Blood Lead Reference Value Research Articles

State-Level Childhood Lead Poisoning Prevention Policies and Practices in the United States: 2022-2023.

The purpose of this analysis is to better understand laws and practices guiding prevention activities in childhood lead poisoning prevention programs funded by the Centers for Disease Control and Prevention (CDC). In 2022, CDC surveyed 62 funded programs using the Awardee Lead Profile Assessment. Information was collected about childhood lead poisoning-related laws and guidance, surveillance and prevention strategies, and program services including at what blood lead levels (BLLs) various activities are performed. Separately, CDC reviewed state health department websites to obtain information on which states implemented CDC's updated blood lead reference value. Awardee Lead Profile Assessment results are only reported for 47 states, the District of Columbia, and Puerto Rico. Almost all programs (96%) have laws requiring reporting of BLLs, and 51% require BLLs be reported electronically to jurisdictional health departments. Most programs (80%) prioritize areas and populations that are high risk for lead poisoning prevention activities. Approximately half of the programs (51%) have a lead elimination plan or goal. Thirty-nine percent of the programs have already implemented policies, laws, or regulations to achieve lead elimination, and 74% are in the Northeast and Midwest regions of the country. As of March 2023, 71% of the programs have implemented CDC's updated blood lead reference value, and most (65%) did so via guidance for health care providers and laboratories for what BLL should initiate case management and other services for lead-exposed children. Almost all programs have mandatory BLL reporting laws, and about two-thirds of the programs updated their BLLs that trigger public health action.

Low-Level, Early Life Lead Exposure and School Behavior.

To measure how early childhood exposure to lead affects school behavior from third to eighth grade, measured by the number and days of total school suspensions and out-of-school suspensions (OSS). We estimate Poisson models using a cohort of 284 701 students with school records from 2006-2008 in North Carolina. We adjust for demographic and socioeconomic variables and school-grade-year cohort effects, and use coarsened exact matching to ensure similar characteristics across children with blood lead levels (BLLs) 2-10 μg/dL and children in the reference group with BLLs ≤1 μg/dL. BLLs ≥3 µg/dL are positively and significantly associated with all school suspension measures for sixth through eighth graders. The estimated effects on OSS for sixth through eighth graders are larger than the effects on total suspensions. For example, students with BLL = 3 µg/dL receive OSS 16% (95% confidence interval 3.6%-30%) more often and for 22% (95% confidence interval 7.3%-33%) more days than students with BLL ≤1 µg/dL. For third through fifth grade students, we only find a significant effect of lead exposure on suspensions at relatively high BLLs of 8-10 µg/dL. Our analysis demonstrates that BLL has significant adverse effects on third through eighth grade students' behavior, including at levels below the current Centers for Disease Control and Prevention's blood lead reference value of 3.5 μg/dL. We find that the adverse effects of lead are most strongly associated with more severe disruptive behavior in sixth through eighth graders, as measured by OSS. Our results underscore the long-term benefits of preventing early childhood exposure to lead.

Lead Poisoning in a Mother and Her Four Children Using a Traditional Eye Cosmetic - New York City, 2012-2023.

Even low levels of lead in children's blood are associated with developmental delays, difficulty learning, and behavioral issues. Adults are also vulnerable to the detrimental health effects of lead exposure. The New York City (NYC) Department of Health and Mental Hygiene receives blood lead test results for NYC residents and conducts investigations of lead poisoning cases. Blood lead testing of a child aged 4 years in 2012 led to the discovery of blood lead levels above the CDC blood lead reference value of 3.5 μg/dL in the child as well as four other family members over a period of 11 years, including the child's mother and three younger siblings born during 2012-2016. The only potential source of lead exposure identified for all cases was the use of surma, a traditional eye cosmetic, which was found to contain 390,000 ppm lead. The cases in this report highlight the challenges of risk communication when deeply ingrained cultural practices, such as the use of surma, persist despite health warnings. Moreover, they highlight the intergenerational nature of such practices and the need for comprehensive family follow-up once a member is identified as being at risk. These products continue to be available globally, even in places such as the United States where sales are prohibited. Multistakeholder efforts involving local and global engagement could promote reformulation of these products at the countries of origin to eliminate lead as an ingredient.

