Elevated Levels Of Selenium Research Articles

Double-sided effect of selenium on blood lipids: A dose-response meta-analysis

Abstract Background Selenium, a trace element with both nutritional and toxicological properties, has been suggested to increase cardiovascular risk, particularly concerning diabetes and blood pressure levels. However, the impact of selenium exposure on the risk of dyslipidemia remains uncertain. This meta-analysis explored the shape of the relation between selenium exposure and its effects on lipid profiles in the most relevant experimental human studies, randomized controlled trials (RCTs). Materials and methods The review was registered in PROSPERO (ID: CRD42022380432). Through a bibliographic search conducted on PubMed, Web of Science, Embase, and the Cochrane Library, we identified RCTs investigating the impact of selenium supplementation on lipid profile. We then compared the results between intervention and control groups and, whenever possible, evaluated the non-linear relationship using a dose-response approach. Results We could include 26 RCTs involving different populations, i.e. healthy individuals, pregnant women, and subjects with health conditions such as cardiovascular diseases and Alzheimer’s dementia. Study endpoints were levels of total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides. Our dose-response analysis indicated that selenium supplementation exceeding 200 µg/day adversely affected total cholesterol, HDL, and triglyceride levels. Hence, a threshold for such a detrimental effect of selenium was observed on total and HDL cholesterol and triglycerides, while opposite and inconsistent results emerged for levels below 200 µg/day and for LDL-cholesterol. Blood selenium levels at the end of the studies were positively associated with adverse effects on all endpoints. Conclusions This first dose-response meta-analysis of the effects of selenium on blood lipids highlights the potentially adverse effects of this trace element, in the amount and the chemical forms used in the trials. Key messages • Elevated selenium levels correlated with adverse effects on lipid profile. • Selenium doses exceeding 200 µg/day showed adverse effects on total and HDL cholesterol and triglycerides levels.

Exploring mercury detoxification in fish: The role of selenium from tuna byproduct diets for sustainable aquaculture

Exposure to mercury (Hg) through fish consumption poses significant environmental and public health risks, given its status as one of the top ten hazardous chemicals. Aquaculture is expanding, driving a surge in demand for sustainable aquafeeds. Tuna byproducts, which are rich in protein, offer potential for aquafeed production, yet their use is challenged by the high content of heavy metals, particularly Hg. However, these byproducts also contain elevated levels of selenium (Se), which may counteract Hg adverse effects. This study examines the fate of dietary Hg and Se in an aquaculture model fish. Biomolecular speciation analyses through hyphenated analytical approaches were conducted on the water-soluble protein fraction of key organs of juvenile rainbow trout (Oncorhynchus mykiss) exposed to various combinations of Hg and Se species, including diets containing tuna byproducts, over a six-month period. The findings shed light on the dynamics of Hg and Se compounds in fish revealing potential Hg detoxification mechanisms through complexation with Hg-biomolecules, such as cysteine, glutathione, and metallothionein. Furthermore, the trophic transfer of selenoneine is demonstrated, revealing novel opportunities for sustainable aquafeed production. Understanding the interactions between Hg and Se in aquaculture systems is crucial for optimizing feed formulations and mitigating environmental risks. This research contributes to the broader goal of advancing sustainable practices in aquaculture while addressing food security challenges.

Association between Parkinson disease and selenium levels in the body: A systematic review and meta-analysis.

