Modeled Impacts of Drinking Water Pb Reduction Scenarios on Children's Exposures and Blood Lead Levels

Unveiling the occurrence and ecological risks of triclosan in surface water through meta-analysis

Triclosan, a widely used antimicrobial agent, is frequently detected in aquatic environments, prompting concerns about its toxic effects on aquatic species. Understanding its occurrence and ecological risks is crucial for mitigating triclosan contamination, formulating water quality criteria, and protecting aquatic organisms. This study systematically analyzed triclosan occurrence and ecological risks in surface water across China using the Risk Quotient methodology. A total of 139 and 134 data points were collected for triclosan concentrations and toxicities of aquatic organisms, respectively. Triclosan concentrations in surface water across China ranged from 0.06 to 612 ng/L. Higher triclosan levels were observed in Eastern China compared to Central and Western China, with the average concentration being 4.21- and 7.25-fold higher, respectively. Specifically, the Southeast Rivers Basin (132.98 ng/L) and Pearl River Basin (86.64 ng/L) exhibited maximum triclosan levels, 2.57-19.58 times higher than the other river basins. Further analysis revealed elevated triclosan concentrations in small rivers and surface water within residential areas, with values of 246.1 ng/L in Zhejiang, 86.64 ng/L in Guangdong, 67.58 ng/L in Jiangsu, and 127.99 ng/L in Beijing. Additionally, species sensitivity distribution curves indicated that algae was the most sensitive species to triclosan exposure, followed by invertebrates, while fish exhibited the highest tolerance. The Predicted No-Effect Concentration for the algae, invertebrates, fish, and combined aquatic species were determined to be 0.09, 2.95, 4.44, and 1.51 μg/L, respectively. The occurrence of triclosan in surface water across China did not pose widespread ecological risks. However, targeted monitoring and mitigation efforts are needed, especially in highly developed regions. This study provides crucial insights into the status of triclosan contaminations and risks in China and contributes valuable knowledge to global efforts aimed at safeguarding aquatic ecosystems.

Impact of orthophosphate on the solubility and properties of lead orthophosphate nanoparticles

Orthophosphate (PO4) is a commonly used corrosion control treatment to reduce lead (Pb) concentrations in drinking water. PO4 reduces Pb concentrations by forming relatively insoluble lead phosphate (Pb-PO4) minerals. In some cases, however, Pb-PO4 minerals have been observed to form nanoparticles, and if suspended in water, these nanoparticles can be mobile and reach consumer taps. Although recent research on Pb-PO4 particles has been performed, there remains a need to improve our understanding of the nature of Pb-PO4 nanoparticles. For that reason, Pb precipitation experiments were conducted to generate Pb-PO4 nanoparticles in bench scale studies for analysis. The study objective was to observe how pH, dissolved inorganic carbon (DIC), and PO4 impacted the properties of Pb-PO4 particles. Specifically, particle size, surface charge, mineralogy, and solubility were analysed. Hydrocerussite was precipitated when no PO4 was present, hydroxypyromorphite (Pb5(PO4)3OH) nanoparticles (<100 nm diameter) were precipitated when excess PO4 relative to Pb necessary to completely precipitate the mineral was present, and a mixture of the two minerals was precipitated when an insufficient amount of PO4 was present. Hydroxypyromorphite particles were less soluble than hydrocerussite by up to two orders of magnitude. The estimated K sp,OH of 10-66.87 in this work closely aligned with previous K sp,OH estimates that ranged from 10-66.77 to 10-62.79. Hydroxypyromorphite particles would not settle in water which was likely due to their small size and high negative charge. The mobility and size of these particles indicates that there are potential implications for such particulate Pb to remain suspended in water and thus be present in the tap water.

