Little is known about how the timing of Pb exposure throughout life may influence these relationships. Quantifying the amount of Pb present in various tissues of the body provides measurements of exposure from different periods of life. These include bone, tooth enamel, which is the hard outer layer of the crown, and tooth cementum, which is the calcified connective tissue covering the tooth root. The purpose of the study was to examine Pb exposure at multiple periods throughout life, including childhood (enamel), adulthood (cementum), and later life (bone), and to estimate their associations with age at death.

METHODS

208 skeleton donors (born 1910-1960) from an ongoing case-control study were included in this study. Pb was measured in tibia (shin), bone using X-Ray Florescence and in teeth using Laser-Ablation Inductively Coupled Plasma Mass Spectroscopy. After excluding unusually high measurements (>2sd), this resulted in a final sample of 111 with all exposure measures. Correlations across measures were determined using partial Spearman correlations. Associations between Pb exposure and age at death were estimated using Multivariable Linear Regression.

RESULTS

Pb measures across exposure periods were all significantly correlated, with the highest correlation between cementum and tibia measures (r = 0.61). Donors were largely female (63.0 %), White (97.3 %), and attended some college (49.5 %). Single exposure models found that higher tooth cementum Pb (-1.27; 95 % CI: -2.48, -0.06) and tibia bone Pb (-0.91; 95 % CI: -1.67, -0.15) were significantly associated with an earlier age at death. When considered simultaneously, only cementum Pb remained significant (-1.51; 95 % CI: -2.92, -0.11). Secondary analyses suggest that the outer cementum Pb may be especially associated with an earlier age at death.

CONCLUSION

Results suggest that higher Pb exposure is associated with an earlier age at death, with adulthood as the life period of most relevance. Additional studies using Pb exposure measures from different life stages should be conducted.

Do we underestimate risk of cardiovascular mortality due to lead exposure?

BACKGROUND

Studies using data from the National Health and Nutrition Examination Survey-III (NHANES-III) have demonstrated significant prospective associations between blood lead levels and increased mortality. Bone lead represents cumulative lead burden and thus is a better biomarker for assessing chronic impacts, but its in vivo assessment requires special K-x-ray fluorescence (KXRF) instrumentation. Our team recently developed an algorithm predicting bone lead levels from a combination of blood lead levels, age and other socioeconomic and behavioral variables. We examined the associations of our algorithm-estimated bone lead levels and mortality in NHANES-III.

METHODS

We included 11,628 adults followed up to December 31, 2019. Estimated tibia lead and patella lead levels were calculated using our prediction algorithms. We used survey-weighted Cox proportional hazards models to compute hazard ratios (HRs) and 95 % confidence intervals (CIs).

RESULTS

During the median follow-up of 26.8 years, 4900 participants died (mortality rate = 1398 per 100,000 adults/year). Geometric means (95 % CIs) of blood lead, predicted tibia lead, and predicted patella lead were 2.69 μg/dL (2.54, 2.84), 6.73 μg/g (6.22, 7.25), and 16.3 μg/g (15.9, 16.8), respectively. The associations for all-cause mortality were similar between blood lead and bone lead. However, the associations for cardiovascular mortality were much greater with predicted bone lead markers compared to blood lead: for comparing participants at the 90th vs. 10th percentiles of exposure, HR = 3.32 (95 % CI: 1.93-5.73) for tibia lead, 2.42 (1.56-3.76) for patella lead, 1.63 (1.25-2.14) for blood lead. The population attributable fractions for cardiovascular disease mortality if everyone's lead concentrations were declined to the 10th percentiles were 45.8 % (95 % CI: 28.1-59.4) for tibia lead, 33.1 % (18.1-45.8) for patella lead, and 22.8 % (10.4-33.8) for blood lead.

CONCLUSIONS

These findings suggest that risk assessment for cardiovascular mortality based on blood lead levels may underestimate the true mortality risk of lead exposure.

Federal Housing Assistance and Blood Lead Levels in a Nationally Representative US Sample Age 6 and Older: NHANES, 1999-2018

BACKGROUND

Federal housing assistance is an important policy tool to ensure housing security for low-income households. Less is known about its impact on residential environmental exposures, particularly lead.

OBJECTIVES

We conducted a quasi-experimental study to investigate the association between federal housing assistance and blood lead levels (BLLs) in a nationally representative US sample age 6 y and older eligible for housing assistance.

METHODS

We used the 1999-2018 National Health and Nutrition Examination Survey (NHANES) linked with US Department of Housing and Urban Development (HUD) administrative records to assess BLLs of NHANES participants with concurrent HUD housing assistance (i.e., current recipients, n = 3 , 0 71 ) and those receiving assistance within 2 y after the survey (i.e., pseudo-waitlist recipients, n = 1,235 ). We estimated BLL least squares geometric means (LSGMs), odds ratio (OR) for BLL ≥ 3.5 μ g / dL , and percent differences in LSGMs by HUD housing assistance status adjusting for age, sex, family income-to-poverty ratio, education, country of birth, race/ethnicity, region, and survey year. We also examined effect modification using interaction terms and stratified analyses by program type [i.e., public housing, multifamily, housing choice vouchers (HCV)], and race/ethnicity.

RESULTS

Current HUD recipients had a significantly lower LSGM [1.07 μ g / dL ; 95% confidence interval (CI): 1.02, 1.12] than pseudo-waitlist recipients (1.21   μ g / dL ; 95% CI: 1.14, 1.28), with an adjusted OR of 0.60 (95% CI: 0.42, 0.87) for BLL ≥ 3.5 μ g / dL . Some effect modification were observed: The protective association of HUD assistance on BLL was strongest among public housing (- 19.5 % LSGM; 95% CI: - 27.5 % , - 1 0 . 7 % ), multifamily (- 12.5 % LSGM; 95% CI: - 2 0 . 7 % , - 3.5 % ), and non-Hispanic White (- 2 0 . 6 % LSGM; 95% CI: - 29.8 % , - 1 0 . 3 % ) recipients. It was weaker to null among HCV (- 5.7 % LSGM; 95% CI: - 12.7 , 1.7%), non-Hispanic Black (- 1.6 % LSGM; 95% CI: - 8.1 % , 5.4%), and Mexican American (-12.5% LSGM; 95% CI: - 31.9 % , 12.5 % ) recipients.

DISCUSSION

Our research underscores the importance of social-structural determinants like federal housing assistance in providing affordable, stable, and healthy housing to very low-income households. More attention is needed to ensure housing quality and racial equity across HUD's three major housing assistance programs. https://doi.org/10.1289/EHP12645.

The Involvement of Lactic Acid Bacteria and Their Exopolysaccharides in the Biosorption and Detoxication of Heavy Metals in the Gut

Heavy metal pollution has become one of the most important global environmental issues. The human health risk posed by heavy metals encountered through the food chain and occupational and environmental exposure is increasing, resulting in a series of serious diseases. Ingested heavy metals might disturb the function of the gut barrier and cause toxicity to organs or tissues in other sites of the body. Probiotics, including some lactic acid bacteria (LAB), can be used as an alternative strategy to detoxify heavy metals in the host body due to their safety and effectiveness. Exopolysaccharides (EPS) produced by LAB possess varied chemical structures and functional properties and take part in the adsorption of heavy metals via keeping the producing cells vigorous. The main objective of this paper was to summarize the roles of LAB and their EPS in the adsorption and detoxification of heavy metals in the gut. Accumulated evidence has demonstrated that microbial EPS play a pivotal role in heavy metal biosorption. Specifically, EPS-producing LAB have been reported to show superior absorption, tolerance, and efficient abatement of the toxicity of heavy metals in vitro and/or in vivo to non-EPS-producing species. The mechanisms underlying EPS-metal binding are mainly related to the negatively charged acidic groups and unique steric structure on the surface of EPS. However, whether the enriched heavy metals on the bacterial cell surface increase toxicity to local mammal cells or tissues in the intestine and whether they are released during excretion remain to be elucidated.

A systematic analysis of chronic kidney disease burden attributable to lead exposure based on the global burden of disease study 2019

AIM

As an important toxic heavy metal, lead exposure can lead to the occurrence of chronic kidney disease (CKD). However, the analysis of its disease burden pattern on a global scale is lacking. This study aimed to analyze the CKD burden attributable to lead exposure globally, regionally and temporally, as well as to examine the role of socio-economic factors.