Parkinson disease (PD) is a common neurodegenerative disorder, but its pathogenesis is still not entirely understood. While some trace elements, such as selenium, iron, and copper, are considered pivotal in PD onset due to their role in oxidative stress, the association between selenium concentrations and PD susceptibility remains ambiguous. A systematic review and meta-analysis was conducted in adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and framed by the Patient, Intervention, Comparison, Outcome paradigm. Data were sourced from 4 prominent electronic databases: PubMed, Embase, Web of Science, and Cochrane Library. Eligible studies must have had a PD case group and a control group, both of which presented data on selenium concentrations. The quality of the studies was assessed using the Newcastle-Ottawa Scale. Of 1541 initially identified articles, 12 studies comprising a total of 597 PD cases and 733 controls were selected for the meta-analysis. Pronounced heterogeneity was observed among these studies. When assessing blood selenium levels, no significant difference was found between patients with PD and the controls. However, when examining the cerebrospinal fluid, selenium levels in PD patients were significantly elevated compared to controls (standard mean difference = 1.21, 95% CI 0.04-2.39, P < .05). Subgroup analyses, sensitivity analyses, and evaluation of publication bias were performed to ensure data robustness. Elevated selenium levels in cerebrospinal fluid may be associated with a higher risk of Parkinson. Further prospective research is required to solidify this potential link and to offer avenues for novel therapeutic interventions or preventive measures.

Transcriptome and co-expression network revealed molecular mechanism underlying selenium response of foxtail millet (Setaria italica).

Selenium-enriched foxtail millet (Setaria italica) represents a functional cereal with significant health benefits for humans. This study endeavors to examine the impact of foliar application of sodium selenite (Na2SeO4) on foxtail millet, specifically focusing on selenium (Se) accumulation and transportation within various plant tissues. To unravel the molecular mechanisms governing selenium accumulation and transportation in foxtail millet, we conducted a comprehensive analysis of selenium content and transcriptome responses in foxtail millet spikelets across different days (3, 5, 7, and 12) under Na2SeO4 treatment (200 μmol/L). Foxtail millet subjected to selenium fertilizer exhibited significantly elevated selenium levels in each tissue compared to the untreated control. Selenate was observed to be transported and accumulated sequentially in the leaf, stem, and spikes. Transcriptome analysis unveiled a substantial upregulation in the transcription levels of genes associated with selenium metabolism and transport, including sulfate, phosphate, and nitrate transporters, ABC transporters, antioxidants, phytohormone signaling, and transcription factors. These genes demonstrated intricate interactions, both synergistic and antagonistic, forming a complex network that regulated selenate transport mechanisms. Gene co-expression network analysis highlighted three transcription factors in the tan module and three transporters in the turquoise module that significantly correlated with selenium accumulation and transportation. Expression of sulfate transporters (SiSULTR1.2b and SiSULTR3.1a), phosphate transporter (PHT1.3), nitrate transporter 1 (NRT1.1B), glutathione S-transferase genes (GSTs), and ABC transporter (ABCC13) increased with SeO4 2- accumulation. Transcription factors MYB, WRKY, and bHLH were also identified as players in selenium accumulation. This study provides preliminary insights into the mechanisms of selenium accumulation and transportation in foxtail millet. The findings hold theoretical significance for the cultivation of selenium-enriched foxtail millet.

Association between blood heavy metal exposure levels and risk of metabolic dysfunction associated fatty liver disease in adults: 2015-2020 NHANES large cross-sectional study.

The relationships between heavy metals and fatty liver, especially the threshold values, have not been fully elucidated. The objective of this research was to further investigate the correlation between blood heavy metal exposures and the risk of Metabolic dysfunction Associated Fatty Liver Disease (MAFLD) in adults. Laboratory data on blood metal exposure levels were obtained from National Health and Nutrition Examination Survey (NHANES) data for the period 2015 to 2020 for a cross-sectional study in adults. Associations between blood levels of common heavy metals and the risk of MAFLD in adults were analyzed using multifactorial logistic regression and ranked for heavy metal importance using a random forest model. Finally, thresholds for important heavy metals were calculated using piecewise linear regression model. In a multifactorial logistic regression model, we found that elevated levels of selenium (Se) and manganese (Mn) blood exposure were strongly associated with the risk of MAFLD in adults. The random forest model importance ranking also found that Se and Mn blood exposure levels were in the top two positions of importance for the risk of disease in adults. The restricted cubic spline suggested a non-linear relationship between Se and Mn blood exposure and adult risk of disease. The OR (95% CI) for MAFLD prevalence was 3.936 (2.631-5.887) for every 1 unit increase in Log Mn until serum Mn levels rose to the turning point (Log Mn = 1.10, Mn = 12.61 μg/L). This correlation was not significant (p > 0.05) after serum Mn levels rose to the turning point. A similar phenomenon was observed for serum Se levels, with a turning point of (Log Se = 2.30, Se = 199.55 μg/L). Blood heavy metals, especially Se and Mn, are significantly associated with MAFLD in adults. They have a non-linear relationship with a clear threshold.

