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PubMed2003

Selenium and thyroid function in infants, children and adolescents.

Selenium is an integral component of the enzymes glutathione peroxidase (GPx) and iodothyronine deiodinases. Although selenium nutrition could conceivably affect thyroid function in infants, children and adolescents, available data suggest that the effect of selenium deficiency on thyroid function is relatively modest. In patients with isolated selenium deficiency (such as patients with phenylketonuria receiving a low-protein diet), peripheral thyroid hormone metabolism is impaired but there are no changes in thyrotropin (TSH) or clinical signs of hypothyroidism, suggesting that these patients are euthyroid. Selenium supplementation may be advisable to optimize tissue GPx activity and prevent potential oxidative stress damage. In areas where combined selenium and iodine deficiencies are present (such as endemic goiter areas in Central Africa), selenium deficiency may be responsible for the destruction of the thyroid gland in myxoedematous cretins but may also play a protective role by mitigating fetal hypothyroidism. In these areas, selenium supplementation should only be advocated at the same time or after iodine supplementation. In patients with absent or decreased production of thyroid hormones and who rely solely on deiodination of exogenous L-thyroxine for generation of the active triiodothyronine (such as patients with congenital hypothyroidism), selenium supplementation may optimize thyroid hormone feedback at the pituitary level and decrease stimulation of the residual thyroid tissue.

Adolescent↗
PubMed2004

Sequential changes in plasma selenium concentration after cadaveric renal transplantation.

BACKGROUND: Previous investigations have shown that plasma selenium concentrations are significantly lower in patients with established chronic graft nephropathy (CGN) than in healthy transplant controls. The aims of this study were to determine when in the transplant process low selenium concentrations become apparent and to explore the relationship between selenium levels and risk factors for CGN. METHODS: Plasma selenium concentrations were measured in 40 patients (20 receiving cyclosporin, 20 receiving tacrolimus) undergoing transplantation. Samples were obtained immediately before transplantation and at 3, 6 and 12 months after transplantation. RESULTS: A low plasma selenium concentration was found in 30 patients at the time of transplantation but this had normalized in the majority of patients by 3 months. Plasma selenium concentrations at 3, 6 and 12 months were significantly higher than baseline values for both treatment arms, but were significantly lower at 3 months in patients who experienced either clinical acute rejection (CAR) or cytomegalovirus (CMV) infection during the preceding months. CONCLUSION: Low plasma selenium concentrations are common at the time of transplantation but appear to normalize thereafter. The identification of low selenium levels in patients who experience CAR or CMV (two important risk factors for clinically apparent CGN) suggests that the relationship between selenium and CGN warrants further investigation.

Adolescent↗
PubMed1989

Selenium and the immune response: 1. Modulation of alloreactive human lymphocyte functions in vitro.

A role for the dietary trace mineral element selenium in the reduction of cancer incidence has been documented in numerous epidemiological and experimental studies. The precise mechanism of this antitumor effect is not well understood, but published data suggest that both inhibition of tumor cell growth and enhancement of host immunity are likely to be involved. In this study we report that selenium at physiologic concentrations can inhibit human lymphocyte proliferation in response to irradiated tumor cells in mixed lymphocyte/tumor cell cultures (MLTC). In addition, we demonstrate that the various lymphocyte functional activities generated in these cultures exhibit different levels of sensitivity to the effects of selenium. The generation of suppressor-cell activity in MLTC was strongly inhibited by the presence of physiologic levels of selenium, while the development of cytotoxic T-lymphocyte activity in identical cultures was not affected by selenium. Production of interleukin-2 in these cultures showed an intermediate sensitivity to the effects of selenium. Thus, selenium appears to be capable of selectively regulating the generation of functional lymphocyte subsets in vitro. Such selective regulation could explain the published effects of selenium on immunity and would be consistent with a role for immunity in the observed reduction of cancer incidence associated with elevated selenium intake.

Humans↗
PubMed1989

Selenium and the immune response: 2. Enhancement of murine cytotoxic T-lymphocyte and natural killer cell cytotoxicity in vivo.