A U.S. Lead Exposure Hotspots Analysis

To identify U.S. lead exposure risk hotspots, we expanded upon geospatial statistical methods from a published Michigan case study. The evaluation of identified hotspots using five lead indices, based on housing age and sociodemographic data, showed moderate-to-substantial agreement with state-identified higher-risk locations from nine public health department reports (45-78%) and with hotspots of children's blood lead data from Michigan and Ohio (e.g., Cohen's kappa scores of 0.49-0.63). Applying geospatial cluster analysis and 80th-100th percentile methods to the lead indices, the number of U.S. census tracts ranged from ∼8% (intersection of indices) to ∼41% (combination of indices). Analyses of the number of children <6 years old living in those census tracts revealed the states (e.g., Illinois, Michigan, New Jersey, New York, Ohio, Pennsylvania, Massachusetts, California, Texas) and counties with highest potential lead exposure risk. Results support use of available lead indices as surrogates to identify locations in the absence of consistent, complete blood lead level (BLL) data across the United States. Ground-truthing with local knowledge, additional BLL data, and environmental data is needed to improve identification and analysis of lead exposure and BLL hotspots for interventions. While the science evolves, these screening results can inform "deeper dive" analyses for targeting lead actions.

Children's lead exposure in the U.S.: Application of a national-scale, probabilistic aggregate model with a focus on residential soil and dust lead (Pb) scenarios

Lead (Pb) exposures from soil and dust ingestion contribute to children's blood lead levels (BLLs) in the United States. The U.S. Environmental Protection Agency (EPA)'s Strategy to Reduce Lead Exposures and Disparities in U.S. Communities and the Federal Action Plan to Reduce Childhood Lead Exposure describe multi-pronged collaborative approaches. These include reducing multi-media lead exposures nationally using analytical tools such as EPA's Stochastic Human Exposure and Dose Simulation model for lead [SHEDS-Pb; formerly known as SHEDS-IEUBK (Integrated Exposure Uptake Biokinetic model)], which was initially developed and applied with a focus on children's drinking water exposures. In this study we applied SHEDS-Pb to determine what residential soil Pb and dust Pb concentrations (individually and their sum) can keep BLLs of potentially exposed young children in the general U.S. population below specified values, considering aggregate exposures from water, soil, dust, food, and air. We considered two age groups (1 to <2 years and 2 to <6 years), two BLL values (5 μg/dL and 3.5 μg/dL), and two population percentiles (95th and 97.5th). Sensitivity analyses were conducted using several alternative model inputs and data sets, yielding 15 scenarios summarized in the paper. Of those scenarios, we focused on ones with the most recent science and available data. Modeled soil Pb concentrations by age group, population percentile and reference BLL scenarios for the focus scenarios ranged from 70 ppm to 220 ppm; and modeled dust Pb concentrations ranged from 110 ppm to 240 ppm. These results are consistent with current soil and dust Pb concentrations in the U.S. general population and are lower than most of the current U.S. Federal standards. Estimated BLLs compared well with measured BLLs from CDC's NHANES 2009-2016 (0-27 % relative error for focus scenarios). This analysis can be used to inform EPA and other federal Pb efforts.

Removing Michigan's Lead Water Service Lines: Economic Savings, Health Benefits, And Improved Health Equity

Michigan's recently revised Lead and Copper Rule requires water utilities to inventory existing water service lines by 2025 and replace all lead-containing lines by 2041. This article summarizes a cost-benefit analysis using new inventory data on the number of lead service lines in the state, the projected cost of their replacement, and the estimated lifetime benefits from reduced lead exposure. Replacing 423,479 lead service lines would reduce lead exposure for 420,800 newborns and result in $3.24 billion in future benefits (compared with replacement costs of $1.33 billion). This would generate net savings of $1.91 billion and a societal return on investment of $2.44 per dollar invested. These estimates are conservative and include only quantified benefits for newborn children in Michigan for the period 2020-60. More than 153,100 of the children benefiting would be non-White (of whom 78,400 would be Black or African American), and 106,900 would be in households with incomes below the federal poverty level. Sensitivity analyses show that accelerating the replacement pace would increase the societal return on investment. This primary prevention-driven policy has the potential to reduce childhood lead exposure and improve health equity.

