Trends and variability in blood lead concentrations among US children and adolescents

Hidden toxins: bathtubs as a potential source of lead exposure in children

Exposure to lead (Pb) remains a serious health concern for children in the United States, particularly those residing in deteriorating housing. While some sources of Pb such as deteriorating paint and lead waterworks are relatively well understood and widely known, other sources remain hidden. One potential hidden source is bathtubs. In this experiment, water resting in a leaded bathtub was tested over a course of 60 min to determine the extent of metal leaching from the tub to the water. Lead levels in the water increased from 6.8 μg/L at baseline to 13 μg/L after resting in the tub for 60 min. Further research is needed to understand if this is typical, the contributing factors, and clinical significance of this finding.

Early childhood lead exposure and adolescent heart rate variability: A longitudinal cohort study

Lead is a known neurotoxicant with many detrimental health effects, including neurocognitive deficits and cardiovascular and metabolic disorders. However, few studies have tested the association between lead exposure and the physiological stress response, which in and of itself may act as a precursor to and/or underlying mechanism of detrimental health outcomes. The purpose of this study was to examine the influence of early childhood and early adolescent low-level lead exposure on early adolescent heart rate variability, a widely-used measure of physiological stress. Participants were 408 children from Jintan, China for whom blood lead levels were measured between 3 and 5 years (early childhood) and again at 12 years (early adolescence). Heart rate variability was assessed at 12 years while participants underwent an induced stress task utilizing the ratio of low to high frequency (LF/HF) ECG measures. Mean blood lead levels in the cohort were 6.63 mcg/dl and 3.10 mcg/dl at 3-5 years and 12 years, respectively. Blood lead levels at 3-5 years of age (β 0.06, p = 0.027), but not at age 12 (β -0.05, p = 0.465), were significantly associated with LF/HF measures while controlling for multiple sociodemographic variables, potentially reflecting a dysregulated stress response with a shift towards sympathetic dominance. These findings suggest that early childhood lead exposure may have a detrimental influence on early adolescent autonomic responses to acute stress, which holds implications for cardiovascular health and overall growth and development.

Children's exposure to environmental lead: A review of potential sources, blood levels, and methods used to reduce exposure

Lead has been used for thousands of years in different anthropogenic activities thanks to its unique properties that allow for many applications such as the manufacturing of drinking water pipes and its use as additives to gasoline and paint. However, knowledge of the adverse impacts of lead on human health has led to its banning from several of its applications, with the main goal of reducing environmental pollution and protecting human health. Human exposure to lead has been linked to different sources of contamination, resulting in high blood lead levels (BLLs) and adverse health implications, primarily in exposed children. Here, we present a summary of a literature review on potential lead sources affecting blood levels and on the different approaches used to reduce human exposure. The findings show a combination of different research approaches, which include the use of inspectors to identify problematic areas in homes, collection and analysis of environmental samples, different lead detection methods (e.g. smart phone applications to identify the presence of lead and mass spectrometry techniques). Although not always the most effective way to predict BLLs in children, linear and non-linear regression models have been used to link BLLs and environmental lead. However, multiple regressions and complex modelling systems would be ideal, especially when seeking results in support of decision-making processes. Overall, lead remains a pollutant of concern and many children are still exposed to it through environmental and drinking water sources. To reduce exposure to lead through source apportionment methods, recent technological advances using high-precision lead stable isotope ratios measured on multi-collector induced coupled plasma mass spectrometry (MC-ICP-MS) instruments have created a new direction for identifying and then eliminating prevalent lead sources associated with high BLLs.

Pervasive structural racism in environmental epidemiology

BACKGROUND

Epistemological biases in environmental epidemiology prevent the full understanding of how racism's societal impacts directly influence health outcomes. With the ability to focus on "place" and the totality of environmental exposures, environmental epidemiologists have an important opportunity to advance the field by proactively investigating the structural racist forces that drive disparities in health.

OBJECTIVE

This commentary illustrates how environmental epidemiology has ignored racism for too long. Some examples from environmental health and male infertility are used to illustrate how failing to address racism neglects the health of entire populations.

