Metal Exposure in Veterans With Embedded Fragments From War-Related Injuries: Early Findings From Surveillance Efforts

Toxic chemical exposures among civilians in armed conflicts: the need for research equity, justice, and accountability

OBJECTIVE

Armed conflicts result in the release of toxic chemicals into the surrounding environment and civilians are commonly exposed to these toxicants. This paper reviews the evidence on civilian exposure to toxic chemicals, including but not limited to inhaled toxic substances, in post-World War II armed conflicts, and proposes a framework for the implementation of long-term surveillance programs for these populations.

MATERIALS AND METHODS

Four databases of peer-reviewed health articles were searched for all English-language articles with a primary focus on toxic chemical exposures among civilians in armed conflicts since World War II. The review was supplemented substantially by the gray literature.

RESULTS

In the 66 articles that met the inclusion criteria, the authors categorized the chemical toxicants to which civilians have been exposed in modern armed conflicts as ubiquitous (e.g. smoke, dust, and munitions components present in all conflicts) or particular agents (e.g. specific chemical agents used in a few conflicts). While most studies focused on particular agents, the vast majority of civilians are in fact exposed to ubiquitous agents both in the acute conflict phase and through persistent environmental exposures after the cessation of hostilities.

DISCUSSION/CONCLUSION

There is a dearth of research concerning civilian exposures to toxic chemicals during armed conflicts. In line with principles of equity, justice, and accountability, robust research and surveillance programs are urgently needed to document exposures and provide ongoing assessments and any necessary treatment for these long-ignored populations, most of whom live in the Global South.

Early transcriptomic signatures and biomarkers of renal damage due to prolonged exposure to embedded metal

BACKGROUND

Prolonged exposure to toxic heavy metals leads to deleterious health outcomes including kidney injury. Metal exposure occurs through both environmental pathways including contamination of drinking water sources and from occupational hazards, including the military-unique risks from battlefield injuries resulting in retained metal fragments from bullets and blast debris. One of the key challenges to mitigate health effects in these scenarios is to detect early insult to target organs, such as the kidney, before irreversible damage occurs.

METHODS

High-throughput transcriptomics (HTT) has been recently demonstrated to have high sensitivity and specificity as a rapid and cost-effective assay for detecting tissue toxicity. To better understand the molecular signature of early kidney damage, we performed RNA sequencing (RNA-seq) on renal tissue using a rat model of soft tissue-embedded metal exposure. We then performed small RNA-seq analysis on serum samples from the same animals to identify potential miRNA biomarkers of kidney damage.

RESULTS

We found that metals, especially lead and depleted uranium, induce oxidative damage that mainly cause dysregulated mitochondrial gene expression. Utilizing publicly available single-cell RNA-seq datasets, we demonstrate that deep learning-based cell type decomposition effectively identified cells within the kidney that were affected by metal exposure. By combining random forest feature selection and statistical methods, we further identify miRNA-423 as a promising early systemic marker of kidney injury.

CONCLUSION

Our data suggest that combining HTT and deep learning is a promising approach for identifying cell injury in kidney tissue. We propose miRNA-423 as a potential serum biomarker for early detection of kidney injury.

Succimer chelation does not produce lasting reductions of blood lead levels in a rodent model of retained lead fragments

Retained lead fragments from nonfatal firearm injuries pose a risk of lead poisoning. While chelation is well-established as a lead poisoning treatment, it remains unclear whether chelation mobilizes lead from embedded lead fragments. Here, we tested whether 1) DMSA/succimer or CaNa2EDTA increases mobilization of lead from fragments in vitro, and 2) succimer is efficacious in chelating fragment lead in vivo, using stable lead isotope tracer methods in a rodent model of embedded fragments. DMSA was > 10-times more effective than CaNa2EDTA in mobilizing fragment lead in vitro. In the rodent model, succimer chelation on day 1 produced the greatest blood lead reductions, and fragment lead was not mobilized into blood. However, with continued chelation and over 3-weeks post-chelation, blood lead levels rebounded with mobilization of lead from the fragments. These findings suggest prolonged chelation will increase fragment lead mobilization post-chelation, supporting the need for long-term surveillance in patients with retained fragments.

