Arsenic Exposure, Blood DNA Methylation, and Cardiovascular Disease.

BACKGROUND: Epigenetic dysregulation has been proposed as a key mechanism for arsenic-related cardiovascular disease (CVD). We evaluated differentially methylated positions (DMPs) as potential mediators on the association between arsenic and CVD. METHODS: Blood DNA methylation was measured in 2321 participants (mean age 56.2, 58.6% women) of the Strong Heart Study, a prospective cohort of American Indians. Urinary arsenic species were measured using high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry. We identified DMPs that are potential mediators between arsenic and CVD. In a cross-species analysis, we compared those DMPs with differential liver DNA methylation following early-life arsenic exposure in the apoE knockout (apoE-/-) mouse model of atherosclerosis. RESULTS: A total of 20 and 13 DMPs were potential mediators for CVD incidence and mortality, respectively, several of them annotated to genes related to diabetes. Eleven of these DMPs were similarly associated with incident CVD in 3 diverse prospective cohorts (Framingham Heart Study, Women's Health Initiative, and Multi-Ethnic Study of Atherosclerosis). In the mouse model, differentially methylated regions in 20 of those genes and DMPs in 10 genes were associated with arsenic. CONCLUSIONS: Differential DNA methylation might be part of the biological link between arsenic and CVD. The gene functions suggest that diabetes might represent a relevant mechanism for arsenic-related cardiovascular risk in populations with a high burden of diabetes.

Urinary concentrations of metals before and after volcanic eruption: a natural experiment surrounding the eruption of Volcán de Fuego, 2018.

Volcanic eruptions increase environmental heavy metal concentrations, yet little research has been performed on their extrapulmonary human health effects. We fortuitously collected biological samples in a cohort of Guatemalan sugarcane cutters in the area surrounding Volcán de Fuego before and after the June 2018 eruption. We sought to determine whether stratovolcanic activity was associated with changes in urinary concentrations of heavy metals in a cohort of sugarcane workers. In this exploratory analysis, we found significant increases in urinary arsenic, (ß = 1.46, P < 0.0001), cadmium (ß = 1.03, P < 0.0001), and lead (ß = 0.87, P = 0.003) in participants with residential proximity to Volcán de Fuego as compared to participants farther away, suggesting that volcanic activity could be associated with acute heavy metal exposures. This natural experiment is, to our knowledge, the first of its kind and suggests a need for more research into heavy metal exposure-related health impacts of volcanic eruptions.

Metal distribution, bioavailability and isotope variations in polluted soils from Lower Swansea Valley, UK.

Soils in the Lower Swansea Valley, (United Kingdom) contain elevated level of metals, enough to cause direct or indirect effects on human health. This study assesses the severity of soil pollution and bioavailability of Cu and other metals (Ni, Zn, Co, Pb and Cr) in soils with various distances from a Ni refinery. We compare Cu concentrations in operationally defined soil fractions (bioavailable, bound to Fe/Mn oxide and incorporated in organic matter) with other metals (Ni, Zn, Pb, Co, Cr) usually occurring in ores used in metallurgic processes and report their pollution and geoaccumulation indices (PI and Igeo). Further, we use Cu stable isotope ratios (δ65Cu) to trace the fate and mobility of Cu in soils. Our data suggest a point source of contamination for some of the heavy metals including Ni (Igeo = 1.9), Zn (Igeo = 0.28) and Cu (Igeo = 3.6) near the Ni refinery. However, Co (Igeo = 0.15) and Pb (Igeo = 3.3) contaminations are likely to be linked to different sources. No elevated Cr levels (Igeo= -0.07) occur in any of the studied soils. All soil metals are predominantly associated with organic matter (>50%) which  reduces their bioavailibility and thus their risk for ecological and human health. The Cu isotope data show that Cu in soil organic matter is enriched in 65Cu, while the lighter isotopes (63Cu) remain in the dissolved bioavailable Cu fraction (Δ65Cuorganic-bioavailable is +0.12 ± 0.13‰). This suggests the preferential complexation of 65Cu with soil organic matter after dissolution of Cu deposited to the soil. Thus, Cu isotope data can effectively indicate pathways of metal migration in polluted soils.