An inverse correlation between cancer incidence and dietary intake of the trace mineral element selenium has been well established in epidemiological and experimental studies. The mechanisms for this chemoprotective effect are unresolved. Much attention has been focused on the antiproliferative effects of selenium on various normal and neoplastic cell types. However, dietary selenium supplementation can also enhance the expression of various humoral and cellular immune responses. In examining the effects of dietary selenium on cell-mediated immunity in mice, we observed that selenium supplementation caused the enhanced expression of spontaneous natural killer (NK) cytotoxicity in spleen cells and of specific cytotoxic T-lymphocyte (CTL) cytotoxicity in peritoneal exudate cells (PEC). NK activity of spleen-cell suspensions from selenium-supplemented mice increased an average of 70% over that of the control group (basal diet). Cytotoxic activity of PEC from mice injected with tumors intraperitoneally peaked earlier in selenium-supplemented animals, and the appearance of cells staining positively for Thy 1.2 surface antigen in selenium-supplemented animals also preceded the values observed in control animals. We propose here that enhancement of in vivo cytotoxic mechanisms, is likely to act synergistically with tumor growth inhibition in the reduction of tumor incidence associated with selenium intake.

Animals↗
PubMed1993

Teratogenic effects of selenium in natural populations of freshwater fish.

The prevalence of abnormalities and associated tissue selenium residues were assessed for the fish population of Belews Lake, North Carolina, and two reference lakes in 1975, 1978, 1982, and 1992. Teratogenic defects identified included lordosis, kyphosis, scoliosis, and head, mouth, and fin deformities. Many fish exhibited multiple malformations and some were grossly deformed and distorted in appearance. Other abnormalities observed were edema, exophthalmus, and cataracts. Whole-body tissue residues of selenium in the fishes of Belews Lake were up to 130 times those in the reference lakes and the incidence of abnormalities was some 7 to 70 times greater. Teratogenic defects increased as selenium levels rose between 1975 and 1982 and fell with declining selenium levels between 1982 and 1992 as selenium inputs into Belews Lake were curtailed. The relationship between selenium residues and prevalence of malformations approximated an exponential function (R2 = 0.881, P < 0.01; cubic model) for centrarchids over the range of 1-80 micrograms/g dry wt selenium and 0-70% deformities. This relationship could be useful in evaluating the role of teratogenic effects in warm-water fish populations suspected of having selenium-related reproductive failure. Unique conditions may have existed in Belews Lake which led to the high frequency and persistence of deformities in juvenile and adult fish. In other, less-contaminated locations competition and predation may eliminate malformed individuals in all but the larval life stage. Teratogenesis could be an important, but easily overlooked phenomenon contributing to fishery reproductive failure in selenium-contaminated aquatic habitats.

Abnormalities, Drug-Induced↗
PubMed1999

Selenium transport and bioaccumulation in aquatic ecosystems: a proposal for water quality criteria based on hydrological units.

Local water quality criteria for selenium should be based on an assessment of the degree of toxicological hazard to fish and wildlife, which is influenced by the spatial and temporal variation of the selenium cycle at the site under consideration. The physical area from which measurements are taken to evaluate selenium residues and biological effects, i.e., the database for setting site-specific criteria, must encompass more than an isolated segment of river, a tributary stream, etc. Because of hydrological connections between the various aquatic habitats that may be present in a watershed basin-wetlands, rivers, streams, and impoundments-the toxic threat from selenium contamination is also connected. For example, a criterion that is appropriate for a stream or river where low bioaccumulation occurs may result in seemingly harmless concentrations of selenium becoming a problem in downstream impoundments or in off-channel bays and wetlands where bioaccumulation is greater. The hydrologically connected parts of a basin downstream of a selenium discharge (natural or synthetic selenium source), extending to the point at which new sources of low-selenium water dominate the hydrology (e.g., confluence with larger tributary or river, spring or groundwater inflow), should be the area evaluated and given a specific criterion, not isolated components. Thus, a hydrological unit should be identified and used as the "site" for the purpose of setting criteria. Importantly, criteria derived in such a fashion will reflect the transport and bioaccumulation of selenium within the entire hydrological unit rather than simply focusing on a small, artificially designated segment of the system. Failure to use a hydrological unit approach can set the stage for significant biological and legal problems.

Ecosystem↗
PubMed2000

Hazard assessment of selenium and other trace elements in wild larval razorback sucker from the Green River, Utah.

