Quest to identify geochemical risk factors associated with chronic kidney disease of unknown etiology (CKDu) in an endemic region of Sri Lanka-a multimedia laboratory analysis of biological, food, and environmental samples

The emergence of a new form of chronic kidney disease of unknown etiology (CKDu) in Sri Lanka's North Central Province (NCP) has become a catastrophic health crisis. CKDu is characterized as slowly progressing, irreversible, and asymptomatic until late stages and, importantly, not attributed to diabetes, hypertension, or other known risk factors. It is postulated that the etiology of CKDu is multifactorial, involving genetic predisposition, nutritional and dehydration status, exposure to one or more environmental nephrotoxins, and lifestyle factors. The objective of this limited geochemical laboratory analysis was to determine the concentration of a suite of heavy metals and trace element nutrients in biological samples (human whole blood and hair) and environmental samples (drinking water, rice, soil, and freshwater fish) collected from two towns within the endemic NCP region in 2012 and 2013. This broad panel, metallomics/mineralomics approach was used to shed light on potential geochemical risk factors associated with CKDu. Based on prior literature documentation of potential nephrotoxins that may play a role in the genesis and progression of CKDu, heavy metals and fluoride were selected for analysis. The geochemical concentrations in biological and environmental media areas were quantified. Basic statistical measurements were subsequently used to compare media against applicable benchmark values, such as US soil screening levels. Cadmium, lead, and mercury were detected at concentrations exceeding US reference values in many of the biological samples, suggesting that study participants are subjected to chronic, low-level exposure to these elements. Within the limited number of environmental media samples, arsenic was determined to exceed initial risk screening and background concentration values in soil, while data collected from drinking water samples reflected the unique hydrogeochemistry of the region, including the prevalence of hard or very hard water, and fluoride, iron, manganese, sodium, and lead exceeding applicable drinking water standards in some instances. Current literature suggests that the etiology of CKDu is likely multifactorial, with no single biological or hydrogeochemical parameter directly related to disease genesis and progression. This preliminary screening identified that specific constituents may be present above levels of concern, but does not compare results against specific kidney toxicity values or cumulative risk related to a multifactorial disease process. The data collected from this limited investigation are intended to be used in the subsequent study design of a comprehensive and multifactorial etiological study of CKDu risk factors that includes sample collection, individual surveys, and laboratory analyses to more fully evaluate the potential environmental, behavioral, genetic, and lifestyle risk factors associated with CKDu.

Validation of a Metallomics Analysis of Placenta Tissue by Inductively-Coupled Plasma Mass Spectrometry

Trace elements can play an important role in maternal health and fetal development, and deficiencies in some essential minerals including zinc and copper have been correlated in some individuals to the development of birth defects and adverse health outcomes later in life. The exact etiology of conditions like preeclampsia and the effects of fetal exposure to toxic metals has not been determined, making the assessment of trace element levels crucial to the elucidation of the causes of conditions like preeclampsia. Previous studies analyzing serum and placenta tissue have produced conflicting findings, suggesting the need for a robust, validated sample preparation and analysis method for the determination of trace elements in placenta. In this report, an acid digestion method and analysis by ICP-MS for a broad metallomics/mineralomics panel of trace elements is developed and validated over three experimental days for inter- and intraday precision and accuracy, linear range, matrix impact, and dilution verification. Spike recovery experiments were performed for the essential elements chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn), and the toxic elements arsenic (As), cadmium (Cd), and lead (Pb) at levels equal to and in excess of native concentrations in control placenta tissue. The validated method will be essential for the development of scientific studies of maternal health and toxic metal exposure effects in childhood.

Dietary Intake Estimates and Urinary Cadmium Levels in Danish Postmenopausal Women

BACKGROUND

Cadmium is a known carcinogen that can disrupt endocrine signalling. Cigarette smoking and food are the most common routes of non-occupational exposure to cadmium. Cadmium accumulates in the kidney and can be measured in urine, making urine cadmium (U-Cd) a biomarker of long-term exposure. However dietary-cadmium (D-Cd) intake estimates are often used as surrogate indicator of cadmium exposure in non-smoking subjects. It is therefore important to investigate the concordance between D-Cd estimates obtained with Food Frequency Questionnaires and U-Cd.

METHODS

U-Cd levels were compared with estimated dietary-cadmium (D-Cd) intake in 1764 post-menopausal women from the Danish Diet, Cancer and Health cohort. For each participant, a food frequency questionnaire, and measures of cadmium content in standard recipes were used to judge the daily intake of cadmium, normalized by daily caloric intake. Cadmium was measured by ICP-MS in spot urine sampled at baseline and normalized by urinary creatinine. Information on diet, socio-demographics and smoking were self-reported at baseline.