Se Isotopes as Groundwater Redox Indicators: Detecting Natural Attenuation of Se at an in Situ Recovery U Mine.

One of the major ecological concerns associated with the in situ recovery (ISR) of uranium (U) is the environmental release of soluble, toxic selenium (Se) oxyanions generated by mining. Post-mining natural attenuation by the residual reductants in the ore body and reduced down-gradient sediments should mitigate the risk of Se contamination in groundwater. In this work, we investigate the Se concentrations and Se isotope systematics of groundwater and of U ore bearing sediments from an ISR site at Rosita, TX, USA. Our results show that selenate (Se(VI)) is the dominant Se species in Rosita groundwater, and while several up-gradient wells have elevated Se(VI), the majority of the ore zone and down-gradient wells have little or no Se oxyanions. In addition, the δ82SeVI of Rosita groundwater is generally elevated relative to the U ore up to +6.14‰, with the most enriched values observed in the ore-zone wells. Increasing δ82Se with decreasing Se(VI) conforms to a Rayleigh type distillation model with an ε of -2.25‰ ± 0.61‰, suggesting natural Se(VI) reduction occurring along the hydraulic gradient at the Rosita ISR site. Furthermore, our results show that Se isotopes are excellent sensors for detecting and monitoring post-mining natural attenuation of Se oxyanions at ISR sites.

Fate of Selenium in Soils at a Seleniferous Site Recorded by High Precision Se Isotope Measurements.

Selenium poisoning is a significant health problem in parts of Punjab, India, which is an area of intense agricultural productivity. To determine the complex soil dynamics that control distribution of Se in this area, we measured concentrations and δ(82/76)Se of bulk Se and individual Se pools in four soil profiles. This was compared against δ(82/76)Se of crops and groundwater used for irrigation. The isotopic composition of bulk Se and component Se pools reveal spatial heterogeneity. The bulk δ(82/76)Se show progressively lower values with increasing soil depth indicating the preferential migration of isotopically lighter Se downward through the soil profile. The δ(82/76)Se of water-soluble Se is isotopically heavier than δ(82/76)Se of adsorbed Se, suggesting Se isotope fractionation by reduction prior to scavenging by reactive minerals in the soil. The organically bound Se is isotopically lighter than water-soluble Se and correlates with the C/N ratio at different soil depths. Thus, Se immobilization by redox cycling controls the biogeochemical Se cycle in the soil. Se isotope ratios help to trace biochemical processes of Se in agricultural seleniferous soils and provide an important assessment for better soil management mitigating Se concentrations of ecotoxicological levels.

Metal-binding amino acid ligands commonly found in metalloproteins differentially fractionate copper isotopes.

Copper (Cu) is a cofactor in numerous key proteins and, thus, an essential element for life. In biological systems, Cu isotope abundances shift with metabolic and homeostatic state. However, the mechanisms underpinning these isotopic shifts remain poorly understood, hampering use of Cu isotopes as biomarkers. Computational predictions suggest that isotope fractionation occurs when proteins bind Cu, with the magnitude of this effect dependent on the identity and arrangement of the coordinating amino acids. This study sought to constrain equilibrium isotope fractionation values for Cu bound by common amino acids at protein metal-binding sites. Free and bound metal ions were separated via Donnan dialysis using a cation-permeable membrane. Isotope ratios of pre- and post-dialysis solutions were measured by MC-ICP-MS following purification. Sulfur ligands (cysteine) preferentially bound the light isotope (63Cu) relative to water (Δ65Cucomplex-free = - 0.48 ± 0.18‰) while oxygen ligands favored the heavy isotope (65Cu; + 0.26 ± 0.04‰ for glutamate and + 0.16 ± 0.10‰ for aspartate). Binding by nitrogen ligands (histidine) imparted no isotope effect (- 0.01 ± 0.04‰). This experimental work unequivocally demonstrates that amino acids differentially fractionate Cu isotopes and supports the hypothesis that metalloprotein biosynthesis affects the distribution of transition metal isotopes in biological systems.

Tampons as a source of exposure to metal(loid)s.

