Trace element concentrations in hair of healthy Chinese centenarians

Trace element concentrations, as indicators of micronutrient status of healthy centenarians, have not been widely analyzed. This study aimed to assess trace element concentrations in the hair of healthy centenarians. The effects of gender and age on element concentrations were also investigated. Eleven trace elements (Al, Ba, Cd, Cr, Cu, Fe, Mo, Pb, Se, Sr and Zn) in the scalp hair of 107 healthy Chinese centenarians were examined. The overall reference values (RVs) in mg/kg for the hair concentrations of trace elements in centenarians were as follows: Al, 14.95; Ba, 2.68; Cd, 0.06; Cr, 0.59; Cu, 6.21); Fe, 19.37; Mo, 0.50; Pb, 4.64; Se, 0.37; Sr, 4.84; and Zn, 154.37. Data analysis found that only Cu and Zn concentrations show a normal distribution, and there is no significant difference between males and females in any element except Zn. However, the levels of Al, Cd, Cr, Fe, Mo, Pb decrease and the levels of Ba, Cu, Se, Sr, Zn increase with age in the centenarian cohort. Results also revealed that sufficient Zn and Se concentrations as well as low exposure to heavy metals pollution contribute to the longevity of centenarians. The results imply the possibility of manipulating trace element concentrations, especially Zn and Se concentrations in tissues, as a means for therapeutic modality in geriatric disease.     

Heavy metals in wild rice from northern Wisconsin

Wild rice grain samples from various parts of the world have been found to have elevated concentrations of heavy metals, raising concern for potential effects on human health. It was hypothesized that wild rice from north-central Wisconsin could potentially have elevated concentrations of some heavy metals because of possible exposure to these elements from the atmosphere or from water and sediments. In addition, no studies of heavy metals in wild rice from Wisconsin had been performed, and a baseline study was needed for future comparisons. Wild rice plants were collected from four areas in Bayfield, Forest, Langlade, Oneida, Sawyer and Wood Counties in September, 1997 and 1998 and divided into four plant parts for elemental analyses: roots, stems, leaves and seeds. A total of 194 samples from 51 plants were analyzed across the localities, with an average of 49 samples per part depending on the element. Samples were cleaned of soil, wet digested, and analyzed by ICP for Ag, As, Cd, Cr, Cu, Hg, Mg, Pb, Se and Zn. Roots contained the highest concentrations of Ag, As, Cd, Cr, Hg, Pb, and Se. Copper was highest in both roots and seeds, while Zn was highest just in seeds. Magnesium was highest in leaves. Seed baseline ranges for the 10 elements were established using the 95% confidence intervals of the medians. Wild rice plants from northern Wisconsin had normal levels of the nutritional elements Cu, Mg and Zn in the seeds. Silver, Cd, Hg, Cr, and Se were very low in concentration or within normal limits for food plants. Arsenic and Pb, however, were elevated and could pose a problem for human health. The pathway for As, Hg and Pb to the plants could be atmospheric.     

Kidney and liver levels of some major, minor and trace elements in two Ontario communities

The contents of Ag, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, P, Pb, Se, Sr, Th, Ti and Zn in 143 autopsied liver and kidney specimens from two Ontario communities (Kingston and Ottawa) were determined using the techniques of inductively-coupled plasma--atomic emission spectrometry, and electrothermal atomization--atomic absorption spectrometry coupled with hydride evolution (As, Se), reduction--aeration (Hg), or solvent extraction (Pb). The majority of samples came from individuals older than 50 y. In general, the data for the various elements were independent of age or sex but showed some dependence on location for elements such as Cu, Fe, K, Mg, Mn, Na, P, Se and Zn. Despite these differences the elemental values of the liver and kidney samples from both the communities were within the normal range.     

