Estimation of leaded (Pb) gasoline's continuing material and health impacts on 90 US urbanized areas

Significant lead isotope 'fractionation' in maize records plant lead uptake, transfer, and detoxification mechanisms

Lead isotope analysis is the main method to trace the sources and cycling of Pb in the biosphere system. The linchpin of such application hinges on the assumption that there is negligible or no biologically mediated isotopic fractionation of Pb occurs in the environment. However, recent measurements by high-precision multi-collector mass spectrometry revealed that biological isotope fractionation of heavy mass elements is a prevalent phenomenon. This study shows that compared with the Pb sources, the maize plant (Zea mays L.) organs exhibit a wider range of Pb isotope compositions and a depletion of radioactive Pb isotopes (206Pb, 207Pb, and 208Pb). Moreover, three independent studies consistently indicate that the 206Pb/207Pb ratio of maize organs varies as root/leaf > stem/grain, reflecting a continuous loss of light Pb isotopes during transportation. The conventional wisdom fails to account for these phenomena, suggesting that maize may undergo Pb isotope fractionation during the absorption and transportation of Pb. However, compared with other non-traditional metal isotopes, Pb isotope exhibits a more significant fractionation magnitude. We tentatively attribute this fractionation to the Pb tolerance mechanism of maize and its selective absorption of various forms of Pb, which requires further research to validate. Findings from this study mandate caution in future Pb source tracing in plants using Pb isotope methods and open up applications in using Pb isotopic fractionation to track Pb uptake and transfer pathways and decipher the associated detoxification mechanisms in plants.

Evaluating the portable X-ray fluorescence reliability for metal(loid)s detection and soil contamination status

Marginalized communities experience barriers that can prevent soil monitoring efforts and knowledge transfer. To address this challenge, this study compared two analytical methods: portable X-ray fluorescence spectroscopy (pXRF, less time, cost) and inductively coupled plasma mass spectrometry (ICP-MS, "gold standard"). Surface soil samples were collected from residential sites in Arizona, USA (N = 124) and public areas in Troy, New York, USA (N = 33). Soil preparation differed between groups to account for community practice. Statistical calculations were conducted, paired t test, Bland-Altman plot, and a two-way ANOVA indicated no significant difference for As, Ba, Ca, Cu, Mn, Pb, and Zn concentrations except for Ba in the t test. Iron, Ni, Cr, and K were statistically different for Arizona soils and V, Ni, Fe, and Al concentrations were statistically different for New York soils. Zinc was the only element with high R2 and low p value. Pollution load index (PLI), enrichment factors (EF), and geo-accumulation index (Igeo) were calculated for both methods using U.S. Geological Survey data. The PLI were > 1, indicating soil pollution in the two states. Between pXRF and ICP-MS, the Igeo and EF in Arizona had similar degree of contamination for most elements except Zn in garden and Pb in yard, respectively. For New York, the Igeo of As, Cu, and Zn differed by only one classification index between the two methods. The pXRF was reliable in determining As, Ba, Ca, Cu, Mn, Pb, and Zn in impacted communities. Therefore, the pXRF can be a cost-effective alternative to using ICP-MS techniques to screen soil samples for several environmentally relevant contaminants to protect environmental public health.

Mitigating Toxic Metal Exposure Through Leafy Greens: A Comprehensive Review Contrasting Cadmium and Lead in Spinach

Metals and metalloids (hereafter, metal(loid)s) in plant-based foods are a source of exposure to humans, but not all metal(loid)-food interactions are the same. Differences exist between metal(loid)s in terms of their behavior in soils and in how they are taken up by plants and stored in the edible plant tissue/food. Thus, there cannot be one consistent solution to reducing toxic metal(loid)s exposure to humans from foods. In addition, how metal(loid)s are absorbed, distributed, metabolized, and excreted by the human body differs based on both the metal(loid), other elements and nutrients in the food, and the nutritional status of the human. Initiatives like the United States Food and Drug Administration's Closer to Zero initiative to reduce the exposure of young children to the toxic elements cadmium, lead, arsenic, and mercury from foods warrant careful consideration of each metal(loid) and plant interaction. This review explores such plant-metal(loid) interactions using the example of spinach and the metals cadmium and lead. This review highlights differences in the magnitude of exposure, bioavailability, and the practicality of mitigation strategies while outlining research gaps and future needs. A focus on feasibility and producer needs, informed via stakeholder interviews, emphasizes the need for better analytical testing facilities and grower and consumer education. More research should focus on minimization of chloride inputs for leafy greens to lessen plant-availability of Cd and the role of oxalate in reducing Cd bioavailability from spinach. These findings are applicable to other leafy greens (e.g., kale, lettuce), but not for other plants or metal(loid)s.

Lead Speciation, Bioaccessibility, and Sources for a Contaminated Subset of House Dust and Soils Collected from Similar United States Residences

Residential lead (Pb) exposure is of critical concern to families globally as Pb promotes severe neurological effects in children, especially those less than 5 years old, and no blood lead level is deemed safe by the US Center for Disease Control. House dust and soils are commonly thought to be important sources of Pb exposure. Probing the relationship between house dust and soil Pb is critical to understanding residential exposure, as Pb bioavailability is highly influenced by Pb sources and/or species. We investigated paired house dust and soil collected from homes built before 1978 to determine Pb speciation, source, and bioaccessibility with the primary goal of assessing chemical factors driving Pb exposure in residential media. House dust was predominately found to contain (hydro)cerussite (i.e., Pb (hydroxy)carbonate) phases commonly used in Pb-based paint that, in-turn, promoted elevated bioaccessibility (>60%). Pb X-ray absorption spectroscopy, μ-XRF mapping, and Pb isotope ratio analysis for house dust and soils support house dust Pb as chemically unique compared to exterior soils, although paint Pb is expected to be a major source for both. Soil pedogenesis and increased protection from environmental conditions (e.g., weathering) in households is expected to greatly impact Pb phase differences between house dust and soils, subsequently dictating differences in Pb exposure.

Elevated lead (Pb) in urban European starling (Sturnus vulgaris) feathers is not correlated to physiology or behavior

Urbanization is rapidly changing the environment and creating new challenges in the lives of animals across the globe. Anthropogenic contaminants-like heavy metals-can persist within the environment for prolonged periods of time and present a widespread problem for those living near contaminated areas. Lead (Pb) was a commonly used heavy metal that continues to threaten the health of all organisms despite being phased out, especially in urban areas where historical use was more common. In this study, a common urban-adapter, the European starling (Sturnus vulgaris), was trapped to explore whether feather Pb burden is greater in birds from urban habitats than rural habitats, as well as whether Pb burdens were correlated with behavior, physiology, and feather development. Across four sites (two rural and two urban), soil Pb concentrations were measured and 197 free-living starlings were captured to measure feather Pb concentrations. Using linear mixed models, this study found that urban starling nestlings had elevated feather Pb burdens compared to rural nestlings. In contrast, there was no correlation between Pb and urbanization in adult birds whose exposure to Pb may reflect a larger spatial range compared to nestlings. For both nestlings and adults, feather Pb was uncorrelated to corticosterone, testosterone, aggressive behavior, or feather growth rates. These findings suggest that starlings may be a useful biomonitoring tool to detect Pb in the local environment, however, the age and spatial range of birds is a critical consideration in applying this tool. Further work is needed to understand the intricate relationship between heavy metals, behavior, morphological development, and physiology in free-living organisms.

Prenatal and early life lead exposure induced neurotoxicity

Lead (Pb) has become a major environmental contaminant. There are several ways in which lead can enter the human body and cause toxic effects on human health. This review focuses on the impact of lead toxicity at prenatal and early life stages and its effect on neurodevelopment. Lead exposure to the developing foetus targets foetal neural stem cells. Hence, it has detrimental effects on developing neural and glial cells, adversely influencing cognition and behaviour. Lead has a profound influence on the movement of calcium ions (Ca2+), which can be attributed to most of the mechanisms by which lead affects neurodevelopment. There is no known safe threshold of lead exposure for children. Lead can affect foetal neurodevelopment leading to various neurological disorders, and neurotoxic effects on behavioural and cognitive outcomes. In this review, we discuss prenatal and early-life lead exposure, its mechanism, and consequences for neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease in later stages of life. This review further highlights the importance of lead exposure during pregnancy and lactation periods as well as early development of the child in understanding the extent of lead-induced neurological damage to the foetus/children and the associated future risks.