METHOD

This study used data from the Global Burden of Disease (GBD) study 2019. We obtained the global burden of CKD caused by lead exposure between 1990 and 2019, and stratified this burden according to factors such as gender, age, GBD regions, and countries. From 1990 to 2019, the changing trend of the disease burden of CKD attributed to lead exposure was estimated using Joinpoint regression model with the average annual percent change (AAPC) estimated. Finally, the relationship between country-level socio-economic factors and lead exposure related CKD burden was explored using a panel data model analysis.

RESULTS

In 2019, worldwide, there were 52.94 thousand deaths (95 % uncertainty interval (UI): 31.64, 76.23) and 1225.2 thousand disability-adjusted life years (DALYs) (95 % UI: 707.88, 1818) of CKD caused by lead exposure, accounting for 3.71 % of total CKD deaths and 2.95 % of total CKD DALYs. The age-standardized death and DALY rates per 100,000 population were 0.68 (95 % UI: 0.40, 0.98) and 15.02 (95 % UI: 8.68, 22.26) respectively, indicating an upward trend and stable trend between 1990 and 2019. However, the age-standardized rates attributed to lead exposure showed a wide variability across regions, with the highest rates in Central Latin America and the lowest in Eastern Europe. Moreover, the results of panel model analysis indicated that GDP growth was positively associated with lead exposure related CKD death rate and DALY rate. However, there were inverse associations between life expectancy at birth and hospital beds (per 1000 people) with lead exposure-related CKD DALY rate.

CONCLUSION

In summary, a significant burden of CKD can be attributed to lead exposure, with noticeable regional discrepancies. Findings here are valuable to deploy efficient measures at curbing lead exposure worldwide.

A State-of-the-Science Review on Metal Biomarkers

PURPOSE OF REVIEW

Biomarkers are commonly used in epidemiological studies to assess metals and metalloid exposure and estimate internal dose, as they integrate multiple sources and routes of exposure. Researchers are increasingly using multi-metal panels and innovative statistical methods to understand how exposure to real-world metal mixtures affects human health. Metals have both common and unique sources and routes of exposure, as well as biotransformation and elimination pathways. The development of multi-element analytical technology allows researchers to examine a broad spectrum of metals in their studies; however, their interpretation is complex as they can reflect different windows of exposure and several biomarkers have critical limitations. This review elaborates on more than 500 scientific publications to discuss major sources of exposure, biotransformation and elimination, and biomarkers of exposure and internal dose for 12 metals/metalloids, including 8 non-essential elements (arsenic, barium, cadmium, lead, mercury, nickel, tin, uranium) and 4 essential elements (manganese, molybdenum, selenium, and zinc) commonly used in multi-element analyses.

RECENT FINDINGS

We conclude that not all metal biomarkers are adequate measures of exposure and that understanding the metabolic biotransformation and elimination of metals is key to metal biomarker interpretation. For example, whole blood is a good biomarker of exposure to arsenic, cadmium, lead, mercury, and tin, but it is not a good indicator for barium, nickel, and uranium. For some essential metals, the interpretation of whole blood biomarkers is unclear. Urine is the most commonly used biomarker of exposure across metals but it should not be used to assess lead exposure. Essential metals such as zinc and manganese are tightly regulated by homeostatic processes; thus, elevated levels in urine may reflect body loss and metabolic processes rather than excess exposure. Total urinary arsenic may reflect exposure to both organic and inorganic arsenic, thus, arsenic speciation and adjustment for arsebonetaine are needed in populations with dietary seafood consumption. Hair and nails primarily reflect exposure to organic mercury, except in populations exposed to high levels of inorganic mercury such as in occupational and environmental settings. When selecting biomarkers, it is also critical to consider the exposure window of interest. Most populations are chronically exposed to metals in the low-to-moderate range, yet many biomarkers reflect recent exposures. Toenails are emerging biomarkers in this regard. They are reliable biomarkers of long-term exposure for arsenic, mercury, manganese, and selenium. However, more research is needed to understand the role of nails as a biomarker of exposure to other metals. Similarly, teeth are increasingly used to assess lifelong exposures to several essential and non-essential metals such as lead, including during the prenatal window. As metals epidemiology moves towards embracing a multi-metal/mixtures approach and expanding metal panels to include less commonly studied metals, it is important for researchers to have a strong knowledge base about the metal biomarkers included in their research. This review aims to aid metals researchers in their analysis planning, facilitate sound analytical decision-making, as well as appropriate understanding and interpretation of results.

Early childhood lead exposure is not reflected in adult bone lead: Results of a sub-cohort of African American women in the Cincinnati lead study

INTRODUCTION

Pb in bone may serve as a biomarker for cumulative Pb dose over decades. We hypothesized that adult female bone Pb concentrations (BoPb) would be significantly associated with average childhood blood Pb levels (BlPb) in a birth cohort exposed to relatively high levels of Pb from Pb paint residues.

METHODS

94 African American women with a mean age of 32.7 years were recruited from the Cincinnati Lead Study (CLS) cohort. Subjects were born to women residing where there had been a high incidence of childhood Pb poisoning. Biomarkers of Pb exposure were serial BlPb concentrations spanning the prenatal period to approximately 6.5 years of age. BoPb was assessed in the tibia using the McMaster 109Cd K-XRF fourth generation system. Covariates included nutritional variables related to bone health.

RESULTS

BlPb concentrations began to rise around 6 months of age and declined at later ages. Study participants were obese with a mean Body Mass Index of 34.4 and suboptimal vitamin D status as indicated by a mean 25-OH-D of 18.5 ng/ml. Average tibia Pb was -2.0 ± 8.6 μgPb/g bone mineral. In multiple linear regression, there was no significant association between BoPb at approximately age 30 and childhood cumulative BlPb(CumBlPb).

DISCUSSION

Collectively, BoPb of this group of subjects was not detectable. We suggest that the reason these subjects' BoPb did not reflect their early exposure was that a significantly smaller proportion of Pb body burden resides in bone in young children. As the child grows what Pb there was in bone is diluted and any remaining signal is weak. It has been claimed that BoPb in older children, adolescents, and adults can recapitulate historical exposure to Pb during earlier development; however, in some populations, BoPb at later ages may not be an adequate biomarker to capture childhood exposure to Pb.

Bone lead variability in bone repository skeletal samples measured with portable x-ray fluorescence

Bone lead serves as a better, more accessible biomarker to many communities experiencing chronic exposure to lead. A new method using low energy x-ray fluorescence in a handheld device (portable XRF) allows us to measure this chronic biomarker in only a few minutes. However, many unknowns remain about this biomarker measured using a new low energy x-ray technique. The low energy of the new method was theorized to measure a slightly different portion of the bone than previous techniques, which could influence measurements at different bone sites and types. We tested how bone measurements varied across five bone sites: mid-tibial shaft, proximal tibia, distal tibia (ankle), ilium, and cranium. We found bone lead measurements are not significantly different between skeletal elements when measured using a portable XRF. On average, bone lead in the repository samples was measured to be 21.6 ± 21.3 μg/g with an XRF detection limit of 2.1 ± 0.5 μg/g. Cumulative lead exposure can be effectively measured using the portable XRF on a variety of bone types, but the tibia should be preferentially measured to compare between studies and individuals.

Increased hypertension risk for the elderly with high blood levels of strontium and lead

Hypertension has long been recognized as the global health burden. Heavy metal pollution may be one of the environmental risk factors of hypertension. However, the association remains unclear. We studied the levels of aluminum (Al), vanadium (V), manganese (Mn), arsenic (As), selenium (Se), strontium (Sr), barium (Ba), titanium (Ti), lead (Pb) and cobalt (Co) in whole blood, and the relationship between trace element exposure and hypertension in the elderly community-based Chinese population. A total of 1013 participants from the west of Anhui Province in China were consecutively enrolled in this study in 2016. The general sociodemographic characteristics, lifestyles, disease history and physical examination information were collected by face-to-face survey and physical examination. The levels of ten trace elements were determined by inductively coupled plasma mass spectrometry (ICP-MS). Multivariable logistic regression model was used to assess the association of trace element exposure with the risk of hypertension. Results showed that the odds ratio of hypertension in the highest quartile was 1.811 (95% CI 1.175-2.790, P trend = 0.005) and 1.772 (95% CI 1.121-2.800, P trend = 0.022), respectively, after adjusting for potential confounders, as compared with the lowest quartile of blood Pb and Sr levels.

Association of blood lead with estradiol and sex hormone-binding globulin in 8-19-year-old children and adolescents

BACKGROUND

Metals can interfere with hormonal functioning through indirect mechanisms and by binding at the receptor site; thus, they may be associated with hormonal changes. However, there have been few studies on the health impact of metal exposure among children and adolescents. Thus, we aimed to examine the associations of blood lead level (BLL) with estradiol (E2) and sex hormone-binding globulin (SHBG) among children and adolescents aged 8-19 years in the National Health and Nutrition Examination Survey (NHANES) database.