DISCUSSION

While research on environmental justice has attended to the structural sources of environmental racism, this work has not been fully integrated into the mainstream of environmental epidemiology. Epidemiology's dominant paradigm that reduces race to a mere data point avoids the social dimensions of health and thus fails to improve population health for all. Failing to include populations who are Black, Indigenous, and people of color (BIPOC) in health research means researchers actually know very little about the effect of environmental contaminants on a range of population health outcomes. This commentary offers different practical solutions, such as naming racism in research, including BIPOC in leadership positions, mandating requirements for discussing "race", conducting far more holistic analyses, increasing community participation in research, and improving racism training, to address the myriad of ways in which structural racism permeates environmental epidemiology questions, methods, results and impacts.

Trends in Blood Lead Levels in the U.S. From 1999 to 2016

INTRODUCTION

Trends in blood lead levels in the same birth cohort (generation) are necessary to identify the lead load in the population. This analysis uses a nationally representative sample to investigate the trends in blood lead levels from 1999 to 2016 by birth cohort and to revisit the association between blood lead levels and age.

METHODS

Data from the 1996 to 2016 National Health and Nutrition Examination Surveys were used to describe the distribution of blood lead levels. Trends in blood lead levels were analyzed using joinpoint regression models. Association of blood lead levels with age was conducted with both cross-sectional and birth cohort analysis. Analyses were conducted in 2020.

RESULTS

In total, 68,877 participants were included (weighted mean age=38.4 years, 50.6% female). From 1999 to 2016, the geometric mean of blood lead levels decreased from 1.68 µg/dL (95% CI=1.63, 1.74) to 0.82 µg/dL (95% CI=0.77, 0.87). The annual percentage change estimated by the joinpoint model was -4.26% (p<0.05). The associations between blood lead levels and age were "U"-shaped by cross-sectional analysis, with higher risks for the lowest and highest ages. However, by birth cohort analysis the blood lead levels declined monotonically with age. The joinpoint analysis indicated the inflection point of age 13-17 years and statistically significant differences in decline slopes before and after this age.

CONCLUSIONS

In this nationally representative study of the U.S. population, estimates of blood lead levels showed an overall decrease from 1999 to 2016. Blood lead levels are highest in childhood.

Exploring persistent racial/ethnic disparities in lead exposure among American children aged 1-5 years: results from NHANES 1999-2016

OBJECTIVE

The aim of this study was to determine whether long-standing racial disparities in lead exposure still exists for children age 1-5 years old. We examined if blood lead levels were higher among non-Hispanic Black children and others compared to non-Hispanic White children.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) from 1999-2016 were used. Geometric mean blood lead levels (BLLs) were compared by race/ethnicity using log-transformed simple linear regression. Associations between race and elevated BLL were assessed using weighted Chi-square tests. Log-transformed multiple weighted linear regression was used to assess what factors affected BLLs.

RESULTS

A total of 6772 children were included in this study. In 1999-2000, the geometric mean BLL for non-Hispanic Black children was 3.08 μg/dL, compared to 2.03 μg/dL for non-Hispanic White children (p = 0.01). The difference in geometric mean BLL between non-Hispanic Black children and non-Hispanic White children continued to be statistically significant in later years (all p < 0.05) until 2015-2016 (0.89 μg/dL vs 0.74 μg/dL, p = 0.17). Log-transformed linear regression showed that being non-Hispanic Black and having low family income were independently associated with higher BLL.

CONCLUSION

Although lead exposure in the general population continued to decline for all racial/ethnic groups, non-Hispanic Black children still had higher BLL than non-Hispanic White children. In more recent years, the racial/ethnic gap was lesser but persisted. Racial/ethnic disparity in childhood BLL could be partially explained by socio-economic factors.

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.