Assessment of source-oriented health risk associated with the oral ingestion of heavy metals in dust within an iron/steel smelting-affected area of the North China Plain

Heavy metals (HMs) from iron/steel smelting activities pose notable risks to human health, especially to those living around industrial facilities of North China Plain, the base of China's steel production. In this study, 78 outdoor windowsill dust samples were collected around a large-scale iron/steel smelter with more than 65 years of production history in the western North China Plain. Nine HMs were analysed to comprehensively assess the health risks by integrating Monte Carlo simulation, oral bioaccessibility, and source apportionment. Results showed serious pollution with Cd, Pb, and Zn based on their geo-accumulation index values and concentrations. Four potential sources including industrial sources (49.85%), traffic sources (21.78%), natural sources (20.58%), and coal combustion (7.79%) were quantitatively identified by multivariate statistical analysis. The oral bioaccessibilities of HMs determined by the physiologically based extraction test ranged from 0.02% to 65.16%. Zn, Mn, Cd, and Pb had higher bioaccessibilities than other HMs. After incorporating oral bioavailability adjustments, noncarcinogenic and carcinogenic risks were significantly reduced, especially for adults. The mean hazard index (HI) for children and adults was below the safety threshold (1.0), whereas the mean of the total carcinogenic risk (TCR) based on HM bioaccessibilities in the gastric phase remained above the acceptable level (1.0E-06) (children: 5.20E-06; adults: 1.16E-06). Traffic sources warranted increased concern as it substantially increased TCR. Cd was identified as the priority pollution in iron/steel smelting areas. Assessing source-oriented health risks associated with oral ingestion exposure can guide the management and control of HM contamination within iron/steel smelting-affected areas.

Assessing Unequal Airborne Exposure to Lead Associated With Race in the USA

Recent research applied the United States Environmental Protection Agency's Chemical Speciation Network and Interagency Monitoring of Protected Visual Environments monitoring stations and observed that mean concentrations of atmospheric lead (Pb) in highly segregated counties are a factor of 5 higher than in well-integrated counties and argument is made that regulation of existing airborne Pb emissions will reduce children's Pb exposure. We argue that one of the main sources of children's current Pb exposure is from resuspension of legacy Pb in soil dust and that the racial disparity of Pb exposure is associated with Pb-contaminated community soils.

Heavy metal pollution in Mongolian-Manchurian grassland soil and effect of long-range dust transport by wind

Grasslands provide a range of valuable ecosystem services, but they are also particularly fragile ecosystems easily threatened by human activities, such as long-term open-pit mining and related industrial activities. In grassland area, dust containing heavy metal(loid)s generated by mines may further migrate to remote places, but few studies have focused on the long-range transport of contaminants as an important pollution source. In the present study, one of the largest and most intact grassland ecosystems, the Mongolian-Manchurian steppe, was selected to investigate its pollution status and track potential sources. A total of 150 soil samples were collected to explore reginal distribution of nine heavy metal(loid)s that has potential risk in grassland. We conducted a combined multi-variant analysis of positive matrix factorization (PMF) and machine learning, which foregrounded the source of long-range transport of contaminants and inspired the hypothesis of a novel stochastic model to describe contaminants distribution. Results showed four different sources accounting for 44.44% (parent material), 20.28% (atmospheric deposition), 20.39% (farming), and 14.89% (transportation) of the total concentration, respectively. Factor 2 indicated that coal surface mining lead to a significant enrichment of As and Se with their concentration far above the global average level, which was different from other reported grassland areas. Machine learning results further confirmed that atmospheric and topographic features were their contamination controlling factors. The model results proposed that As, Se and Cu released by surface mining will be transported over long distance under prevailing monsoon, until finally deposited in the windward slope of mountain due to terrain obstruction. The long-range transport by wind and deposition of contaminants may be a prevailing phenomenon in temperate grassland, making it a pollution source that cannot be ignored. Evidence from this study reveals the urgency of precautions for fragile grassland ecosystems around industrial areas and provides a basis for its management and risk control policies.

Positive outcomes from U.S. lead regulations, continued challenges, and lessons learned for regulating emerging contaminants

Albeit slow and not without its challenges, lead (Pb) emissions and sources in the United States (U.S.) have decreased immensely over the past several decades. Despite the prevalence of childhood Pb poisoning throughout the twentieth century, most U.S. children born in the last two decades are significantly better off than their predecessors in regard to Pb exposure. However, this is not equal across demographic groups and challenges remain. Modern atmospheric emissions of Pb in the U.S. are nearly negligible since the banning of leaded gasoline in vehicles and regulatory controls on Pb smelting plants and refineries. This is evident in the rapid decrease of atmospheric Pb concentrations across the U.S. over the last four decades. One of the most significant remaining contributors to air Pb is aviation gasoline (avgas), which is minor compared to former Pb emissions. However, continual exposure risks to Pb exist in older homes and urban centers, where leaded paint and/or historically contaminated soils + dusts can still harm children. Thus, while effective in eliminating nearly all primary sources of Pb in the environment, the slow rate of U.S. Pb regulation has led to legacy sources of Pb in the environment. More proactive planning, communication, and research of commonly used emerging contaminants of concern that can persist in the environment long after their initial use (i.e., PFAS) should be prioritized so that the same mistakes are not made again.

Pond Sediments Reveal the Increasing Importance of Road Runoff as a Source of Metal Contamination in Industrialized Urban Environments Downwind of Pittsburgh, Pennsylvania (USA)

Toxic levels of trace metals from human activities accumulate in natural environments, yet these metal mixtures are rarely characterized or quantified. Metal mixtures accumulate in historically industrial urban areas and change as economies shift. Previous research has often focused on the sources and fate of a specific element, which limits our understanding of metal contaminant interactions in our environment. Here, we reconstruct the history of metal contamination in a small pond downstream of an interstate highway and downwind of fossil fuel and metallurgical industries that have been active since the middle of the nineteenth century. Metal contamination histories were reconstructed from the sediment record using metal ratio mixing analysis to attribute the relative contributions of contamination sources. Cadmium, copper, and zinc concentrations in sediments accumulated since the construction of major road arteries in the 1930s and 40s are, respectively, 3.9, 2.4, and 6.6 times more concentrated than those during industry-dominated time periods. Shifts in elemental ratios suggest these changes in metal concentrations coincide with increased contributions from road and parking lot traffic, and to a lesser extent, from airborne sources. The metal mixture analysis demonstrates that in near-road environments, contributions from modern surface water pathways can obscure historical atmospheric industrial inputs.

Sentinel animals for monitoring the environmental lead exposure: combination of traditional review and visualization analysis

In nature, certain animals share a common living environment with humans, thus these animals have become biomonitors of health effects related to various environmental exposures. As one of the most toxic environmental chemicals, lead (Pb) can cause detriment health effects to animals, plants, and even humans through different exposure pathways such as atmosphere, soil, food, water, and dust, etc. Sentinel animals played an "indicative" role in the researches of environmental pollution monitoring and human health. In order to comprehend the usage of sentinel animals in the indication of environmental Pb pollution and human Pb exposure completely, a combination of traditional review and visualization analysis based on CiteSpace literature was used to review earlier researches in this study. In the first instance, present researches on exposure sources and exposure pathways of Pb were summarized briefly, and then the studies using sentinel animals to monitor environmental heavy metal pollution and human health were combed. Finally, visualization software CiteSpace 5.8.R3 was used to explore and analyze the hotspots and frontiers of lead exposure and sentinel animals researches at home and abroad. The results showed that certain mammals were good indicators for human lead exposure. Sentinel animals had been widely used to monitor the ecological environment and human lead exposure. Among them, the blood lead levels of small mammals, particularly for domestic dogs and cats, had a significant correlation with the blood lead levels of human living in the same environment. It indicated that certain biological indicators in animals can be used as surrogates to monitor human body exposure to heavy metals. This study also explored the challenges and perspectives that may be faced in sentinel animal research, in order to provide a certain theoretical basis and train of thought guidance for future research.

Health risk assessment of heavy metals in road dust from the fourth-tier industrial city in central China based on Monte Carlo simulation and bioaccessibility

Health risks caused by heavy metal (HM) exposure in road dust has attracted extensive attention, but few studies have focused on the health risks of residents living in small- and medium-sized cities with rapid industrialization and urbanization. Thus, 140 road dust samples were collected across Anyang, a typical fourth-tier industrial city in central China, which were analysed for 10 different HMs (Mn, Zn, Pb, V, Cr, As, Cd, Ni, Cu and Co). Monte Carlo simulation and bioaccessibility were used to quantify the health risks of heavy metals comprehensively in road dust. Results revealed a remarkable accumulation of Mn, Zn, Pb, Cd and Cu. According to the Geo-accumulation index and potential ecological risk index, Cd was priority control pollutant. Moreover, 55.0% of the road dust samples reached heavily polluted level, and 52.86% of the samples were at high ecological risk levels. These results illustrated that HM contamination was serious and universal in the road dust of Anyang. The occurrences of HMs were allocated to traffic emissions, natural sources, industrial activities and agricultural activities with contribution rates of 35.4%, 6.0%, 41.6% and 17.0%, respectively. Except for Zn in the gastric phase, all other HMs had relatively low bioaccessibilities in the gastrointestinal system, usually less than 20%. The bioaccessibilities of most HMs were higher in the gastric phase, except for Cr, Ni and Cu, which remained higher in the intestinal phase. The non-carcinogenic risk and carcinogenic risk were remarkably reduced when considering the HM bioaccessibilities in the gastrointestinal system, especially for adults. The outcomes of this paper are valuable for understanding HM contamination in road dust and highlight the importance of risk assessment for populations living in the fourth- and fifth-tier cities.