Lead and calcium crosstalk tempted acrosome damage and hyperpolarization of spermatozoa: signaling and ultra-structural evidences

BackgroundExposure of humans and animals to heavy metals is increasing day-by-day; thus, lead even today remains of significant public health concern. According to CDC, blood lead reference value (BLRV) ranges from 3.5 µg/dl to 5 μg/dl in adults. Recently, almost 2.6% decline in male fertility per year has been reported but the cause is not well established. Lead (Pb2+) affects the size of testis, semen quality, and secretory functions of prostate. But the molecular mechanism(s) of lead toxicity in sperm cells is not clear. Thus, present study was undertaken to evaluate the adverse effects of lead acetate at environmentally relevant exposure levels (0.5, 5, 10 and 20 ppm) on functional and molecular dynamics of spermatozoa of bucks following in vitro exposure for 15 min and 3 h.ResultsLead significantly decreased motility, viable count, and motion kinematic patterns of spermatozoa like curvilinear velocity, straight-line velocity, average path velocity, beat cross frequency and maximum amplitude of head lateral displacement even at 5 ppm concentration. Pb2+ modulated intracellular cAMP and Ca2+ levels in sperm cells through L-type calcium channels and induced spontaneous or premature acrosome reaction (AR) by increasing tyrosine phosphorylation of sperm proteins and downregulated mitochondrial transmembrane potential. Lead significantly increased DNA damage and apoptosis as well. Electron microscopy studies revealed Pb2+ -induced deleterious effects on plasma membrane of head and acrosome including collapsed cristae in mitochondria.ConclusionsPb2+ not only mimics Ca2+ but also affects cellular targets involved in generation of cAMP, mitochondrial transmembrane potential, and ionic exchange. Lead seems to interact with Ca2+ channels because of charge similarity and probably enters the sperm cell through these channels and results in hyperpolarization. Our findings also indicate lead-induced TP and intracellular Ca2+ release in spermatozoa which in turn may be responsible for premature acrosome exocytosis which is essential feature of capacitation for fertilization. Thus, lead seems to reduce the fertilizing capacity of spermatozoa even at 0.5 ppm concentrations.Graphical

B-328 Analytical Performance of a Screening Test for Lead Using Dried Blood Spots and ICP-MS

Abstract Introduction There is no safe blood lead levels (BLL) in children and exposure can cause irreversible neurological harm. In 2021, the CDC decreased the blood lead reference value (BLRV) to 3.5 ug/dL from 5.0 ug/dL, based on the 97.5th percentile of BLL among US children under 5 years of age. Despite this, lead poisoning disproportionately affects Black children, those below poverty levels, and living in houses built before 1978. The American Academy of Pediatrics recommends targeted screening for BLL in children aged 12–24 months living in high prevalence areas. Children enrolled in Medicaid also require screening by 24 months of age. Only one-third of children who require screening receive it and lead screening declined by >50% during the COVD-19 pandemic. Quality improvement strategies have included electronic health record alerts and point of care testing. To improve screening rates in our pediatric population, we developed a screening method utilizing dried blood spot (DBS) cards. This study aimed to validate the accuracy and precision of this screening method with emphasis on the performance around the BLRV cut-offs, which would be used to determine the need to follow up with a confirmatory venous lead test. Methods The method was calibrated using certified reference material traceable to NIST SRM 3128 (VHG labs, Manchester, NH, USA) in whole blood. The calibrators, controls and patient samples were spotted onto Whatman 903 cards. A 6 mm filter paper disc in extraction buffer was vortexed, allowed to sit at room temperature for 30 min and centrifuged. The samples were analyzed on the Thermo Fisher iCAP RQ and TQ (Whaltman, MA) in kinetic energy discrimination mode. The assay has a linear range of 1–100 µg/dL, and the recovery ranged from 92%–102%. We evaluated this method for reproducibility, and accuracy across the measurement range. In this study, we focused on the reproducibility and accuracy of DBS at lead concentrations around the BLRV cut-offs. We used in 2 samples spiked with NIST CRM 3128 (Inorganic Ventures, Christiansburg, VA, USA) analyzed 10 times over 3 days and 13 leftover patient samples run over at least 5 days. The total allowable error was 2 µg/dL or 10%. Results In two samples spiked to BLL of 3.5 and 3.9 µg/dL, interday precision (n = 10) ranged from 3.4% to 17.4% (SD 0.1–0.7) in samples run for 3 days. Removal of an apparent outlier decreased the %CV ranged observed to <8.5%. The average bias for each day ranged from 0.1 to 0.6 µg/dL. In 13 patient samples with concentrations around the BLRV ranging from 1.4 to 5.8 µg/dL, the coefficient of variation (CV) ranged from 0.2% to 32% with the largest SD at 0.8 µg/dL. The average bias for this sample set was -0.3 (11.7%). Conclusion The assay’s analytical performance is sufficient for screening purposes, but the clinical performance and the impact of introducing this test to enhance screening rates during 1 and 2 years well visits need to be evaluated further.