Relationships between trace elements and atherosclerosis

The possible relationship between trace element (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Zn) concentrations in various human tissues (heart, liver, kidney, aorta, rib and head hair) and cardiovascular diseases was studied on the basis of indications in the literature that trace elements may be directly or indirectly involved in cardiovascular disease processes. The underlying theme was that (slightly) reduced, as well as (slightly) elevated, concentrations compared with optimum values could, in the long term, lead to atherosclerotic lesions. In this project the tissues were obtained by autopsy involving 200 individuals (hospitalised patients and victims of traffic accidents). The seriousness of cardiovascular disease was quantitatively expressed by the degree of atherosclerosis of the descending branch of the left coronary artery (LAD) and of the abdominal aorta, for which a special measurement method was developed. Correlations were evaluated by two different methods, i.e. by a comparison of patients with extremely high or extremely low degrees of atherosclerosis and by means of stepwise multiple linear regression (SMLR) analysis. Corrections were made for the influence of age. The element Cd was found to be positively, and the elements Cu, Co, Se and Zn negatively, correlated with the degree of atherosclerosis. The inclusion of risk factors (diabetes mellitus, hypercholesterolaemia, hypertension, obesity and smoking) did not improve the explained variance.     

Trace element accumulations in 13 avian species collected from the Kanto area, Japan

In the present study, concentrations of 13 elements (Li, Cr, Mn, Cu, Zn, As, Se, Rb, Sr, Mo, Ag, Cd, Hg) were measured in the tissues of the livers, the kidneys, pectoral muscles, lungs and brains of 13 avian species collected from the Kanto area of Japan. The difference in hepatic heavy metal levels of the grey herons from the two sites was compared. Metal levels in the sediment of the Tama River estuary, situated in the Haneda area, were also measured. These results revealed that heavy metal pollution is present in an aquatic area of Haneda. The accumulation patterns of Cu and Zn in the livers of grey herons appeared to be separated into two groups. Additionally, the present study includes the properties of other metal accumulations and their relationships in avian species.     

Effects of microelements on soil nematode assemblages seven years after contaminating an agricultural field

Long-term effects of Cd, Cr, Cu, Se and Zn were studied 7 years after artificially contaminating plots of an agricultural field on a calcareous chernozem soil. Effects of three to four different contamination levels (originally 10, 30, 90 and 270 mg kg⁻¹) were studied. Nematode density was significantly reduced by 90 and 270 mg kg⁻¹ Se as well as by 270 mg kg⁻¹ Cr, while 90 and 270 mg kg⁻¹ Se also reduced nematode generic richness. Maturity Index values (calculated for c-p 2–5 nematodes) consistently decreased with increasing Cr and Se concentration and to a lesser extent in Zn plots as well. Structure Index showed decreasing trends in increasing Cr, Se and (to a lesser extent) in Zn treatments, while in Cd it shows a moderate increase. Distribution of c-p groups was negatively affected by the increasing Cr and Se concentration, while in Zn plots, this decrease was not significant. Response of feeding groups to pollutions was similar to other parameters: Cr and Se caused significant changes toward the loss of variability. The proportion of the most sensitive omnivorous and predatory nematodes decreased clearly as a consequence of Cr and Se treatments. Zn pollution also resulted in a slight decrease in this group, while Cd caused an increase. Nematode diversity profiles showed a significant decrease in the plots of increased Cr and Se concentrations, while increased concentrations of Cu and Zn resulted in ambiguous effects. Besides providing evidence on the harmful effects of Cr and Se on a soil nematode assemblage, our results suggest that simultaneous analysis of Maturity Index, Structure Index and diversity profiles provide a promising tool in nematological indication of soil pollution.     

Reference values for elemental concentrations in some human samples of clinical interest: A preliminary evaluation

Over 60 investigators, some of them with an outstanding international reputation as analysts, were requested to identify reliable data from their countries for elemental concentrations in normal adult human samples of clinical interest by contributing their own data as well as screening the literature information. A set of samples consisting of whole blood and its components, urine, milk, liver and hair were chosen and considered for 15 elements of biological significance: Zn, Cu, Fe, Se, Mn, Pb, Cd, Hg, As, Mo, Cr, Co, I, Ni and F. The results partly cover over 40 countries from the global regions of Africa, Asia, Europe, North, South and Central America, Australia and New Zealand.This survey has been useful in demonstrating certain trends of trace element picture around the world, at least qualitatively. Both diet and environment have a strong influence on the distribution pattern of several elements such as As, Cd, Mn, Pb, Se and Zn. A limited comparison of the available information on soil status of different countries revealed interesting associations for elements such as Mn and Zn.Importantly, this study revealed that only a few countries were in a position to supply a reasonable amount of data on samples requested here. In particular, for a number of countries, reliable data for even very essential elements such as Cu, Zn and Fe were not available. In view of the nutritional importance of several elements the time is ripe for international organizations to intervene and help produce some reference data for selected global regions which lack data of any kind.     