RESULTS

Linear regressions between U-Cd and D-Cd alone revealed minimal but significant positive correlation in never smokers (R2 = 0.0076, β = 1.5% increase per 1 ng Cd kcal(-1), p = 0.0085, n = 782), and negative correlation in current smokers (R2 = 0.0184, β = 7.1% decrease per 1 ng Cd kcal(-1) change, p = 0.0006, n = 584). In the full study population, most of the variability in U-Cd was explained by smoking status (R2 = 0.2450, n = 1764). A forward selection model revealed that the strongest predictors of U-Cd were age in never smokers (Δ R2 = 0.04), smoking duration in former smokers (Δ R2 = 0.06) and pack-years in current smokers (Δ R2 = 0.07). Food items that contributed to U-Cd were leafy vegetables and soy-based products, but explained very little of the variance in U-Cd.

CONCLUSIONS

Dietary-Cd intake estimated from food frequency questionnaires correlates only minimally with U-Cd biomarker, and its use as a Cd exposure indicator may be of limited utility in epidemiologic studies.

Development, validation, and application of an ultra-performance liquid chromatography-sector field inductively coupled plasma mass spectrometry method for simultaneous determination of six organotin compounds in human serum

Organotin compounds (OTCs) are heavily employed by industry for a wide variety of applications, including the production of plastics and as biocides. Reports of environmental prevalence, differential toxicity between OTCs, and poorly characterized human exposure have fueled the demand for sensitive, selective speciation methods. The objective of this investigation was to develop and validate a rapid, sensitive, and selective analytical method for the simultaneous determination of a suite of organotin compounds, including butyl (mono-, di-, and tri-substituted) and phenyl (mono-, di-, and tri-substituted) species in human serum. The analytical method utilized ultra-performance liquid chromatography (UPLC) coupled with sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). The small (sub-2 µm) particle size of the UPLC column stationary phase and the sensitivity of the SF-ICP-MS enabled separation and sensitive determination of the analyte suite with a runtime of approximately 3 min. Validation activities included demonstration of method linearity over the concentration range of approximately 0.250-13.661 ng mL(-1), depending on the species; intraday precision of less than 21%, interday precision of less than 18%, intraday accuracy of -5.3% to 19%, and interday accuracy of -14% to 15% for all species; specificity, and matrix impact. In addition, sensitivity, and analyte stability under different storage scenarios were evaluated. Analyte stability was found to be limited for most species in freezer, refrigerator, and freeze-thaw conditions. The validated method was then applied for the determination of the OTCs in human serum samples from women participating in the Snart-Foraeldre/MiljØ (Soon-Parents/Environment) Study. The concentration of each OTC ranged from below the experimental limit of quantitation to 10.929 ng tin (Sn) mL(-1) serum. Speciation values were confirmed by a total Sn analysis.

Development of an analytical method for assessment of silver nanoparticle content in biological matrices by inductively coupled plasma mass spectrometry

Silver nanoparticles (AgNPs) are a broad class of synthetic nanoparticles that are utilized in a wide variety of consumer products as antimicrobial agents. Despite their widespread use, a detailed understanding of their toxicological characteristics and biological and environmental hazards is not available. To support research into the biodistribution and toxicology of AgNPs, it is necessary to develop a suitable method for the assessment of AgNP content in biological samples. Two methods were developed and validated to analyze citrate-coated AgNP content that utilize acid digestion of rodent feces and liver tissue samples, and a third method was developed for the dilution and direct analysis of rodent urine samples. Following sample preparation, the silver content of each sample was determined by inductively coupled plasma mass spectrometry (ICP-MS) to quantify the silver and AgNP levels present. Analysis of rat feces matrix yielded analytical recoveries ranging from 82 to 93 %. Liver tissue spiked with a formulation of AgNPs over a range of concentrations yielded analytical recoveries between 88 and 90 %, providing acceptable accuracy results. The analysis of silver in urine samples exhibited recovery values ranging from 80 to 85 % for AgNP formulations and 62-84 % for standard silver ion solutions. All determinations exhibited a high degree of analytical precision. The results obtained here suggest that matrix interference plays a minimal role in AgNP recovery in feces and liver tissue, while the urine matrix can exhibit a significant effect on the determination of silver content.