A-327 Pre-analytical and Analytical Modifications to Improve the Quality of Pediatric Lead Tests

Abstract Background The recent decrease in the CDC Blood Lead Reference Value (BLRV) to 3.5 ug/dL has highlighted the need for systematic changes that some clinicians and laboratories need to implement to assure the quality of reported pediatric lead results. Building upon the recommendations of the Blood Lead Reference Value Workgroup, APHL has developed specific recommendations and resources designed to assist medical professionals and laboratory scientists in minimizing the likelihood of contamination when collecting and testing blood specimens. Also included are analytical practices that can improve precision, accuracy, and sensitivity of pediatric lead assays. Methods Evaluation of existing protocols and practices to identify potential sources of contamination and opportunities for process improvement. Results APHL will provide practical recommendations to systematically improve point of care and fixed laboratory testing to improve confidence in reported pediatric lead concentrations. These improved measurements will improve environmental health surveillance and inform public health intervention and patient care. Conclusion Rigorous pre-analytical practices including education, updated specimen collection guidance, pre-screening of collection materials, improvement of point of care technology and refinement of spectroscopic analytical methods result in less ambient contamination, improved sensitivity, precision and accuracy of pediatric lead testing. Clinician office practices, public health and commercial clinical laboratories will all benefit from implementing these strategies.

Trends in Blood Lead Levels Quantified by ICP-MS: A Reference Laboratory Retrospective Study.

Exposure to lead may cause severe adverse effects such as anemia, neurologic damage, developmental disorders, and reproductive disorders. Consequently, in 2021, the Centers for Disease Control and Prevention (CDC) reduced its blood lead reference value from 5 µg/dL to 3.5 µg/dL in pediatric patients, 1 to 5 years old. The objective of this study was to perform a retrospective analysis of patient blood lead concentrations reported by ARUP Laboratories to evaluate the frequency of blood lead concentrations greater than 3.5 µg/dL. The analysis of blood lead concentration was performed in venous whole blood specimens using inductively coupled plasma mass spectrometry (ICP-MS). In addition, retrospective data analysis was performed to evaluate zinc protoporphyrin (ZPP) concentrations in adult patients with corresponding lead results, using the lead industrial exposure panel. The analysis for ZPP was performed using quantitative hematofluorometry. Retrospective data analysis identified a decline in blood lead concentrations from 2012 to 2021 for pediatric and adult patients. The calculated nonparametric 95% range for ZPP blood was 15 to 43 μg/dL and the ZPP heme ratio 26 to 74 μmol ZPP/mol heme. Lowering the blood lead reference value (BLRV) to 3.5 μg/dL presents an opportunity for healthcare providers and public health agencies to extend medical or environmental interventions for lead exposure in pediatric patients.

Identifying the Blood Lead Reference Value Based on the Advisory Committee on Childhood Lead Poisoning Prevention Guidelines and Factors Associated with Elevated Blood Lead Levels among Preschool Children in Thailand, 2019