METHODS

This was a cohort study of 2188 individuals from the NHANES. BLL was taken as independent variables, E2 and SHBG as dependent variable. We conducted weighted multivariate linear regression models and smooth curve fittings to evaluate the association between them.

RESULTS

The BLL was significantly positively associated with serum SHBG level in females, especially when the LnBLL quartiles are between Q3 and Q4. There was an inverted U-shaped association between BLL and E2 with the point of inflection at 1.86 μg/L and a U-shaped association between BLL and SHBG with the point of inflection at 1.86 μg/L in female adolescents aged 16-19 years. Meanwhile, In males, there was a positive trend of correlation between BLL and E2 in the 8-11 years, and 16-19 years groups.

CONCLUSIONS

This study found an inverted U-shaped association of BLL with E2 and a U-shaped association between BLL and SHBG in female adolescents aged 16-19 years. This indicates that adjusting blood lead exposure to mitigate the effects of lead on growth and development is important for adolescents aged 16-19 years. Controlling the BLL below 1.86 μg/L may minimize the damage to E2.

Predicting cumulative lead (Pb) exposure using the Super Learner algorithm

Chronic lead (Pb) exposure causes long term health effects. While recent exposure can be assessed by measuring blood lead (half-life 30 days), chronic exposures can be assessed by measuring lead in bone (half-life of many years to decades). Bone lead measurements, in turn, have been measured non-invasively in large population-based studies using x-ray fluorescence techniques, but the method remains limited due to technical availability, expense, and the need for licensing radioactive materials used by the instruments. Thus, we developed prediction models for bone lead concentrations using a flexible machine learning approach--Super Learner, which combines the predictions from a set of machine learning algorithms for better prediction performance. The study population included 695 men in the Normative Aging Study, aged 48 years and older, whose bone (patella and tibia) lead concentrations were directly measured using K-shell-X-ray fluorescence. Ten predictors (blood lead, age, education, job type, weight, height, body mass index, waist circumference, cumulative cigarette smoking (pack-year), and smoking status) were selected for patella lead and 11 (the same 10 predictors plus serum phosphorus) for tibia lead using the Boruta algorithm. We implemented Super Learner to predict bone lead concentrations by calculating a weighted combination of predictions from 8 algorithms. In the nested cross-validation, the correlation coefficients between measured and predicted bone lead concentrations were 0.58 for patella lead and 0.52 for tibia lead, which has improved the correlations obtained in previously-published linear regression-based prediction models. We evaluated the applicability of these prediction models to the National Health and Nutrition Examination Survey for the associations between predicted bone lead concentrations and blood pressure, and positive associations were observed. These bone lead prediction models provide reasonable accuracy and can be used to evaluate health effects of cumulative lead exposure in studies where bone lead is not measured.

Environmental exposures to lead, cadmium, and mercury and pterygium in Korean adults

Pterygium, one of the most common eye disorders, is an abnormal fibrovascular proliferation extending from the conjunctiva to the cornea. The mechanism of development in pterygium has not been fully elucidated; however, oxidative stress is suggested to be one of the major causes. Heavy metals such as lead (Pb), cadmium (Cd), and mercury (Hg) enter the human body and induce oxidative stress. However, no study has investigated the association of these heavy metals with pterygium. Therefore, this study aimed to evaluate the associations of environmental exposures to Pb, Cd, and Hg with pterygium in the Korean general adults. We analyzed data from 6,587 adults (≥ 20 years of age) who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2011. Pterygium was diagnosed as the presence of a wing-shaped fibrovascular growth. The exposures of Pb, Cd, and Hg were estimated by measuring blood concentrations. The prevalence of pterygium in this study population was 4.0% (348 subjects). After adjusting for potential confounders, the Pb level in blood was found to have a significant dose-dependent association with pterygium (p for trend = 0.001), and its highest quintile (vs. the lowest) had an odds ratio (OR) of 2.22 (95% CI: 1.30, 3.78) for pterygium. The Hg level in blood in the second quintile (vs. the lowest) had an OR of 1.64 (95% CI: 1.04, 2.59) for pterygium. In conclusion, this study suggests that environmental exposures to Pb and Hg in the Korean general adults may be related to the development of pterygium.

Occupational lead exposure on genome-wide DNA methylation and DNA damage

Lead (Pb) exposure can induce DNA damage and alter DNA methylation but their inter-relationships have not been adequately determined. Our overall aims were to explore such relationships and to evaluate underlying epigenetic mechanisms of Pb-induced genotoxicity in Chinese workers. Blood Pb levels (BLLs) were determined and used as individual's Pb-exposure dose and the Comet assay (i.e., % tail DNA) was conducted to evaluate DNA damage. In the screening assay, 850 K BeadChip sequencing was performed on peripheral blood from 10 controls (BLLs ≤100 μg/L) and 20 exposed workers (i.e., 10 DNA-damaged and 10 DNA-undamaged workers). Using the technique, differentially methylated positions (DMPs) between the controls and the exposed workers were identified. In addition, DMPs were identified between the DNA-undamaged and DNA-damaged workers (% tail DNA >2.14%). In our validation assay, methylation levels of four candidate genes were measured by pyrosequencing in an independent sample set (n = 305), including RRAGC (Ras related GTP binding C), USP1 (Ubiquitin specific protease 1), COPS7B (COP9 signalosome subunit 7 B) and CHEK1 (Checkpoint kinase 1). The result of comparisons between the controls and the Pb-exposed workers show that DMPs were significantly enriched in genes related to nerve conduction and cell cycle. Between DNA-damaged group and DNA-undamaged group, differentially methylated genes were enriched in the pathways related to cell cycle and DNA integrity checkpoints. Additionally, methylation levels of RRAGC and USP1 were negatively associated with BLLs (P < 0.05), and the former mediated 19.40% of the effect of Pb on the % tail DNA. These findings collectively indicated that Pb-induced DNA damage was closely related to methylation of genes in cell cycle regulation, and methylation levels of RRAGC were involved in Pb-induced genotoxicity.

Plasma Lead Concentration and Risk of Late Kidney Allograft Failure: Findings From the TransplantLines Biobank and Cohort Studies

RATIONALE & OBJECTIVE

Heavy metals are known to induce kidney damage, and recent studies have linked minor exposures to cadmium and arsenic with increased risk of kidney allograft failure, yet the potential association of lead with late graft failure in kidney transplant recipients (KTRs) remains unknown.

STUDY DESIGN

Prospective cohort study in The Netherlands.

SETTING & PARTICIPANTS

We studied outpatient KTRs (n = 670) with a functioning graft for ≥1 year recruited at a university setting (2008-2011) and followed for a median of 4.9 (interquartile range, 3.4-5.5) years. Additionally, patients with chronic kidney disease (n = 46) enrolled in the ongoing TransplantLines Cohort and Biobank Study (2016-2017, ClinicalTrials.gov identifier NCT03272841) were studied at admission for transplant and at 3, 6, 12, and 24 months after transplant.

EXPOSURE

Plasma lead concentration was log₂-transformed to estimate the association with outcomes per doubling of plasma lead concentration and also considered categorically as tertiles of lead distribution.

OUTCOME

Kidney graft failure (restart of dialysis or repeat transplant) with the competing event of death with a functioning graft.

ANALYTICAL APPROACH

Multivariable-adjusted cause-specific hazards models in which follow-up of KTRs who died with a functioning graft was censored.

RESULTS

Median baseline plasma lead concentration was 0.31 (interquartile range, 0.22-0.45) μg/L among all KTRs. During follow-up, 78 (12%) KTRs experienced graft failure. Higher plasma lead concentration was associated with increased risk of graft failure (hazard ratio, 1.59 [95% CI, 1.14-2.21] per doubling; P = 0.006) independent of age, sex, transplant characteristics, estimated glomerular filtration rate, proteinuria, smoking status, alcohol intake, and plasma concentrations of cadmium and arsenic. These findings remained materially unchanged after additional adjustment for dietary intake and were consistent with those of analyses examining lead categorically. In serial measurements, plasma lead concentration was significantly higher at admission for transplant than at 3 months after transplant (P = 0.001), after which it remained stable over 2 years of follow-up (P = 0.2).

LIMITATIONS

Observational study design.