Analysis of human serum and whole blood for mineral content by ICP-MS and ICP-OES: development of a mineralomics method

Minerals are inorganic compounds that are essential to the support of a variety of biological functions. Understanding the range and variability of the content of these minerals in biological samples can provide insight into the relationships between mineral content and the health of individuals. In particular, abnormal mineral content may serve as an indicator of illness. The development of robust, reliable analytical methods for the determination of the mineral content of biological samples is essential to developing biological models for understanding the relationship between minerals and illnesses. This paper describes a method for the analysis of the mineral content of small volumes of serum and whole blood samples from healthy individuals. Interday and intraday precision for the mineral content of the blood (250 μL) and serum (250 μL) samples was measured for eight essential minerals--sodium (Na), calcium (Ca), magnesium (Mg), potassium (K), iron (Fe), zinc (Zn), copper (Cu), and selenium (Se)--by plasma spectrometric methods and ranged from 0.635 to 10.1% relative standard deviation (RSD) for serum and 0.348-5.98% for whole blood. A comparison of the determined ranges for ten serum samples and six whole blood samples provided good agreement with literature reference ranges. The results demonstrate that the digestion and analysis methods can be used to reliably measure the content of these minerals and potentially of other minerals.

The Affinity of Indium(III) for Nitrogen-donor Ligands in Aqueous Solution. A Study of the Complexing of Indium(III) with Polyamines by Differential Pulse Voltammetry, Density Functional Theory, and Crystallography

The affinity of In(III) for N-donor ligands was investigated by differential pulse voltammetry, DFT calculations, and crystallography. The structure of [In(tpen)(CH3COO)](ClO4)2 ・ 0.5H2O (1) is reported (tpen = N,N,N´ ,N´-tetrakis(2-pyridylmethyl)ethylenediamine): Monoclinic, P21/n, a = 8.687(4), b = 7.767(8), c = 20.432(10) Å , β = 93.372(8)°, Z = 4, R = 0.0518. The In(III) center is 7-coordinate, with six In-N bonds to the tpen ligand in the range 2.306 - 2.410 Å, and a unidentate acetate group with In-O = 2.247 Å. The formation constants of In3+ in 0.1 M NaNO3+ at 25 °C are (M = In(III), L = ligand, H = proton): L = triethylenetetramine, logβ (MLH2) = 25.3±}0.3, logK1 = 14.43±}0.09, and logβ (ML(OH)2) = 27.7±}0.1; tetraethylenepentamine, logβ (MLH) = 20.8±}0.2, and ML (logβ (ML) = 20.1±}0.3); diglycolic acid, (logβ (MLH) = 8.06±}0.06), logK1 = 6.02±} 0.06, logβ2 = 9.40±}0.08; tpen, logK1 = 17.71±}0.07; N,N´-bis(2-pyridylmethyl)ethylenediamine, logK1 = 14.69±}0.05; 1,10-phenanthroline, logK1 = 6.81±}0.07, logK2 = 6.44±}0.07, logK3 = 6.20±}0.08. Correlations are shown between the determined formation constants for the polyamines and logK1(NH3) values for a wide variety of metal ions. For M(II) ions, the log K1(NH3) values are experimental data, but for M(III) ions the data are predicted by an empirical dual-basicity equation, including logK1(NH3) = 4.0 for In(III). DFT calculations are used to obtain ΔE for the reaction [M(H2O)6]n+ + NH3 ⇆[M(H2O)5NH3]n+ + H2O for M(II) through M(IV) ions in water, represented as a structureless medium with the dielectric constant of water. Correlations are found that support the predicted value of logK1(NH3) for In(III) of 4.0. The nature of the intercepts on such correlations are discussed.

Evaluation of methods for analysis of lead in air particulates: an intra-laboratory and inter-laboratory comparison

In 2008, the United States Environmental Protection Agency (USEPA) set a new National Ambient Air Quality Standard (NAAQS) for lead in total suspended particulate matter (Pb-TSP) which called for significant decreases in the allowable limits. The Federal Reference Method (FRM) for Pb-TSP promulgated in 1978 prescribes analysis of Pb by flame atomic absorption spectroscopy (FAAS), but the new limits approach the limits of quantitation of FAAS. On August 2, 2013, the USEPA finalized a new FRM for Pb-TSP. This new FRM describes two extraction methods and analysis by inductively coupled plasma-mass spectrometry (ICP-MS). The study described here was performed to evaluate the use of ICP-MS in the analysis of Pb-TSP for implementation of this new FRM. A multi-laboratory study of the new FRM demonstrated acceptable intra- and inter-laboratory precision and comparability for glass fiber, quartz, and PTFE filters, and acceptable accuracy for the analysis of three National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs). A comparison was made between analytical results obtained using the 1978 FRM and those obtained using the new FRM. The results demonstrate that the ICP-MS method performs acceptably for the determination of Pb-TSP with lower limits of quantitation and strong inter- and intra-laboratory precision.

