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.

Effectiveness of washing in reducing lead concentrations of lettuce grown in urban garden soils.

Urban gardeners contribute to sustainable cities and often take great care to limit exposure to soil contaminants like lead (Pb). Although best management practices (BMPs) like mulching to reduce soil splash can limit crop contamination, they may not eliminate all contamination for leafy greens, which trap soil particles. How effective is washing at removing Pb contamination from leafy greens when using BMPs? Are certain washing techniques more effective than others? We present results from two experiments addressing these questions. We grew lettuce (Lactuca sativa L.) in homogenized high-Pb (∼1,150 mg kg-1 ) and low-Pb (∼90 mg kg-1 ) soils in Brooklyn, NY, and Ithaca, NY. Our results show that washing can remove 75-94% of Pb from lettuce, including that remaining after the use of contamination-reducing BMPs. It was estimated that washing removed 97% of Pb deposited by splash, which is the dominant source of Pb, and removed 91% deposited by downward deposition. All washing techniques were effective at reducing Pb levels, with differences in effectiveness ranked as: commercial soak > vinegar soak > water soak (and water rinse not significantly different from vinegar or water soak). Washing crops grown in low-Pb soils is also important. Without washing, lettuce grown in low-Pb soil may still have Pb levels above the European Commission comparison value. We offer these empirical findings and recommendations in support of urban growers.

Soil lead (Pb) and urban grown lettuce: Sources, processes, and implications for gardener best management practices.

Urban community gardeners employ a range of best practices that limit crop contamination by toxicants like lead (Pb). While Pb root uptake is generally low, the relative significance of various Pb deposition processes and the effectiveness of best practices in reducing these processes have not been sufficiently characterized. This study compared leafy lettuce (Lactuca sativa) grown in high Pb (1150 mg/kg) and low Pb (90 mg/kg) soils, under three different soil cover conditions: 1) bare soil, 2) mulch cover to limit splash, and 3) mulch cover under hoophouses to limit splash and air deposition, in a New York City (NYC) community garden and a rural site in Ithaca, New York (NY). The lettuces were further compared to greenhouse (Ithaca) and supermarket (NYC) samples. Atmospheric deposition was monitored by passive trap collection through funnel samplers. Results show that in low Pb soils, splash and atmospheric deposition accounted for 84 and 78% of lettuce Pb in NYC and Ithaca, respectively. In high Pb soils, splash and atmospheric deposition accounted for 88 and 93% of Pb on lettuces, with splash being the dominant mechanism. Soil covers were shown to be effective at significantly (p < 0.05) reducing lettuce Pb contamination, and mulching is strongly recommended as a best practice.

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.

The limits of lead (Pb) phytoextraction and possibilities of phytostabilization in contaminated soil: a critical review.

This review article focuses on lead (Pb), one of the most ubiquitous and harmful toxicants found in soil. Our objective is to address misconceptions regarding the ability of plants to uptake Pb through their roots and translocate it to above-ground tissues, and their ability to act as hyperaccumulators and thereby phytoextract Pb. In accordance with a number of cited definitions, we suggest that species capable of Pb phytoextraction can be rated with the following three criteria: (1) root uptake above a nominal threshold of 1,000 mg Pb/kg, (2) bioconcentration factor (BCF or shoot/soil concentration) >1, and (3) translocation factor (TF or shoot/root concentration) > 1. We review the literature in the updated USDA Phytoremediation Database and conclude that without amendments: no plant has met all three criteria; no plant has been confirmed as a Pb hyperaccumulator. Our analysis suggests that Pb phytoextraction is not a viable remediation option. Pb phytostabilization, however, may be an effective remediation tool in a variety of settings. Planting some of the many species capable of tolerating soil Pb exposure and sequestering it in or around the root zone will limit Pb movement into other ecosystems, prevent resuspended dusts, and mitigate Pb exposure.

Remediation of an urban garden with elevated levels of soil contamination.

Urban gardening is popular in many cities. However, many urban soils are contaminated and pose risks to human health. This study was conducted in a highly publicized urban garden in Brooklyn, NY with elevated Pb and As levels. Our objectives were to: (1) assess the nature and extent of Pb and As contamination at this site; (2) evaluate the effectiveness of amendments on reducing the bioaccessibility and phytoavailability of Pb and As in soil; and (3) assess the potential exposure of children to Pb and As through direct and indirect exposure pathways. Field surveys of the site revealed that contamination was highly concentrated in one area of the garden associated with fruit tree production. Field plots were established in this area, with three different treatments (bone meal, compost, sulfur) and an unamended control. Bioaccessibility of Pb was significantly reduced by all three treatments compared to the control (33%): bone meal (24%), compost (23%), sulfur (24%). In this study, As bioaccessibility remained high (80-93%) with or without treatments. We found that the effectiveness of soil remediation with amendments is variable and often limited, and contaminated sites can still pose a significant risk to urban gardeners. The results of a simple assessment model suggested that Pb and As exposure was mostly from soil and dust ingestion, rather than vegetable consumption. This work is unique in that it evaluates actual elevated levels of contamination, in actively gardened urban soils, in a highly visible public context. It fills important gaps between basic research and analysis of human exposure to toxic trace metals that can be a constraint on a highly beneficial activity.

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.

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

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.

Sediment exchange to mitigate pollutant exposure in urban soil.

Urban soil is an ongoing source for lead (Pb) and other pollutant exposure. Sources of clean soil that are locally-available, abundant and inexpensive are needed to place a protective cover layer over degraded urban soil to eliminate direct and indirect pollutant exposures. This study evaluates a novel sediment exchange program recently established in New York City (NYC Clean Soil Bank, CSB) and found that direct exchange of surplus sediment extracted from urban construction projects satisfies these criteria. The CSB has high total yield with 4.2 × 105 t of sediment exchanged in five years. Average annual yield (8.5 × 104 t yr-1) would be sufficient to place a 15-cm (6-in.) sediment cover layer over 3.2 × 105 m2 (80 acres) of impacted urban soil or 1380 community gardens. In a case study of sediment exchange to mitigate community garden soil contamination, Pb content in sediment ranged from 2 to 5 mg kg-1. This sediment would reduce surface Pb concentrations more than 98% if it was used to encapsulate soil with Pb content exceeding USEPA residential soil standards (400 mg kg-1). The maximum observed sediment Pb content is a factor of 42 and 71 lower than median surface soil and garden soil in NYC, respectively. All costs (transportation, chemical testing, etc.) in the CSB are paid by the donor indicating that urban sediment exchange could be an ultra-low-cost source for urban soil mitigation. Urban-scale sediment exchange has advantages over existing national- or provincial-scale sediment exchanges because it can retain and upcycle local sediment resources to attain their highest and best use (e.g. lowering pollutant exposure), achieve circular urban materials metabolism, improve livability and maximize urban sustainability.