CONCLUSIONS

Pretransplant plasma lead concentrations, which decrease after transplant, are associated with increased risk of late kidney allograft failure. These findings warrant further studies to evaluate whether preventive or therapeutic interventions to decrease plasma lead concentration may represent novel risk-management strategies to decrease the rate of kidney allograft failure.

Higher R2* in the Red Nucleus Is Associated With Lead Exposure in an Asymptomatic Welder Cohort

Lead is a nonessential metal and may be a coexposure in welding fumes. Preclinical data indicate lead may affect iron regulation. The current study investigated blood lead concentrations and their association with brain iron accumulation in workers with chronic welding fume exposure, with a focus on iron-rich subcortical regions of the cerebellum and basal ganglia. Occupational exposure, whole blood metal, and brain MRI data were obtained from 29 controls and 42 welders. R2* (1/T2*) and R1 (T1 relaxation rate) values were used to estimate brain iron and manganese content, respectively. Blood metals and brain R2* (in the red nucleus [RN], dentate nucleus, caudate, putamen, globus pallidus, and substantia nigra) were compared between groups. Associations between brain R2* values and exposure metrics were tested within each group, and analyses were adjusted for potential confounders. Welders had significantly higher levels of whole blood lead, manganese, iron, and copper. Welders also had higher R2* RN (p = .002), but not R1. A 2nd-order polynomial modeled the association between R2* RN and a long-term welding exposure metric. In welders, but not controls, R2* RN was associated positively with whole blood lead (r = 0.54, p = .003), and negatively with whole blood manganese (r = -0.43, p = .02). Higher blood Pb and lower blood Mn independently accounted for variance in high RN R2*. Together, these data suggest that higher RN R2* values may mark lead exposure in welders. Because lead is a known neurotoxicant, additional studies are warranted to confirm this finding, and ascertain its scientific and public/occupational health implications.

Toxic metal pollution and ecological risk assessment in water and sediment at ship breaking sites in the Bay of Bengal Coast, Bangladesh

Quantification of four toxic metals (As, Cr, Cd, and Pb) in water and sediments at the Sitakunda ship breaking area in Bangladesh was studied. Along with this, sediment quality and ecological risk were evaluated for the metal intrusion to the study area. A total sample number of 120 (water; n = 60 and sediment; n = 60) were analyzed for both winter and summer seasons using atomic absorption spectrophotometer (AAS). The trace metal concentration in both water and sediment showed decreasing trend as follows; Cr (mean-W: 0.118 mg/L; mean-S:121.87 mg/kg) > Pb (mean-W: 0.064 mg/L; mean-S: 65.31 mg/kg) > As (mean-W: 0.03 mg/L; mean-S: 32.53 mg/kg) > Cd (mean-W: 0.004 mg/L; mean-S: 4.81 mg/kg). However, in both segments, the concentrations of the toxic metals exceeded the recommended acceptable limits. As and Cd showed significant variation (water and sediment) between the seasons, while Pb and Cr had no seasonal impact. Metal pollution index (MPI) and contamination factor (CF) was evaluated and revealed that the study area exhibited the critical score of water quality (MPI > 100). The cumulative effect of the metal concentrations was high (CI > 3). The assessed mean geoaccumulaiton index (I_geo) revealed that the study area was moderate to strongly polluted except for Cr. According to the contamination factor (CF), the sediment samples were moderate to highly contaminated by Cd, Pb, and As. Moreover, the explored range of pollution load index (PLI) in all sampling sites in the ship breaking region was from 1.75 to 3.10, suggesting that the sediment in the study area was highly polluted by heavy metals (PLI > 1). The risk index and the potential ecological risk index (PERI) suggested that the study area was at high risk due to metals pollution. Therefore, it is obligatory to maintain some crucial efforts for the betterment of the surrounding environment near the investigated sites.

Human Body Burden of Heavy Metals and Health Consequences of Pb Exposure in Guiyu, an E-Waste Recycling Town in China

Guiyu accommodates millions of tons of e-waste from overseas and domestic sources each year and is notorious for its e-waste dismantling industry. As a consequence, Guiyu has been described as "the world's most toxic place" and "junk town". Informal e-waste recycling activities have caused severe pollution to the local environment and are associated with extensive health problems to the residents. This review provides updated insights on the body burden of heavy metals derived from e-waste and health outcomes resulted from lead (Pb) exposure. The review identified that Guiyu has been highly contaminated by heavy metals, especially Pb. Excessive exposure to Pb has been associated with multi-system and long-term effects in neonates and children, covering nervous, cardiovascular, adaptive immune, and hematologic systems as well as chromosome and DNA damage. Our review indicates strong associations that emphasize the need to develop strong regulations for prevention of exposure and health consequences in Guiyu and similar sites around the world.

Evaluation of the Role of KIM-1 in Detecting Early Nephrotoxicity in Lead-Exposed Workers

OBJECTIVES

Lead nephropathy usually starts silent. This study aimed to evaluate using kidney injury molecule 1 (KIM-1) as an early nephrotoxicity predictor of long-term low-level occupational lead exposure.

METHODS

History, examination, and laboratory investigations including: blood lead, urinary KIM-1, serum uric acid, creatinine, urea, sodium, potassium, serum albumin, and urine analysis were done on 35 lead-exposed workers and a matched control group.

RESULTS

Higher blood lead levels were found among the exposed group compared to the control one. No statistically significant difference was found regarding renal failure manifestations or standard renal functions (uric acid, blood urea, and creatinine). Urinary KIM-1 was statistically significantly increased among the exposed group.

CONCLUSION

Renal adverse effects were associated to lead fumes exposure. KIM-1 can be used as biomarker for detecting early renal affection among lead-exposed workers.

Global and gene-specific promoter methylation, and micronuclei induction in lead-exposed workers: A cross-sectional study

Perturbation of epigenetic regulation is a well-established mechanism for cancer but its role for lead (Pb)-associated toxicity has not been adequately investigated. We aimed to investigate whether occupational Pb exposure is associated with micronuclei (MN) frequency and to further explored the mediating roles of epigenetic gene regulation. All the Pb-exposed workers recruited from a Chinese acid battery factory, blood lead levels (BLLs) and MN frequency in lymphocytes were measured. In addition, methylation levels of seven genes (Line-1, RASSF1A, RUNX3, p16, CYP26C1, hMLH1, p15) were examined among 230 workers. Robust Poisson regression model was used to investigate the association between BLLs and MN frequency. Mediation analysis was used to explore the mediating role of specific DNA methylation. Among total 677 participants, 71% were male, median BLLs was 229.1 μg/L (P₂₅  = 155.5, P₇₅  = 319.3; ranged from 8.9 to 647.7 μg/L), mean MN frequency was 2.5‰ (SD = 1.8‰; ranged from 0 to 9‰). Results from base model, adjusted for age, sex, and body mass index, showed that MN frequency would increase 1.38 (95%confidential interval: 1.34, 1.43) per 100 μg/L increment in BLLs. Using categorized exposure variable analyses, a BLLs dose-response increase in MN frequency was observed: 2.74 (2.13, 3.51), 3.43 (2.73, 4.32), 4.41 (3.89, 5.01) to 6.86 (6.02, 7.81). Mediation analysis indicated that Line-1 methylation significantly mediated 3.6% of the association of BLLs with MN frequency. Occupational Pb exposure induces MN frequency in a dose-response relationship. Part of this association was mediated by Line-1 promotor methylation.

Heavy Metal Toxicity in Chronic Renal Failure and Cardiovascular Disease: Possible Role for Chelation Therapy

Exposure to heavy metals is common. This exposure is related to environmental contamination of air, water and soil, occupational exposure, accumulation in food, tobacco, and other factors. Cadmium and lead are notable for their widespread contamination, long-lasting effects in the body, and renal as well as cardiovascular toxicity. Acute toxicity due to high-level exposure, as well as chronic low-level exposure are now well-established pathogenic entities. Both chronic renal failure and ischemic heart disease patients have been treated separately in recent studies with ethylenediaminetetraacetic acid (EDTA) chelation therapy. In patients with chronic kidney disease (serum creatinine: 1.5-4.0 mg/dL) and increased body lead burden, weekly low-dose chelation with calcium EDTA slowed the rate of decline in renal function in patients with diabetes and in non-diabetic patients. In patients with a history of myocardial infarction, the Trial to Assess Chelation Therapy study showed that EDTA chelation decreased the likelihood of cardiovascular events, particularly in patients with diabetes. However, heavy metal levels were not measured in this study. It is clear that more research is needed in this area. There is also a need to more frequently consider and test for the possibility of cadmium and lead toxicity in patients with increased risk, such as those with hypertension, diabetes mellitus, and chronic renal disease.