Incidence and variability of some elements in the non tidal region of the River Thames,and River Kennet,U.K.

Element incidence and variability in the soluble and suspended particulate fractions of water taken during an extended period from four sampling locations on the Rivers Thames and Kennet is presented. Neutron activation analysis was used to determine 30 elements in the river water samples. One way analysis of variance was applied to investigate the significant variation in metal concentration between the four sampling stations and correlation analysis was used to study the relationship between elemental concentrations and river water parameters. Dissolved Cr, Fe and Se correlated positively with river flow rate whereas Rb and Zn had a significant negative correlation.     

Trace element reference values in tissues from inhabitants of the European Community. III. The control of preanalytical factors in the biomonitoring of trace elements in biological fluids.

In the context of a programme concerning the determination of trace elements in body fluids and tissues to establish trace element reference values, research has been undertaken on the control of preanalytical factors in order to develop sufficiently accurate and precise guidelines to be applied in routine work by using techniques such as graphite furnace atomic absorption spectroscopy (GFAAS). Aspects investigated are related to the risk of contamination during blood collection and the use of anticoagulants; the risk of losses during storage and freeze-drying as well as the possible risk of contamination arising from trace elements in airborne particulates of the laboratory environment. For the analysis of Al, Ba, Cd, Co, Cr, Mn, Mo, Ni, Sb, W, V and Zn in blood, Teflon cannula is the method of choice. The anticoagulants do not introduce disturbing contaminations of Rb, Se, Zn, while contaminations were observed for Co, Cr, Mn. Radiotracers in 'metabolized form' (radiolabelled rat or rabbit tissues from animals administered with radioisotopes) show that samples stored for 1 month at -20 degrees C have no significant trace metal losses. Strict ambient air quality standard has to be respected (continuous monitoring) due to the possibility of element contaminations inside the laboratory. The use of matrix modifiers could represent a toxicological risk to the operators. Critical factors should be considered ('metal sheets') for each element in each matrix. For instance 27 factors for Cr in serum have been suggested.     

Concentrations of some trace elements in hair, liver and kidney from autopsy subjects--relationship between hair and internal organs

Autopsy samples of hair, liver and kidney cortex from 30 Swedish subjects (Caucasian) were analysed for Ag, Co, Cr, Hg, Sb, Se and Zn by neutron activation analysis (NAA). The following elements were observed to have higher concentrations in hair than in liver and kidney cortex: Ag, (Co), Cr and Hg (on a dry weight basis). Selenium was highly concentrated in kidney cortex, and Fe in liver. The observed concentrations of most of the elements were very variable for each tissue. In particular, Co values for hair showed more than a 5000-fold difference. However, Se values for hair were relatively constant. A highly significant positive correlation was observed between Hg concentrations in hair and kidney cortex. Somewhat weaker correlations were found between Hg in kidney cortex and liver and Se in hair and kidney cortex. The concentration of Co in liver correlated with that in kidney cortex. It was concluded that, with the exception of mercury, and to a lesser degree selenium, hair analysis did not provide a useful measure of the trace element status of the subjects included in this study.     

Arsenic and other elements in hair, nails, and skin-scales of arsenic victims in West Bengal, India

For the first time, biological tissues (hair, nails, and skin-scales) of arsenic victims from an arsenic affected area of West Bengal (WB), India were analyzed for trace elements. Analysis was carried out by inductively coupled plasma-mass spectrometry (ICP-MS) for 10 elements (As, Se, Hg, Zn, Pb, Ni, Cd, Mn, Cu, and Fe). A microwave digester was used for digestion of the tissue samples. To validate the method, certified reference materials--human hair (GBW 07601) and bovine muscle (CRM 8414)--were analyzed for all elements. The W test was used to study the normal/log normal distribution for each element in the tissue samples. For hair (n=44) and nails (n=33), all elements show log-normal distribution. For skin-scale samples (n=11), data are not sufficient to provide the information about the trend. Geometric mean, standard error, and range for each element were presented and compared with literature values for other populations. This study reveals the higher levels of toxic elements As, Mn, Pb, and Ni in the tissue samples compared with available values in the literature. The elevated levels of these toxic metals in the tissues may be due to exposure of these elements through drinking water and food. The correlations of Mn and Ni with other essential elements, e.g. Fe, Cu, Zn, suggest that Mn and Ni may substitute for those elements in hair, nails, and skin-scales. However, correlation represents the relation between two elements only and does not take into consideration of the presence of other elements. Principle component analysis was applied to explain the behavior among the elements present in hair and nails. This study reveals that in the arsenic-affected areas of WB, the concentrations of other toxic elements in drinking water and foodstuff should be monitored to evaluate the arsenic poisoning.     