The blood lead reference value (BLRV) is used for guiding lead prevention and control measures. It is usually defined as the 97.5th percentile of the population-based blood lead level in each country. This study aims to determine the BLRV and factors associated with elevated (≥5 µg/dL) blood lead levels among children aged 1–5 years in Thailand. A cross-sectional study was conducted using secondary data extracted from a national survey, implemented in 171 hospitals during October 2018–September 2019. Demographic characteristics and potential risk factors including lead-related industries were collected. Multilevel logistic regression was used. Of 3,184 children included in the survey, the BLRV was 6.9 µg/dL. Three significant risk factors were identified: living near a lead factory (adjusted odds ratio (AOR) 2.09, 95% CI 1.27–3.42), exposure to the manufacture of fishing tackle (AOR 4.39, 95% CI 1.54–12.50), and exposure to the manufacture of shot and ammunition (AOR 6.30, 95% CI 1.81–21.93). Despite a calculated BLRV of 6.9 µg/dL, we propose a BLRV of 5 μg/dL in Thailand based on guidelines from the United Kingdom. Surveillance of blood lead levels should be established among children at high risk of lead exposure.

Implementation of a pharmacy-based blood lead testing program: A retrospective analysis

In 2014, a change in the water source in Flint, Michigan, exposed residents to dangerous levels of lead in their drinking water. The concern for lead toxicity created the opportunity for pharmacies to provide quick and accessible blood lead testing services. The primary objective was to create a pharmacy-based blood lead testing program through collaboration with the Michigan Department of Health & Human Services and community pharmacies in Flint, Michigan. The partnership was established in 2016 and Magellan LeadCare II blood analyzers were placed at three pharmacies. Walk-in testing was offered from June 2016 to August2016. Community pharmacists aimed to provide more accessible lead screening services to limit health disparities and medical complications. A retrospective analysis using descriptive statistics was conducted to assess the benefits of early blood lead screening and to determine when a patient should seek further evaluation. Blood lead screening values were based on the Center for Disease Control (CDC) and Prevention's blood lead reference value (BLRV). The BLRV at the time of the study was ≥ 5 μg/dL, but this was eventually changed to ≥3.5 μg/dL. A total of 77 individuals were screened in the pharmacies. Four (5%) individuals had lead levels ≥5 μg/dL. Of these, two patients were <6 years of age. Fifteen (19%) patients had lead levels ≥3.5 μg/dL. The highest lead level detected was 24.2 μg/dL in a 70-year-old patient. If the result was ≥5 μg/dL, patients were instructed to follow up with their physician or the Genesee County Health Department. All patients with elevated blood levels were referred to the appropriate health care provider. This model demonstrates the feasibility of a public health/community pharmacy collaborative lead testing program. This program can serve as a template for future crisis-focused collaborative models.

The CDC's updated blood lead reference value and community implications in pediatrics.

Robin Lynch Varela is an NP at Rowan University, Glassboro, N.J., and a lecturer at the University of Pennsylvania School of Nursing, Philadelphia, Pa. The author has disclosed no financial relationships related to this article.

The Use of Pb Isotope Ratios to Determine Environmental Sources of High Blood Pb Concentrations in Children: A Feasibility Study in Georgia.

The incidence of lead (Pb) poisoning in children in Georgia has been identified as a major health concern, with a recent national survey identifying that 41% of children aged 2-7 years had blood lead concentrations (BLCs) greater than the blood lead reference value (BLRV) of ≥5 µg dL-1. This study collected samples of blood, spices, paint, soil, dust, flour, tea, toys, milk, and water from 36 households in Georgia where a child had previously been identified as having a BLC > BLRV. The Pb concentrations of these samples were determined and compared to Georgian reference values. Samples from 3 households were analysed for their Pb isotope composition. The Pb isotope composition of the environmental and blood samples were compared to identify the most likely source(s) of Pb exposure. This approach identified that some spice and dust samples were the likely sources of Pb in the blood in these cases. Importantly, some soil, paint, and dust sources with high Pb concentrations could be discounted as contributing to blood Pb based on their distinct isotope composition. The data presented demonstrate the significant contribution that Pb surveillance and Pb isotope ratio analyses can make to managing Pb exposure in regions where high BLCs are identified.