Association between Musculoskeletal Pain and Bone Turnover Markers in Long-Term Pb-Exposed Workers

BACKGROUND

On chronic exposure, Lead (Pb) deposits in the skeletal system, replaces calcium ions, and alters the normal physiological processes, which in turn, lead to stunting, delayed fracture healing, and high resorption of collagen molecules. The present study aimed to assess the association of musculoskeletal pain and discomfort with bone turnover markers (BTMs) among long-term Pb-exposed workers.

STUDY DESIGN

A cross-sectional study.

METHODS

The study recruited 176 male Pb-exposed workers and 80 control subjects who were matched for age, gender, and socio-economic status. Blood lead levels (BLLs), bone growth markers, such as serum osteocalcin (OC), alkaline phosphatase (ALP), bone alkaline phosphatase (BAP), and bone resorption markers: serum pyridinoline (Pry), deoxypyridinoline (DPry), tartrate-resistant acid phosphatase-5b(TRACP-5b), and hydroxyproline in urine (HyP-U) of participants were investigated. Pain and discomfort in the musculoskeletal system were assessed using Nordic Musculoskeletal Questionnaire.

RESULTS

Pb-exposure was significantly associated with musculoskeletal discomfort of the lower back (P<0.001), upper back (P<0.001), and ankle/foot (P=0.011). Among bone formation markers, serum OC was significantly lower in musculoskeletal discomfort of elbows (P=0.033) and ankle/foot (P=0.042). Among bone resorption markers, serum DPry was significantly lower in musculoskeletal discomfort of the neck (P=0.049) and shoulders (P=0.023). HyP-U was significantly higher in musculoskeletal discomfort of shoulders (P=0.035) and lower back (P=0.036).

CONCLUSION

As evidenced by the obtained results, Pb-exposure was associated with musculoskeletal discomfort of the lower back, upper back, and ankle/foot. Lower bone formation (serum OC) marker was noted with musculoskeletal discomfort of elbows and ankle/foot. Furthermore, bone resorption markers were associated with musculoskeletal discomfort of the neck, shoulders, and lower back. The findings of the present study suggested that long-term Pb-exposure and BTMs were associated with musculoskeletal discomfort.

Trace elements exposure and risk in age-related eye diseases: a systematic review of epidemiological evidence

This systematic review aimed to evaluate existing evidence on the associations between trace elements exposure and age-related eye diseases. PubMed and Google scholar databases were searched for epidemiological and postmortem studies on the relationship between exposure to trace elements and Age-related eye diseases such as age-related macular degeneration (AMD), cataract, glaucoma and diabetic retinopathy (DR), in population groups aged 40 years and above. Available evidence suggests that cadmium (Cd) exposure may be positively associated with the risks of AMD and cataract. There is also evidence that exposure to lead (Pb) may be positively associated with higher risk of cataract and glaucoma. There is limited number of relevant studies and lack of prospective studies for most of the investigated associations. Evidence for other trace elements is weak and inconsistent, and the number of available studies is small. Likewise, there are very few relevant studies on the role of trace elements in DR. Chemical elements that affect the distribution and absorption of other trace elements have never been investigated. The suggestive but limited evidence motivates large and quality prospective studies to fully characterize the impact of exposure to trace (toxic and essential) elements on age-related eye diseases.

The Case For Cadmium and Lead Heavy Metal Screening

Exposure to cadmium and lead is widespread, and is related to environmental contamination, occupational sources, food, tobacco and other consumer products. Lower socioeconomic status increases the risk of heavy metal exposure and the diseases associated with cadmium and lead toxicity. Concurrent toxicity with both cadmium and lead is likely but has not often been assessed. There is now substantial evidence linking cadmium and lead to many diseases including hypertension, diabetes mellitus, obesity, cancer, coronary artery disease, chronic kidney disease (CKD) and lung disease. Both chronic renal failure and ischemic heart disease patients have been treated separately in recent studies with calcium disodium ethylenediaminetetraacetic acid (Ca EDTA) chelation therapy. In patients with CKD, serum creatinine 1.5-4.0 mg/dL, and increased body lead burden, weekly low dose chelation with Ca EDTA slowed the rate of decline in renal function in diabetics and non-diabetics. In patients with a history of myocardial infarction, the Trial to Assess Chelation Therapy (TACT) study showed that Ca EDTA chelation decreased the likelihood of cardiovascular events, particularly in diabetics. Ca EDTA chelation administered carefully at lower dosage (<50 mg/kg per week) is generally safe. In the past, acute renal failure associated with much higher dosage was reported. We suggest that the preponderance of the evidence favors a more activist approach towards diagnosis and possible intervention in heavy metal toxicity.

Blood lead levels and their associated risk factors in Chinese adults from 1980 to 2018

In China, studies on lead exposure to grownup are scarce compared to children, although relevant disease burdens for adults are much severe than that in developed countries. The present study evaluated blood lead levels (BLLs) in Chinese adults by data mining using Monte Carlo simulation. A total of 115 scientific studies published between January 1980 and March 2021 reflecting 45,514 Chinese adults were included in the study. After a continuous increase in Chinese adult BLLs from 1980-1983 (GM 74.84 μg/L) to 1994-1996 (GM 92.27 μg/L), BLLs began to decline from 2000--2002 (GM 80.32 μg/L) to 2016-2018 (GM 21.57 μg/L). This decline implied that the lead phase-out policy in gasoline was effective over the past two decades. The study indicated that North, South, and Southwest China were still relatively high compared to other regions in the past decade. Statistical analysis showed that BLLs of males (GM 68.45 μg/L) were higher than females (GM 56.51 μg/L), smokers (GM 80.96 μg/L) higher than nonsmokers (GM 58.95 μg/L), and populations over 40 (GM 40.43 μg/L) higher than younger populations (GM 40.37 μg/L). The significantly positive correlation between the concentrations of PM2.5 and topsoil lead and BLLs in Chinese adults indicated that air and soil pollution affect adult BLLs. Taken together, our results showed that strict lead control strategies and regular bio-monitoring are needed to maintain low BLLs in the population.

Blood lead levels and lung cancer mortality: An updated analysis of NHANES II and III

Previous analyses within the National Health and Nutrition Examination Survey (NHANES) II and III cycles suggested an association between blood lead levels (BLLs) and lung cancer mortality, although the evidence was limited by small case numbers. To clarify this relationship, we conducted updated analyses of 4,182 and 15,629 participants in NHANES II and III, respectively, (extending follow-up 20 and 8 years) aged ≥20 with BLL measurements and mortality follow-up through 2014. We fit multivariable Cox models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) relating BLLs and lung cancer with adjustment for smoking and other factors. We did not observe an overall association between BLLs and lung cancer after adjustment for smoking (both surveys) and serum cotinine and environmental tobacco smoke exposure (NHANES III), although suggestive associations were observed among women (NHANES II: HR 2.7, 95% CI 0.7, 10.0 for ≥20.0 µg/dl vs. <10.0 µg/dl, P_trend = 0.07; NHANES III: HR 11.2, 95% CI 2.1, 59.4 for ≥10.0 µg/dl vs. <2.5 µg/dl, P_trend = 0.04). After stratifying on smoking status, an association with elevated BLLs was observed in NHANES II only among former smokers (HR 3.2, 95% CI 1.3, 8.0 for ≥15 vs. <15 µg/dl) and in NHANES III only among current smokers (HR 1.7, 95% CI 1.1, 2.8 for ≥5 vs. <5 µg/dl). In summary, we found elevated BLLs to be associated with lung cancer mortality among women in both NHANES II and III. Given the absence of an association among non-smokers, we cannot rule out residual confounding as an explanation for our findings.

Association between cumulative childhood blood lead exposure and hepatic steatosis in young Mexican adults

BACKGROUND

Exposure to environmental toxicants may play a role in the pathogenesis of Non Alcoholic Fatty Liver Disease (NAFLD). Cumulative exposure to lead (Pb) has chronic and permanent effects on liver function. Pediatric populations are vulnerable to the toxic effects of Pb, even at low exposure levels. The purpose of the study was to estimate the association between cumulative Pb exposure during childhood and hepatic steatosis biomarkers in young Mexican adults.