Effects of Sub-chronic Lead Exposure on Essential Element Levels in Mice

Lead (Pb), a corrosion-resistant heavy non-ferrous metal, is one of the most common environmental neurotoxic metals. The effects of Pb on other essential metal elements are contradictory. Therefore, this in vivo study addressed the effects of sub-chronic Pb exposure on the distribution of other divalent metals, exploring the relationships between Pb levels in blood, teeth, bones, hair, and brain tissues. Thirty-two healthy male C57BL/6 mice received intragastric administration (i.g.) with 0, 12.5, 25, and 50 mg/kg Pb acetate, once a day for 8 weeks. Levels of Pb and other metal elements [including iron(Fe), zinc (Zn), magnesium (Mg), copper (Cu), and calcium(Ca)] in the whole blood, teeth, the right thighbone, hair, and brain tissues (including cortex, hippocampus, striatum, and hypothalamus) were detected with inductively coupled plasma-mass spectrometry (ICP-MS). Pb levels in all detected organs were increased after Pb-exposed for 8 weeks. The results of relationship analysis between Pb levels in the tissues and lifetime cumulative Pb exposure (LCPE) showed that Pb levels in the blood, bone, and hair could indirectly reflect the Pb accumulation in the murine brain. These measures might serve as valuable biomarkers for chronic Pb exposure reflective of the accumulation of Pb in the central nervous system (CNS). Sub-chronic Pb exposure for 8 weeks altered Ca, Cu, Fe, and Zn levels, but no effects were noted on Mg levels in any of the analyzed tissues. Pb decreased Ca in teeth, Cu in thighbone and teeth, Zn in whole blood and hair, and Fe in hair. In contrast, Pb increased Ca levels in corpus striatum and hypothalamus, Cu levels in striatum, Zn levels in teeth, and Fe levels in hippocampus, thighbone, and teeth. The Pb-induced changes in metal ratios in various tissues may serve as valuable biomarkers for chronic Pb exposure as they are closely related to the accumulations of Pb in the murine CNS. The results suggest that altered distribution of several essential metal elements may be involved in Pb-induced neurotoxicity. Additional studies should address the interaction between Pb and essential metal elements in the CNS and other organs.

Source apportionment based on lead isotope ratios: Could domestic dog's blood lead be used to identify the level and sources of lead pollution in children?

Domestic dogs have been proved to be used as "sentinel organisms" to monitor human lead exposure. However, whether dogs' blood can be used to identify the levels and pollution source of children's lead exposure still needs evidence. To evaluate the potential use of domestic dogs' blood lead as an indicator of lead exposure levels and pollution source of children, accompanying with potential environmental media samples, lead concentrations and isotope ratios (expressed as ²⁰⁷Pb/²⁰⁶Pb, ²⁰⁸Pb/²⁰⁶Pb) in blood were investigated and compared between children and dogs, who came from a Pb-Zn smelter area, a coal fired area and a control area without industrial activity. The results showed that there were significant correlations in blood lead levels (BLLs) between children and dogs in the study areas (p < 0.01). The lead isotope ratios (LIRs) in blood of children and dogs were disparate among the three areas, however, the LIRs of dogs were quite correlated with those of children in each area (p < 0.01). With the comparison of LIRs between potential pollution sources (slag, ore, coal, paint) and blood samples, the identified lead sources based on dogs' blood were found to be coincident with those based on children's blood. Ore smelting and coal combustion were the main sources of lead exposure for the dogs and children in the smelting area, and coal combustion was the predominant source for the children and dogs living in the coal burning area and control area. The results showed that dogs' BLLs might be used to estimate children's BLLs, and blood LIRs measurements of dogs' could be used as an alternative for identifying the sources of children's lead exposure. This study further provided relevant evidence for dogs to be sentinels exposed to human lead exposure and an alternative method for source apportionment of children's lead exposure.

Metal Exposures in Residents Living Near an Urban Oil Drilling Site in Los Angeles, California

Urban environmental justice communities are potentially exposed to multiple toxic metals, through contaminated air, soil, water, and food. However, information on metals and their sources is lacking. This study uses non-negative matrix factorization (NMF) in a community-based participatory research study to identify potential sources and to understand how these metals cluster in a population near an urban oil drilling site. We recruited 203 Latinx, Black, and Asian residents who lived within 1 km of an oil drilling site in south Los Angeles and collected toenail clippings to assess exposure to arsenic (As), cadmium (Cd), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and antimony (Sb). Using NMF, we identified three clusters based on concentrations in the participants' toenails. As, Cd, Pb, and Sb grouped together, indicative of an industrial source. A second grouping was composed of Ni and Mn, which may be related to oil drilling. We also identified a third source factor predominantly driven by Hg and As, which may arise from dietary sources. Utilizing NMF, a dimension reduction method, we identified a source factor high in Ni and Mn in residents living in a neighborhood near an active oil drilling site.

The effect of residential proximity to brownfields, highways, and heavy traffic on serum metal levels in the Detroit Neighborhood Health Study

Research in environmental sciences has demonstrated that land in close proximity to brownfields and heavily trafficked highways is contaminated with toxic metals. Despite this, little is known about the influence of brownfields and highways on metal levels in residents living nearby. We used data from 774 participants in the Detroit Neighborhood Health Study to estimate the effect of residential proximity to brownfields, highways, and present-day traffic on serum levels of lead, mercury, manganese, and copper using generalized estimating equations. We found that a 1 standard deviation increase in residential brownfield density within 200m was associated with increased serum lead levels (β: 0.04, 95% CI: -0.01, 0.09). The same modeled increase in a subset of historic industrial-use brownfields was associated with elevated serum mercury (β: 0.06, 95% CI: 0.03, 0.09). Increased highway and traffic density was positively associated with serum manganese (β: 0.02, 95% CI: 0.01, 0.04). Highway and traffic density was also positively associated with serum lead (β: 0.02, 95% CI: 0.01, 0.03) after restricting the analysis to participants who did not move during the study follow-up period. These findings draw attention to the importance of remediating polluted post-industrial sites in heavily populated areas, particularly as residents continue to move into densely populated cities around the globe.

Use of historical mapping to understand sources of soil-lead contamination: Case study of Santa Ana, CA

This paper investigates the historical sources of soil-lead contamination in Santa Ana, California. Even though dangerous levels of soil-lead have been found in a wide variety of communities across the United States, public health institutions lack clarity on the historical origins of these crises. This study uses geo-spatial data collected through archival research to estimate the impact of two potential sources of lead contamination in the past -- lead-paint and leaded gasoline. It examines, through a combination of statistical and historical methods, the association between lead concentrations in contemporary soil samples and patterns in the evolution of the city's physical features, such as the growth of urbanized areas and the historical flow of traffic. We emphasize the value of historical data collected through archival research for understanding the sources of environmental lead, particularly leaded gasoline, which our study found to be the most likely and most prominent contributor to soil-lead in Santa Ana's environment. This research contributes to environmental-justice advocacy efforts to reframe lead poisoning as a systemic environmental issue and outlines the path forward to community-level remediation strategies.

Fruit lead concentrations of tomato (Solanum lycopersicum L.) grown in lead-contaminated soils are unaffected by phosphate amendments and can vary by season, but are below risk thresholds

Urban agriculture in post-industrial cities faces concerns on human health risks posed by elevated lead (Pb) concentrations of edible plant tissues grown in Pb-enriched soils. A recommended mitigation strategy to decrease soil Pb bioavailability to humans is the addition of soluble phosphate (PO₄^3--P), but it is unclear if this strategy can also reduce crop Pb uptake and accumulation in edible tissues. Across urban agriculture sites in Chicago, Illinois (6 site-years) with elevated total soil Pb, we tested the hypothesized decrease in tomato fruit Pb following soil-based application of three phosphate-based mitigation amendments: triple superphosphate, composted biosolids, and air dried biosolids. Fruit Pb concentrations (mg Pb kg^-1 dry mass) and loads (mg Pb m^-2) were unaffected by mitigation amendments. However, fruit Pb concentrations were higher by an order of magnitude in 2020 (≥0.13 mg kg^-1) compared to 2019 (0.01 mg kg^-1) for two of the three sites. Though highly variable across site-years, the bioconcentration factor (BCF) of Pb from soil to fruit varied was unaffected by mitigation amendments. Relatively low BCF values were consistent with fruit Pb concentrations being below FAO/WHO risk limits. Collectively, our findings support previous propositions that fruits of plants grown in soils with elevated Pb generally pose lower risk to consumers. To mitigate health risks of consuming tomatoes grown in soils with Pb contamination, the seasonality of Pb uptake should be investigated, and greater focus should be placed on where tomatoes are grown rather than phosphate-based immobilization strategies originally designed to mitigate human bioavailability.