Measuring clinical lead testing coverage to support a population health initiative

Abstract Despite national efforts to reduce lead exposure, some children are still exposed to lead, leading to damage to the nervous system, delayed development, and learning and behavioral problems. CDC has recommended targeting high-risk groups for screening. In addition, Texas Department of State Health Services reported a concerning 17% lead testing coverage of 0-to-5-year-olds in in Harris County (where Houston is located). With the eventual goal of improving lead-related clinical care in a large pediatric hospital network, we asked the following questions: 1) What are the high-risk groups specific to our patient population? 2) For patients who are screened positive, are we adequately confirming the results? 3) For those with confirmed lead exposure, are we providing adequate follow-up care? To answer these questions, we analyzed lead testing and hemoglobin testing data on all children less than 6 years of age from the Texas Children’s Hospital’s electronic health record between 2017 and 2021. Lead screening could be performed on capillary or venous blood, but for elevations on capillary blood we analyzed if the results were confirmed with a venous blood test, as recommended by CDC. We used hemoglobin testing as an indicator of follow-up care of lead-exposed children, because an anemia work-up is recommended for such children. We repeated analysis using two different lead level thresholds, because of recent change to the CDC blood lead reference value from 5 mcg/dL to 3.5 mcg/dL in May 2021. We found 273 children (0.33% of children with capillary blood test) to have cBLL = 3.5mcg/dL. There was a significant racial disparity in the rate of lead screening. For example, the screening rate of Black children was 14%, whereas that of White children were 23%. There was a geographic discrepancy between the areas with most elevated cBLL and testing volume. For example, the area where cBLL was most frequently elevated (3.7%) received less than a fifth of tests compared to the most well-tested area. Only 75% of children with a cBLL = 5mcg/dL received a timely venous blood lead test for confirmation, and this dropped to 43% for children with a cBLL = 3.5mcg/dL. Similarly, only 75% of children with a confirmed venous lead level = 5 mcg/dL received a follow-up repeat vBLL test, and 55% received a follow-up hemoglobin measurement. There is room for improvement in population lead health, in terms of both equity and resource distribution. Improvement of lead-related clinical practice could benefit hundreds of children in the Houston metropolitan area.

Detecting New Sources of Childhood Environmental Lead Exposure Using a Statistical Surveillance System, 2015-2019.

Objectives. To design and implement a statistical surveillance system to prospectively identify potential clusters of elevated blood lead levels (EBLLs) in children younger than 6 years in the Denver, Colorado, metro area. Methods. We evaluated the ability of 2 independent statistical surveillance methods to detect synthetic clusters of EBLLs in Denver between 2015 and 2019. Results. Together, the statistical surveillance methods took an average of 9 months to detect the synthetic clusters. This is faster than similar real-world clusters that have been reported in the past. The system was relatively unaffected by changes in the testing rate and to the blood lead reference value. Conclusions. The adequate design of a statistical surveillance system can help increase the rate at which clusters of EBLLs are detected in Denver, but doing so requires an accurate model of the spatial distribution of EBLLs. Earlier detection of clusters can help guide more effective public health interventions at the local level. (Am J Public Health. 2022;112(S7):S715-S722. https://doi.org/10.2105/AJPH.2022.307009).

Determination of lead in blood by graphite furnace atomic absorption spectrometry with Zeeman background correction: Improving a well-established method to support a lower blood lead reference value for children

Lead is ubiquitous in the environment and exposure can have adverse health effects even at low concentrations, particularly in young children. Blood Pb levels are the best indicator of recent Pb exposure. The Centers for Disease Control and Prevention (CDC) recently lowered the blood Pb reference value from 5 μg/dL to 3.5 μg/dL, based on data calculated from the 97.5th percentile of children 1–5 years old in the National Health and Nutrition Examination Survey (NHANES). The established method for determining Pb in blood by GFAAS has an estimated detection limit (LOD) of ≈1 μg/dL. This presents an analytical challenge for its clinical use in the US, given that the current population mean blood Pb level is 0.82 μg/dL. Accuracy and precision may be insufficient to quantitate low blood Pb levels in the 1–5 μg/dL range, which is essential now that the CDC blood Pb reference value is 3.5 μg/dL.The original GFAAS method for blood Pb published in 1993 has been significantly improved to achieve a lower LOD of 0.2 μg/dL, with the ability to quantitate blood Pb levels down to 1 μg/dL. This method is fit for the purpose of detecting blood Pb levels currently, with excellent accuracy and precision in the 1–5 μg/dL range. Results from analyzing SRMs, PT materials and human blood samples were in good agreement between two different GFAAS platforms, as well as with results obtained by ICP-MS. The improvements provide evidence of an GFAAS method capable of achieving lower LODs with improved accuracy and precision at lower blood Pb levels, which can support the lower blood Pb reference value for children at 3.5 μg/dL.