The Department of Veterans' Affairs Depleted Uranium Cohort in the Time of COVID-19: Translating a Traditional Surveillance Protocol to a Telehealth Platform

OBJECTIVE

In 2021, 37 members of a cohort of depleted uranium-exposed Gulf War I veterans were evaluated using a protocol tailored to accommodate COVID-19 safety practices on a telehealth platform.

METHODS

Individual elements of the legacy protocol were reviewed for urgency and feasibility of inclusion in a modified, telehealth platform.

RESULTS

The redesigned protocol included a participant readiness for telehealth assessment, nurse and physician telehealth visits, collection of usual health questionnaires, and urine collections for exposure monitoring for uranium and other fragment-related metal measures.

CONCLUSIONS

Despite some limitations in scope, the telehealth platform permitted a visual "visit" with surveillance participants who expressed a high comfort level with the format. The telehealth platform has apparent utility for occupational surveillance and should be explored as a standard approach for surveillance outside of public health emergencies.

Local Effect of Ballistic Fragments Embedded Along the Carotid Sheath of a Porcine Animal Model

INTRODUCTION

Energized ballistic fragments from improvised explosive devices were the most common cause of injury to coalition service personnel during conflicts in Iraq and Afghanistan. Surgical excision of retained fragments is not routinely performed unless there is a concern for injury to vital structures. However, no clear guidelines dictate when or if a fragment should be removed, reflecting a lack of objective evidence of their long-term effects. Using a porcine model, we aimed to evaluate changes to the carotid artery produced by retained fragments over time.

MATERIALS AND METHODS

Institutional Animal Care and Use Committee approval for all experiments was obtained before commencement of the study. Eighteen female swine (mean mass 62.0 ± 3.4 kg) were randomized into three study groups corresponding to the time of survival after implantation of ballistic fragments: 1, 6, and 12 weeks. Two animals from each group were randomly assigned to have one of the three different fragments implanted within the right carotid sheath in zones 1-3 of the neck. The left carotid served as the control. The vascular flow rate and arterial diameter were measured at each level before implantation and again after the survival interval. Baseline and interval angiograms were performed to identify gross vascular changes.

RESULTS

No abnormalities were identified on baseline or interval angiograms. No significant difference was found when the baseline was compared to interval measurements or when compared to the control side for all gross and physiological measures at 1 and 6 weeks (P = .053-.855). After 12 weeks, the flow and diameter changed significantly (P < .001-.03), but this significant change was found in both the control and affected carotid.

CONCLUSIONS

The lack of significant gross anatomical and physiological changes at 6 weeks postimplantation lends evidence toward the current policy that early removal of retained ballistic fragments around cervical vessels is not required. Changes were significant after 12 weeks which suggest that surveillance may be required; however, such changes could be explained by physiological animal growth.

Tungsten toxicity and carcinogenesis

Tungsten is an emerging contaminant in the environment. Research has demonstrated that humans are exposed to high levels of tungsten in certain settings, primarily due to increased use of tungsten in industrial applications. However, our understanding of the potential human health risks of tungsten exposure is still limited. An important point we have learned about the toxicity profile of tungsten is that it is complex because tungsten can often augment the effects of other co-exposures or co-stressors, which could result in greater toxicity or more severe disease. This has shaped the tungsten toxicology field and the types of research questions being investigated. This has particularly been true when evaluating the toxicity profile of tungsten metal alloys in combination with cobalt. In this chapter, the current state of the tungsten toxicology field will be discussed focusing on data investigating tungsten carcinogenicity and other major toxicities including pulmonary, cardiometabolic, bone, and immune endpoints, either alone or in combination with other metals. Environmental and human monitoring data will also be discussed to highlight human populations most at risk of exposure to high concentrations of tungsten, the forms of tungsten present in each setting, and exposure levels in each population.