BACKGROUND: Between 52-86% of people who menstruate in the United States use tampons-cotton and/or rayon/viscose 'plugs'-to absorb menstrual blood in the vagina. Tampons may contain metals from agricultural or manufacturing processes, which could be absorbed by the vagina's highly absorptive tissue, resulting in systemic exposure. To our knowledge, no previous studies have measured metals in tampons. OBJECTIVES: We evaluated the concentrations of 16 metal(loid)s in 30 tampons from 14 tampon brands and 18 product lines and compared the concentrations by tampon characteristics. METHODS: About 0.2 - 0.3 g from each tampon (n = 60 samples) were microwave-acid digested and analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine concentrations of arsenic, barium, calcium, cadmium, cobalt, chromium, copper, iron, manganese, mercury, nickel, lead, selenium, strontium, vanadium, and zinc. We compared concentrations by several tampon characteristics (region of purchase, organic material, brand type) using median quantile mixed models. RESULTS: We found measurable concentrations of all 16 metals assessed. We detected concentrations of several toxic metals, including elevated mean concentrations of lead (geometric mean [GM] = 120 ng/g), cadmium (GM = 6.74 ng/g), and arsenic (GM = 2.56 ng/g). Metal concentrations differed by region of tampon purchase (US versus European Union/United Kingdom), by organic versus non-organic material, and for store- versus name-brand tampons. Most metals differed by organic status; lead concentrations were higher in non-organic tampons while arsenic was higher in organic tampons. No categoriy had consistently lower concentrations of all or most metals. DISCUSSION: Tampon use is a potential source of metal exposure. We detected all 16 metals in at least one sampled tampon, including some toxic metals like lead that has no "safe" exposure level. Future research is needed to replicate our findings and determine whether metals can leach out of tampons and cross the vaginal epithelium into systemic circulation.

Analysis of urinary potassium isotopes and association with pancreatic health: healthy, diabetic and cancerous states.

Background: More than 700 million people worldwide suffer from diseases of the pancreas, such as diabetes, pancreatitis and pancreatic cancer. Often dysregulation of potassium (K+) channels, co-transporters and pumps can promote development and progression of many types of these diseases. The role of K+ transport system in pancreatic cell homeostasis and disease development remains largely unexplored. Potassium isotope analysis (δ41K), however, might have the potential to detect minute changes in metabolic processes relevant for pancreatic diseases. Methods: We assessed urinary K isotope composition in a case-control study by measuring K concentrations and δ41K in spot urines collected from patients diagnosed with pancreatic cancer (n=18), other pancreas-related diseases (n=14) and compared those data to healthy controls (n=16). Results: Our results show that urinary K+ levels for patients with diseased pancreas (benign and pancreatic cancer) are significantly lower than the healthy controls. For δ41K, the values tend to be higher for individuals with pancreatic cancer (mean δ41K = -0.58 ± 0.33‰) than for healthy individuals (mean δ41K = -0.78 ± 0.19‰) but the difference is not significant (p=0.08). For diabetics, urinary K+ levels are significantly lower (p=0.03) and δ41K is significantly higher (p=0.009) than for the healthy controls. These results suggest that urinary K+ levels and K isotopes can help identify K disturbances related to diabetes, an associated factors of all-cause mortality for diabetics. Conclusion: Although the K isotope results should be considered exploratory and hypothesis-generating and future studies should focus on larger sample size and δ41K analysis of other K-disrupting diseases (e.g., chronic kidney disease), our data hold great promise for K isotopes as disease marker.

Method validation for (ultra)-trace element concentrations in urine for small sample volumes in large epidemiological studies: application to the population-based epidemiological multi-ethnic study of atherosclerosis (MESA).