Contaminant investigations of the Green River in northeastern Utah have documented selenium contamination at sites receiving irrigation drainage. The Green River provides critical habitat for four endangered fishes including the largest extant riverine population of endangered razorback sucker. Although 2175 larval razorback suckers were collected from the river between 1992 and 1996, very few juveniles have been captured within recent decades. Selenium concentrations were measured in larval razorback suckers collected from five sites in the Green River (Cliff Creek, Stewart Lake Drain, Sportsman's Drain, Greasewood Corral, and Old Charlie Wash) to assess the potential for adverse effects on recruitment of larvae to the juvenile stage and the adult population. Larvae from all sites contained mean selenium concentrations ranging from 4.3 to 5.8 microg/g. These values were at or above the proposed toxic threshold of 4 microg/g for adverse biological effects in fish, which was derived from several laboratory and field studies with a wide range of fish species. At two sites, Cliff Creek and Stewart Lake Drain, selenium concentrations in larvae increased over time as fish grew, whereas selenium concentrations decreased as fish grew at Sportsman's Drain. Evaluation of a 279-larvae composite analyzed for 61 elements demonstrated that selenium and, to a lesser extent, vanadium were elevated to concentrations reported to be toxic to a wide range of fish species. Elevated selenium concentrations in larval razorback suckers from the five sites suggest that selenium contamination may be widespread in the Green River, and that survival and recruitment of larvae to the juvenile stage may be limited due to adverse biological effects. Selenium contamination may be adversely affecting the reproductive success and recruitment of endangered razorback sucker.

Animals↗
PubMed1987

Comparison of the protection given by selenite, selenomethionine and biological selenium against the renotoxicity of mercury.

The protective effect of selenite, seleno-dl-methionine and biological selenium against the renotoxicity of mercury was tested in rats. As the source of biological selenium, the liver soluble fraction of rats given 60 mumoles/kg selenite 3 days before sacrifice was used. The aim of the experiments was to test whether protective efficiency follows the reported order of ability to form HgSe. Mercury was given subcutaneously in doses of 2.5, 5.0 and 7.5 mumoles/kg HgCl2 and selenium was given in equimolar doses at the same time as Hg2+. Liver soluble fraction, biological selenium or liver soluble fraction supplemented with selenite or seleno-dl-methionine were given orally, while in experiments without liver soluble fraction the two selenium compounds were given subcutaneously. Biological selenium was tested only at the two lower dose levels. Both biological selenium and seleno-dl-methionine decreased the urinary excretion of mercury in the first 48 h, but less so than selenite and only selenite decreased the renal content of mercury at the end of this period. Urinary alkaline phosphatase activity and plasma urea nitrogen at the 2.5 and 5.0 mumoles/kg dose levels decreased in the order of no selenium greater than biological selenium greater than seleno-dl-methionine greater than selenite. As the reported HgSe formation increases in the same order, the experiments support the role of HgSe formation in the protective effect. The degree of necrotic damage in the P2 and P3 regions of the proximal tubular cells increased in the same order as the biochemical indicators at the 5.0 and 7.5 mumoles/kg dose levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effects of elevated foodborne selenium on growth and reproduction of the fathead minnow (Pimephales promelas).

Several field studies of selenium-contaminated lakes and reservoirs have indicated the possibility of selenium-induced reproductive failure in important populations of fish. These investigators have hypothesized that bioaccumulation of selenium through the food chain led to fish selenium levels high enough to elicit toxic responses. The present investigation was designed to determine the effects of elevated foodborne selenium on the fathead minnow (Pimephales promelas). Fish were fed a diet spiked with a mixture of inorganic (selenite and selenate) and organic (seleno-L-methionine) selenium and effects on growth and reproduction were determined. Growth was significantly inhibited at the highest selenium treatment levels evaluated (20 and 30 ppm Se). There were no significant treatment effects on any of the reproductive parameters measured. Reasons for the disparity between selenium-induced reproductive impairment observed in other species and apparent lack of impairment in fathead minnows may involve reduced bioaccumulation of selenium by minnows due to differences in gut morphology and physiology.

Animal Feed↗
PubMed1988

Decreased hepatic selenium content in alcoholic cirrhosis.