The mechanism of Se(IV) multisystem resistance in Stenotrophomonas sp. EGS12 and its prospect in selenium-contaminated environment remediation

Human activities have led to elevated levels of selenium (Se) in the environment, which poses a threat to ecosystems and human health. Stenotrophomonas sp. EGS12 (EGS12) has been identified as a potential candidate for the bioremediation of repair selenium-contaminated environment because of its ability to efficiently reduce Se(IV) to form selenium nanospheres (SeNPs). To better understand the molecular mechanism of EGS12 in response to Se(IV) stress, a combination of transmission electron microscopy (TEM), genome sequencing techniques, metabolomics and transcriptomics were employed. The results indicated that under 2 mM Se(IV) stress, 132 differential metabolites (DEMs) were identified, and they were significantly enriched in metabolic pathways such as glutathione metabolism and amino acid metabolism. Under the Se(IV) stress of 2 mM, 662 differential genes (DEGs) involved in heavy metal transport, stress response, and toxin synthesis were identified in EGS12. These findings suggest that EGS12 may respond to Se(IV) stress by engaging various mechanisms such as forming biofilms, repairing damaged cell walls/cell membranes, reducing Se(IV) translocation into cells, increasing Se(IV) efflux, multiplying Se(IV) reduction pathways and expelling SeNPs through cell lysis and vesicular transport. The study also discusses the potential of EGS12 to repair Se contamination alone and co-repair with Se-tolerant plants (e.g. Cardamine enshiensis). Our work provides new insights into microbial tolerance to heavy metals and offers valuable information for bio-remediation techniques on Se(IV) contamination.

Comparison of Serum Selenium, Homocysteine, Zinc, and Vitamin D Levels in Febrile Children with and without Febrile Seizures: A Prospective Single-Center Study.

Febrile seizure is a complication that makes physicians and families uneasy when detected in children with a high fevers. This study aimed to compare children with febrile seizures and children without seizures in blood selenium, zinc, homocysteine, vitamin D, vitamin B12, and magnesium levels. The study group included sixty-one children between the ages of 1-5 who came to the pediatric emergency department with febrile seizure. The control group had 61 children with fever without seizure, who were compatible with the study group in age, sex, and elapsed time since the onset of fever. Blood samples were taken from the patients during their admission. Selenium, zinc, vitamin D, homocysteine, vitamin B12, and magnesium levels were measured, and the data of the two groups were compared. Additionally, patients in the study group had two subgroups, simple and complex febrile seizures, and their parameters were compared. Selenium, zinc, vitamin D, and vitamin B12 levels were significantly lower in the study group than in the control group (p < 0.001), and there was no significant difference in homocysteine (p = 0.990) and magnesium levels (p = 0.787) between the two groups. Moreover, no significant difference was found between those with simple and complex febrile seizures in selenium, vitamin D, homocysteine, vitamin B12, and magnesium levels. Elevated levels of selenium, zinc, vitamin D, and vitamin B12 in the blood of children with fevers help to prevent febrile seizures.