Lead in Air, Soil, and Blood: Pb Poisoning in a Changing World

(1) Background: Leaded petrol became a worldwide vehicle fuel during the 20th century. While leaded petrol was totally banned on 30 August 2021, its lead (Pb) dust legacy remains in the environment as soil Pb. The health impacts of Pb are well known and risks occur when exposures are above zero. The inextricable links between air Pb, soil Pb, and blood Pb are not widely A. Exposure risks continue even after banning leaded petrol and must be explored. (2) Methods: This article evaluates selected examples of temporal measurements of atmospheric Pb and human Pb exposure and the effect of soil Pb on blood Pb. Several search engines were used to find articles on temporal changes in air Pb and human Pb exposures. New Orleans studies provided empirical data on the association between soil Pb and blood Pb. (3) Results: Vehicle Pb emission trends are closely associated with air Pb and blood Pb. Air Pb deposited in soil becomes a reservoir of Pb dust that is known to be remobilized into the atmosphere. (4) Conclusions: The dust from leaded petrol continues to pose major exposure risks to humans. Exogenous sources of Pb in soil and its remobilization into air along with endogenous bone Pb establish the baseline exposure of children and adults. Reducing human exposure to Pb requires novel policies to decrease exogenous contact from the reservoir of Pb in soil and curtailing remobilization of soil Pb into the atmosphere. Mitigating exposure to soil Pb must therefore play a central role in advancing primary prevention.

Toxic Neighborhoods: The Effects of Concentrated Poverty and Environmental Lead Contamination on Early Childhood Development

Although socioeconomic disparities in cognitive ability emerge early in the life course, most research on the consequences of living in a disadvantaged neighborhood has focused on school-age children or adolescents. In this study, we outline and test a theoretical model of neighborhood effects on cognitive development during early childhood that highlights the mediating role of exposure to neurotoxic lead. To evaluate this model, we follow 1,266 children in Chicago from birth through school entry and track both their areal risk of lead exposure and their neighborhoods' socioeconomic composition over time. With these data, we estimate the joint effects of neighborhood poverty and environmental lead contamination on receptive vocabulary ability. We find that sustained exposure to disadvantaged neighborhoods reduces vocabulary skills during early childhood and that this effect operates through a causal mechanism involving lead contamination.

Road sediment, an underutilized material in environmental science research: A review of perspectives on United States studies with international context

Road sediment is a pervasive environmental medium that acts as both source and sink for a variety of natural and anthropogenic particles and often is enriched in heavy metals. Road sediment is generally understudied in the United States (U.S.) relative to other environmental media and compared to countries such as China and the United Kingdom (U.K.). However, the U.S. is an ideal target for these studies due to the diverse climates and wealth of geochemical, socioeconomic, demographic, and health data. This review outlines the existing U.S. road sediment literature while also providing key international perspectives and context. Furthermore, the most comprehensive table of U.S. road sediment studies to date is presented, which includes elemental concentrations, sample size, size fraction, collection and analytical methods, as well as digestion procedure. Overall, there were observed differences in studies by sampling time period for elemental concentrations, but not necessarily by climate in the U.S. Other key concepts addressed in this road sediment review include the processes controlling its distribution, the variety of nomenclature used, anthropogenic enrichment of heavy metals, electron microscopy, health risk assessments, remediation, and future directions of road sediment investigations. Going forward, it is recommended that studies with a higher geographic diversity are performed that consider smaller cities and rural areas. Furthermore, environmental justice must be a focus as community science studies of road sediment can elucidate pollution issues impacting areas of high need. Finally, this review calls for consistency in sampling, data reporting, and nomenclature to effectively expand work on understudied elements, particles, and background sediments.

Key considerations for assessing soil ingestion exposures among agricultural workers

BACKGROUND

Soil ingestion is a critical, yet poorly characterized route of exposure to contaminants, particularly for agricultural workers who have frequent, direct contact with soil.

OBJECTIVE

This qualitative investigation aims to identify and characterize key considerations for translating agricultural workers' soil ingestion experiences into recommendations to improve traditional exposure science tools for estimating soil ingestion.

METHODS

We conducted qualitative in-depth interviews with 16 fruit and vegetable growers in Maryland to characterize their behaviors and concerns regarding soil contact in order to characterize the nature of soil ingestion in the agricultural context.

RESULTS

We identified and discussed four emergent themes: (1) variability in growers' descriptions of soil and dust, (2) variability in growers' soil contact, (3) growers' concerns regarding soil contact, (4) growers' practices to modify soil contact. We also identified environmental and behavioral factors and six specific agricultural tasks that may impact soil ingestion rates.

SIGNIFICANCE

Our investigation fills an important gap in occupational exposure science methodology by providing four key considerations that should be integrated into indirect measurement tools for estimating soil ingestion rates in the agricultural context. Specifically, a task-based framework may provide a structure for future investigations of soil contact that may be useful in other populations.

Legacy of anthropogenic lead in urban soils: Co-occurrence with metal(loids) and fallout radionuclides, isotopic fingerprinting, and in vitro bioaccessibility

Anthropogenic lead (Pb) in soils poses risks to human health, particularly to the neuropsychological development of exposed children. Delineating the sources and potential bioavailability of soil Pb, as well as its relationship with other contaminants is critical in mitigating potential human exposure. Here, we present an integrative geochemical analysis of total elemental concentrations, radionuclides of ¹³⁷Cs and ²¹⁰Pb, Pb isotopic compositions, and in vitro bioaccessibility of Pb in surface soils sampled from different locations near Durham, North Carolina. Elevated Pb (>400 mg/kg) was commonly observed in soils from urban areas (i.e., near residential house foundation and along urban streets), which co-occurred with other potentially toxic metal(loids) such as Zn, Cd, and Sb. In contrast, soils from city parks and suburban areas had systematically lower concentrations of metal(loids) that were comparable to geological background. The activities of ¹³⁷Cs and excess ²¹⁰Pb, coupled with their correlations with Pb and co-occurring metal(loids) were used to indicate the persistence and remobilization of historical atmospherically deposited contaminants. Coupled with total Pb concentrations, the soil Pb isotopic compositions further indicated that house foundation soils had significant input of legacy lead-based paint (mean = 1.1895 and 2.0618 for ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb, respectively), whereas urban streetside soils exhibited a clear mixed origin, dominantly of legacy leaded gasoline (1.2034 and 2.0416) and atmospheric deposition (1.2004-1.2055 and 2.0484-2.0525). The in vitro bioaccessibility of Pb in contaminated urban soils furthermore revealed that more than half of Pb in the contaminated soils was potentially bioavailable, whose Pb isotope ratios were identical to that of bulk soils, demonstrating the utility of using Pb isotopes for tracking human exposure to anthropogenic Pb in soils and house dust. Overall, this study demonstrated a holistic assessment for comprehensively understanding anthropogenic Pb in urban soils, including its co-occurrence with other toxic contaminants, dominant sources, and potential bioavailability upon human exposure.

Lead, Soils, and Children: An Ecological Analysis of Lead Contamination in Parks and Elevated Blood Lead Levels in Brooklyn, New York

Although the prevalence of elevated childhood blood lead levels (BLLs) has been declining, there are still an estimated 500,000 children (1 to 5 years) with BLLs above the CDC's reference value (≥ 5 μg/dL). The objective of this study was to evaluate the ecological association between soil lead (Pb) concentrations in greenspaces in Brooklyn, NY and elevated BLLs of children aged 1 to 5 years old. Soil samples (n = 1504) were collected from a wide variety of parks within 43 neighborhood tabulation areas (NTAs) located in Brooklyn, NY, analyzed with a portable XRF with a subset (n = 350), and also analyzed by ICP-MS. Lead concentrations were right skewed with a mean of 160.4 ppm and a median of 113.1 ppm. The Pb concentration range spanned three orders of magnitude with most samples (66.7%) ≥ 80 ppm and 6.7% of samples ≥ 400 ppm. Elevated BLL (≥ 5ug/dL) data on children 1 to 5 years were obtained from the New York City Department of Health and Mental Hygiene (2011-2015). Weighted median soil Pb concentrations were calculated for each NTA and stratified into quartiles. The overall median rate of children from 1 to 5 years old with BLLs ≥ 5 µg/dL was 28.6 per 1000; the median rate was highest (p = 0.070) in the fourth quartile (Pb concentrations ≥ 150 ppm) compared to the first quartile (Pb concentrations < 88 ppm), 37.2 vs. 28.3 per 1000, respectively. We then used multivariable linear regression to determine the ecological association between BLL rates and soil Pb concentrations. In the final stepwise multivariable regression model, controlling for known risk factors, there was a significant positive association between soil Pb concentrations and increased childhood BLL rates (beta = 0.0008; p = 0.004). Our findings suggest that there is an ecological association between high soil Pb levels and increased rates of elevated childhood BLLs.