Heavy metals in drilling‐waste leachates from East Java,Indonesia

This study examined the leaching toxicity characteristics of heavy metals in drilling‐waste mud by the toxicity characteristic leaching procedure (TCLP). Ten heavy metal elements As, Ba, Cd, Cr, Cu, Pb, Se, Ag, Zn and Hg were investigated. Test drilling‐waste mud samples were collected from eight active exploration wells. The TCLP results showed that the concentrations of the metals were below the Indonesian Regulatory Standards Nos. 18 and 85 (1999) regarding hazardous waste management. Barium was detected in all the leachates, and ranged from 0.40 to 6.59 mg/l. Mercury was below detectable levels at only two stations. Values of the other metals varied significantly from one station to another.     

Trace element concentrations in blood of harbor seals (Phoca vitulina) from the Wadden Sea

Concentrations of 23 elements (Be, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Mo, Pd, Cd, Sn, Pt, Pb) were evaluated in whole blood samples of live harbor seals (Phoca vitulina) from two different locations in the Wadden Sea, the Lorenzenplate in Germany, and the Danish island R?m?. Elemental blood levels were compared to data from literature of seals, other marine mammals and humans. While homeostatically controlled elements showed no differences, concentrations of As, Cr, Mn, Mo, Se, and V were higher than human levels. Furthermore, animals from both locations showed significant geographical differences in whole blood concentrations of Al, Mn, Cu, and Pt. These findings could be explained by differences in feeding areas. The element pattern was not affected by gender. In conclusion, these findings indicate an impact of the environment on biochemical blood parameters of the harbor seals. The significant differences of elements in blood samples of two groups of seals, which were associated with geographical variations of prey support the use of element pattern in blood as tool for investigation of environmental impact on seals.     

Metals contained and leached from rubber granulates used in synthetic turf areas

The aim of this study was to quantify metals contained in and leached from different types of rubber granulates used in synthetic turf areas. To investigate the total content of metals, ca 0.5 g of material was added with HNO₃, HF and HClO₄ and microwave digested with power increasing from 250 W to 600 W. Leachates were prepared by extraction of about 5.0 g of material at room temperature for 24 h in an acidic environment (pH 5). Leaching with deionized water was also performed for comparison. Aluminium, As, Ba, Be, Cd, Co, Cr, Cu, Hg, Fe, Li, Mg, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, Tl, V, W and Zn were quantified by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) and ICP optical emission spectrometry (ICP-OES).Results indicated that the developed method was accurate and precise for the multi-element characterization of rubber granulates and leachates. The total amount and the amount leached during the acidic test varied from metal to metal and from granulate to granulate. The highest median values were found for Zn (10,229 mg/kg), Al (755 mg/kg), Mg (456 mg/kg), Fe (305 mg/kg), followed by Pb, Ba, Co, Cu and Sr. The other elements were present at few units of mg/kg. The highest leaching was observed for Zn (2300 μg/l) and Mg (2500 μg/l), followed by Fe, Sr, Al, Mn and Ba. Little As, Cd, Co, Cr, Cu, Li, Mo, Ni, Pb, Rb, Sb and V leached, and Be, Hg, Se, Sn, Tl and W were below quantification limits. Data obtained were compared with the maximum tolerable amounts reported for similar materials, and only the concentration of Zn (total and leached) exceeded the expected values.     

Design of an aquatic biomonitoring network for an environmental specimen bank

The aim of the present study was to establish an aquatic biomonitoring network for the Galician Environmental Specimen Bank (BEAG) (NW Spain). For this, a sampling system was designed that comprised of 121 points distributed throughout Galician rivers, from which samples of water and of three species of bryophytes were collected. The results obtained allowed selection of 74 sampling points and 2 species (Fontinalis antipyretica Hedw. and F. squamosa Hedw.) as the most suitable for use in future BEAG sampling surveys. The two species selected showed a strong similarity in their capacity to accumulate the 17 elements determined (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Se and Zn), as well as in their ecological preferences. Furthermore, the levels of contamination of epicontinental waters were lower than those observed in previous surveys.     