Serum Indicators of Oxidative Damage from Embedded Metal Fragments in a Rat Model

Injuries suffered in armed conflicts often result in embedded metal fragments. Standard surgical guidance recommends leaving embedded fragments in place except under certain circumstances in an attempt to avoid the potential morbidity that extensive surgery often brings. However, technological advances in weapon systems and insurgent use of improvised explosive devices now mean that practically any metal can be found in these types of wounds. Unfortunately, in many cases, the long-term toxicological properties of embedded metals are not known, further complicating treatment decisions. Because of concerns over embedded metal fragment injuries, the U.S. Departments of Defense and Veterans' Affairs developed a list of “metals of concern” for these types of injuries. In this study, we selected eight of these metals including tungsten, nickel, cobalt, iron, copper, aluminum, lead, and depleted uranium to investigate the long-term health effects using a rodent model developed in our Institute to study embedded fragment injuries. In this report, we show that metals surgically implanted into the gastrocnemius muscle of laboratory rats to simulate a shrapnel wound induce a variety of cytokines including IFN-γ, IL-4, IL-5, IL-6, IL-10, and IL-13. TNF-α and KC/GRO were not affected, and IL-1β was below the limit of detection. Serum levels of C-reactive protein were also affected, increasing with some metals and decreasing with others. The TBARS assay, an assessment of lipid peroxidation, demonstrated that implanted aluminum and lead increased markers of lipid peroxidation in serum. Taken together, the results suggest that serum cytokine levels, as well as other indicators of oxidative damage, may prove useful in identifying potential adverse health effects of embedded metals.

Oxidative damage in metal fragment-embedded Sprague-Dawley rat gastrocnemius muscle

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War often results in shrapnel injuries with metals whose toxicity might be unknown.

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A rodent model was used to study-eight military-relevant metals implanted in muscle.

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Creatine kinase activity, protein oxidation and antioxidant capacity were assessed.

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Data obtained were metal-dependent and not all metals showed identical results.

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Results suggest that subtle damage occurs in muscle surrounding metal shrapnel.

Injuries suffered in armed conflicts often result in wounds with embedded metal fragments. Standard surgical guidance has been to leave fragments in place except under certain circumstances; meaning that individuals may carry these retained fragments for their lifetime. Because of advancements in weapon design and the use of improvised explosive devices, the list of metals that could be found in a wound is extensive. In most cases the toxicological properties of these metals when embedded in the body are not known. To assess the potential damage embedded metals may cause to surrounding tissue, we utilized a rodent model to investigate the effect of a variety of military-relevant metals on markers of oxidative damage. The metals tested included tungsten, nickel, cobalt, iron, copper, aluminum, lead, and depleted uranium. Herein we report our findings on creatine kinase activity, lipid and protein oxidation, total antioxidant capacity, and glutathione levels in gastrocnemius homogenates from Sprague-Dawley rats surgically implanted with metal pellets for periods up to 12 months. Not all embedded metals affected the measured markers equally. However, metal-associated effects were seen at various times for muscle and serum creatinine levels, protein oxidation, total antioxidant capacity, and glutathione levels. No metal-induced effects on lipid peroxidation were observed. Taken together, these data suggest that subtle oxidative damage may be occurring in the muscle surrounding an embedded metal and indicates the need for medical surveillance of those individuals wounded by metal shrapnel.