Role of Selenium in the Body: A Narrative Review

The maintenance of required levels of essential micronutrients and macronutrients is necessary for the smooth and proper functioning of the body. Any increase or decrease in the levels of these required micronutrients will have an adverse effect on the metabolic activities carried out in the body. The intake of micronutrients differs from region to region, and many micronutrients do not function in their natural form. Selenium is one of the most vital micronutrients required by the body. Numerous organs and systems, such as the cardiovascular system and reproductive system, are affected by selenium deficiency, which is characterised by diminished activity. Consuming selenium in physiologically suitable doses is necessary for maintaining reproductive and general health. Selenium levels that are beyond the permissible range have been associated with infertility. Prolonged exposure to selenium in the environment has been shown to pose a significant danger to human health. It is still unknown how different dietary selenium sources are processed in human bodies, as well as the ideal type or quantity of dietary selenium to maintain metabolic homeostasis and enhance reproductive health. Throughout the world, selenium deficiency is a relatively prevalent cause of various diseases. It is possible to take supplements for selenium deficiency; however, increased levels of selenium, which are toxic, are very close to normal levels. Therefore, it is important to rule out the toxicity brought on by elevated selenium levels when determining the normal selenium concentration.

Microbial selenate detoxification linked to elemental sulfur oxidation: Independent and synergic pathways

Elevated selenium levels in the environment, with soluble selenate [Se(VI)] as the common chemical species, pose a severe threat to human health. Anaerobic Se(VI) bioreduction is a promising approach for selenium detoxification, and various organic/inorganic electron donors have proved effective in supporting this bioprocess. Nevertheless, autotrophic Se(VI) bioreduction driven by solid inorganic electron donors is still not fully understood. This work is the first to employ elemental sulfur [S(0)] as electron donor to support Se(VI) bioreduction. A batch trial with mixed culture demonstrated the feasibility of this bioprocess, with Se(VI) removal efficiency of 92.4 ± 0.7% at an initial Se(VI) concentration of 10 mg/L within 36 h. Continuous column tests showed that increased initial concentration, flow rate, and introduction of NO3--N depressed Se(VI) removal. Se(VI) was mainly bioreduced to solid elemental Se with trace selenite in the effluent, while S(0) was oxidized to SO42-. Enrichment of Thiobacillus, Desulfurivibrio, and Sulfuricurvum combined with upregulation of genes serA, tatC, and soxB indicated Se(VI) bioreduction was coupled to S(0) oxidation. Thiobacillus performed S(0) oxidation and Se(VI) reduction independently. Intermediate metabolites as volatile fatty acids, hydrogen and methane from S(0) oxidation were utilized by heterotrophic Se(VI) reducers for Se(VI) detoxification, indicative of microbial synergy.

Interplay between Selenium, selenoprotein genes, and oxidative stress in honey bee Apis mellifera L.

The honey bee, Apis mellifera L., is a major pollinator insect that lacks novel “selenoprotein genes”, rendering it susceptible to elevated levels of Selenium (Se) occurring naturally in the environment. We investigated the effects of two inorganic forms of Se on biological traits, oxidative stress, and gene regulation. Using bioassay arenas in the laboratory, one-day old sister bees were fed ad libitum 4 different concentrations of selenate and selenite, two common inorganic forms of Se. The transcription levels of 4 honey bee antioxidant genes were evaluated, and three putative selenoprotein-like genes (SELENOT, SELENOK, SELENOF) were characterized as well as Sbp2, a Selenium binding protein required for the translation of selenoproteins mRNA. Oxidative stress and Se residues were subsequently quantified in honey bee bodies throughout the experiment.Se induced higher oxidative stress in treated honey bees leading to a significantly elevated protein carbonyl content, particularly at the highest studied concentrations. Early upregulations of Spb2 and MsrA were identified at day 2 of the treatment while all genes except SELENOT were upregulated substantially at day 8 to alleviate the Se-induced oxidative stress levels. We determined that doses between 60 and 600 mg.Se.L−1 were acutely toxic to bees (<48 h) while doses between 0.6 and 6 mg.Se.L−1 led to much lower mortality (7–16)%. Furthermore, when fed ad libitum, Se residue data indicated that bees tolerated accumulation up to 0.12 µg Se bee−1 for at least 8 days with a Se LC50 of ∼6 mg/L, a field realistic concentration found in pollen of certain plants in a high Se soil environment.