Extending Regulatory Biokinetic Lead Models towards Food Safety: Evaluation of Consumer Baby Food Contribution to Infant Blood Lead Levels and Variability

The U.S. Food and Drug Administration released proposed lead (Pb) action levels for foods intended for babies and young children in January 2023 based on the agency's interim reference value of 2.2 µg/day for dietary Pb. Since the 1980s, biokinetic models have estimated blood lead levels (BLLs) associated with environmental contamination, but their use in food safety assessment has been limited. We compared three recent biokinetic models (IEUBK Model, ICRP Model Version 5, and AALM) to develop insights on contributors to variability in potential exposures to Pb in consumer baby food products. While modest variation was observed for babies, the predictions trended to convergence for children aged 3 and older, approaching the U.S. FDA dietary conversion factor of 0.16 µg Pb/dL blood per µg Pb intake/day. We applied the IEUBK model in a probabilistic exposure assessment framework characterizing the distribution of Pb in soil, dust, water, and food intake in the United States. Soil and dust were the primary contributors to variance in infant BLLs, while food and water contributed <15% combined. Thus, reductions in upper-bound soil and dust concentrations will be necessary before achieving appreciable reductions in the frequency of BLLs greater than the BLRV of 3.5 µg/dL.

Endocytosis-Mediated Transport of Pb in Rat Blood Cells

Blood is an important reservoir for Pb storage in living organisms, and the storage of Pb in blood cells inhibits its discharge from blood. However, the mechanism and molecular targets of Pb entry and exit from blood cells have not been elucidated, which is the major barrier to reducing blood Pb levels in normal human beings. In this study, we explored the effect of Pb-binding proteins on blood Pb levels in rats at environmentally relevant concentrations (0.32 μg/g) by identifying the functions of Pb-binding proteins and validating them with inhibitors. The results showed that Pb-binding proteins in blood cells were mainly related to phagocytosis, while in plasma, they were mainly involved in the regulation of endopeptidase activity. Meanwhile, at the normal population Pb levels, endocytosis inhibitors, endopeptidase activity inhibitors, and coadministration of both can reduce the level of Pb in MEL (mouse erythroleukemia cells) cells by up to 50, 40, and 50%, respectively, while in rat blood, the reduction can reach up to 26, 13, and 32%, respectively. Collectively, these findings reveal that endocytosis increases blood Pb levels and provides a possible molecular target for Pb excretion at ambient concentrations.

A national survey of lead and other metal(loids) in residential drinking water in the United States

BACKGROUND

Exposure to lead (Pb), arsenic (As) and copper (Cu) may cause significant health issues including harmful neurological effects, cancer or organ damage. Determination of human exposure-relevant concentrations of these metal(loids) in drinking water, therefore, is critical.

OBJECTIVE

We sought to characterize exposure-relevant Pb, As, and Cu concentrations in drinking water collected from homes participating in the American Healthy Homes Survey II, a national survey that monitors the prevalence of Pb and related hazards in United States homes.

METHODS

Drinking water samples were collected from a national survey of 678 U.S. homes where children may live using an exposure-based composite sampling protocol. Relationships between metal(loid) concentration, water source and house age were evaluated.

RESULTS

18 of 678 (2.6%) of samples analyzed exceeded 5 µg Pb L-1 (Mean = 1.0 µg L-1). 1.5% of samples exceeded 10 µg As L-1 (Mean = 1.7 µg L-1) and 1,300 µg Cu L-1 (Mean = 125 µg L-1). Private well samples were more likely to exceed metal(loid) concentration thresholds than public water samples. Pb concentrations were correlated with Cu and Zn, indicative of brass as a common Pb source is samples analyzed.

SIGNIFICANCE

Results represent the largest national-scale effort to date to inform exposure risks to Pb, As, and Cu in drinking water in U.S. homes using an exposure-based composite sampling approach.

IMPACT STATEMENT

To date, there are no national-level estimates of Pb, As and Cu in US drinking water collected from household taps using an exposure-based sampling protocol. Therefore, assessing public health impacts from metal(loids) in drinking water remains challenging. Results presented in this study represent the largest effort to date to test for exposure-relevant concentrations of Pb, As and Cu in US household drinking water, providing a critical step toward improved understanding of metal(loid) exposure risk.