Metal distribution patterns in tissues from implanted Sprague-Dawley rats

Background: Injuries with fragments of embedded metal are a common occurrence in armed conflicts. Unfortunately, the list of metals encountered on the modern battlefield are practically endless while the short- and long-term health effects, especially when embedded as in a shrapnel wound, are not well understood. One of the major concerns with these types of injuries is the solubilization of the embedded metal and the translocation and deposition to various organs of the body. Methods: Using a rodent model system developed in our laboratory to assess the health effects of embedded metal fragments, we surgically implanted metal pellets into the gastrocnemius muscles of male Sprague-Dawley rats. Test metals were chosen from a list promulgated by the U.S. Department of Defense as “metals of concern” with respect to embedded fragment wounds and included tungsten, nickel, cobalt, iron, copper, aluminum, lead, and depleted uranium. Tantalum was used as a control metal. Cohorts of the metal-implanted rats were humanely euthanized at 1, 3, 6, and 12-months post-implantation and a variety of tissues collected and analyzed for metal content using inductively coupled plasma-mass spectrometry. Results: With few exceptions, the embedded metal fragments eventually released solubilized metal ions, with the metals deposited in numerous tissues in the rats. Not all of the embedded metals localized to all tissues at significant levels. Copper, iron, and aluminum were not found in statistically significant levels, versus control, in any of the tissues analyzed. The other metals tested all appeared in elevated levels in the kidney which is not surprising since previous research has shown that they are also excreted in the urine at appreciable amounts. Tungsten and nickel were found in only a small number of tissues, tungsten in spleen, and nickel in liver and testes. Cobalt, lead, and depleted uranium showed the widest distribution with significant levels in liver, spleen, testes, lung, tibia, fibula, and femur. Conclusion: In this study, we showed that embedded metal fragments, such as those suffered in a shrapnel wound, could solubilize and metals become deposited in tissues far from the original site of implantation. Tissue deposition was metal-specific and many of the metals were found to cross the blood-testes barrier and were also found in bone. Since standard surgical guidance recommends leaving embedded fragments in place except for certain circumstances, this report will expand the understanding of tissue deposition of the solubilized metals and will hopefully aid healthcare professionals in developing long-term treatment strategies for dealing with these types of wounds.

Sub-chronic oral exposure of tungsten induces markers of kidney injury

Tungsten is a naturally occurring transition element used in a broad range of applications. As a result of its extensive use, we are increasingly exposed to tungsten from our environment, including potable water, since tungsten can become bioaccessible in ground sources. The kidneys are particularly susceptible to tungsten exposure as this is the main site for tungsten excretion. In this study, we investigated the prolonged effects of tungsten on the kidneys and how this may impact injury and function. When mice were exposed to tungsten in their drinking water for 1-month, kidney function had not significantly changed. Following 3-month exposure, mice were presented with deterioration in kidney function as determined by serum and urine creatinine levels. During 3-months of tungsten exposure, murine kidneys demonstrated significant increases in the myofibroblast marker ⍺SMA, and extracellular matrix products: fibronectin, collagen, and matricellular proteins. In addition, Masson's trichrome and H&E staining revealed an increase in fibrotic tissue and vacuolization of tubular epithelial cells, respectively, from kidneys of tungsten-treated mice, indicative of renal injury. In vitro treatment of kidney fibroblasts with tungsten led to increased proliferation and upregulation of Transforming Growth Factor Beta 1 (TGFβ1), which was consistent with the appearance of fibroblast-to-myofibroblast transition (FMT) markers. Our data suggest that continuous exposure to tungsten impairs kidney function that may lead to the development of chronic kidney disease (CKD).