Simulating selenium and nitrogen fate and transport in coupled stream-aquifer systems of irrigated regions

Elevated levels of selenium (Se) in aqueous environments can harm aquatic life and endanger livestock and human health. Although Se occurs naturally in the rocks and soils of many alluvial aquifers, mining and agricultural activities can increase its rate of mobilization and transport to surface waters. Attention is given here to regions where nonpoint source return flows from irrigated lands carry pollutant loads to aquifers and streams, contributing to concentrations that violate regulatory and performance standards. Of particular concern is the heightened level and mobilization of Se influenced by nitrate (NO3), a harmful pollutant in its own right. We present a numerical model that simulates the reactive transport of Se and nitrogen (N) species in a coupled groundwater-surface water system. Building upon a conceptual model that incorporates the major processes affecting Se and NO3 transport in an irrigated watershed, the model links the finite-difference models MODFLOW, UZF-RT3D, and OTIS, to simulate flow and reactive transport of multiple chemical species in both the aquifer and a stream network, with mass exchange between the two. The capability of the new model is showcased by calibration, testing, and application to a 500 km2 region in Colorado’s Lower Arkansas River Valley using a rich data set gathered over a 10-yr period. Simulation of spatial and temporal distributions of Se concentration reveals conditions that exceed standards in groundwater for approximately 20% of the area. For the Arkansas River, standards are exceeded by 290%–450%. Simulation indicates that river concentrations of NO3 alone are near the current interim standard for the total of all dissolved N species. These results indicate the need for future use of the developed model to investigate the prospects for land and water best management practices to decrease pollutant levels.

Selenium speciation and localization in chironomids from lakes receiving treated metal mine effluent

A lake system in northern Saskatchewan receiving treated metal mine and mill effluent contains elevated levels of selenium (Se). An important step in the trophic transfer of Se is the bioaccumulation of Se by benthic invertebrates, especially primary consumers serving as a food source for higher trophic level organisms. Chironomids, ubiquitous components of many northern aquatic ecosystems, were sampled at lakes downstream of the milling operation and were found to contain Se concentrations ranging from 7 to 80mgkg−1dry weight. For comparison, laboratory-reared Chironomus dilutus were exposed to waterborne selenate, selenite, or seleno-DL-methionine under laboratory conditions at the average total Se concentrations found in lakes near the operation. Similarities in Se localization and speciation in laboratory and field chironomids were observed using synchrotron-based X-ray fluorescence (XRF) imaging and X-ray absorption spectroscopy (XAS). Selenium localized primarily in the head capsule, brain, salivary glands and gut lining, with organic Se species modeled as selenocystine and selenomethionine being the most abundant. Similarities between field chironomids and C. dilutus exposed in the laboratory to waterborne selenomethionine suggest that selenomethionine-like species are most readily accumulated, whether from diet or water.

Extreme selenium and tellurium contamination in soils — An eighty year-old industrial legacy surrounding a Ni refinery in the Swansea Valley

Elevated levels of selenium (maximum 200 mg/kg) and tellurium (maximum 11 mg/kg) are reported in topsoils (< 5 cm) from around a long-established nickel refinery at Clydach in the Lower Swansea Valley, UK. Se and Te are correlated with each other and when these data are plotted as contour diagrams they show a concentric pattern centred on the refinery site. The origin of the Se and Te contamination is investigated. A review of the changes in the refinery practices at the site is presented and used to link the soil contamination to industrial pollution which took place over 80 years ago. The most recent air quality data available cannot rule out some Se contamination up to 2003.