METHODS

A subsample of 93 participants from the ELEMENT cohort were included in this study. Childhood blood samples were collected annually from ages 1-4 years and were used to calculate the Cumulative Childhood Blood Lead Levels (CCBLL). Hepatic steatosis during adulthood was defined as an excessive accumulation of hepatic triglycerides (>5%) determined using Magnetic Resonance Imaging (MRI). Liver enzymes were also measured at this time, and elevated liver enzyme levels were defined as ALT (≥30 IU/L), AST (≥30 IU/L), and GGT (≥40 IU/L). Adjusted linear regression models were fit to examine the association between CCBLL (quartiles) and the hepatic steatosis in young adulthood.

RESULTS

In adulthood, the mean age was 21.4 years, 55% were male. The overall prevalence of hepatic steatosis by MRI was 19%. Elevate levels of the enzymes ALT, AST, and GGT were present in 25%, 15%, and 17% of the sample, respectively. We found a positive association between the highest quartile of CCBLL with the steatosis biomarkers of hepatic triglycerides (Q4 vs. Q1: β = 6.07, 95% CI: 1.91-10.21), elevated ALT (Q4 vs. Q1: β = 14.5, 95% CI: 1.39-27.61) and elevated AST (Q4 vs. Q1: β = 7.23, 95% CI: 0.64-13.82). No significant associations were found with GGT.

CONCLUSIONS

Chronic Pb exposure during early childhood is associated with a higher levels of hepatic steatosis biomarkers and hepatocellular injury in young adulthood. More actions should be taken to eliminate sources of Pb during the first years of life.

DNA methylation biomarker for cumulative lead exposure is associated with Parkinson's disease

Lead, a known neurotoxicant, has previously received attention in Parkinson’s disease (PD) research, but epidemiologic studies have been limited in sample size and findings are equivocal. We generated two methylation-based biomarkers for cumulative tibia and patella bone-measured lead exposure in 1528 PD patients and 1169 controls. PD status was associated with increased levels of the DNAm biomarker for tibia-lead levels. We estimated a meta-OR for PD of 1.89 per unit DNAm tibia-lead increase (95% CI 1.59, 2.24; p = 8.1E−13). The current study supports the notion that chronic and long-term lead exposure tracked via DNAm may contribute to PD pathogenesis.

Blood DNA methylation biomarkers of cumulative lead exposure in adults

BACKGROUND

Lead is a ubiquitous toxicant following three compartment kinetics with the longest half-life found in bones. Patella and tibia lead levels-validated measures of cumulative exposure-require specialized X-ray-fluorescence-spectroscopy available only in a few centers worldwide. We developed minimally invasive biomarkers reflecting individual cumulative lead exposure using blood DNA methylation profiles-obtainable via Illumina 450K or IlluminaEPIC bead-chip assays.

METHODS

We developed and tested two methylation-based biomarkers from 348 Normative Aging Study (NAS) elderly men. We selected methylation sites with strong associations with bone lead levels via robust regressions analysis and constructed the biomarkers using elastic nets. Results were validated in a NAS subset, reporting specificity, and sensitivity.

FINDINGS

Participants were 73 years old on average (standard deviation, SD = 6), with moderate lead levels of (mean ± SD patella: 27 ± 18 µg/g; tibia:21 ± 13 µg/g). Methylation-based biomarkers for lead in patella and tibia included 59 and 138 DNA methylation sites, respectively. Estimated lead levels were significantly correlated with actual measured values, (r = 0.62 patella, r = 0.59 tibia) and had low mean square error (MSE) (MSE = 0.68 patella, MSE = 0.53 tibia). Means and distributions of the estimated and actual lead levels were not significantly different across patella and tibia bones (p > 0.05). Methylation-based biomarkers discriminated participants highly exposed (>median) to lead with a specificity of 74 and 73% for patella and tibia lead levels, respectively, with 70% sensitivity.

INTERPRETATION

DNA methylation-based lead biomarkers are novel tools that can be used to reconstruct decades' worth of individual cumulative lead exposure using only blood DNA methylation profiles and may help identify the consequences of cumulative exposure.

DNA Methylation-Based Biomarkers of Environmental Exposures for Human Population Studies

PURPOSE OF REVIEW

This manuscript orients the reader to the underlying motivations of environmental biomarker development for human population studies and provides the foundation for applying these novel biomarkers in future research. In this review, we focus our attention on the DNA methylation-based biomarkers of (i) smoking, among adults and pregnant women, (ii) lifetime cannabis use, (iii) alcohol consumption, and (iv) cumulative exposure to lead.

RECENT FINDINGS

Prior environmental exposures and lifestyle modulate DNA methylation levels. Exposure-related DNA methylation changes can either be persistent or reversible once the exposure is no longer present, and this combination of both persistent and reversible changes has essential value for biomarker development. Here, we present available biomarkers representing past and cumulative exposures using individual DNA methylation profiles. In the present work, we describe how the field of environmental epigenetics can leverage machine learning algorithms to develop exposure biomarkers and reduce problems of misreporting exposures or limited access technology. We emphasize the crucial role of the individual DNA methylation profiles in those predictions, providing a summary of each biomarker, and highlighting their advantages, and limitations. Future research can cautiously leverage these DNA methylation-based biomarkers to understand the onset and progression of diseases.

Biomonitoring findings for occupational lead exposure in battery and ceramic tile workers using biochemical markers, alkaline comet assay, and micronucleus test coupled with fluorescence in situ hybridisation

Manufacture of lead-containing products has long been associated with various health risks. To get an insight into the related genotoxic risks, we conducted a biomonitoring study in 50 exposed workers and 48 matched controls using a battery of endpoints that sensitively detect the extent of genome instability in peripheral blood lymphocytes. The levels of primary DNA damage were estimated with the alkaline comet assay, while cytogenetic abnormalities were determined with the cytokinesis-block micronucleus (CBMN) cytome assay. Additionally, CBMN slides of 20 exposed and 16 control participants were subjected to fluorescence in situ hybridisation (FISH), coupled with pancentromeric probes to establish the incidence of centromere-positive micronuclei, nuclear buds, and nucleoplasmic bridges. Blood lead levels (B-Pb) were measured with atomic absorption spectrometry. To further characterise cumulative effects of occupational exposure, we measured erythrocyte protoporphyrin (EP) concentrations and delta-aminolevulinic acid dehydratase (ALAD) activity in blood. We also assessed the influence of serum folate (S-folate) and vitamin B12 (S-B12) on genome stability. Compared to controls, occupationally exposed workers demonstrated significantly higher B-Pb (298.36±162.07 vs 41.58±23.02), MN frequency (18.71±11.06 vs 8.98±7.50), centromere positive MN (C+ MN) (8.15±1.8 vs 3.69±0.47), and centromere negative MN (C- MN) (14.55±1.80 vs 4.56±0.89). Exposed women had significantly higher comet tail intensity (TI) and length (TL) than control women. Furthermore, workers showed a positive correlation between age and nuclear buds and MN, between MN and years of exposure, and between S-B12 levels and TI and ALAD activity, while a negative correlation was found between TI and B-Pb. These findings suggest that occupational settings in the manufacture of lead-containing products pose significant genotoxic risks, which calls for developing more effective work safety programmes, including periodical monitoring of B-Pb and genetic endpoints.

Association between blood lead levels and metabolic syndrome considering the effect of the thyroid-stimulating hormone based on the 2013 Korea National health and nutrition examination survey

Imbalances in thyroid-stimulating hormone (TSH) levels are associated with metabolic syndrome (MetS), and the underlying mechanism is partly in alignment with that of lead exposure causing MetS. Many studies have reported the association between lead exposure and MetS, but no study has considered the possibility of TSH mediating lead's effect on MetS. Therefore, we aimed to examine the association between lead exposure and MetS considering TSH as a partial mediator. The data of 1,688 adults (age ≥19 years) from the Korea National Health and Nutrition Examination Survey in 2013 were analyzed. The prevalence of MetS in the Korean population was 21.9%, and the geometric mean of blood lead and serum TSH levels were 1.96 μg/dL and 2.17 μIU/mL, respectively. The associations between blood lead levels, serum TSH levels, and MetS were determined through a multiple logistic regression analysis. Blood lead levels were positively associated with high TSH levels (upper 25%) with an odds ratio (OR) and 95% confidence interval (CI) of 1.79 (1.24, 2.58) per doubled lead levels. The increase in blood lead and serum TSH levels both positively increased the odds of developing MetS. The OR of MetS per doubling of blood lead level was 1.53 (1.00, 2.35), and was not attenuated after adjusting for TSH levels. These findings suggest that higher levels of blood lead are positively associated with serum TSH levels and MetS. By exploring the role of TSH as a partial mediator between lead and MetS, we verified that lead exposure has an independent relationship with MetS, regardless of TSH levels.