Effects of various Fe compounds on the bioavailability of Pb contained in orally ingested soils in mice: Mechanistic insights and health implications

Reducing lead (Pb) exposure via oral ingestion of contaminated soils is highly relevant for child health. Elevating dietary micronutrient iron (Fe) intake can reduce Pb oral bioavailability while being beneficial for child nutritional health. However, the practical performance of various Fe compounds was not assessed. Here, based on mouse bioassays, ten Fe compounds applied to diets (100-800 mg Fe kg^-1) reduced Pb oral relative bioavailability (RBA) in two soils variedly depending on Fe forms. EDTA-FeNa was most efficient, which reduced Pb-RBA in a soil from 79.5 ± 14.7 % to 23.1 ± 2.72 % (71 % lower) at 100 mg Fe kg^-1 in diet, more effective than other 9 compounds at equivalent or higher doses (3.6-68 % lower). When EDTA-FeNa, ferrous gluconate, ferric citrate, and ferrous bisglycinate were supplemented, Fe-Pb co-precipitation was not observed in the intestinal tract. EDTA-FeNa, ferrous gluconate, ferric citrate, and ferrous sulfate suppressed duodenal divalent metal transporter 1 (DMT1)mRNA relative expression similarly (27-68 % lower). In comparison, among ten compounds, EDTA-FeNa elevated Fe concentrations in mouse liver, kidney, and blood (1.50-2.69-fold higher) most efficiently, suggesting the most efficient Fe absorption that competed with Pb. In addition, EDTA was unique from other organic ligands, ingestion of which caused 12.0-fold higher Pb urinary excretion, decreasing Pb concentrations in mouse liver, kidney, and blood by 68-88 %. The two processes (Fe-Pb absorption competition and Pb urinary excretion with EDTA) interacted synergistically, leading to the lowest Pb absorption with EDTA-FeNa. The results provide evidence of a better inhibition of Pb absorption by EDTA-FeNa, highlighting that EDTA-FeNa may be the most appropriate supplement for intervention on human Pb exposure. Future researches are needed to assess the effectiveness of EDTA-FeNa for intervention on human Pb exposure.

Early phase effects of silicate and orthophosphate on lead (Pb) corrosion scale development and Pb release

Orthophosphate is widely used to control lead (Pb) release in drinking water distribution systems, but phosphorus addition is not sustainable. Alternative corrosion control treatments are needed, and sodium silicate is one possibility. Here, pre-corroded Pb coupons-with and without free chlorine-were used to examine early-phase corrosion scale development after silicate addition, with orthophosphate as a reference corrosion inhibitor. Scale development was evaluated in terms of total Pb release, phase transformation, electrochemical impedance, morphological changes, Pb dissolution kinetics, and short-term Pb-Cu galvanic corrosion. Elevated Pb release occurred for approximately one month after silicate addition, and total Pb release peaked at 1968.1 μg/L and 1176.9 μg/L from systems with and without free chlorine, respectively. In contrast, orthophosphate-treated coupons exhibited fewer, less pronounced spikes in Pb release. By day 354, the median total Pb release from orthophosphate-treated coupons with and without free chlorine had decreased to 3.7 and 5.0 μg/L, respectively, while the median total Pb release from corresponding silicate-treated coupons was much higher, at 44.9 μg/L and 34.3 μg/L. Calcium lead apatite (Ca_0.56Pb_3.77(PO₄)₃OH_0.67) was identified in orthophosphate-treated scales, with hydroxylpyromorphite (Pb₅(PO₄)₃OH) present in the absence of free chlorine. Plattnerite occurred on coupons in all chlorinated systems. Pb silicate compounds were not detected, but Ca₂SiO₄ and Na₂Ca₂(SiO₃)₃ were identified by X-ray powder diffraction. The charge transfer: film resistance ratio characterizing the orthophosphate-treated coupons decreased slowly while that of the silicate-treated coupons increased after silicate was added. These variations suggest orthophosphate provided better corrosion control than silicate did. Silicate treatment generally caused degradation of the top Pb scale layer, resulting in elevated Pb release, while orthophosphate encouraged the growth of more structured, generally thicker, corrosion scales that were effective in limiting Pb release.

Lead contamination of public drinking water and academic achievements among children in Massachusetts: a panel study

Background

Public drinking water can be an important source exposure to lead, which can affect children’s cognitive development and academic performance. Few studies have looked at the impact of lead exposures from community water supplies or their impact on school achievements. We examined the association between annual community water lead levels (WLLs) and children’s academic performances at the school district level.

Methods

We matched the 90th percentile WLLs with the grade 3–8 standardized test scores from the Stanford Education Data Archive on Geographic School Districts by geographic location and year. We used multivariate linear regression and adjusted for urbanicity, race, socioeconomic characteristics, school district, grade, and year. We also explored potential effect measure modifications and lag effects.