Toxic structures: Speculation and lead exposure in Detroit's single-family rental market

Foreclosure sales permitted investors to purchase large volumes of low-cost residential properties after the last financial crisis, reshaping patterns of property ownership in low-income housing markets across the US. This study links post-foreclosure property acquisitions by investor landlords to subsequent lead poisoning cases among children under age six living in Detroit, Michigan. We find that the odds of exhibiting elevated blood lead levels (≥5 μg/dL) are higher for children living in investor-owned homes purchased through tax foreclosure sale. These findings highlight the potential for property speculation in post-foreclosure housing markets to exacerbate severe and racialized burdens of excess lead toxicity in low-income communities.

Developmental exposure to Pb2+ induces transgenerational changes to zebrafish brain transcriptome

Lead (Pb2+) is a major public health hazard for urban children, with profound and well-characterized developmental and behavioral implications across the lifespan. The ability of early Pb2+ exposure to induce epigenetic changes is well-established, suggesting that Pb2+-induced neurobehavioral deficits may be heritable across generations. Understanding the long-term and multigenerational repercussions of lead exposure is crucial for clarifying both the genotypic alterations behind these behavioral outcomes and the potential mechanism of heritability. To study this, zebrafish (Danio rerio) embryos (<2 h post fertilization; EK strain) were exposed for 24 h to waterborne Pb2+ at a concentration of 10 μM. This exposed F0 generation was raised to adulthood and spawned to produce the F1 generation, which was subsequently spawned to produce the F2 generation. Previous avoidance conditioning studies determined that a 10 μM Pb2+ dose resulted in learning impairments persisting through the F2 generation. RNA was extracted from control- and 10 μM Pb2+-lineage F2 brains, (n = 10 for each group), sequenced, and transcript expression was quantified utilizing Quant-Seq. 648 genes were differentially expressed in the brains of F2 lead-lineage fish versus F2 control-lineage fish. Pathway analysis revealed altered genes in processes including synaptic function and plasticity, neurogenesis, endocrine homeostasis, and epigenetic modification, all of which are implicated in lead-induced neurobehavioral deficits and/or their inheritance. These data will inform future investigations to elucidate the mechanism of adult-onset and transgenerational health effects of developmental lead exposure.

Nutrition Monitoring of Children Aged Birth to 24 Mo (B-24): Data Collection and Findings from the NHANES

The first 2 y of life are characterized by several transitions that can affect growth, development, and eating patterns long term. These include a shift from a primarily milk-based eating pattern to introduction of complementary foods at ∼4-6 mo of age, and passage to family-meal patterns in toddler years. Recognizing the importance of this critical period, the Dietary Guidelines for Americans from 2020 onwards will include guidance for children aged birth to 24 mo (B-24). Few large-scale surveys provide comprehensive, nationally representative, quantitative, recent data on infant and toddler nutrition in the United States. The continuous NHANES has collected data relevant to this initiative since 1999 using standardized interview and examination protocols. These include data on infant feeding practices, dietary intakes (foods, beverages, and supplements), anthropometry, and blood-based nutritional status on nationally representative samples of infants and toddlers. NHANES data can be used to describe large group-level consumption patterns, as well as trends over time for B-24 children overall, and by demographic groups (e.g., race-ethnic and income groups). In addition, NHANES data can be analyzed to examine adherence to nutrition-related recommendations, such as those from the American Academy of Pediatrics (AAP), and to track Healthy People 2020 objectives. This paper provides an update on NHANES nutrition monitoring in B-24 children since our previous publication (which provided details through NHANES 2009-2010) and describes data collection since 2010 and plans for upcoming cycles. It also describes key NHANES-based findings published in the last 5 y on infant feeding practices, dietary intakes and supplement use, and nutritional status of US children aged <2 y. Findings related to existing recommendations, such as from the AAP, are presented when available. This information can inform researchers and policymakers on the state of nutrition in the US B-24 population and its subgroups of interest.