Quantification of Pb pollution sources in complex urban environments through a multi-source isotope mixing model based on Pb isotopes in lichens and road sediment

Despite a growing focus on anthropogenic toxic metal pollution in urban environments, few studies have addressed the problem of quantification when more than two pollution sources are likely present, particularly within complex urban settings in the United States (U.S.). In this study, we utilize the MixSIAR package in R for source apportionment based on Pb isotopic signatures in lichen and road sediment in two urban-industrial centers in SW Ohio (OH). We show that ranges of pollutant contributions are more useful than only visualizing mean or raw values of source apportionment, because this avoids overinterpretation of data when certain sources have a large range of uncertainty. We point out both the dominance of industrial pollution as well as the legacy of leaded gasoline pollution in typical mid-sized U.S. cities, which is evident in both road sediment and lichens. Leaded gasoline contribution to Pb in Middletown, OH lichens mostly vary between ~10 and 25%, while in Hamilton, OH the contribution to lichens and road sediment tends to be relatively negligible except for two road sediment samples and one lichen sample, where median contributions are ~20-30%. Industrial combustion pollution source contributions vary between ~25 and 75% in Hamilton, and ~50-100% in Middletown, OH. Furthermore, comparing pollution sources in lichens to modern particulate matter can provide a record of how pollutant sources change over time, such as our traffic lichen (Sample Li-9) plotting closer to leaded gasoline on a bivariate mixing diagram than modern traffic particulate matter, or our coke plant lichen containing slightly less Pb contribution from industrial combustion sources relative to modern coke plant particulate matter. Lastly, when applicable, multi-source mixing models should be complimented in future studies with additional isotopic source tracers such as Cu, Zn, Nd, and Os to further elucidate unique sources of metal pollutants in addition to Pb.

The Safe Urban Harvests Study: A Community-Driven Cross-Sectional Assessment of Metals in Soil, Irrigation Water, and Produce from Urban Farms and Gardens in Baltimore, Maryland

BACKGROUND

Emerging evidence suggests social, health, environmental, and economic benefits of urban agriculture (UA). However, limited work has characterized the risks from metal contaminant exposures faced by urban growers and consumers of urban-grown produce.

OBJECTIVES

We aimed to answer community-driven questions about the safety of UA and the consumption of urban-grown produce by measuring concentrations of nine metals in the soil, irrigation water, and urban-grown produce across urban farms and gardens in Baltimore, Maryland.

METHODS

We measured concentrations of 6 nonessential [arsenic (As), barium (Ba), cadmium (Cd), chromium (Cr), lead (Pb), nickel (Ni)] and three essential [copper (Cu), manganese (Mn), zinc (Zn)] metals in soil, irrigation water, and 13 types of urban-grown produce collected from 104 UA sites. We compared measured concentrations to existing public health guidelines and analyzed relationships between urban soil and produce concentrations. In the absence of guidelines for metals in produce, we compared metals concentrations in urban-grown produce with those in produce purchased from farmers markets and grocery stores (both conventionally grown and U.S. Department of Agriculture-certified organic).

RESULTS

Mean concentrations of all measured metals in irrigation water were below public health guidelines. Mean concentrations of nonessential metals in growing area soils were below public health guidelines for Ba, Cd, Pb, and Ni and at or below background for As and Cr. Though we observed a few statistically significant differences in concentrations between urban and nonurban produce items for some combinations, no consistent or discernable patterns emerged.

DISCUSSION

Screening soils for heavy metals is a critical best practice for urban growers. Given limitations in existing public health guidelines for metals in soil, irrigation water, and produce, additional exposure assessment is necessary to quantify potential human health risks associated with exposure to nonessential metals when engaging in UA and consuming urban-grown produce. Conversely, the potential health benefits of consuming essential metals in urban-grown produce also merit further research. https://doi.org/10.1289/EHP9431.

A citizen science approach to identifying trace metal contamination risks in urban gardens

We launched the VegeSafe program in 2013 to assist Australians concerned about exposure to contaminants in their soils and gardens. VegeSafe analyses garden soils provided by citizens for trace metals at our laboratory at little to no cost, with easy-to-follow guidance on any intervention required. The response was overwhelming-Australians submitted 17,256 soils from 3,609 homes, and in turn VegeSafe researchers now have unparalleled household-scale data, providing new insights into urban trace metal contamination. The results are sobering, with 35% of homes, particularly those that are older, painted and located in inner cities having soils above the Australian residential guideline (300 mg/kg) for the neurotoxic trace metal lead (Pb). Exposure pathway, blood Pb concentration and vegetable uptake modelling showed the communities in these locations were most at risk. VegeSafe is transformative: 94% of participants better understood contaminants, 83% felt safer in their home environment and 40% undertook remedial action based on their results. The two-way nature of this program enables education of citizens about environmental contaminants, advances public health, and delivers impactful science.

Agreement ℜ of Four Analytical Methods Applied to Pb in Soils from the Small City of St. John's, Newfoundland, Canada

In the small city of St. John's, NL (2020 population ~114,000), 100% of the soils of the pre-1926 properties exceeded the Canadian soil Pb standard, 140 mg/kg. The Pb was traced to high-Pb coal ash used for heating and disposed on the soils outside. Analytical instruments became available in the late 1960s and 1970s and were first used for blood Pb and clinical studies and repurposed for measuring environmental Pb. The environmental research part of this study compared four common soil Pb analysis methods on the same set (N = 96) of St. John's soil samples. The methods: The US EPA method 3050B, portable X-ray fluorescence spectrometry (pXRF), The Chaney-Mielke leachate extraction (1 M nitric acid), and the relative bioaccessibility leaching procedure (US EPA method 1340). Correlation is not the same as agreement ℜ. There is strong agreement (Berry-Mielke's Universal ℜ) among the four soil Pb analytical methods. Accordingly, precaution is normally advisable to protect children from the high-Pb garden soils and play areas. A public health reality check by Health Canada surveillance of St. John's children (N = 257) noted remarkably low blood Pb. The low blood Pb of St. John's' children is contrary to the soil Pb results. Known urban processes causing the rise of environmental Pb and children's Pb exposure includes particle size, aerosol emission by traffic congestion, and quantities of leaded petrol during the 20th century. Smaller cities had minor traffic congestion and limited combustion particles from leaded petrol. From the perspective of the 20th century era of urban Pb pollution, St. John's, NL, children have blood Pb characteristics of a small city.

Urban-Soil Pedogenesis Drives Contrasting Legacies of Lead from Paint and Gasoline in City Soil

This study analyzed the impact of urban-soil pedogenesis on soil lead (Pb) contamination from paint and gasoline in the historic core of Durham, North Carolina. Total soil Pb in 1000 samples from streetsides, residential properties, and residual upland and floodplains ranged from 6 to 8825 mg/kg (mean = 211 mg/kg), with 50% of samples between 50 and 200 mg/kg soil Pb. The highest Pb concentrations were within 1 m of pre-1978 residential foundations, with concentrations inversely correlated with house age. Streetside soil Pb concentrations were elevated over the geologic background of <30 mg/kg and correlated with traffic flow. Streetside soil Pb concentrations were lower than Durham streetside soils collected in the 1970s, which was attributed to urban pedogenesis, the complex of natural and human processes that change soils over time. Accelerated erosion redistributes legacy Pb and floodplain sampling indicates sedimentation rates of up to 4 mm/year. Mixing and burial of soil with elevated Pb are also lowering soil Pb concentrations over time. These mechanisms are likely of greater significance on streetsides than near foundation soils. The development of an urban-pedogenesis framework can help guide public health approaches to Pb exposure by incorporating pedogenic processes that reduce and dissipate soil Pb contamination.

Regional and global perspectives of honey as a record of lead in the environment

Honey from Apis mellifera is a useful and inexpensive biomonitor for mapping metal distributions in urban centers. The sampling resolution of a biomonitoring survey (e.g., city versus global scale) determines which geochemical processes are reflected in the results. This study presents Pb isotopic compositions and metal concentrations in honey from around the world, sampled at varying resolutions: honey from Canada (n = 21), the United States (n = 111), Belgium (n = 25), and New Zealand (n = 10), with additional samples from Afghanistan, Brazil, Cuba, Germany, Liberia, Taiwan, and Turkey. Honey was sampled at high resolution in two uniquely different land-use settings (New York Metro Area and the Hawaiian island of Kaua'i), at regional-scale resolution in eastern North America (including the Great Lakes region), and Pb isotopic compositions of all samples were compared on a global scale. At high sampling resolution, metal concentrations in honey reveal spatially significant concentration gradients: in New York City, metals associated with human activity and city infrastructure (e.g., Pb, Sb, Ti, V) are more concentrated in honey collected within the city compared to honey from upstate New York, and metal concentrations in honey from Kaua'i suggest polluting effects of nearby agricultural operations. At lower resolution (regional and global scales), lead isotopic compositions of honey are more useful than metal concentrations in revealing large-scale Pb processes (e.g., the enduring legacy of global leaded gasoline use throughout the twentieth century) and the continental origin of the honey. Lead isotopic compositions of honey collected from N. America (especially from the eastern USA) are more radiogenic (²⁰⁶Pb/²⁰⁷Pb: 1.132-1.253, ²⁰⁸Pb/²⁰⁶Pb: 2.001-2.129) compared to European honey, and honey from New Zealand, which has the least radiogenic isotopic compositions measured in this study (²⁰⁶Pb/²⁰⁷Pb: 1.077-1.160, ²⁰⁸Pb/²⁰⁶Pb: 2.090-2.187). Thus, biomonitoring using honey at different resolutions reflects differing processes and, to some extent, a honey terroir defined by the Pb isotopic composition. The data presented here provide important (and current) global context for future studies that utilize Pb isotopes in honey. Moreover, this study exhibits community science in action, as most of the honey was collected by collaborators around the world, working directly with local apiarists and hobby beekeepers.