Evaluation of lead body burden in US adolescents

The objective was to examine key determinants in the body burden of lead in adolescents as lead poisoning remains a major public health challenge. Data from 2,925 teenagers aged 12-18 older in the National Health and Nutrition Examination Survey (NHANES), 1999-2012 were analyzed. Lead in both blood and urine was significantly correlated among individuals. Despite higher blood lead in males, urinary lead measures corrected for dilution were similar between male and female adolescents. Thus, the urine-to-blood ratio was approximately 30% lower in male than female adolescents, suggesting that differences in renal disposal contributed to the greater body burden for young males. Differences in urinary lead disposal appear to be a key determinant in lead accumulation and thus, the degree of lead poisoning. Direct renal studies should be conducted to determine mechanisms and potential solutions.

Erythrocyte levels of cadmium and lead and risk of B-cell non-Hodgkin lymphoma and multiple myeloma

Cadmium and lead are persistent environmental toxins that are known or probable carcinogens, based on evidence for causality for nonhematologic cancers. Associations of these metals with risk of non-Hodgkin lymphoma (NHL) and multiple myeloma (MM) are unknown but biologically plausible. To examine the associations of circulating levels of lead and cadmium exposure with risk of B-cell NHL (B-NHL) and multiple myeloma, we conducted a nested case-control study among 299 incident B-cell NHLs and 76 MM cases within the Cancer Prevention Study-II Nutrition Cohort (CPS-II NC). Each case was incidence-density matched to two eligible controls on age, race, sex and blood draw date. Conditional logistic regression was used to estimate relative risks (RR) and 95% confidence intervals (CI) for lymphoid malignancies overall and stratified by subtype. We observed a significant positive association between high erythrocyte lead concentration and risk of lymphoid malignancies overall (RR = 1.16, 95% CI: 1.02-1.33 per 17.6 μg/L (1 standard deviation [SD])) and follicular lymphoma in particular (RR = 1.80, 95% CI: 1.15-2.80 per SD). In contrast, there was no association between erythrocyte cadmium and risk of B-NHL (RR = 0.89, 95% CI: 0.75-1.06 per 0.37 μg/L [1 SD]), or any B-NHL subtypes; but a strong inverse association with MM risk (RR = 0.59, 95% CI: 0.38-0.89, per SD). Results from our study suggest a positive association between erythrocyte lead level and risk of lymphoid malignancies and a possible inverse association between cadmium and myeloma. Additional research is needed to confirm and further explore these findings.

Effect of Heavy Metal Contamination in the Environment on Antioxidant Function in Wumeng Semi-fine Wool Sheep in Southwest China

Many environmental accidents have led to worldwide heavy metal pollution, raising concern about heavy metal toxicity in Southwest China. To study the effects of Cd and Pb in the environment on antioxidant function in Wumeng semi-fine wool sheep, contents of Cu, Zn, Mn, Mo, Fe, Se, Cd, and Pb were measured in irrigation water, soil, herbage, and animal tissues. Hematological and biochemical parameters were also determined. The concentrations of Cu, Zn, Cd, and Pb in affected samples of irrigation water, soil, herbage, and tissues were significantly higher than those in the control (P < 0.01). There was no significant difference in other element contents between affected pastures and control areas. The occurrence of anemia affected Wumeng semi-fine wool sheep. The activities of SOD, CAT, and GSH-Px in affected animals were significantly decreased than those in the control (P < 0.01). Content of MDA in serum in affected animals was significantly increased than that in control (P < 0.01). Serum T-AOC in affected animal was significantly lower than that in control (P < 0.01). Consequently, it is suggested that heavy metal contamination in natural habitat caused serious harm to antioxidant function in Wumeng semi-fine wool sheep.

Associations of blood lead levels with multiple genotoxic biomarkers among workers in China: A population-based study

Carcinogenic effects from low doses of lead (Pb) exposure to populations have been suspected but not concluded. Therefore, a large-scale cross-sectional study was conducted by us to investigate genotoxic effects from Pb exposure during 2016-2018 in North China. Blood lead levels (BLLs) and cumulative blood lead levels (CBLLs) were measured. Multiple relevant biomarkers were used to assess genotoxicity of Pb: mitochondrial DNA copy number (mtDNAcn, n = 871), Comet Tail Intensity (n = 872), γ-H2AX (n = 345), relative telomere length (rTL, n = 757), micronuclei (MN, n = 934) and phosphatidylinositol glycan class A mutation (PIG-A, n = 362). The BLL data show right-skewed distribution, with increase of the median (P25, P75) from 17.4 (8.9, 26.4) μg/dl in 2016 to 18.5 (10.5, 27.2) μg/dl in 2017, and to 20.8 (11.3, 31.0) μg/dl in 2018. Multivariate regression analyses show that mtDNAcn was non-linearly associated with BLLs or CBLLs, i.e. decreased at low levels but increased at the higher levels. Comet and Micronuclei data show positive dose-response relationships with BLLs as well as CBLLs. γ-H2AX data show an overall increased trend with BLLs while rTL data show a shortening trend. No associations were found for PIG-A mutation with Pb exposure. Our findings indicate that current low dose exposure to Pb can still cause health hazards to occupational populations, and the mechanism may be via the induction of DNA & chromosome damage rather than via the mutagenesis pathway.

Cadmium and Lead Exposure, Nephrotoxicity, and Mortality

The present review aims to provide an update on health risks associated with the low-to-moderate levels of environmental cadmium (Cd) and lead (Pb) to which most populations are exposed. Epidemiological studies examining the adverse effects of coexposure to Cd and Pb have shown that Pb may enhance the nephrotoxicity of Cd and vice versa. Herein, the existing tolerable intake levels of Cd and Pb are discussed together with the conventional urinary Cd threshold limit of 5.24 μg/g creatinine. Dietary sources of Cd and Pb and the intake levels reported for average consumers in the U.S., Spain, Korea, Germany and China are summarized. The utility of urine, whole blood, plasma/serum, and erythrocytes to quantify exposure levels of Cd and Pb are discussed. Epidemiological studies that linked one of these measurements to risks of chronic kidney disease (CKD) and mortality from common ailments are reviewed. A Cd intake level of 23.2 μg/day, which is less than half the safe intake stated by the guidelines, may increase the risk of CKD by 73%, and urinary Cd levels one-tenth of the threshold limit, defined by excessive ß₂-microglobulin excretion, were associated with increased risk of CKD, mortality from heart disease, cancer of any site and Alzheimer's disease. These findings indicate that the current tolerable intake of Cd and the conventional urinary Cd threshold limit do not provide adequate health protection. Any excessive Cd excretion is probably indicative of tubular injury. In light of the evolving realization of the interaction between Cd and Pb, actions to minimize environmental exposure to these toxic metals are imperative.

Nonlinear association between blood lead and hyperhomocysteinemia among adults in the United States

Evidence regarding the association between blood lead levels (BLL) and hyperhomocysteinemia (HHcy) in US adults was limited. We aimed to investigate the association of BLL with the risk of HHcy, and to examine possible effect modifiers using US National Health and Nutrition Examination Survey (NHANES) database. We performed a cross-sectional study using data from up to 9,331 participants aged ≥ 20 years of NHANES from 2001 to 2006. BLL was measured by atomic absorption spectrometry. HHcy was defined as plasma homocysteine level > 15 µmol/L. The weighted prevalence of HHcy was 6.87%. The overall mean BLL was 1.9 μg/dL. Overall, there was a nonlinear positive association between Ln-transformed BLL (LnBLL) and the risk of HHcy. The Odds ratios (95% CI) for participants in the second (0.04–0.49 μg/dL), third (0.5–0.95 μg/dL) and fourth quartiles (> 0.95 μg/dL) were 1.12 (95% CI: 0.71, 1.76), 1.13 (95% CI: 0.73, 1.77), and 1.67 (95% CI: 1.07, 2.61), respectively, compared with those in quartile 1. Consistently, a significantly higher risk of HHcy (OR: 1.49; 95% CI: 1.19, 1.88) was found in participants in quartile 4 compared with those in quartiles 1–3. Furthermore, a strongly positive association between LnBLL and HHcy was observed in participants with estimated glomerular filtration rate (eGFR) < 60 mL/min⁻¹/1.73 m⁻². Our results suggested that a higher level of BLL (LnBLL > 0.95 μg/dL) was associated with increased risk of HHcy compared with a lower level of BLL (LnBLL ≤ 0.95 μg/dL) among U.S. adults, and the association was modified by the eGFR.