Sequential drinking water sampling as a tool for evaluating lead in flint, Michigan

Eliminating the sources of human lead exposure is an ongoing public health goal. Identifying the make-up of household plumbing and service line material type is important for many reasons including understanding lead release sources and mechanisms, targeting locations for lead service line (LSL) removal, and assessing the effectiveness of lead remediation strategies. As part of the response to Flint, Michigan's drinking water lead public health crisis, a return to their original drinking water source (Lake Huron) and an increase in orthophosphate dose was implemented in late 2015. In 2016, EPA performed multiple rounds of sequential or "profiling" water sampling to evaluate corrosion control effectiveness and identify lead sources in homes and service lines, as well as to evaluate the effectiveness of corrosion control treatment with time on the different plumbing components. The results showed that lead levels, including high lead levels likely associated with particles, decreased with time in homes sampled during the 11-month evaluation period. Although sequential sampling indicated that brass fittings, brass fixtures, and galvanized pipes were lead sources, LSLs were the greatest source of lead when present. Following the removal of LSLs, the total mass of lead contributed to the drinking water decreased by 86% on average.

Blood Lead Levels Among Resettled Refugee Children in Select US States, 2010-2014

BACKGROUND

Elevated blood lead levels (EBLLs; ≥5 µg/dL) are more prevalent among refugee children resettled in the United States than the general US population and contribute to permanent health and neurodevelopmental problems. The Centers for Disease Control and Prevention recommends screening of refugee children aged 6 months to 16 years on arrival in the United States and retesting those aged 6 months to 6 years between 3- and 6-months postarrival.

METHODS

We analyzed EBLL prevalence among refugee children aged 6 months to 16 years who received a domestic refugee medical examination between January 1, 2010 and September 30, 2014. We assessed EBLL prevalence by predeparture examination country and, among children rescreened 3 to 6 months after initial testing, we assessed EBLL changes during follow-up screening.

RESULTS

Twelve sites provided data on 27 284 children representing nearly 25% of refugee children resettling during the time period of this analysis. The EBLL prevalence during initial testing was 19.3%. EBLL was associated with younger age, male sex, and overseas examination country. Among 1121 children from 5 sites with available follow-up test results, EBLL prevalence was 22.7%; higher follow-up BLLs were associated with younger age and predeparture examination country.

CONCLUSIONS

EBLL decreased over the time period of our analysis in this population of refugee children. Refugee children may be exposed to lead before and after resettlement to the United States. Efforts to identify incoming refugee populations at high risk for EBLL can inform prevention efforts both domestically and overseas.

Associations between environmental heavy metal exposure and childhood asthma: A population-based study

BACKGROUND/PURPOSE

The health risks of environmental heavy metals have been of concern are well known. The greater likelihood of heavy metal contamination in the physical environment increases the risk of asthma, especially in children. This cross-sectional, population-based study sought to investigate associations between heavy metal exposure and childhood asthma or wheezing.

METHODS

Data from 5866 subjects, stratified into age groups of 2-5, 6-11, and 12-15 years, from the National Health and Nutrition Examination Survey 2007-2012 conducted by the Centers for Disease Control and Prevention were analyzed retrospectively. The primary outcome was active asthma. Variables included demographics, anthropometric, and clinical data. Univariate and multivariate logistic regression analyses were used to identify associations between blood heavy metal concentrations and adjusted odds (aORs) of active asthma.

RESULTS

Higher concentration of blood lead was associated with higher adjusted odds of having asthma (aOR = 1.08, 95% CI = 1.00-1.16), but no significant effect was shown for current wheezing or whistling. Age-stratified analysis showed that higher blood lead concentration was associated with higher risk for active asthma (aOR = 1.24, 95% CI = 1.08-1.42) and current wheezing or whistling (aOR = 1.19, 95% CI = 1.04-1.38) in the 6-11 years age group, while higher blood mercury concentration was associated with lower risk of current wheezing or whistling (aOR = 0.95, 95% CI = 0.90-0.99). The medium concentration of blood lead was associated with decreased risks of current wheezing or whistling (aOR = 0.54, 95% CI = 0.30-0.96) in the 2-5 years age group.

CONCLUSION

Higher concentrations of blood lead are associated with higher odds of asthma in children aged 2-15 years.