Analysis of essential and non-essential trace elements in urine has emerged as a valuable tool for assessing occupational and environmental exposures, diagnosing nutritional status and guiding public health and health care intervention. Our study focused on the analysis of trace elements in urine samples from the Multi-Ethnic Study of Atherosclerosis (MESA), a precious resource for health research with limited sample volumes. Here we provide a comprehensive and sensitive method for the analysis of 18 elements using only 100 µL of urine. Method sensitivity, accuracy, and precision were assessed. The analysis by inductively coupled plasma mass spectrometry (ICP-MS) included the measurement of antimony (Sb), arsenic (As), barium (Ba), cadmium (Cd), cesium (Cs), cobalt (Co), copper (Cu), gadolinium (Gd), lead (Pb), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), strontium (Sr), thallium (Tl), tungsten (W), uranium (U), and zinc (Zn). Further, we reported urinary trace element concentrations by covariates including gender, ethnicity/race, smoking and location. The results showed good accuracy and sensitivity of the ICP-MS method with the limit of detections rangings between 0.001 µg L-1 for U to 6.2 µg L-1 for Zn. Intra-day precision for MESA urine analysis varied between 1.4% for Mo and 26% for Mn (average 6.4% for all elements). The average inter-day precision for most elements was <8.5% except for Gd (20%), U (16%) and Mn (19%) due to very low urinary concentrations. Urinary mean concentrations of non-essential elements followed the order of Sr > As > Cs > Ni > Ba > Pb > Cd > Gd > Tl > W > U. The order of urinary mean concentrations for essential trace elements was Zn > Se > Mo > Cu > Co > Mn. Non-adjusted mean concentration of non-essential trace elements in urine from MESA participants follow the order Sr > As > Cs > Ni > Ba > Pb > Cd > Gd > Tl > W > U. The unadjusted urinary mean concentrations of essential trace elements decrease from Zn > Se > Mo > Cu > Co > Mn.

Contribution of arsenic and uranium in private wells and community water systems to urinary biomarkers in US adults: The Strong Heart Study and the Multi-Ethnic Study of Atherosclerosis.

BACKGROUND: Chronic exposure to inorganic arsenic (As) and uranium (U) in the United States (US) occurs from unregulated private wells and federally regulated community water systems (CWSs). The contribution of water to total exposure is assumed to be low when water As and U concentrations are low. OBJECTIVE: We examined the contribution of water As and U to urinary biomarkers in the Strong Heart Family Study (SHFS), a prospective study of American Indian communities, and the Multi-Ethnic Study of Atherosclerosis (MESA), a prospective study of racially/ethnically diverse urban U.S. communities. METHODS: We assigned residential zip code-level estimates in CWSs (µg/L) and private wells (90th percentile probability of As >10 µg/L) to up to 1485 and 6722 participants with dietary information and urinary biomarkers in the SHFS (2001-2003) and MESA (2000-2002; 2010-2011), respectively. Urine As was estimated as the sum of inorganic and methylated species, and urine U was total uranium. We used linear mixed-effects models to account for participant clustering and removed the effect of dietary sources via regression adjustment. RESULTS: The median (interquartile range) urine As was 5.32 (3.29, 8.53) and 6.32 (3.34, 12.48) µg/L for SHFS and MESA, respectively, and urine U was 0.037 (0.014, 0.071) and 0.007 (0.003, 0.018) µg/L. In a meta-analysis across both studies, urine As was 11% (95% CI: 3, 20%) higher and urine U was 35% (5, 73%) higher per twofold higher CWS As and U, respectively. In the SHFS, zip-code level factors such as private well and CWS As contributed 46% of variation in urine As, while in MESA, zip-code level factors, e.g., CWS As and U, contribute 30 and 49% of variation in urine As and U, respectively. IMPACT STATEMENT: We found that water from unregulated private wells and regulated CWSs is a major contributor to urinary As and U (an estimated measure of internal dose) in both rural, American Indian populations and urban, racially/ethnically diverse populations nationwide, even at levels below the current regulatory standard. Our findings indicate that additional drinking water interventions, regulations, and policies can have a major impact on reducing total exposures to As and U, which are linked to adverse health effects even at low levels.

Effect of an Arsenic Mitigation Program on Arsenic Exposure in American Indian Communities: A Cluster Randomized Controlled Trial of the Community-Led Strong Heart Water Study Program.