Selenium deficiency has been implicated as contributing to hepatic injury in alcoholics. The mechanism by which this occurs is most likely lipoperoxidation secondary to decreased activity of the selenoenzyme glutathione peroxidase. To further assess this relationship, we measured selenium content in autopsy livers in 12 patients with alcoholic cirrhosis compared to 13 patients matched for age and sex dying from other causes, mostly with cardiopulmonary diseases. The mean (+/- SEM) hepatic selenium content in cirrhosis was 0.731 +/- 0.077 microgram/g dry weight versus 1.309 +/- 0.166 microgram/g in controls (P less than 0.005; Student's t test). Clinical and biochemical indices of significant hepatic dysfunction, including encephalopathy, ascites, and elevations of serum bilirubin or prothrombin time, were only present in the cirrhotic group. A significant inverse correlation between hepatic selenium content and the prothrombin time was noted (r = -0.50; P less than 0.02). No significant relationships between hepatic selenium and the abnormalities of bilirubin, albumin, or aspartate aminotransferase were found. We conclude that significantly decreased hepatic selenium stores are present in patients with severe alcoholic cirrhosis compared to controls. The magnitude of that selenium deficit does correlate with some indices of hepatic function, specifically the prothrombin time. These data lend further support to a true selenium deficiency state in alcoholic cirrhosis. It is highly possible that selenium deficiency represents an important link, synergistically joining the nutritional and hepatotoxic backgrounds of alcoholic liver injury and cirrhosis.

Bilirubin↗
PubMed1986

Blood selenium concentrations of sheep and goats from selected areas of Kenya.

A systematic mapping technique based on blood, forage and soil selenium levels was employed to locate areas of selenium deficiency, adequacy or excess in areas of Kenya where grazing of small ruminants predominates. A total of 1,478 blood samples from both sheep and goats, 180 forage samples and 90 soil samples were analysed for selenium levels. During the wet seasons 28% of the sheep and 15% of the goats had marginal to deficient blood selenium concentrations while during the dry season 20% of the sheep and 12% of the goats had marginal to deficient blood selenium concentrations. Forage samples had a range of 0.03 to 0.66 ppm selenium while soil samples had a range of 0.06 to 0.98 ppm selenium. Although many animals had blood selenium levels of less than 0.05 ppm, below which selenium deficiency signs might occur, none of the animals manifested these signs.

Animals↗
PubMed1999

Environmental factors, health-related habits, and serum selenium levels in cancer patients and healthy controls.

Previous studies conducted in Yugoslavia indicated that the concentration of selenium in soil, food items, and serum of the population is very low. The aim of the study was to investigate the possible relationship among environmental, health-related habits, nutrition, and selenium serum levels in cancer patients and the healthy population. The case-control study included a group of cancer patients and a matched group of healthy controls: 57 cancer patients and 41 healthy controls living in Stari Grad (an urban area of Belgrade), as well as 17 cancer patients and 13 healthy controls living in Barajevo (a rural community in the vicinity of Belgrade). The healthy controls were matched to cancer patients in sex and age; they were not blood related. The selenium serum levels were measured by atomic absorption spectrophotometry. Health-related habits and relevant dietary factors ("food frequency" method) that may influence the selenium serum levels were assessed by questionnaires. The differences in average values of selenium serum levels between the cancer patients and healthy controls were not significantly different, but both were below the lowest recorded in referential studies. A significant difference between the values obtained from urban and rural subgroups was noted. The most important factors that influenced the level of selenium included the residence place in the region with selenium deficiency (Barajevo), age, associated chronic diseases, and some dietary factors potentially related to the intake of selenium. The results obtained in this investigation pointed out that use of selenium supplementation in this area should be seriously considered.

Aged↗
PubMed1999

[Selenium therapy in colorectal tumors?].

BACKGROUND: Is the complementary supplementation of selenium useful in the therapy of colorectal cancer? PATIENTS AND METHODS: Fifty-three patients with primary colorectal cancer received a selenium treatment for 19 days in addition to a complete in-patient rehabilitation cure based on a behavioural approach. A comparative control group consisted of 41 patients. Measured factors were the selenium content in serum and whole blood, GSH-Px activity and TBARS in serum. Both the intake of selenium by nutrition and the patients' life quality were determined additionally on day 1 and 19. The tumor marker CA 19-9 was measured only on day 1. RESULTS: A latent selenium deficiency was observed while gsh-px activity or concentration of TBARS were normal. The selenium status corresponds to the concentration of the tumor marker CA 19-9. The selenium status improves through supplementation, accompanied by a further increase of GSH-Px activity. During supplementation the patients' life quality improves; subjective physical complaints decrease. CONCLUSION: Further research will be necessary on both the dependency of the selenium status on the tumor marker concentration and on the development of the cancer. Optimum GSH-Px activity and individually different responses also need additional investigation. The influence of selenium on the patients' life quality should be investigated in the context of immunomodulation.