Exposure histories derived from selenium in otoliths of three cold-water fish species captured downstream from coal mining activity

Establishing exposure to contaminants within a given environment is often difficult for fish species with large home ranges. Chemical analyses of muscle or visceral tissue are useful indicators of recent exposure, but depuration, metabolic transformation, and tissue redistributions can alter temporal resolution. Otoliths are metabolically stable and thus provide complete chemical records within their calcified tissues that, when coupled to the annular structure, can provide temporal resolution for exposure to trace metals. Otoliths from bull trout, cutthroat trout, and mountain whitefish from an area rich in seleniferous soils and with active coal mining activity were analyzed for selenium to determine any history of exposure to elevated levels of selenium. Selenium concentrations in otolith primordia tended to be low, indicating that these fish emerged in low selenium areas. Later life stages showed peaks of high Se concentrations, suggesting that individuals moved into areas of increased selenium later in life. Individuals captured from the same area had a wide variety of selenium exposure profiles, indicating that these fish do not move en masse into and out of high-selenium areas. Year-to-year variability of selenium exposure patterns within an otolith suggests inconsistent utilization of high- and low-selenium areas by the individual. The inconsistent exposure profiles for these fish, in addition to their home range of tens of kilometres, indicate that soft tissue concentrations, while useful indicators of recent exposure, cannot be relied upon to provide a life history recording of exposure.

Selenium and bladder cancer risk: a meta-analysis.

Selenium is considered to be an antioxidant, and its high levels have been inversely associated with cancer risk of several sites. This meta-analysis examined the relationship between levels of selenium measured in serum and toenails, and the risk of bladder cancer. A meta-analysis using data from seven published epidemiologic studies (three case-control, three nested case-control, one case-cohort) published before March 2010 was done to examine the association between levels of selenium and bladder cancer. Fixed and random effects analyses were done to calculate meta-odds ratio (mOR) and 95% confidence intervals (CI). Heterogeneity among studies was measured by the I(2) statistic. Overall, the risk of bladder cancer was inversely associated with elevated levels of selenium according to a random-effects model (mOR = 0.61; 95% CI, 0.42-0.87). The mORs were 0.95 (95% CI, 0.69-1.27) and 0.55 (95% CI, 0.32-0.95) among men and women, respectively. Sex, type of sample specimen, smoking status, and study design were found to be potential sources of heterogeneity. A significant protective effect of selenium, observed mainly among women, may result from gender-specific differences in its accumulation and excretion. The heterogeneity found among studies was mainly linked to the different biological sample specimens used to measure the selenium concentrations and the small size of the studies. Although these results suggest a protective effect of selenium for bladder cancer risk, additional large studies are warranted to support these preliminary evidence. The present results suggest a beneficial effect of high selenium intake for bladder cancer risk.

Selenium Speciation in Whole Sediment using X-ray Absorption Spectroscopy and Micro X-ray Fluorescence Imaging

A field survey was conducted in a freshwater lake system in the Athabasca Basin, northern Saskatchewan, Canada that receives treated metal mining and milling process effluent containing elevated levels of selenium. Whole sediment, pore water, surface water, and chironomid larvae were analyzed in an attempt to link whole sediment selenium speciation to various environmental factors, including selenium availability to benthic macro-invertebrates, a trophic level through which selenium can enter the diet of higher trophic level organisms. Speciation was measured using synchrotron-based selenium K-edge X-ray absorption spectroscopy (XAS). All lake averages of sediment samples (reference or exposure sites) contained a significant proportion (approximately 50%) of elemental selenium which is relatively insoluble in water, immobile, and not considered to be bioavailable. The presence of elemental selenium was confirmed by extended X-ray absorption fine structure (EXAFS) analysis of select samples. Inorganic metal selenides were also found in whole sediment samples and confirmed using micro X-ray fluorescence imaging. Dissolved selenium concentrations in pore water were correlated to the amount of selenite in whole sediments provided that the sites were classified according to whole sediment sand content. Sand content itself is likely inversely correlated to sediment organic matter content, adsorption sites, and redox potential.