BACKGROUND: Chronic arsenic exposure has been associated with an increased risk of cardiovascular disease; diabetes; cancers of the lung, pancreas and prostate; and all-cause mortality in American Indian communities in the Strong Heart Study. OBJECTIVE: The Strong Heart Water Study (SHWS) designed and evaluated a multilevel, community-led arsenic mitigation program to reduce arsenic exposure among private well users in partnership with Northern Great Plains American Indian Nations. METHODS: A cluster randomized controlled trial (cRCT) was conducted to evaluate the effectiveness of the SHWS arsenic mitigation program over a 2-y period on a) urinary arsenic, and b) reported use of arsenic-safe water for drinking and cooking. The cRCT compared the installation of a point-of-use arsenic filter and a mobile Health (mHealth) program (3 phone calls; SHWS mHealth and Filter arm) to a more intensive program, which included this same program plus three home visits (3 phone calls and 3 home visits; SHWS Intensive arm). RESULTS: A 47% reduction in urinary arsenic [geometric mean (GM)=13.2 to 7.0µg/g creatinine] was observed from baseline to the final follow-up when both study arms were combined. By treatment arm, the reduction in urinary arsenic from baseline to the final follow-up visit was 55% in the mHealth and Filter arm (GM=14.6 to 6.55µg/g creatinine) and 30% in the Intensive arm (GM=11.2 to 7.82µg/g creatinine). There was no significant difference in urinary arsenic levels by treatment arm at the final follow-up visit comparing the Intensive vs. mHealth and Filter arms: GM ratio of 1.21 (95% confidence interval: 0.77, 1.90). In both arms combined, exclusive use of arsenic-safe water from baseline to the final follow-up visit significantly increased for water used for cooking (17% to 53%) and drinking (12% to 46%). DISCUSSION: Delivery of the interventions for the community-led SHWS arsenic mitigation program, including the installation of a point-of-use arsenic filter and a mHealth program on the use of arsenic-safe water (calls only, no home visits), resulted in a significant reduction in urinary arsenic and increases in reported use of arsenic-safe water for drinking and cooking during the 2-y study period. These results demonstrate that the installation of an arsenic filter and phone calls from a mHealth program presents a promising approach to reduce water arsenic exposure among private well users. https://doi.org/10.1289/EHP12548.

Endotracheal nebulization of gold nanoparticles for noninvasive pulmonary drug delivery.

Background & aims: Gold nanoparticles (AuNPs) are useful tools for noninvasive drug delivery. AuNP nebulization has shown poor deposition results, and AuNP tracking postadministration has involved methods inapplicable to clinical settings. The authors propose an intratracheal delivery method for minimal AuNP loss and computed tomography scans for noninvasive tracking. Materials & methods: Through high-frequency and directed nebulization postendotracheal intubation, the authors treated rats with AuNPs. Results & conclusion: The study showed a dose-dependent and bilateral distribution of AuNPs causing no short-term distress to the animal or risk of airway inflammation. The study demonstrated that AuNPs do not deposit in abdominal organs and show targeted delivery to human lung fibroblasts, offering a specific and noninvasive strategy for respiratory diseases requiring long-term therapies.

This study presents an alternative method for drug delivery involving gold nanoparticle aerosolization directly into the major airways. Direct nebulization prevents particle loss and avoids drug administration through the blood. The particles can be detected successfully via upper body scans, which are noninvasive and allow for on-demand monitoring. Nanoparticles are flexible tools that can be modified to target specific cells of interest and can be excreted upon completion of their function. These results could represent an alternative method of drug administration in patients needing repeated cytotoxic therapies with known off-target effects.

Urinary Metal Levels and Coronary Artery Calcification: Longitudinal Evidence in the Multi-Ethnic Study of Atherosclerosis (MESA).