Adult↗
PubMed2002

HPLC-ICP-MS determination of selenium distribution and speciation in different types of nut.

In addition to determination of total selenium in nuts, the element distribution among different fractions (lipid extract, low molecular weight, and protein fractions), and speciation analysis were studied. Improved precision for total selenium determination was observed after elimination of lipids. Because selenium was not detected in any of the lipid extracts obtained from the different types of nuts (ICP-MS), in each determination and/or speciation procedure used in this work lipids were extracted (chloroform-methanol, 2:1) and discarded before analysis. In agreement with previously reported data, high selenium levels were found in Brazil nuts (those purchased without shells contained approximately a quarter the content than those purchased with shells) and significantly lower levels in walnuts, cashews, and pecans nuts. Low-molecular-weight compounds were extracted with perchloric acid (0.4 mol L(-1)) to furnish a fraction containing 3 to 15% of the total selenium in different types of nuts. The proteins were isolated from nut samples by dissolution in 0.1 mol L(-1) sodium hydroxide and subsequent precipitation with acetone. They were then dissolved in phosphate buffer pH 7.5. Analysis of protein fractions focused on selenium in two possible states - weakly and firmly bound to proteins. Results obtained for Brazil nuts by size-exclusion chromatography with on-line ICP-MS detection, in the absence and in the presence of beta-mercaptoethanol, showed that approximately 12% of total selenium was weakly bound to proteins. To obtain information about firmly bound selenium, the protein extracts were hydrolyzed enzymatically with proteinase K. Speciation was performed by means of ion-pairing HPLC-ICP-MS. The primary species found in all types of nuts was Se-methionine (19-25% of total selenium for different types of nuts).

Chromatography, High Pressure Liquid↗
PubMed2002

Selenium in a Wyoming grassland community receiving wastewater from an in situ uranium mine.

Water, soil, vegetation, grasshoppers, bird eggs, and bird livers collected at a 23.5-ha (58 acres) grassland irrigated with wastewater from an in situ uranium mine (study area) and a reference site in 1998 were analyzed for selenium and other trace elements. Selenium concentrations in the uranium mine wastewater applied onto the grassland ranged from 340 to 450 microg/L. Selenium in the upper 15 cm (6 in) of soil from the irrigated grassland at the mine ranged from 2.6 to 4.2 microg/g dry weight (DW). Mean selenium concentrations in soil and water were 5 and 15 times higher at the study area than at the reference site. Selenium concentrations in grasses and grasshoppers ranged from 6.8 to 24 microg/g and 11 to 20 microg/g DW, respectively. Selenium in red-winged blackbird eggs and livers collected from the study area ranged from 13.2 to 22 microg/g and 33 to 53 microg/g DW, respectively, and concentrations were well in excess of toxic thresholds. Mean selenium concentrations in grasses, grasshoppers, and bird eggs and livers were 5.8 to 30 times higher at the study area than at the reference site. Elevated selenium concentrations in water, soil, grasshoppers, and red-winged blackbird eggs and livers collected from the study area demonstrate that selenium is being mobilized and is bioaccumulating in the food chain.

Animals↗
PubMed2005

Accumulation of selenium and lack of severe effects on productivity of American dippers (Cinclus mexicanus) and spotted sandpipers (Actitis macularia).