Update of the Blood Lead Reference Value - United States, 2021.

The negative impact of lead exposure on young children and those who become pregnant is well documented but is not well known by those at highest risk from this hazard. Scientific evidence suggests that there is no known safe blood lead level (BLL), because even small amounts of lead can be harmful to a child's developing brain (1). In 2012, CDC introduced the population-based blood lead reference value (BLRV) to identify children exposed to more lead than most other children in the United States. The BLRV should be used as a guide to 1) help determine whether medical or environmental follow-up actions should be initiated for an individual child and 2) prioritize communities with the most need for primary prevention of exposure and evaluate the effectiveness of prevention efforts. The BLRV is based on the 97.5th percentile of the blood lead distribution in U.S. children aged 1-5 years from National Health and Nutrition Examination Survey (NHANES) data. NHANES is a complex, multistage survey designed to provide a nationally representative assessment of health and nutritional status of the noninstitutionalized civilian adult and child populations in the United States (2). The initial BLRV of 5 μg/dL, established in 2012, was based on data from the 2007-2008 and 2009-2010 NHANES cycles. Consistent with recommendations from a former advisory committee, this report updates CDC's BLRV in children to 3.5 μg/dL using NHANES data derived from the 2015-2016 and 2017-2018 cycles and provides helpful information to support adoption by state and local health departments, health care providers (HCPs), clinical laboratories, and others and serves as an opportunity to advance health equity and environmental justice related to preventable lead exposure. CDC recommends that public health and clinical professionals focus screening efforts on populations at high risk based on age of housing and sociodemographic risk factors. Public health and clinical professionals should collaborate to develop screening plans responsive to local conditions using local data. In the absence of such plans, universal BLL testing is recommended. In addition, jurisdictions should follow the Centers for Medicare & Medicaid Services requirement that all Medicaid-enrolled children be tested at ages 12 and 24 months or at age 24-72 months if they have not previously been screened (3).

Blood Lead Levels in U.S. Children Ages 1-11 Years, 1976-2016.

Background:Lead can adversely affect child health across a wide range of exposure levels. We describe the distribution of blood lead levels (BLLs) in U.S. children ages 1–11 y by selected sociodemographic and housing characteristics over a 40-y period.Methods:Data from the National Health and Nutrition Examination Survey (NHANES) II (1976–1980), NHANES III (Phase 1: 1988–1991 and Phase II: 1991–1994), and Continuous NHANES (1999–2016) were used to describe the distribution of BLLs (in micrograms per deciliter; ) in U.S. children ages 1–11 y from 1976 to 2016. For all children with valid BLLs (), geometric mean (GM) BLLs [95% confidence intervals (CI)] and estimated prevalence (95% CI) were calculated overall and by selected characteristics, stratified by age group (1–5 y and 6–11 y).Results:The GM BLL in U.S. children ages 1–5 y declined from (95% CI: 14.3, 16.1) in 1976–1980 to (95% CI: 0.78, 0.88) in 2011–2016, representing a 94.5% decrease over time. For children ages 6–11 y, GM BLL declined from (95% CI: 11.9, 13.4) in 1976–1980 to (95% CI: 0.58, 0.63) in 2011–2016, representing a 95.3% decrease over time. Even so, for the most recent period (2011–2016), estimates indicate that approximately 385,775 children ages 1–11 y had BLLs greater than or equal to the CDC blood lead reference value of . Higher GM BLLs were associated with non-Hispanic Black race/ethnicity, lower family income-to-poverty-ratio, and older housing age.Discussion:Overall, BLLs in U.S. children ages 1–11 y have decreased substantially over the past 40 y. Despite these notable declines in population exposures to lead over time, higher GM BLLs are consistently associated with risk factors such as race/ethnicity, poverty, and housing age that can be used to target blood lead screening efforts. https://doi.org/10.1289/EHP7932

DNA Methylation Biomarkers of IQ Reduction are Associated with Long-term Lead Exposure in School Aged Children in Southern China.