Soil Lead (Pb) in New Orleans: A Spatiotemporal and Racial Analysis

Spatialized racial injustices drive morbidity and mortality inequalities. While many factors contribute to environmental injustices, Pb is particularly insidious, and is associated with cardio-vascular, kidney, and immune dysfunctions and is a leading cause of premature death worldwide. Here, we present a revised analysis from the New Orleans dataset of soil lead (SPb) and children’s blood Pb (BPb), which was systematically assembled for 2000–2005 and 2011–2016. We show the spatial–temporal inequities in SPb, children’s BPb, racial composition, and household income in New Orleans. Comparing medians for the inner city with outlying areas, soil Pb is 7.5 or 9.3 times greater, children’s blood Pb is ~2 times higher, and household income is lower. Between 2000–2005 and 2011–2016, a BPb decline occurred. Long-standing environmental and socioeconomic Pb exposure injustices have positioned Black populations at extreme risk of adverse health consequences. Given the overlapping health outcomes of Pb exposure with co-morbidities for conditions such as COVID-19, we suggest that further investigation be conducted on Pb exposure and pandemic-related mortality rates, particularly among Black populations. Mapping and remediating invisible environmental Pb provides a path forward for preventing future populations from developing a myriad of Pb-related health issues.

Spatial-temporal association of soil Pb and children's blood Pb in the Detroit Tri-County Area of Michigan (USA)

Lead is a well-known toxicant associated with numerous chronic diseases. Curtailing industrial emissions, leaded paint, lead in food, and banning highway use of leaded gasoline effectively decreased children's exposure. In New Orleans, irrespective of Hurricane Katrina flooding, lead declined concurrently in topsoil and children's blood. We postulate that topsoil lead and blood lead decreases are associated and common in U.S. cities. This study tests that concept. A small 2002 soil lead survey of 8 Detroit Tri-County Area census tracts was repeated in October 2019. Between 2002 and 2019, Detroit median soil lead decreased from 183 to 92 mg/kg (or 5.4 mg/kg/yr.) and declined in Pontiac from 93 to 68 mg/kg (or 1.4 mg/kg/yr.). Median soil lead remained ~10 mg/kg in outlying communities. Median soil lead (in mg/kg) in communities at < 21 km compared to ≥ 21 km from central Detroit, respectively, decreased from 183 to 33 (P-value 10^-12) in 2002 and from 92 to 35 (P-value 10^-07) in 2019. Children's lead exposures were highest in Detroit (population 0.7 million in 2010) and lower by more than half in Pontiac (population 60 thousand in 2010). Between 2002 and 2018, children with blood lead ≥4.5 μg/dL in Detroit declined from 44% to 5%, and in Pontiac from 17% to 2%. The most vulnerable children live in the most lead contaminated communities. To meet the goal of primary prevention for children, along with other efforts, this study supports landscaping with low lead soil to reduce exposure in lead contaminated communities.

The distribution and transport of lead over two centuries as recorded by lake sediments from northeastern North America

We evaluated anthropogenic Pb deposition along a west-east transect from the Adirondack Mountains, New York, USA (ADIR) region, the Vermont-New Hampshire-Maine, USA (VT-NH-ME) region, and Nova Scotia, Canada (NS) region using 47 ²¹⁰Pb-dated lake sediment records. We used focus-corrected Pb inventories to evaluate cumulative deposition and breakpoint analysis to evaluate possible differences in timings among regions. Peak Pb concentrations decreased from west to east (ADIR region: 52-378 mg kg^-1, VT-NH-ME region: 54-253 mg kg^-1, NS: 38-140 mg kg^-1). Cumulative deposition of anthropogenic Pb also decreased from west to east (ADIR region: 791-1344 mg m^-2, VT-NH-ME region: 209-1206 mg m^-2, NS: 52-421 mg m^-2). The initiation of anthropogenic Pb deposition occurred progressively later along the same transect (ADIR region: 1869-1900, VT-NH-ME region: 1874-1905, NS region: 1901-1930). Previous lead isotope studies suggest that eastern Canadian Pb deposition over the past ~150 years has originated from a mix of both Canadian and U.S. sources. The results of this study indicate that anthropogenic Pb from sources west of the ADIR region were deposited in lesser amounts from west to east and/or Pb sources reflect less population density from west to east. The timing of the initiation of anthropogenic Pb deposition in the NS region suggests that Pb from gasoline may be an important source in this region.

Mechanisms of children's soil exposure

Pollution is a concerning and highly studied area, especially in the arena of children's health. The focus of this concern, however, is typically limited to air and water pollution, leaving an important source under-studied and out of the concern of the general public. Soil pollution provides a unique threat to children's health, due to their increased exposure and susceptibility to its contaminants. The microbiome of a child is developed prior to birth and continues to evolve over their lifetime with each encounter to the outside world. The environment a child inhabits directly affects their microbiome and their overall health, and through interactions with contaminated soil, a child can accumulate adverse health outcomes. The aim of this article is to summarize the methods by which soil becomes contaminated and how children become exposed to the resulting toxicants.

Blood lead levels in children in urban and rural areas: Using multilevel modeling to investigate impacts of gender, race, poverty, and the environment

Many studies of children's exposure to lead (Pb) are carried out in urban and industrialized environments. This study analyzed blood lead level (BLL) data collected from 2011 to 2016 from approximately 140,000 children ages <1 to 6 years across South Carolina (SC), including urban and rural areas. Individual-level characteristics included children's age, and race/ethnicity. Block group variables examined included population by race and ethnicity, households below the poverty level, median year homes built, urban/rural classification, and percent road coverage. BLL were higher in urban compared to rural children but increased to a greater extent in rural children from age < 1 year to 2 years. Road coverage was strongly associated with higher BLL in urban areas, and with home age more weakly, but neither road coverage nor home age was associated with BLL in rural areas. Young urban children may receive greater exposure to Pb from house dust and outdoor legacy Pb contamination, and young rural children through diet and drinking water. Black children had higher BLL in urban areas than white children, and the converse was true in rural areas. Population data indicated that rural areas had more poverty than urban areas, but strong associations between increased children's BLL and either ethnicity or socio-economic status (SES) at the block group level was not observed, likely due to distinct characteristics of poverty and geographic distribution by ethnicity in urban as compared to rural areas of SC. Individual demographics and environmental characteristics may be more closely associated with BLL than geographically aggregated SES and race/ethnicity characteristics. Interventions to reduce children's exposure to Pb should occur at as early an age as possible, and differences between rural and urban areas should be considered as interventions are developed to reduce children's BLL.

Neuropathological lesions in the brains of goats in North-Western Nigeria: possible impact of artisanal mining

Indiscriminate small-scale artisanal gold mining activities were reported to have caused anthropogenic heavy metal environmental pollution in Zamfara State, north-western Nigeria. There is little or no information on the neurotoxic effects and related neuropathological lesions due to environmental pollution in the animal population. Therefore, this work investigated the concentration of heavy metal and associated lesions in the brain of goats around an artisanal mining site in Zamfara. Brain samples were collected from 40 goats at slaughter slabs in Bagega (Zamfara State) while 15 goats with the same demography but without a history of environmental exposure at the time of this study served as controls. The concentration of lead and cadmium in brain tissue and histopathologic changes were assessed using atomic absorption spectrophotometry, histology and immunohistochemistry. The metal concentrations were significantly higher in exposed goats than in the unexposed animals. Cresyl violet staining and glial fibrillary acidic protein (GFAP) immunohistochemistry indicated chromatolysis and increased astrocytic activity respectively in the exposed goats. This study is of epidemiological importance as it shows a generalised increase of the metal concentrations in the brain of goats exposed to artisanal mining in Zamfara, north-western Nigeria. This could have health effects on the animals associated with nervous co-ordination, growth and development and as a good sentinel for pathogenesis of the heavy metal exposure.