Selenium has been found at elevated concentrations in water, sediments, and aquatic biota in the Elk River (British Columbia, Canada) and some of its tributaries downstream of several coal mines. Selenium water concentrations in those areas exceed Canadian and British Columbia guidelines and are above levels at which adverse effects to fish and waterfowl could occur. We compared selenium concentrations in the eggs of two riverine waterbirds, American dippers and spotted sandpipers, with measures of productivity: the number of eggs laid, egg hatchability, and nestling survival. In American dippers, the mean egg selenium concentration from the exposed areas, 1.10 +/- SE 0.059 microg/g wet weight, was indistinguishable from the reference areas, 0.96 +/- SE 0.059 microg/g wet weight. For spotted sandpipers, the mean egg selenium concentration in the exposed areas, 2.2 +/- 0.5 microg/g wet weight, was significantly higher than in the reference areas, 1.2 +/- 0.14 microg/g wet weight, but less than reported thresholds for waterfowl and other shorebirds. There were no significant differences in egg hatchability between dippers in reference and exposed areas, but reduced hatchability was apparent for sandpipers in exposed locations. Despite the slightly reduced hatchability in sandpipers, overall productivity was higher than regional norms for both species; thus, selenium did not affect the number of young recruited to local populations. We did not observe teratogenic effects in either species, although none was expected at these concentrations. Despite moderately high selenium concentrations in the water, mean egg selenium concentrations were less than predicted from uptake models. We hypothesise that the relatively low uptake of selenium into the eggs of the two waterbirds in this study is likely due to their lotic environment's low biological transformation and uptake rates.

Alberta↗
PubMed2000

Selenium concentrations in the Colorado pikeminnow (Ptychocheilus lucius): relationship with flows in the upper Colorado River.

A Department of the Interior (DOI) irrigation drainwater study of the Uncompahgre Project area and the Grand Valley in western Colorado revealed high selenium concentrations in water, sediment, and biota samples. The lower Gunnison River and the Colorado River in the study area are designated critical habitat for the endangered Colorado pikeminnow (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus). Because of the endangered status of these fish, sacrificing individuals for tissue residue analysis has been avoided; consequently, little information existed regarding selenium tissue residues. In 1994, muscle plugs were collected from a total of 39 Colorado pikeminnow captured at various Colorado River sites in the Grand Valley for selenium residue analysis. The muscle plugs collected from 16 Colorado pikeminnow captured at Walter Walker State Wildlife Area (WWSWA) contained a mean selenium concentration of 17 microg/g dry weight, which was over twice the recommended toxic threshold guideline concentration of 8 microg/g dry weight in muscle tissue for freshwater fish. Because of elevated selenium concentrations in muscle plugs in 1994, a total of 52 muscle plugs were taken during 1995 from Colorado pikeminnow staging at WWSWA. Eleven of these plugs were from fish previously sampled in 1994. Selenium concentrations in 9 of the 11 recaptured fish were significantly lower in 1995 than in 1994. Reduced selenium in fish may in part be attributed to higher instream flows in 1995 and lower water selenium concentrations in the Colorado River in the Grand Valley. In 1996, muscle plugs were taken from 35 Colorado squawfish captured at WWSWA, and no difference in mean selenium concentrations were detected from those sampled in 1995. Colorado River flows during 1996 were intermediate to those measured in 1994 and 1995.

Animals↗
PubMed2006

The American dipper as a bioindicator of selenium contamination in a coal mine-affected stream in west-central Alberta, Canada.

Elevated levels of selenium have been found in water and aquatic biota downstream from two open-pit coal mines in the Rocky Mountain foothills of Alberta. Birds are particularly sensitive to excessive dietary selenium. However, there is relatively little information on selenium accumulation in birds' eggs on fast-flowing mountain streams. We determined levels of selenium in water samples, caddisfly larvae and eggs of American dippers (Cinclus mexicanus) nesting on the Gregg River, downstream from the mines, and on reference streams in the same general vicinity. Selenium levels (mean, 95% confidence limits) in water samples and caddisflies collected from sites near dipper nests on the Gregg River (water: 4.26, 1.90-9.56 microg L(-1); caddisflies: 8.43, 7.51-9.46 microg g dry wt(-1)) were greater than those collected from sites near nests on reference rivers (water: 0.38, 0.21-0.71 microg L(-1); caddisflies: 4.65, 4.35-4.97 microg g dry wt(-1)). The mean (+/- 1SE) selenium level in dipper eggs from the Gregg River (6.3 +/- 0.2 microg g(-1) dry wt) was significantly higher than it was in eggs from reference streams (4.9 +/- 0.2 microg g(-1) dry wt). Concentrations of selenium in eggs were significantly correlated with those in water samples (r = 0.45). The maximum selenium level in eggs from the Gregg River (9.0 microg g(-1)) may have been high enough to warrant concern from an ecotoxicological perspective. The American dipper can serve as a useful bioindicator of selenium contamination in mountainous, lotic ecosystems.

Alberta↗