Objective: Growing evidence indicates that exposure to metals are risk factors for cardiovascular disease (CVD). We hypothesized that higher urinary levels of metals with prior evidence of an association with CVD, including non-essential (cadmium , tungsten, and uranium) and essential (cobalt, copper, and zinc) metals are associated with baseline and rate of change of coronary artery calcium (CAC) progression, a subclinical marker of atherosclerotic CVD. Methods: We analyzed data from 6,418 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) with spot urinary metal levels at baseline (2000-2002) and 1-4 repeated measures of spatially weighted coronary calcium score (SWCS) over a ten-year period. SWCS is a unitless measure of CAC highly correlated to the Agatston score but with numerical values assigned to individuals with Agatston score=0. We used linear mixed effect models to assess the association of baseline urinary metal levels with baseline SWCS, annual change in SWCS, and SWCS over ten years of follow-up. Urinary metals (adjusted to µg/g creatinine) and SWCS were log transformed. Models were progressively adjusted for baseline sociodemographic factors, estimated glomerular filtration rate, lifestyle factors, and clinical factors. Results: At baseline, the median and interquartile range (25th, 75th) of SWCS was 6.3 (0.7, 58.2). For urinary cadmium, the fully adjusted geometric mean ratio (GMR) (95%Cl) of SWCS comparing the highest to the lowest quartile was 1.51 (1.32, 1.74) at baseline and 1.75 (1.47, 2.07) at ten years of follow-up. For urinary tungsten, uranium, and cobalt the corresponding GMRs at ten years of follow-up were 1.45 (1.23, 1.71), 1.39 (1.17, 1.64), and 1.47 (1.25, 1.74), respectively. For copper and zinc, the association was attenuated with adjustment for clinical risk factors; GMRs at ten years of follow-up before and after adjustment for clinical risk factors were 1.55 (1.30, 1.84) and 1.33 (1.12, 1.58), respectively, for copper and 1.85 (1.56, 2.19) and 1.57 (1.33, 1.85) for zinc. Conclusion: Higher levels of cadmium, tungsten, uranium, cobalt, copper, and zinc, as measured in urine, were associated with subclinical CVD at baseline and at follow-up. These findings support the hypothesis that metals are pro-atherogenic factors.

Prevalence of behaviour-related fertility disorders in a clinical sample: results of a pilot study.

INTRODUCTION: There is no doubt that lifestyle factors can be detrimental to fertility. The aim of the present pilot study was to identify initial prevalence rates for behaviour-related fertility disorders in a clinical sample of couples wanting a child. METHODS: Between February 2010 and August 2010, all patients coming for the first time to Heidelberg University's Women's Hospital for consultation on involuntary childlessness were asked to fill out a questionnaire designed by the authors of this article. The questionnaire was based on a review of the relevant literature, with special reference to the latest research findings on behaviour detrimental to fertility. Of the 156 couples addressed, 110 women and 100 men took part in the study. RESULTS: For behaviour-related infertility, 9 % of the women and 3 % of the men in our sample were classified on the basis of BMI <18.5, sexual disorders, or abuse of anabolic steroids. If we include smokers, these figures increase: 11 % female smokers and 18 % male smokers. A further 19 % of the women practised sport to an excessive degree; and 26 % of the women and 53 % of the men had a BMI ≥25. DISCUSSION: The prevalence of behaviour-related fertility disorders should not be underestimated. For the prevention of behaviour-related fertility disorders, it is important to inform the population about lifestyle-mediated fertility risks.

Sociodemographic inequalities in uranium and other metals in community water systems across the USA, 2006-11: a cross-sectional study.

BACKGROUND: The US Environmental Protection Agency (EPA) currently sets maximum contaminant levels (MCLs) for ten metals or metalloids in public drinking water systems. Our objective was to estimate metal concentrations in community water systems (CWSs) across the USA, to establish if sociodemographic or regional inequalities in the metal concentrations exist, and to identify patterns of concentrations for these metals as a mixture. METHODS: We evaluated routine compliance monitoring records for antimony, arsenic, barium, beryllium, cadmium, chromium, mercury, selenium, thallium, and uranium, collected from 2006-11 (2000-11 for uranium; timeframe based on compliance monitoring requirements) by the US EPA in support of their second and third Six-Year Reviews for CWSs. Arsenic, barium, chromium, selenium, and uranium (detectable in >10% records) were included in the main analyses (subgroup and metal mixture analyses; arsenic data reported previously). We compared the mean, 75th percentile, and 95th percentile contaminant concentrations and the percentage of CWSs with concentrations exceeding the MCL across subgroups (region, sociodemographic county-cluster, size of population served, source water type, and CWSs exclusively serving correctional facilities). We evaluated patterns in CWS metal concentration estimate profiles via hierarchical cluster analysis. We created an online interactive map and dashboard of estimated CWS metal concentrations for use in future analyses. FINDINGS: Average metal concentrations were available for a total of 37 915 CWSs across the USA. The total number of monitoring records available was approximately 297 000 for arsenic, 165 000 for barium, 167 000 for chromium, 165 000 for selenium, and 128 000 for uranium. The percentage of analysed CWSs with average concentrations exceeding the MCL was 2·6% for arsenic (MCL=10 µg/L; nationwide mean 1·77 µg/L; n=36 798 CWSs), 2·1% for uranium (MCL=30 µg/L; nationwide mean 4·37 µg/L; n=14 503 CWSs), and less than 0·1% for the other metals. The number of records with detections was highest for uranium (63·1%). 75th and 95th percentile concentrations for uranium, chromium, barium, and selenium were highest for CWSs serving Semi-Urban, Hispanic communities, CWSs reliant on groundwater, and CWSs in the Central Midwest. Hierarchical cluster analysis revealed two distinct clusters: an arsenic-uranium-selenium cluster and a barium-chromium cluster. INTERPRETATIONS: Uranium is an under-recognised contaminant in CWSs. Metal concentrations (including uranium) are elevated in CWSs serving Semi-Urban, Hispanic communities independent of location or region, highlighting environmental justice concerns. FUNDING: US National Institutes of Health Office of the Director, US National Institutes for Environmental Health Sciences, and US National Institute of Dental and Craniofacial Research.