Accessing Disadvantaged Pregnant Women in Houston, Texas, and Characterizing Biomarkers of Metal Exposure: A Feasibility Study

Communities of color or low socioeconomic status are disproportionately affected by metal exposure given spatial variability of the ambient levels of these contaminants. Despite this, there is little research characterizing metal concentrations in blood among disadvantaged populations in the U.S., especially among pregnant women who are particularly vulnerable and difficult to access. Thus, we conducted a pilot study among disadvantaged pregnant women in Houston, Texas to assess willingness to participate in key activities of an epidemiologic study and characterize exposures to 16 metals. Thirty-one women attending a Medicaid-serving prenatal clinic were included in this pilot study and completed an interviewer-administered questionnaire. We obtained and measured metal compounds in whole blood samples for 22 of these women during third-trimester prenatal visits. Median whole blood concentrations of Ni, As, Cd, and Pb were 27, 1.4, 0.6, and 6.3 µg/L, respectively. Most women were willing to participate in critical aspects of a research study, including wearing a personal air-sampling badge for 2–3 days (87.1%), receiving ultrasounds (83.9%), and providing blood draws (64.5%). Despite the small sample, our results provide evidence of women’s metal exposure and their willingness to participate in future research studies to elucidate exposure pathways and explore related health effects experienced among this population of disadvantaged pregnant women.

Continual Decrease in Blood Lead Level in Americans: United States National Health Nutrition and Examination Survey 1999-2014

BACKGROUND

Lead is toxic and affects neurodevelopment in children even at low levels. There has been a long-term effort in the United States to reduce exposure to lead in the environment. We studied the latest US population blood lead levels and analyzed its trend.

METHOD

Blood lead levels in 63,890 participants of the National Health Nutrition and Examination Survey 1999-2014 were analyzed using SPSS Complex Samples v22.0 (IBM Corp, Armonk, NY).

RESULTS

Mean blood lead levels and 95% confidence intervals (CIs) were 1.65 μg/dL (1.62-1.68), 1.44 μg/dL (1.42-1.47), 1.43 μg/dL (1.40-1.45), 1.29 μg/dL (1.27-1.32), 1.27 μg/dL (1.25-1.29), 1.12 μg/dL (1.10-1.14), 0.97 μg/dL (0.95-0.99), and 0.84 μg/dL (0.82-0.86) in 1999-2000, 2001-2002, 2003-2004, 2005-2006, 2007-2008, 2009-2010, 2011-2012, and 2013-2014, respectively. Blood lead levels decreased significantly (P <.001), and the trend remained significant when stratified by age, gender, ethnicity, and pregnancy status (P <.05). Estimated percentages of children with blood lead level ≥5 μg/dL were 9.9% (95% CI, 7.5-12.9), 7.4% (95% CI, 5.9-9.4), 5.3% (95% CI, 4.1-6.9), 2.9% (95% CI, 2.1-3.9), 3.1% (95% CI, 2.0-4.8), 2.1% (95% CI, 1.5-3.1), 2.0% (95% CI, 1.0-3.6), and 0.5% (95% CI, 0.3-1.0) in 1999-2000, 2001-2002, 2003-2004, 2005-2006, 2007-2008, 2009-2010, 2011-2012, and 2013-2014, respectively. The decreasing trend was significant (P <.05). In children aged 1 to 5 years in the National Health Nutrition and Examination Survey 2011-2014, the estimated 97.5 percentile of blood lead level was 3.48 μg/dL.

CONCLUSIONS

Blood lead levels have been decreasing in the US population. The reference level also should decrease. It is still important to monitor blood lead levels in the population, especially among pregnant women and children aged 1 to 5 years.