Results

After adjusting for potential confounders, a 5 μg/L increase in 90th percentile WLLs in a GSD was associated with a 0.00684 [0.00021, 0.01348] standard deviation decrease in the average math test score in the same year. No association was found for English Language Arts.

Conclusions

We found an association between the annual fluctuation of WLLs and math test scores in Massachusetts school districts, after adjusting for confounding by urbanicity, race, socioeconomic factors, school district, grade, and year. The implications of a detectable effect of WLLs on academic performance even at the modest levels evident in MA are significant and timely. Persistent efforts should be made to further reduce lead in drinking water.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-12474-1.

Rapid and simple lead service line detection screening protocol using water sampling

Many water systems are challenged with uncertainty regarding service line material type. This work investigated using a simple drinking water flushed sampling approach and a more complicated and invasive sequential profile sampling approach to predict whether homes had an existing lead service line (LSL). Homes that never had an LSL (control groups) and homes with LSLs (study groups) in two communities having different degrees of corrosion control were sampled. Using control groups' results, community-specific "threshold" lead levels were determined and compared to results from study groups. The flushed sampling maximum lead concentration (FMC) of lead accurately predicted 100% and 60% of LSL sites for the community with poor and good corrosion control, respectively. The weighted average sequential profile lead concentration (WASLC) increased the 40% not identified as LSL sites by fully flushed samples to 100%. The WASLC closely followed by the maximum sequential profile lead concentration were most reliable in identifying LSLs.

A probabilistic toxicokinetic modeling approach to the assessment of the impact of daily variations of lead concentrations in tap water from schools and daycares on blood lead levels in children

The aim of this study was to assess the impact of exposure to tap water lead concentration ([Pb]_TW) occurring in schools or daycares on blood lead level (BLL) of attending children. Given the potentially wide variations in space and time of ([Pb]_TW) documented in the literature, a simple probabilistic toxicokinetic (STK) model that allows the simulation of the time-varying evolution of BLL in response to these variations was developed. Thus, basic toxicokinetic equations were assembled to simulate BLL in a typical infant, toddler and pupil. The STK model's steady-state BLL predictions showed good correspondence when validated against Integrated Exposure and Uptake BioKinetic model predictions for comparable [Pb]_TW values. Exposures to three distributions of [Pb]_TW in specific sets of Canadian schools and daycares documented in the scientific literature were simulated probabilistically with Monte Carlo simulations. For the highest distribution of [Pb]_TW simulated (median, 90th percentile = 24, 412 μg/L), average annual BLL (median, 97.5th percentile) varies between 1.5 and 6.4 μg/dL in infant and 1.1 and 3 μg/dL in pupils. Toddler's results were midway between those from the infants and pupils. Under this exposure scenario, the infant may present BLL > 5 μg/dL for a significant number of days over the course of the academic year (median; 97.5th: 17; 227 days). However, peak exposure may remain unnoticed if rare and drowned out by the background BLL. In conclusion, even if they may be sparse, peak exposure episodes to [Pb]_TW in schools and daycares may suffice to increased BLL in attending individuals. This finding emphasizes the need for further characterization of [Pb]_TW in schools and daycares in order to identify potentially problematic institutions and therefore avoid undesirable exposures for the children attending them.

Lead service line identification: A review of strategies and approaches

Lead service lines (LSLs) represent the greatest source of lead in drinking water. Identifying the locations of LSLs can be challenging, and recent service line (SL) material surveys in Michigan, Illinois, Wisconsin, and Indiana found that on average the materials making up 16% of SLs in these states are unknown and may be lead. Given the large number of possible LSLs in the United States, new and pending regulatory requirements, LSL replacement costs, associated lead exposure risks, and the public's desire to reduce lead exposure, there is a need to rapidly and cost-effectively identify where LSLs are located, on public and private property. This review summarizes current industry LSL identification methods, including records screening, basic visual examination of indoor plumbing, water sampling, excavation, and predictive data analyses. A qualitative comparison of method cost, accuracy, disturbance, and other impacts is provided as a starting point for utilities that are developing a feasible approach for their specific needs/constraints. Lastly, an example stepwise approach to identify unknown SL materials is proposed.