Distribution patterns of chalcogens (S, Se, Te, and 210Po) in various tissues of a squid, Todarodes pacificus

In order to elucidate the relationship between the chemically similar chalcogen elements S, Se, Te, and 210Po in marine invertebrates, we conducted a comparative study of the distribution patterns of these elements in a squid, Todarodes pacificus. Elemental concentrations of the four chalcogens were determined in (mantle) muscle, gill, stomach, and hepatopancreas tissues. No relationship between chalcogen concentrations and morphological parameters (mantle length, body weight, and sex) was evident. Gills showed slightly elevated levels of Se and 210Po, which may indicate absorption and uptake of these elements over the gill surface. All four chalcogens have their highest concentrations in the hepatopancreas and the lowest concentrations in the muscle tissue. However, concentration differences between tissues, revealed by (1) bioaccumulation values based on reference seawater values and (2) internal relative enrichment factors (IREF) based on enrichment of hepatopancreas compared to muscle tissue, were least pronounced for S, most distinct for 210Po, and moderate for Se and Te. Furthermore, no significant correlation for Se, Te, and 210Po with S within tissue concentrations, and only a slightly negative correlation between S and 210Po in the squid muscle and hepatopancreas tissues were found, which indicates either an antagonistic effect between, or a disconnection of the two elements through metabolic processing. Overall, the distribution patterns of Se and Te resemble those of essential trace elements, such as Zn and Cu, whereas 210Po is partitioned in a manner similar to toxic heavy metals, such as Cd and Ag.     

Evaluation of trace elements in human lung tissue III. Correspondence analysis

The concentrations of 22 trace elements in 13 segments of both lungs of eight individuals were subjected to correspondence analysis, a display method based on principal components analysis. Sample groups were isolated which coincide with the age of the individuals. The firmness of the clusters decreased however with aging. The elements Br, Cd, Co, Cr, Cs, Pb, Sc, Se and V had the most important influence on the grouping. It can be assumed that they are enriched in the tissue by inhaled particulate matter, deposited and accumulated in an insoluble form. The correlation between the elements is proof for their similar behaviour in the lungs: Co, Cr, Sb, Sc and V have a long biological half-life in the tissue, whereas Zn and K are easily removed.     

Assessment of inorganic content of PM(2.5) particles sampled in a rural area north-east of Hanoi, Vietnam

Atmospheric aerosols from seven rural sites in northern Vietnam, east of Hanoi, were sampled and analyzed. The aim of the study was to evaluate trace elemental and black carbon (BC) concentrations in fine particles (PM(2.5)) and to investigate the influence of the Pha Lai power plant and other pollution sources on regional air quality. Seven measurement stations were set up at selected rural sites and a campaign consisting of 12 two-day measurement periods was conducted from the end of May until the end of October 2000. At each location a pair of samplers was installed consisting of a cyclone loaded with Teflon filters and a modified Millipore air monitoring cartridge loaded with glass fibre filters. The obtained samples were analyzed for trace elements by Energy Dispersive X-ray Fluorescence (EDXRF), while a black smoke detector was used for BC analysis. Seventeen trace elements were analyzed; Br, Ca, Cl, Cr, Cu, Fe, K, Mn, Ni, Pb, Rb, S, Se, Sr, Ti, V and Zn and their concentrations evaluated. The results showed that BC, Ca, Cl, Fe, K and S dominated in the sampled atmospheric aerosols. The measured concentrations of the potentially hazardous trace elements Cr, Mn, Ni and Pb were all below the limits defined by Vietnamese standards of ambient air quality. Statistical evaluations indicated that coal and heavy fuel oil combustion were major sources of atmospheric pollutants in the area and that biomass burning and road transport had a marked influence on regional air quality. It was concluded that the Pha Lai power plant was the major source of coal combustion emissions. Trace element emissions originating from river transportation were suggested as another major source of atmospheric pollutants. The results indicate that the elemental concentrations in PM(2.5) are strongly influenced by seasonal variations. Further measurements are required to identify the impact of long-range transported continental air masses on the air quality of the investigated rural area.     