Dietary Lead and Phosphate Interactions Affect Oral Bioavailability of Soil Lead in the Mouse

Effects of dietary P level on the oral bioavailability of Pb present in soil were examined in a mouse model. Adult female C57BL/6 mice had free access to AIN-93G purified rodent diet amended with Pb as a soluble salt, Pb acetate, or in a soil matrix (NIST SRM 2710a). In these studies, the basal diet contained P at a nutritionally sufficient level (0.3% w/w) and the modified diets contained P at a lower (0.15%) or a higher (1.2%) level. For either dietary Pb source (Pb acetate or NIST SRM 2710a), low dietary P level markedly increased accumulation of Pb in bone, blood, and kidney. Tissue Pb levels in mice fed a high P in diet were not different from mice fed the basal P diet. Dietary P and Pb interacted to affect body weight change and feed efficiency in mice. The relative contribution of different Pb species in diet and feces was also affected by dietary P level. Differences in Pb species between diet and feces indicated that transformation of Pb species can occur during gastrointestinal tract transit. These interactions between Pb and P that alter Pb speciation may be important determinants of the bioavailability of Pb ingested in soil.

Risky bismuth: Distinguishing between lead contamination sources in soils

In a broad environmental study in St. Joseph County, Indiana, elemental data from ∼2000 soil samples and ∼800 paint samples were collected with X-ray Fluorescence (XRF) spectroscopy. The observed lead concentrations were compared to other elemental concentrations in these data. A strong correlation between lead and bismuth concentrations was observed in a subset of the soil samples and in nearly all of the paint samples, with lead levels approximately 150 times higher than bismuth. However, some soil samples contained lead with no bismuth present. Since most lead sources likely contain bismuth as an impurity from refining of native lead ore, but leaded gasoline does not contain any bismuth impurities due to the manufacturing process of tetraethyl lead, it may be possible to distinguish environmental lead sources by XRF. To test if leaded gasoline could be the source of lead in the subset of soil samples containing no bismuth, leaded paint samples were analyzed with Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES), which confirmed the presence of bismuth in leaded paint. Aviation gasoline, which contains tetraethyl lead, was also analyzed by ICP-OES to confirm the absence of bismuth in leaded gasoline. This discovery suggests that XRF can be used to rapidly distinguish different legacy lead contamination sources from one another. For low lead concentrations, elemental measurements of bismuth by ICP-OES can be used in environmental forensics to distinguish leaded gasoline contamination from other sources of lead.

The concurrent decline of soil lead and children's blood lead in New Orleans

The inextricable link between topsoil lead (Pb) and children’s blood lead (BPb) has not been widely accepted. Pb is associated with multiple health adversities. Urban residents are at risk from exposure to legacy Pb dust in topsoil resulting from smelting, industrial discharges, leaded gasoline emissions, leaded paint, and incineration. In New Orleans, topsoil median Pb decreased in ∼15 y from 99 mg/kg to 54 mg/kg, or ∼2.4 mg⋅kg⋅y⁻¹. In ∼12 y, children’s median BPb declined from 3.6 μg/dL to 1.3 μg/dL, or ∼0.2 μg⋅dL⋅y⁻¹. We argue that depletion of topsoil Pb is an important factor in the continuous decline of children’s BPb. Similar processes are expected in all US cities. Primary prevention requires curtailing Pb in all sources, including topsoil.

Lead (Pb) is extremely toxic and a major cause of chronic diseases worldwide. Pb is associated with health disparities, particularly within low-income populations. In biological systems, Pb mimics calcium and, among other effects, interrupts cell signaling. Furthermore, Pb exposure results in epigenetic changes that affect multigenerational gene expression. Exposure to Pb has decreased through primary prevention, including removal of Pb solder from canned food, regulating lead-based paint, and especially eliminating Pb additives in gasoline. While researchers observe a continuous decline in children’s blood lead (BPb), reservoirs of exposure persist in topsoil, which stores the legacy dust from leaded gasoline and other sources. Our surveys of metropolitan New Orleans reveal that median topsoil Pb in communities (n = 274) decreased 44% from 99 mg/kg to 54 mg/kg (P value of 2.09 × 10⁻⁰⁸), with a median depletion rate of ∼2.4 mg⋅kg⋅y⁻¹ over 15 y. From 2000 through 2005 to 2011 through 2016, children’s BPb declined from 3.6 μg/dL to 1.2 μg/dL or 64% (P value of 2.02 × 10⁻⁸⁵), a decrease of ∼0.2 μg⋅dL⋅y⁻¹ during a median of 12 y. Here, we explore the decline of children’s BPb by examining a metabolism of cities framework of inputs, transformations, storages, and outputs. Our findings indicate that decreasing Pb in topsoil is an important factor in the continuous decline of children’s BPb. Similar reductions are expected in other major US cities. The most contaminated urban communities, usually inhabited by vulnerable populations, require further reductions of topsoil Pb to fulfill primary prevention for the nation’s children.

Availability of lead in agricultural soils amended with compost of biosolid with wood shavings and yard trimmings

Lead-polluted agricultural soils are a serious problem for food safety, with organic amendment being a promising mitigation method from the environmental perspective. Therefore, the purpose of this study was to evaluate lead availability and the effectiveness of the application of compost of biosolid with wood shavings and yard trimmings in contaminated soils. The physicochemical (Pb distribution, organic matter, pH, electric conductivity, cation exchange capacity, nitrogen, phosphorus, carbon, carbonates, exchangeable cations, sodium) and biological parameters (the microbial activity obtained by fluorescein diacetate hydrolysis) in Pb-polluted and non-polluted agricultural soils were evaluated after the addition of biosolid with wood shavings and yard trimming compost. Topsoils (lead-polluted and control) were collected in the vicinity of a former battery-recycling plant, amended with compost (0%, 5%, and 10%), and incubated in controlled conditions for 118 days. The results showed that lead availability decreased significantly, and the nutritional quality of the soils increased in the soils amended with 10% of compost. Taken together, the results of the present study indicated that compost amendment could be an effective method for mitigating the negative effects of lead in agricultural soils.

Curtailing Lead Aerosols: Effects of Primary Prevention on Declining Soil Lead and Children's Blood Lead in Metropolitan New Orleans

After decades of accumulation of lead aerosols in cities from additives in gasoline, in 1975 catalytic converters (which are ruined by lead) became mandatory on all new cars. By 1 January 1986 the rapid phase-down banned most lead additives. The study objective is to review temporal changes of environmental lead and children's blood lead in communities of metropolitan New Orleans. In 2001, a soil lead survey of 287 census tracts of metropolitan New Orleans was completed. In August-September 2005 Hurricanes Katrina and Rita storm surges flooded parts of the city with sediment-loaded water. In April-June 2006, 46/287 (16%) of the original census tracts were selected for resurvey. A third survey of 44/46 (15%) census tracts was completed in 2017. The census tract median soil lead and children's median blood lead decreased across surveys in both flooded and unflooded areas. By curtailing a major urban source of lead aerosols, children's lead exposure diminished, lead loading of soil decreased, and topsoil lead declined. Curtailing lead aerosols is essential for primary prevention. For the sake of children's and ultimately societal health and welfare, the long-term habitability of cities requires terminating all remaining lead aerosols and cleanup of legacy-lead that persists in older inner-city communities.

The legacy lead deposition in soils and its impact on cognitive function in preschool-aged children in the United States

Surface soil contamination has been long recognized as an important pathway of human lead exposure, and is now a worldwide health concern. This study estimates the causal effects of exposure to lead in topsoil on cognitive ability among 5-year-old children. We draw on individual level data from the 2000 U.S. Census, and USGS data on lead in topsoil covering a broad set of counties across the United States. Using an instrumental variable approach relying on the 1944 Interstate Highway System Plan, we find that higher lead in topsoil increases considerably the probability of 5-year-old boys experiencing cognitive difficulties such as learning, remembering, concentrating, or making decisions. Living in counties with topsoil lead concentration above the national median roughly doubles the probability of 5-year-old boys having cognitive difficulties. Nevertheless, it does not seem to affect 5-year-old girls, consistent with previous studies. Importantly, the adverse effects of lead exposure on boys are found even in counties with levels of topsoil lead concentration considered low by the guidelines from the U.S. EPA and state agencies. These findings are concerning because they suggest that legacy lead may continue to impair cognition today, both in the United States and in other countries that have considerable lead deposition in topsoil.

Sub-lethal exposure to lead is associated with heightened aggression in an urban songbird

Many urban areas have elevated soil lead concentrations due to prior large-scale use of lead in products such as paint and automobile gasoline. This presents a potential problem for the growing numbers of wildlife living in urbanized areas as lead exposure is known to affect multiple physiological systems, including the nervous system, in vertebrate species. In humans and laboratory animals, low-level lead exposure is associated with neurological impairment, but less is known about how lead may affect the behavior of urban wildlife. We focused on the Northern Mockingbird Mimus polyglottos, a common, omnivorous North American songbird, to gain insights into how lead may affect the physiology and behavior of urban wildlife. We predicted that birds living in neighborhoods with high soil lead concentrations would (a) exhibit elevated lead concentrations in their blood and feathers, (b) exhibit lower body condition, (c) exhibit less diverse and consistent vocal repertoires, and (d) behave more aggressively during simulated conspecific territorial intrusions compared to birds living in neighborhoods with lower soil lead concentrations. Controlling for other habitat differences, we found that birds from areas of high soil lead had elevated lead concentrations in blood and feathers, but found no differences in body condition or vocal repertoires. However, birds from high lead areas responded more aggressively during simulated intrusions. These findings indicate that sub-lethal lead exposure may be common among wildlife living in urban areas, and that this exposure is associated with increased aggression. Better understanding of the extent of the relationship between lead exposure and aggression and the consequences this could have for survival and reproduction of wild animals are clear priorities for future work in this and other urban ecosystems.