Rapid speciation and determination of vanadium compounds using ion-pair reversed-phase ultra-high-performance liquid chromatography inductively coupled plasma-sector field mass spectrometry

Environmental vanadium contamination is a potential concern to public health, as evidenced by its place on the U.S. Environmental Protection Agency Drinking Water Contaminant Candidate List as a priority contaminant. Vanadium toxicity varies significantly between different oxidation states; therefore, it is crucial to be able to monitor the speciation of vanadium in environmental samples. In this study, a novel method is described that utilizes ion-pair reversed-phase ultra-high-performance liquid chromatography with inductively coupled plasma-sector field mass spectrometry (IP-RP-UHPLC-ICP-SFMS) to separate vanadyl and vanadate ions and resolve a major polyatomic spectral interference ((35)Cl(16)O(+)) in less than a minute. Detection limits were obtained in the low ngL(-1) (part per trillion) range with linear calibrations across several orders of magnitude (50ngL(-1)-100μgL(-1)). The mechanism of chromatographic retention was elucidated through investigation of the role of ethylenediaminetetraacetic acid, tetrabutylammonium ion and pH on elution. The optimized method was then applied to the speciation of vanadium in local lake water samples.

Amelioration of metal-induced toxicity in Caenorhabditis elegans: utility of chelating agents in the bioremediation of metals

The presence of toxic amounts of transition metals in the environment may originate from a range of human activities and natural processes. One method for the removal of toxic levels of metals is through chelation by small molecules. However, chelation is not synonymous with detoxification and may not affect the bioavailability of the metal. To test the bioavailability of chelated metals in vivo, the effects of several metal/chelator combinations were tested in the environmentally relevant organism Caenorhabditis elegans. The effect of metal exposure on nematode growth was used to determine the toxicity of cadmium, copper, nickel, and zinc. The restoration of growth to levels observed in nonexposed nematodes was used to determine the protective effects of the polydentate chelators: acetohydroxamic acid (AHA), cyclam, cysteine, calcium EDTA, desferrioxamine B, 1,2-dimethyl,3-hydroxy,4-pyridinone, and histidine. Cadmium toxicity was removed only by EDTA; copper toxicity was removed by all of the chelators except AHA; nickel toxicity was removed by cyclam, EDTA, and histidine; and zinc toxicity was removed by only EDTA. These results demonstrate the utility of polydentate chelators in the remediation of metal-contaminated systems. They also demonstrate that although the application of a chelator to metal contaminants may be effective, binding alone cannot be used to predict the level of remediation. Remediation depends on a number of factors, including metal complex speciation in the environment.

Trace metal complexation by the triscatecholate siderophore protochelin: structure and stability

Although siderophores are generally viewed as biological iron uptake agents, recent evidence has shown that they may play significant roles in the biogeochemical cycling and biological uptake of other metals. One such siderophore that is produced by A. vinelandii is the triscatecholate protochelin. In this study, we probe the solution chemistry of protochelin and its complexes with environmentally relevant trace metals to better understand its effect on metal uptake and cycling. Protochelin exhibits low solubility below pH 7.5 and degrades gradually in solution. Electrochemical measurements of protochelin and metal-protochelin complexes reveal a ligand half-wave potential of 200 mV. The Fe(III)Proto(3-) complex exhibits a salicylate shift in coordination mode at circumneutral to acidic pH. Coordination of Mn(II) by protochelin above pH 8.0 promotes gradual air oxidation of the metal center to Mn(III), which accelerates at higher pH values. The Mn(III)Proto(3-) complex was found to have a stability constant of log β(110) = 41.6. Structural parameters derived from spectroscopic measurements and quantum mechanical calculations provide insights into the stability of the Fe(III)Proto(3-), Fe(III)H(3)Proto, and Mn(III)Proto(3-) complexes. Complexation of Co(II) by protochelin results in redox cycling of Co, accompanied by accelerated degradation of the ligand at all solution pH values. These results are discussed in terms of the role of catecholate siderophores in environmental trace metal cycling and intracellular metal release.