Chemistry of trace elements in coalbed methane product water

Extraction of methane (natural gas) from coal deposits is facilitated by pumping of aquifer water. Coalbed methane (CBM) product water, produced from pumping ground water, is discharged into associated unlined holding ponds. The objective of this study was to examine the chemistry of trace elements in CBM product water at discharge points and in associated holding ponds across the Powder River Basin, Wyoming. Product water samples from discharge points and associated holding ponds were collected from the Cheyenne River (CHR), Belle Fourche River (BFR), and Little Powder River (LPR) watersheds during the summers of 1999 and 2000. Samples were analyzed for pH, Al (aluminum), As (arsenic), B (boron), Ba (barium), Cr (chromium), Cu (copper), F (fluoride), Fe (iron), Mn (manganese), Mo (molybdenum), Se (selenium), and Zn (zinc). Chemistry of trace element concentrations were modeled with the MINTEQA2 geochemical equilibrium model. Results of this study show that pH of product water for three watersheds increased in holding ponds. For example the pH of CBM product water increased from 7.21 to 8.26 for LPR watershed. Among three watersheds, the CBM product water exhibited relatively less change in trace element concentrations in CHR watershed holding ponds. Concentration of dissolved Al, Fe, As, Se, and F in product water increased in BFR watershed holding ponds. For example, concentration of dissolved Fe increased from 113 to 135 microg/L. Boron, Cu, and Zn concentrations of product water did not change in BFR watershed holding ponds. However, concentration of dissolved Ba, Mn, and Cr in product water decreased in BFR watershed holding ponds. For instance, Ba and Cr concentrations decreased from 445 to 386 microg/L and from 43.6 to 25.1 microg/L, respectively. In the LPR watershed, Al, Fe, As, Se, and F concentrations of product water increased substantially in holding ponds. For example, Fe concentration increased from 192 to 312 microg/L. However, concentration of dissolved Ba, Mn, Cr, and Zn decreased in holding ponds. Geochemical modeling calculations suggested that observed increase of Al and Fe concentrations in holding ponds was due to increase in concentration of Al(OH)(4)(-) and Fe(OH)(4)(-) species in water which were responsible for pH increases. Decreases in Ba, Mn, Cr, and Zn concentrations were attributed to the increase in pH, resulting in precipitates of BaSO(4) (barite), MnCO(3) (rhodochrosite), Cr(OH)(2) (chromium hydroxide), and ZnCO(3) (smithsonite) in pond waters, respectively.     

Trace element concentrations in skin of free-ranging bottlenose dolphins (Tursiops truncatus) from the southeast Atlantic coast

Concentrations of trace elements (Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Li, Mn, Ni, Pb, Sb, Se, Sn, Tl, U, V, Zn) and total mercury (THg) were determined in skin samples collected from free-ranging bottlenose dolphin (Tursiops truncatus) populations. Dolphins were captured in the estuarine waters of Charleston (CHS), South Carolina (n=74) and the Indian River Lagoon (IRL), Florida (n=75) during 2003, 2004 and 2005. A subset of the skin tissue samples were used to determine methylmercury (MeHg) levels in CHS (n=17) and IRL (n=8) bottlenose dolphins. Distributions of trace element concentrations by age (adult vs. juvenile), gender (male vs. female) and study area (CHS vs. IRL) were examined. In general, higher elemental skin concentrations were found in CHS adult males than those of IRL adult males, except for THg and MeHg. For CHS dolphins, adult females showed significantly higher THg levels than juvenile females while higher Mn levels were found in juvenile females. For IRL dolphins, adult males showed significantly higher As concentrations than that in juvenile males and females while higher Co and V levels were found in juvenile males than adult males. Of all elements measured in this study, significantly higher levels of Fe, Se and Zn concentrations in skin tissue of both dolphin populations were similar to other studies reported previously. Percentage of MeHg/THg in skin tissue of CHS and IRL dolphin was about 72% and 73%, respectively. Dietary levels of trace elements may play an important role in contributing to concentration differences for As, Co, Mn, Sb, Se, THg and Tl between CHS and IRL dolphins. Total Hg concentrations were significantly correlated with the age of CHS dolphins, while an inverse relationship was detected for Cu, Mn, Pb, U and Zn. The only significant correlation found between trace element concentration and IRL dolphins' age was Mn. Geographic differences in several trace element concentrations (As, Co, Mn, Sb, Se, THg and Tl) in skin tissue may be potentially useful to discriminate between dolphin populations and is a possibility that warrants further investigation.