Isotope fractionation of selenium during fungal biomethylation by Alternaria alternata.

The natural abundance of stable Se isotopes may reflect sources and formation conditions of methylated Se. We aimed at (1) quantifying the degree of methylation of selenate [Se(VI)] and (hydro)selenite [Se(IV)] by the fungus Alternaria alternata at pH 4 and 7 and (2) determining the effects of these different Se sources and pH values on 82Se/76Se ratios (δ82/76Se) in methylselenides. Alternaria alternata was incubated with Se(VI) and Se(IV) in closed microcosms for 11-15 days and additionally with Se(IV) for 3-5 days at 30 °C. We determined Se concentrations and δ82/76Se values in source Se(VI) and Se(IV), media, fungi, and trapped methylselenides. In Se(VI) incubations, methylselenide volatilization ended before the 11th day, and the amounts of trapped methylselenide were not significantly different among the 11-15 day incubations. In 11-15 days, 2.9-11% of Se(VI) and 21-29% of Se(IV) were methylated, and in 3-5 days, 3-5% of Se(IV) was methylated. The initial δ82/76Se values of Se(VI) and Se(IV) were -0.69±SD 0.07‰, and -0.20±0.05‰, respectively. The δ82/76Se values of methylselenides differed significantly between Se(VI) (-3.97‰ to -3.25‰) and Se(IV) (-1.44‰ to -0.16‰) as sources after 11-15 days of incubation; pH had little influence on δ82/76Se values. Thus, the δ82/76Se values of methylselenide indicate the source species of methylselenides used in this study. The strong isotope fractionation of Se(VI) is probably attributable to the different reduction steps of Se(VI) to Se(-II) which were rate-limiting explaining the low methylation yields, but not to the methylation itself. The shorter incubation of Se(IV) for 3-5 days showed a large Se isotope fractionation of at least -6‰ before the biomethylation reaction reached its end. This initial Se isotope fractionation during methylation of Se(IV) is much larger than previously published.

A method to quantitatively trap volatilized organoselenides for stable selenium isotope analysis.

If volatile organoselenides are to be analyzed for their stable Se isotope composition to elucidate sources and formation processes, organoselenides need to be trapped quantitatively to avoid artificial Se isotope fractionation. We developed an efficient trap of organoselenides to be used in microcosms designed to determine the Se isotope fractionation by microbial transformation of inorganic Se to volatile organoselenides. The recoveries of volatilized dimethyldiselenide (DMDSe) from aqueous standard solutions by activated charcoal and alkaline peroxide solution with subsequent freeze-drying and purification via a cation exchange resin were tested. Microcosm experiments with the Se-methylating fungus in a growth medium were conducted, and tightness of the microcosm was assessed by comparing mass balances of total Se of the fungus, medium, and trapped organoselenides with the supplied Se mass. At the end of the experiment, we calculated δSe values of the whole microcosm and compared them with the δSe value of supplied Se(IV) and Se(VI). Our results demonstrated that activated charcoal cannot be used for quantitative trapping of organoselenides because generally <64% of the outgassed DMDSe were recovered. The mean recovery of Se volatilized from an aqueous DMDSe standard trapped in alkaline peroxide, in contrast, was 96 ± 11% (SD) after 2 h ( = 4). The mass balances of total Se in microcosm experiments with alkaline peroxide traps run for 11 to 15 d were 96 ± 15 and 102 ± 2.4% for Se(IV) and Se(VI) ( = 3), respectively. The mass-weighted mean δSe values for the Se(IV) and Se(VI) batch experiments were -0.31 ± 0.05‰ ( = 3) and -0.76 ± 0.07‰ ( = 3), compared with -0.20 ± 0.10‰ and -0.69 ± 0.10‰ in the supplied Se oxyanions, respectively. We conclude that the alkaline peroxide trap can reliably be used to determine the Se isotope composition of organoselenides.