Chronic developmental lead exposure increases μ-opiate receptor levels in the adolescent rat brain

Childhood lead (Pb2+) intoxication is a global public health problem best known for producing deficits in learning and poor school performance. Human and preclinical studies have suggested an association between childhood Pb2+ intoxication and proclivity to substance abuse and delinquent behavior. While environmental factors have been implicated in opioid addiction, less is known about the role of exposure to environmental pollutants on the brain opioid system. Opioid receptors are involved in the biological effects of opioids and other drugs of abuse. In this study, we examine the effect of chronic developmental Pb2+ exposure (1500 ppm in the diet) on μ-opioid receptor (MOR) levels in the rat brain using [3H]-d-Ala2-MePhe4-Gly-ol5 enkephalin ([3H]-DAMGO) quantitative receptor autoradiography at different developmental stages (juvenile, early-adolescent, late adolescent and adult) in male and female rats. Our results indicate that chronic developmental Pb2+ exposure increases the levels of [3H]-DAMGO specific binding to MOR in juvenile and early adolescent Pb2+-exposed male and female rat brain with no changes in late-adolescent (PN50) and minor changes in Pb2+-exposed adult male rats (PN120). Specifically, at PN14, Pb2+-exposed males had an increase in MOR binding in the lateral posthalamic nuclei (LPTN), and Pb2+-exposed females had increased MOR binding in LPTN, medial thalamus, and hypothalamus. At PN28, Pb2+-exposed males had increased MOR levels in the striatum, stria medullaris of the thalamus, LPTN, medial thalamus, and basolateral amygdala, while Pb2+-exposed females showed an increase in nucleus accumbens core, LPTN, and medial thalamus. No changes were detected in any brain region of male and female rats at PN50, and at PN120 there was a decrease in MOR binding of Pb2+-exposed males in the medial thalamus. Our findings demonstrate age and gender specific effects of MOR levels in the rat brain as a result of chronic developmental Pb2+ exposure. These results indicate that the major changes in brain MOR levels were during pre-adolescence and early adolescence, a developmental period in which there is higher engagement in reward and drug-seeking behaviors in humans. In summary, we show that chronic exposure to Pb2+, an ubiquitous and well-known environmental contaminant and neurotoxicant, alters MOR levels in brain regions associated with addiction circuits in the adolescent period, these findings have important implications for opioid drug use and abuse.

Variability and sampling of lead (Pb) in drinking water: Assessing potential human exposure depends on the sampling protocol

Lead (Pb) in drinking water has re-emerged as a modern public health threat which can vary widely in space and in time (i.e., between homes, within homes and even at the same tap over time). Spatial and temporal water Pb variability in buildings is the combined result of water chemistry, hydraulics, Pb plumbing materials and water use patterns. This makes it challenging to obtain meaningful water Pb data with which to estimate potential exposure to residents. The objectives of this review paper are to describe the root causes of intrinsic Pb variability in drinking water, which in turn impacts the numerous existing water sampling protocols for Pb. Such knowledge can assist the public health community, the drinking water industry, and other interested groups to interpret/compare existing drinking water Pb data, develop appropriate sampling protocols to answer specific questions relating to Pb in water, and understand potential exposure to Pb-contaminated water. Overall, review of the literature indicated that drinking water sampling for Pb assessment can serve many purposes. Regulatory compliance sampling protocols are useful in assessing community-wide compliance with a water Pb regulatory standard by typically employing practical single samples. More complex multi-sample protocols are useful for comprehensive Pb plumbing source determination (e.g., Pb service line, Pb brass faucet, Pb solder joint) or Pb form identification (i.e., particulate Pb release) in buildings. Exposure assessment sampling can employ cumulative water samples that directly capture an approximate average water Pb concentration over a prolonged period of normal household water use. Exposure assessment may conceivably also employ frequent random single samples, but this approach warrants further investigation. Each protocol has a specific use answering one or more questions relevant to Pb in water. In order to establish statistical correlations to blood Pb measurements or to predict blood Pb levels from existing datasets, the suitability of available drinking water Pb datasets in representing water Pb exposure needs to be understood and the uncertainties need to be characterized.