Environmental and health hazards of military metal pollution

An increasing body of literature has demonstrated that armed conflicts and military activity may contribute to environmental pollution with metals, although the existing data are inconsistent. Therefore, in this paper, we discuss potential sources of military-related metal emissions, environmental metal contamination, as well as routes of metal exposure and their health hazards in relation to military activities. Emission of metals into the environment upon military activity occurs from weapon residues containing high levels of particles containing lead (Pb; leaded ammunition), copper (Cu; unleaded), and depleted uranium (DU). As a consequence, military activity results in soil contamination with Pb and Cu, as well as other metals including Cd, Sb, Cr, Ni, Zn, with subsequent metal translocation to water, thus increasing the risk of human exposure. Biomonitoring studies have demonstrated increased accumulation of metals in plants, invertebrates, and vertebrate species (fish, birds, mammals). Correspondingly, military activity is associated with human metal exposure that results from inhalation or ingestion of released particles, as well as injuries with subsequent metal release from embedded fragments. It is also notable that local metal accumulation following military injury may occur even without detectable fragments. Nonetheless, data on health effects of military-related metal exposures have yet to be systematized. The existing data demonstrate adverse neurological, cardiovascular, and reproductive outcomes in exposed military personnel. Moreover, military-related metal exposures also result in adverse neurodevelopmental outcome in children living within adulterated territories. Experimental in vivo and in vitro studies also demonstrated toxic effects of specific metals as well as widely used metal alloys, although laboratory data report much wider spectrum of adverse effects as compared to epidemiological studies. Therefore, further epidemiological, biomonitoring and laboratory studies are required to better characterize military-related metal exposures and their underlying mechanisms of their adverse toxic effects.

Urine miRNAs as potential biomarkers for systemic reactions induced by exposure to embedded metal

Aim: Explore the potential of urine microRNAs as biomarkers that may reflect the biological responses to pure metals embedded in skeletal muscle over time. Materials & methods: We tested a panel of military-relevant metals embedded in the gastrocnemius muscles of 3-month-old, male, Sprague-Dawley rats (n = 8/group) for a duration of 1, 3, 6 and 12 months, and performed small RNA-sequencing on the urine samples. Results: Results provide potential tissue targets affected by metal exposure and a list of unique or common urine microRNA biomarkers indicative of exposure to various metals, highlighting a complex systemic response. Conclusion: We have identified a panel of miRNAs as potential urine biomarkers to reflect the complex systemic response to embedded metal exposure.

Effect of embedded metal fragments on urinary metal levels and kidney biomarkers in the Sprague-Dawley rat

BACKGROUND

Wounds with embedded metal fragments are an unfortunate consequence of armed conflicts. In many cases the exact identity of the metal(s) and their long-term health effects, especially on the kidney, are not known.

AIM OF STUDY

The aim of this study was to quantitate the urinary levels of metals solubilized from surgically implanted metal pellets and to assess the effect of these metals on the kidney using a battery of biomarker assays.

MATERIALS AND METHODS

Using a rodent model system developed in our Institute to simulate embedded fragment injuries, eight metals considered likely components of an embedded fragment wound were individually implanted into the gastrocnemius muscle of male Sprague-Dawley rats. The rats were followed for 12 months post-implantation with urine collected prior to surgery then at 1-, 3-, 6-, 9-, and 12-months post-implantation to provide a within-subjects cohort for examination. Urinary metal levels were determined using inductively coupled plasma-mass spectrometry and urinary biomarkers assessed using commercially available kits to determine metal-induced kidney effects.

RESULTS

With few exceptions, most of the implanted metals rapidly solubilized and were found in the urine at significantly higher levels than in control animals as early as 1-month post-implantation. Surprisingly, many of the biomarkers measured were decreased compared to control at 1-month post-implantation before returning to normal at the later time points. However, two metals, iron and depleted uranium, showed increased levels of several markers at later time points, yet these levels also returned to normal as time progressed.

CONCLUSION

This study showed that metal pellets surgically implanted into the leg muscle of Sprague-Dawley rats rapidly solubilized with significant levels of the implanted metal found in the urine. Although kidney biomarker results were inconsistent, the changes observed along with the relatively low amounts of metal implanted, suggest that metal-induced renal effects need to be considered when caring for individuals with embedded metal fragment wounds.

The Utility of Spot vs 24-Hour Urine Samples for Metal Determination in Veterans With Retained Fragments

OBJECTIVES

The objective of this investigation is to explore the utility of using a spot urine sample in lieu of a 24-hour collection in assessing fragment-related metal exposure in war-injured veterans.