Signs of adaptation to trace metal contamination in a common urban bird

Metals and metalloids at elevated concentrations can be toxic to both humans and wildlife. In particular, lead exposure can act as a stressor to wildlife and cause negative effects on fitness. Any ability to adapt to stress caused by the negative effects of trace metal exposure would be beneficial for species living in contaminated environments. However, mechanisms for responding adaptively to metal contamination are not fully understood in free-living organisms. The Australian populations of the house sparrow (Passer domesticus) provides an excellent opportunity to study potential adaptation to environmental lead contamination because they have a commensal relationship with humans and are distributed broadly across Australian settlements including many long-term mining and smelting communities. To examine the potential for an evolutionary response to long-term lead exposure, we collected genomic SNP data using the house sparrow 200 K SNP array, from 11 localities across the Australian distribution including two mining sites (Broken Hill and Mount Isa, which are two genetically independent populations) that have well-established elevated levels of lead contamination as well as trace metals and metalloids. We contrast these known contaminated locations to other lesser-contaminated environments. Using an ecological association genome scan method to identify genomic differentiation associated with estimates of lead contamination we identified 60 outlier loci across three tests. A total of 39 genes were found to be physically linked (within 20 kbps) of all outliers in the house sparrow reference genome. The linked candidate genes included 12 genes relevant to lead exposure, such as two metal transporters that can transport metals including lead and zinc across cell membranes. These candidate genes provide targets for follow up experiments comparing resilience to lead exposure between populations exposed to varied levels of lead contamination.

Dietary zinc, calcium and nickel are associated with lower childhood blood lead levels

The potential mitigation of elevated blood lead (PbB) levels with nutrient intake remains debatable. A comprehensive review by Kordas (2017) concluded that careful examination of the links between nutrition (nutritional status, nutrients, diet) and lead (Pb) exposure revealed limited and tenuous evidence. We have measured 20 elements including calcium (Ca), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), nickel (Ni), zinc (Zn), and Pb from 6-day duplicate diets of 108 young children over a 5-year period and expressed these as intakes per body weight. Bivariate analyses showed a weak positive association between the Pb content in the diets of the participants and the level of Pb in their blood, as might be expected. Weak, but negative, associations occurred between the other elements in the diet and PbB. The associations for Ca, Mg, Ni and Zn were statistically significant for both subject-based (between subjects) and within-subject effects: that is, as the levels of elements in diet increased, the PbB level decreased. The largest percentage of variance of PbB in the context of the bivariate model accounted for was 4.23% for Zn, followed by Ca (3.91%) and Fe (2.20%). Supplementary analyses indicated that the between- and within-subject effects did not vary with the age at which participants entered the study, or with the levels of elements at their first measurement. A multivariable analysis using Weighted Quantile Sum Regressions showed that a weighted composite comprised of all the dietary elements had a significant association with PbB when adjusted for Pb in the diet and other covariates and also when adjusted for Pb in house dust; the latter was found to have the strongest association with PbB in earlier analyses. The highest weights were for Ca (0.29), Ni (0.27) and Zn (0.22); these results are generally consistent with those from the mixed model analyses.

Preliminary assessment of surface soil lead concentrations in Melbourne, Australia

Urban soils in many cities have been found to be contaminated with lead from past usage of leaded petrol, deteriorating lead-based exterior paints and industrial sources. Currently, the spatial distribution of soil lead concentrations in the Melbourne metropolitan area is unknown. The objective of this study was to perform a preliminary assessment of the spatial distributions of the surface soil lead (Pb) concentrations in the Melbourne metropolitan area, Australia. Fifty-eight surface soil samples were collected at a depth of 0-2 cm along three linear transects oriented across the Melbourne metropolitan area. Surface soil samples were also collected at a higher density in five Melbourne suburbs. Soil cores (0-50 cm) were collected in four locations, soil transects were collected at intervals with distance away from the roadway (0-50 m) in two inner city parks, and one control soil sample was collected in a rural setting. The median soil Pb concentration of the soil transect samples was 173 mg/kg (range 32-710 mg/kg), and the median soil Pb concentration of the five suburbs was 69 mg/kg (range 9-1750 mg/kg). The suburb of Footscray had the highest soil Pb concentration with a median soil Pb concentration of 192 mg/kg (range 40-1750 mg/kg). Soil Pb concentrations were generally higher nearest the centre of the Melbourne metropolitan area and in the west of Melbourne and lower in the outer suburbs to the east and north of the city centre. Soil Pb concentrations decreased with distance from roadways in the two transects taken from urban parks, and soil lead decreased with depth in the four soil cores. The soil Pb concentrations in the Melbourne metropolitan area appear to be lower than soil lead concentrations observed in inner city areas of Sydney New South Wales (NSW) and Newcastle NSW. The spatial extent of the soil Pb hazard remains undefined in portions of the Melbourne metropolitan area.

Identifying Sources of Environmental Contamination in European Honey Bees (Apis mellifera) Using Trace Elements and Lead Isotopic Compositions

Trace element concentrations (As, Mn, Pb, and Zn) and Pb isotopic compositions were analyzed in honey bees, wax, and honey along with co-located soil and dust samples from Sydney metropolitan and Broken Hill, Australia. Compared with the other trace elements, Pearson correlations show that Pb concentrations in soil and dust had the strongest relationship to corresponding values in honey bees and their products. Dust Pb was not only highly correlated to corresponding soil values (r = 0.806, p = 0.005), it was the strongest predictor of Pb concentrations in honey bees, wax, and honey (p = 0.001, 0.007, 0.017, respectively). Lead isotopic compositions (²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb) showed that honey bees and their products from Broken Hill were nearly identical (95-98%) to the composition of the local ore body. Samples of honey bees and their products collected from background sites adjacent to national parks in Sydney had Pb isotopic compositions (²⁰⁶Pb/²⁰⁷Pb = 1.138-1.159, ²⁰⁸Pb/²⁰⁷Pb = 2.417-2.435) corresponding to local geogenic values (²⁰⁶Pb/²⁰⁷Pb = 1.123-1.176, ²⁰⁸Pb/²⁰⁷Pb = 2.413-2.500). By contrast, honey bees and their products from Sydney metropolitan (²⁰⁶Pb/²⁰⁷Pb = 1.081-1.126, ²⁰⁸Pb/²⁰⁷Pb = 2.352-2.408) were similar to aerosols measured during the period of leaded petrol use (²⁰⁶Pb/²⁰⁷Pb = 1.067-1.148, ²⁰⁸Pb/²⁰⁷Pb = 2.341-2.410). These measurements show Pb concentrations and its isotopic compositions of honey bees, and their products can be used to trace both legacy and contemporary environmental contamination, particularly where sources are well documented. Moreover, this study demonstrates that legacy Pb emissions continue to be remobilized in dust, contaminating both food and ecological systems.

Blood lead and preeclampsia: A meta-analysis and review of implications

BACKGROUND

Multiple cross-sectional studies suggest that there is an association between blood lead and preeclampsia.

OBJECTIVES

We performed a systematic review and meta-analysis to summarize information on the association between preeclampsia and lead poisoning.

METHODS

Searches of Medline, Web of Science, Scopus, Pubmed, Science Direct and ProQuest (dissertations and theses) identified 2089 reports, 46 of which were downloaded after reviewing the abstracts, and 11 studies were evaluated as meeting the selection criteria. Evaluation using the ROBINS-I template (Sterne, et al., 2016), indicated moderate risk of bias in all studies.

RESULTS

We found that blood lead concentrations were significantly and substantially associated with preeclampsia (k = 12; N = 6069; Cohen's d = 1.26; odds ratio = 9.81; odds ratio LCL = 8.01; odds ratio UCL = 12.02; p = 0.005). Eliminating one study produced a homogeneous meta-analysis and stronger estimates, despite the remaining studies coming from eight separate countries and having countervailing risks of bias.

CONCLUSIONS

Blood lead concentrations in pregnant women are a major risk factor for preeclampsia, with an increase of 1μg/dL associated with a 1.6% increase in likelihood of preeclampsia, which appears to be the strongest risk factor for preeclampsia yet reported. Pregnant women with historical lead exposure should routinely have blood lead concentrations tested, especially after mid-term. Women with concentrations higher than 5μg/dL should be actively monitored for preeclampsia and be advised to take prophylactic calcium supplementation. All pregnant women should be advised to actively avoid lead exposure.