Investigations on Zinc Isotope Fractionation in Breast Cancer Tissue Using in vitro Cell Culture Uptake-Efflux Experiments.

Zinc (Zn) accumulates in breast cancer tumors compared to adjacent healthy tissue. Clinical samples of breast cancer tissue show light Zn isotopic compositions (δ66Zn) relative to healthy tissue. The underlying mechanisms causing such effects are unknown. To investigate if the isotopic discrimination observed for in vivo breast cancer tissue samples can be reproduced in vitro, we report isotopic data for Zn uptake-efflux experiments using a human breast cancer cell line. MDA-MB-231 cell line was used as a model for triple receptor negative breast cancer. We determined Zn isotope fractionation for Zn cell uptake (Δ66Znuptake) and cell efflux (Δ66Znefflux) using a drip-flow reactor to enable comparison with the in vivo environment. The MDA-MB-231 cell line analyses show Zn isotopic fractionations in an opposite direction to those observed for in vivo breast cancer tissue. Uptake of isotopically heavy Zn (Δ66Znuptake = +0.23 ± 0.05‰) is consistent with transport via Zn transporters (ZIPs), which have histidine-rich binding sites. Zinc excreted during efflux is isotopically lighter than Zn taken up by the cells (Δ66Znefflux = -0.35 ± 0.06‰). The difference in Zn isotope fractionation observed between in vitro MDA-MB-231 cell line experiments and in vivo breast tissues might be due to differences in Zn transporter levels or intercellular Zn storage (endoplasmic reticulum and/or Zn specific vesicles); stromal cells, such as fibroblasts and immune cells. Although, additional experiments using other human breast cancer cell lines (e.g., MCF-7, BT-20) with varying Zn protein characteristics are required, the results highlight differences between in vitro and in vivo Zn isotope fractionation.

Zinc stable isotopes in urine as diagnostic for cancer of secretory organs.

Breast, prostate, and pancreatic cancers alter the zinc (Zn) metabolism. Combined analyses of urinary Zn concentrations [Zn] and Zn stable isotope compositions (δ66Zn) may provide a non-invasive approach for tracing malignancy-induced Zn dyshomeostasis. In this study, we measured [Zn] and δ66Zn in urine from prostate (n = 22), breast (n = 16), and from women with benign breast disease (n = 14) and compared those with age-matched healthy controls (22-49 years or 50+ years) and published data for pancreatic cancer (n = 17). Our results show that cancer-induced changes are reflected in higher urinary [Zn] and lower urinary δ66Zn for pancreatic and prostate cancer and benign breast disease when compared with healthy controls. For prostate cancer, the progression of low [Zn] and high δ66Zn for patients of low-risk disease toward high [Zn] and low δ66Zn for the higher risk patients demonstrates that [Zn] and δ66Zn in urine could serve as a reliable prognostic tool. Urinary excretion of isotopically light Zn by patients with prostatic and pancreatic cancer is probably the result of increased reactive oxygen species in cancerous cells, which limits the scavenging of hydroxyl radicals and thus facilitates the oxidation of metalloproteins with sulfur-rich ligands. Urine from breast cancer patients shows undistinguishable δ66Zn to healthy controls, implying that the expression of metalloproteins with sulfur-rich ligands is stronger in breast cancer tissues. In conclusion, urinary δ66Zn may provide a non-invasive diagnostic tool for pancreatic cancer and support disease prognosis for prostate cancer. These findings should translate to comprehensive transverse and longitudinal cohort studies in future.