METHODS

Twenty-four veterans collected each urine void over a 24-hour period in separate containers. Concentrations of 13 metals were measured in each void and in a pooled 24-hour sample using inductively coupled plasma mass spectrometry. To assess the reliability of spot sample measures over time, intraclass correlations (ICCs) were calculated across all spot samples. Lin's concordance correlation coefficient was used to assess agreement between a randomly selected spot urine sample and each corresponding 24-hour sample.

RESULTS

In total, 149 spot urine samples were collected. Ten of the 13 metals measured had ICCs more than 0.4, suggesting "fair to good" reliability. Concordance coefficients were more than 0.4 for all metals, suggesting "moderate" agreement between spot and 24-hour concentrations, and more than 0.6 for seven of the 13 metals, suggesting "good" agreement.

CONCLUSIONS

Our fair to good reliability findings, for most metals investigated, and moderate to good agreement findings for all metals, across the range of concentrations observed here, suggest the utility of spot urine samples to obtain valid estimates of exposure in the longitudinal surveillance of metal-exposed populations.

Tungsten Increases Sex-Specific Osteoclast Differentiation in Murine Bone

Tungsten is a naturally occurring metal that is increasingly used in industry and medical devices, and is labeled as an emerging environmental contaminant. Like many metals, tungsten accumulates in bone. Our previous data indicate that tungsten decreases differentiation of osteoblasts, bone-forming cells. Herein, we explored the impact of tungsten on osteoclast differentiation, which function in bone resorption. We observed significantly elevated osteoclast numbers in the trabecular bone of femurs following oral exposure to tungsten in male, but not female mice. In order to explore the mechanism(s) by which tungsten increases osteoclast number, we utilized in vitro murine primary and cell line pre-osteoclast models. Although tungsten did not alter the adhesion of osteoclasts to the extracellular matrix protein, vitronectin, we did observe that tungsten enhanced RANKL-induced differentiation into tartrate-resistant acid phosphatase (TRAP)-positive mononucleated osteoclasts. Importantly, tungsten alone had no effect on differentiation or on the number of multinucleated TRAP-positive osteoclasts. Enhanced RANKL-induced differentiation correlated with increased gene expression of differentiated osteoclast markers Nfatc1, Acp5, and Ctsk. Although tungsten did not alter the RANK surface receptor expression, it did modulate its downstream signaling. Co-exposure of tungsten and RANKL resulted in sustained positive p38 signaling. These findings demonstrate that tungsten enhances sex-specific osteoclast differentiation, and together with previous findings of decreased osteoblastogenesis, implicate tungsten as a modulator of bone homeostasis.

The management of embedded metal fragment patients and the role of chelation Therapy: A workshop of the Department of Veterans Affairs-Walter Reed National Medical Center

Exposure to retained metal fragments from war-related injuries can result in increased systemic metal concentrations, thereby posing potential health risks to target organs far from the site of injury. Given the large number of veterans who have retained fragments and the lack of clear guidance on how to medically manage these individuals, the Department of Veterans Affairs (VA) convened a meeting of chelation experts and clinicians who care for embedded fragment patients to discuss current practices and provide medical management guidance. Based on this group's clinical expertise and review of published literature, the evidence presented suggests that, at least in the case of lead fragments, short-term chelation therapy may be beneficial for embedded fragment patients experiencing acute symptoms associated with metal toxicity; however, in the absence of clinical symptoms or significantly elevated blood lead concentrations (greater than 80 µg/dL), chelation therapy may offer little to no benefit for individuals with retained fragments and pose greater risks due to remobilization of metals stored in bone and other soft tissues. The combination of periodic biomonitoring to assess metal body burden, longitudinal fragment imaging, and selective fragment removal when metal concentrations approach critical injury thresholds offers a more conservative management approach to caring for patients with embedded fragments.