A Case Study of Environmental Injustice: The Failure in Flint

The failure by the city of Flint, Michigan to properly treat its municipal water system after a change in the source of water, has resulted in elevated lead levels in the city’s water and an increase in city children’s blood lead levels. Lead exposure in young children can lead to decrements in intelligence, development, behavior, attention and other neurological functions. This lack of ability to provide safe drinking water represents a failure to protect the public’s health at various governmental levels. This article describes how the tragedy happened, how low-income and minority populations are at particularly high risk for lead exposure and environmental injustice, and ways that we can move forward to prevent childhood lead exposure and lead poisoning, as well as prevent future Flint-like exposure events from occurring. Control of the manufacture and use of toxic chemicals to prevent adverse exposure to these substances is also discussed. Environmental injustice occurred throughout the Flint water contamination incident and there are lessons we can all learn from this debacle to move forward in promoting environmental justice.

Trends and variability in blood lead concentrations among US adults aged 20-64 years and senior citizens aged ≥65 years

Using data from National Health and Nutrition Examination Survey for the period 2003-2012, the objective of this study was to evaluate trends in blood lead levels (BLL) among adults aged 20-64 years (adults) and seniors aged ≥65 years (seniors). In addition, the contribution of other factors like gender, race/ethnicity, smoking, and exposure to secondhand smoke at home in explaining variability in BLL was also evaluated by fitting regression models with log10 transformed values of BLL as dependent variables. BLL decreased over 2003-2012 (p < 0.01). Irrespective of gender, race/ethnicity, and smoking status, seniors were found to have higher BLL than adults. Based on the magnitude of differences between the 5th and 95th percentiles, variability in the levels of blood lead was found to be substantially higher among seniors than among adults. Males had statistically significantly higher adjusted BLL than females (2.32 vs. 1.76 μg/dL for seniors, p < 0.01 and 1.66 vs. 1.13 μg/dL for adults, p < 0.01). Non-Hispanic whites had statistically significantly lower adjusted BLL than non-Hispanic blacks (1.99 vs. 2.42 μg/dL for seniors, p < 0.01 and 1.22 vs. 1.42 μg/dL for adults, p < 0.01). When compared with non-smokers, smokers had statistically significantly higher BLL (2.19 vs. 1.86 μg/dL for seniors, p < 0.01 and 1.54 vs. 1.22 μg/dL for adults, p < 0.01). Non-obese had statistically significantly higher BLL than obese individuals (2.11 vs. 1.93 μg/dL for seniors, p < 0.01 and 1.48 vs. 1.27 μg/dL for adults, p < 0.01). Exposure to secondhand smoke at home (SHS) was associated with statistically significantly higher BLL than when there was no exposure to SHS (β = 0.0683, p = 0.03 for seniors; β = 0.034, p = 0.034, p < 0.01 for adults).

Children's Blood Lead Seasonality in Flint, Michigan (USA), and Soil-Sourced Lead Hazard Risks

In Flint; MI; USA; a public health crisis resulted from the switching of the water supply from Lake Huron to a more corrosive source from the Flint River in April 2014; which caused lead to leach from water lines. Between 2010 and 2015; Flint area children’s average blood lead patterns display consistent peaks in the third quarter of the year. The third quarter blood lead peaks displayed a declining trend between 2010 and 2013; then rose abruptly between the third quarters of 2013 from 3.6% blood lead levels ≥5 µg/dL to a peak of about 7% in the third quarter of 2014; an increase of approximately 50%. The percentage of blood lead level ≥5 µg/dL in the first quarter of 2015 then dropped to 2.3%; which was the same percentage as the first quarter of 2014 (prior to the Flint River water source change). The Flint quarterly blood lead level peak then rose to about 6% blood lead levels ≥ 5 µg/dL in the third quarter of 2015; and then declined to about 2.5% in the fourth quarter of 2015. Soil lead data collected by Edible Flint food collaborative reveal generally higher soil lead values in the metropolitan center for Flint; with lower values in the outskirts of the city. The questions that are not being asked is why did children’s blood lead levels display a seasonal blood lead pattern before the introduction of the new water supply in Flint; and what are the implications of these seasonal blood lead patterns? Based upon previous findings in Detroit and other North American cities we infer that resuspension to the air of lead in the form of dust from lead contaminated soils in Flint appears to be a persistent contribution to lead exposure of Flint children even before the change in the water supply from Lake Huron to the Flint River.