Although lead associated with intelligence decline in children has long been reported, studies combining intelligence determination, molecular mechanisms exploration, and biomarker screen are quite rare. In this study, based on 333 children aged 9-11, we determined the role of DNA methylation (DNAm) in the relationship of lead exposure with children's intelligence. DNAm was measured from children's blood DNA specimens, and mediation analysis was performed to identify DNAm biomarkers mediating the lead-intelligence relationship. We identified forty-three differentially methylated regions (DMRs), and two fragments (FAM50B1 and PTCHD3) significantly mediated the lead-intelligence relationship, with contribution rates of 30.36% (p = 0.010) and 60.36% (p < 0.001), respectively. In addition, blood lead levels (BLLs) lower than 100 μg/L still adversely affected children's IQs and DNAm of the two fragments. Our data suggests that DNAm mediates lead-associated cognitive delay in children and blood lead reference value for school-aged children (100 μg/L) should be revised, and the candidate biomarkers can be used in related neurological diseases in future.

Time for a change in blood lead reference value for Chinese children

In China, the first and also the latest version of national childhood lead exposure control guidelines was issued by the National Health Commission in 2006, when the reference value of high blood lead exposure was set at 100 μg/L and lead poisoning was set at 200 μg/L. Lead exposure levels have been decreasing in China over the last few decades, with almost all blood lead concentrations in children under 7 years of age being under 100 μg/L in non-industrial areas. However, lead concentrations lower than 100 μg/L in blood in children are associated with neurodevelopmental deficits. Thus, if the reference value remains at a high level, a large percent of children with exposure levels that are high but lower than the current reference value will be diagnosed as ‘safe’ and be ignored. Thus, we appeal that the reference value should be lowered according to local actual exposure level. A more stringent reference value would give care givers, doctors, communities, and officials more opportunities to take action earlier.

Control of Lead Sources in the United States, 1970-2017: Public Health Progress and Current Challenges to Eliminating Lead Exposure.

During the past 45 years, exposure to lead has declined dramatically in the United States. This sustained decline is measured by blood and environmental lead levels and achieved through control of lead sources, emission reductions, federal regulations, and applied public health efforts. Explore regulatory factors that contributed to the decrease in exposure to lead among the US population since 1970. We present historical information about the control of lead sources and the reduction of emissions through regulatory and selected applied public health efforts, which have contributed to decreases in lead exposure in the United States. Sources of lead exposure, exposure pathways, blood lead measurements, and special populations at risk are described. From 1976-1980 to 2015-2016, the geometric mean blood lead level (BLL) of the US population aged 1 to 74 years dropped from 12.8 to 0.82 μg/dL, a decline of 93.6%. Yet, an estimated 500 000 children aged 1 to 5 years have BLLs at or above the blood lead reference value of 5 μg/dL established by the Centers for Disease Control and Prevention. Low levels of exposure can lead to adverse health effects. There is no safe level of lead exposure, and child BLLs less than 10 μg/dL are known to adversely affect IQ and behavior. When the exposure source is known, approximately 95% of BLLs of 25 μg/dL or higher are work-related among US adults. Despite much progress in reducing exposure to lead in the United States, there are challenges to eliminating exposure. There are future challenges, particularly from the inequitable distribution of lead hazards among some communities. Maintaining federal, state, and local capacity to identify and respond to populations at high risk can help eliminate lead exposure as a public health problem. The results of this review show that the use of strong evidence-based programs and practices, as well as regulatory authority, can help control or eliminate lead hazards before children and adults are exposed.

Implications of the new Centers for Disease Control and Prevention blood lead reference value.

The Centers for Disease Control and Prevention recently established a new reference value (≥ 5 μg/dL) as the standard for identifying children with elevated blood lead levels (EBLs). At present, 535,000 US children aged 1 to 5 years (2.6%) are estimated to have EBLs according to the new standard, versus 0.8% according to the previous standard (≥ 10 μg/dL). Because EBLs signify the threshold for public health intervention, this new definition increases demands on lead poisoning prevention efforts. Primary prevention has been proven to reduce lead poisoning cases and is also cost effective; however, federal budget cuts threaten the existence of such programs. Protection for the highest-risk children necessitates a reinstatement of federal funding to previous levels.