Developing a Health Impact Model for Adult Lead Exposure and Cardiovascular Disease Mortality

BACKGROUND

Lead (Pb) is a highly toxic pollutant. Evidence suggests it is associated with cardiovascular disease (CVD)-related mortality.

OBJECTIVES

We present a rigorous approach for identifying concentration-response functions that relate adult Pb exposures to CVD mortality to inform a health impact model (HIM). We then use the model in a proof-of-concept example.

METHODS

Building on previously conducted government literature reviews and a de novo supplemental literature review, we compiled and evaluated the available data on Pb and CVD mortality in humans. We applied a set of predefined selection criteria to identify studies that would be most useful in understanding the impact of Pb exposure on CVD mortality risk in adults. Once we identified the studies, we derived a HIM and used each study's concentration-response function in a proof-of-concept example.

RESULTS

Our literature search identified 15 studies for full-text review. Of those 15 studies, 4 fit our criteria for use in the HIM. Using population and CVD mortality rates for 40- to 80-y-olds in 2014, we estimated that 34,000-99,000 deaths have been avoided due to the lowering of blood Pb levels from 1999 to 2014. Based on these values we estimated that approximately 16%-46% of the decreased CVD-related death rate from 1999 to 2014 may be attributable to decreased blood Pb levels.

CONCLUSION

Our results demonstrate that decreases in Pb exposure can result in large benefits for the adult population. We have provided a HIM that can be used in a variety of applications from burden-of-disease estimates to regulatory impact assessments and have demonstrated its sensitivity to the choice of concentration-response function. https://doi.org/10.1289/EHP6552.

Investigative Analysis of Lanthanum Oxide Nanoparticles on Elements in Bone of Wistar Rats After 30 Days of Repeated Oral Administration

Accumulation of lanthanum oxide nanoparticles (La₂O₃NPs) in the femur bone of rats after 30 days of oral administration was explored. Also, the influence of La₂O₃NPs on macro and trace elements in the rats' femur bone was assessed. Inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical spectrometry (ICP OES) were used for total element determination in the bone after decomposition while laser ablation-ICP-MS (LA-ICP-MS) was used to investigate element distribution (bio-imaging) in the bone. Some differences in element concentrations in the bone between the rats treated with La₂O₃NPs at 1.0 mg kg^-1 (T1), 10.0 mg kg^-1 (T2), and 100 mg kg^-1 (T3) body weight (bw) and the control rats (CTR) were observed. More differences were observed in the bone of rat treated with 10.0 mg kg^-1 La₂O₃NPs bw. However, the highest change observed was for Mg, which concentration ranged from 5230 ± 12 μg kg^-1 for the CTR group to 4130 ± 138 μg kg^-1 for the T3 group. Minor changes were observed for Ba, Ca, Cr, Cu, Fe, Mg, Na, Pb, Sr, and Zn between CTR and animals treated with La₂O₃NPs at the different levels of concentration. It was possible to observe from LA-ICP-MS analysis that La₂O₃NPs were accumulated only on the surface of the bone, not deeper than about 5 μm. LA-ICP-MS allowed also to investigate the distribution of La and the other elements in a cross section of the femur bone head, where higher amounts of the elements are present at the external part of the bone. Therefore, it was demonstrated that La₂O₃NPs are incorporated on the surface of the bone and it has a small influence on some of the other elements evaluated.

PIG-A gene mutation as a genotoxicity biomarker in human population studies: An investigation in lead-exposed workers

The rodent Pig-a gene mutation assay has demonstrated remarkable sensitivity in identifying in vivo mutagens, while much less is known about the value of the human PIG-A assay for risk assessment. To obtain more evidence of its potential as a predictive biomarker for carcinogen exposure, we investigated PIG-A mutant frequencies (MFs), along with performing the Comet assay and micronucleus (MN) test, in 267 workers occupationally exposed to lead. Multivariate Poisson regression showed that total red blood cell PIG-A MFs were significantly higher in lead-exposed workers (10.90 ± 10.7 × 10^-6 ) than in a general population that we studied previously (5.25 ± 3.6 × 10^-6 ) (p < .0001). In contrast, there was no increase in lymphocyte MN frequency or in DNA damage as measured by percentage comet tail intensity in whole blood cells. Current year worker blood lead levels (BLL), an exposure biomarker, were elevated (232.6 ± 104.6 μg/L, median: 225.4 μg/L); a cumulative blood lead index (CBLI) also was calculated based on a combination of current and historical worker BLL data. Chi-square testing indicated that PIG-A MFs were significantly related to CBLI (p = .0249), but independent of current year BLL (p = .4276). However, % comet tail intensity and MN frequencies were better associated with current year BLL than CBLI. This study indicates that the PIG-A assay could serve as biomarker to detect the genotoxic effects of lead exposure and demonstrates that a battery of genotoxicity biomarkers having mechanistic complementarity may be useful for comprehensively monitoring human carcinogenic risk.

Altered clearance of beta-amyloid from the cerebrospinal fluid following subchronic lead exposure in rats: Roles of RAGE and LRP1 in the choroid plexus

Formation of amyloid plaques is the hallmark of Alzheimer's disease. Our early studies show that lead (Pb) exposure in PDAPP transgenic mice increases β-amyloid (Aβ) levels in the cerebrospinal fluid (CSF) and hippocampus, leading to the formation of amyloid plaques in mouse brain. Aβ in the CSF is regulated by the blood-CSF barrier (BCB) in the choroid plexus. However, the questions as to whether and how Pb exposure affected the influx and efflux of Aβ in BCB remained unknown. This study was conducted to investigate whether Pb exposure altered the Aβ efflux in the choroid plexus from the CSF to blood, and how Pb may affect the expression and subcellular translocation of two major Aβ transporters, i.e., the receptor for advanced glycation end-products (RAGE) and the low density lipoprotein receptor protein-1 (LRP1) in the choroid plexus. Sprague-Dawley rats received daily oral gavage at doses of 0, 14 (low-dose), and 27 (high-dose) mg Pb/kg as Pb acetate, 5 d/wk, for 4 or 8 wks. At the end of Pb exposure, a solution containing Aβ40 (2.5 μg/mL) was infused to rat brain via a cannulated internal carotid artery. Subchronic Pb exposure at both dose levels significantly increased Aβ levels in the CSF and choroid plexus (p < 0.05) by ELISA. Confocal data showed that 4-wk Pb exposures prompted subcellular translocation of RAGE from the choroidal cytoplasm toward apical microvilli. Furthermore, it increased the RAGE expression in the choroid plexus by 34.1 % and 25.1 % over the controls (p < 0.05) in the low- and high- dose groups, respectfully. Subchronic Pb exposure did not significantly affect the expression of LRP1; yet the high-dose group showed LRP1 concentrated along the basal lamina. The data from the ventriculo-cisternal perfusion revealed a significantly decreased efflux of Aβ40 from the CSF to blood via the blood-CSF barrier. Incubation of freshly dissected plexus tissues with Pb in artificial CSF supported a Pb effect on increased RAGE expression. Taken together, these data suggest that Pb accumulation in the choroid plexus after subchronic exposure reduces the clearance of Aβ from the CSF to blood by the choroid plexus, which, in turn, leads to an increase of Aβ in the CSF. Interaction of Pb with RAGE and LRP1 in choroidal epithelial cells may contribute to the altered Aβ transport by the blood-CSF barrier in brain ventricles.

Association of Blood Lead Levels with the Risk of Depressive Symptoms in the Elderly Chinese Population: Baseline Data of a Cohort Study

Previous studies have reported an association between blood lead (BPb) levels and depressive symptoms in adults. However, the relationship between BPb levels and depression remains unclear in the old population. Our purpose was to investigate the association of BPb levels with depression among the old population. Data were gathered from 994 elderly persons in the Cohort Study of Elderly Health and Environmental Controllable Factors, which was created in Anhui, China. BPb was measured by inductively coupled plasma mass spectrometry. Our subjects were divided into four groups according to BPb quartiles. Multivariate logistic regressions were used to assess the association between BPb levels and depression. The median (25th-75th) BPb level was 26.94 μg/L (20.34 μg/L-36.13 μg/L). BPb levels in participants with depression were higher than those in participants without depression. The prevalence of depression was 27.64%. After multivariate adjustment for confounding factors, participants with BPb level in the highest quartile had 2.03 times higher risk of depression compared with those in the lowest quartile. In rural areas, the risk of depression in higher BPb quartile was higher than that in the lowest quartile. These findings suggest that higher BPb level was associated with increased odds of depression in the old population. This association was obvious among older people living in rural areas.