Elevated levels of selenium in the typical diet of Amazonian riverside populations

Selenium (Se) intake is generally from food, whose Se content depends on soil Se and plant accumulation. For humans, adequate Se intake is essential for several selenoenzymes. In the Lower Tapajós region of the Brazilian Amazon, Se status is elevated with large inter-community variability. Se intake in this region, where Hg exposure is among the highest in the world, may be important to counteract mercury (Hg) toxicity. The present study was conducted in 2006 with 155 persons from four communities of the Lower Tapajós. The objectives were: i) to evaluate Se content in their typical diet and drinking water; ii) to compare food Se concentrations with respect to geographic location; and iii) to examine the contribution of consumption of different food items to blood Se. More than 400 local foods and 40 drinking water samples were collected. Participants responded to an interview-administered food frequency questionnaire and provided blood samples. Food, water and blood Se levels were assessed by ICP-MS. Since Brazil nuts may also contain significant levels of barium (Ba) and strontium (Sr), these elements were likewise analyzed in nuts. The highest Se concentrations were found in Brazil nuts, but concentrations were highly variable (median: 13.9 µg/g; range: 0.4–158.4 μg/g). Chicken, game meat, eggs and beef also contained considerable levels of Se, with median concentrations from 0.3 to 1.4 μg/g. There was no particular geographic distribution of food Se. Se concentration in drinking water was very low (< 1.4 µg/L). Blood Se covered a (103–1500 μg/L), and was positively related to regular consumption of Brazil nuts, domestic chicken and game meat. Brazil nuts were found to contain highly variable and often very high concentrations of Ba (88.0 µg/g, 1.9–1437 µg/g) and Sr (38.7 µg/g, 3.3–173 µg/g). Further studies should address multiple nutrient/toxic interactions in the diet and related effects on health.

Selenium Bioaccumulation in Freshwater Organisms and Antagonistic Effect against Mercury Assimilation

We present evidence of selenium bioaccumulation at lower levels of the aquatic food chain and its antagonistic effect against mercury and methyl mercury assimilation in the aquatic food web. Most of our studies were carried out in freshwater lakes of the mining region of Sudbury, Ontario, Canada where the presence of metal smelters has introduced elevated levels of selenium in the surrounding terrestrial and aquatic ecosystems. The studies with different types of aquatic organisms demonstrate a consistent inverse relationship between concentrations of mercury/methyl mercury and selenium in whole bodies (zooplankton, benthic invertebrates, mayflies and amphipods, beetle larvae and newly hatched perch) or in muscle, liver and brain (perch and walleye). This antagonistic effect was also observed in laboratory controlled experiments with the incubated soil and surface water bacterium Pseudomonas fluorescens. We also present some information on Se accumulation at different levels of the food web with samples c...

Selenium Toxicity: A Case of Selenosis Caused by a Nutritional Supplement

Background: Selenium is a nonmetal element that serves vital roles in normal physiologic function. Substantial toxicity can occur with excessive selenium consumption. In March 2008, the U.S. Food and Drug Administration (FDA) announced that it had received reports of adverse reactions to over-the-counter liquid nutritional supplements marketed as Total Body Formula and Total Body Mega Formula (distributed by Total Body Essential Nutrition, Atlanta, Georgia) (1). A voluntary recall of these products was implemented. In May 2008, the FDA found substantially elevated selenium levels and modestly elevated chromium levels in the products (2).

OBSERVATIONS ON AN ASSOCIATION BETWEEN THE WEEVIL SCAPHOMORPHUS TRIVITTATUS (SAY) AND TWO ASTRAGALUS SPECIES ON SELENIUM-RICH SOILS IN CARBON COUNTY, UTAH

The weevil Scaphomorphus trivittatus (Say) was found in close association with Astragalus praelongus var. elliseae (Rydb.) and Astragalus asclepiadoides (Jones) in selenium-containing soils in Carbon County, Utah. The weevils fed on roots of the Astragalus species and formed soil cocoons, which were attached to the tap roots. The weevils pupated and developed into adults in these cocoons over the fall and winter and then emerged in the spring. The plants and soil cocoons contained highly elevated levels of selenium compared to the soils. The weevils, in contrast, differed little from the soils in selenium content.