Since the environmental levels of selenium (Se) can moderate the bioaccumulation and toxicity of mercury (Hg) in marine organisms, their interactions were studied in seawater, sediments, plankton and ...the benthic (Bull ray
, Eagle ray
) and the pelagic (Pelagic stingray
) rays, as apex predators in the Gulf of Trieste (Northern Adriatic Sea). Male and female rays showed no difference in the Se contents in muscle tissue. Pelagic species contained higher Se levels in muscle but slightly lower levels in the livers of both genders. The Hg/Se ratios in seawater dissolved and colloidal fractions, plankton and sediment were <0.5, while those in particulate matter were <1.3. In benthic ray species, a parallel increase in Se and Hg in muscle was observed, so that an increased in Hg (MeHg) bioaccumulation results in Se coaccumulation. The Hg/Se ratios (molar) in muscle and liver of pelagic and benthic rays were <1.4 and <0.7, respectively. The low levels of Hg in muscle and liver in all the ray species corresponded to low Hg/Se ratios and increases in muscle and liver to 1 at 7 µg/g, dry weight (dw) and 5 µg/g dw, respectively, i.e., about 1.6 µg/g wet weight (ww).
The Idrija Mine, the second largest Hg mine in the world, ceased operation in 1995, but still delivers large quantities of Hg downstream including into the northern Adriatic Sea, 100
km away. ...Transformation of Hg species in sediment in sites over 60
km from the mine, including marine sites in the Adriatic Sea, was measured to determine the ability of the system to transform and mobilize Hg and to produce methylmercury (MeHg). Cores from a freshwater impoundment, a brackish estuarine site, and three marine sites in the Gulf of Trieste were sectioned anaerobically, and Hg methylation and MeHg demethylation activities determined using radio-techniques (
203Hg for methylation and
14C-MeHg for demethylation). Total and dissolved Hg and MeHg were determined as were other geochemical parameters. In addition, rates of SO
4 reduction were determined in marine sediment using a
35S technique. Mercury was readily methylated and demethylated at all sites. Marine sediment was investigated in winter and summer with rates of Hg transformation and SO
4 reduction corresponding only in winter. Methylation of Hg in summer displayed subsurface peaks that may have been influenced by bioturbation. Total Hg and MeHg were most abundant in the freshwater, estuarine, and near-shore marine sites, but dissolved pore water Hg and MeHg were highest in the estuarine region where S cycling appeared ideal for the mobilization of Hg. The impoundment sediment also seemed to be a ‘hotspot’ of Hg transformations. MeHg demethylation occurred via the oxidative demethylation pathway (CO
2 produced from MeHg), except in surficial sediment offshore in the Gulf during winter, where sediment was more oxidizing and significant amounts of CH
4 were liberated during MeHg degradation via reductive demethylation. The CH
4 formation was likely due to an increased influence from the expression of MeHg degradative enzymes encoded by the
mer detoxification bacterial genetic system. The freshwater site also liberated CH
4 from MeHg, but it appeared to be due to oxidative demethylation by methanogenic bacteria.
The difference in arsenic concentration and speciation between benthic (Pteromylaeus bovinus, Myliobatis aquila) and pelagic rays (Pteroplatytrygon violacea) from the northern Adriatic Sea (Gulf of ...Trieste) in relation to their size (age) was investigated. High arsenic concentrations were found in both groups with tendency of more efficient arsenic accumulation in benthic species, particularly in muscle (32.4 to 362 µg·g-1 of total arsenic). This was attributed to species differences in arsenic access, uptake and retention. In liver most arsenic was present in a form of arsenobetaine, dimethylarsinic acid and arsenoipids, whereas in muscle mainly arsenobetaine was found. The good correlations between total arsenic/arsenobetaine and size reflect the importance of accumulation of arsenobetaine with age. Arsenobetaine is an analogue of glycine betaine, a known osmoregulator in marine animals and both are very abundant in mussels, representing an important source of food for benthic species P. bovinus and M. aquila.
Because of increasing awareness of the potential neurotoxicity of even low levels of organomercury compounds, analytical techniques are required for determination of low concentrations of ...ethylmercury (EtHg) and methylmercury (MeHg) in biological samples. An accurate and sensitive method has been developed for simultaneous determination of methylmercury and ethylmercury in vaccines and biological samples. MeHg and EtHg were isolated by acid leaching (H₂SO₄-KBr-CuSO₄), extraction of MeHg and EtHg bromides into an organic solvent (CH₂Cl₂), then back-extraction into Milli-Q water. MeHg and EtHg bromides were derivatized with sodium tetrapropylborate (NaBPr₄), collected at room temperature on Tenax, separated by isothermal gas chromatography (GC), pyrolysed, and detected by cold-vapour atomic fluorescence spectrometry (CV AFS). The repeatability of results from the method was approximately 5-10% for EtHg and 5-15% for MeHg. Detection limits achieved were 0.01 ng g-¹ for EtHg and MeHg in blood, saliva, and vaccines and 5 ng g-¹ for EtHg and MeHg in hair. The method presented has been shown to be suitable for determination of background levels of these contaminants in biological samples and can be used in studies related to the health effects of mercury and its species in man. This work illustrates the possibility of using hair and blood as potential biomarkers of exposure to thiomersal.
Different chemical forms of mercury occur naturally in human milk. The most controversial aspect of early post-natal exposure to organic mercury is ethylmercury (EtHg) in thimerosal-containing ...vaccines (TCV) still being used in many countries. Thus exclusively breastfed infants can be exposed to both, fish derived methylmercury (MeHg) in maternal diets and to EtHg from TCV. The aim of the study is to evaluate a new analytical method for ethyl and methyl mercury in hair samples of breastfed infants who had received the recommended schedule of TCV.
The hair of infants (<12months) that had been exposed to TCV (Hepatitis B and DTaP) was analysed. A method coupling isothermal gas chromatography with cold-vapor atomic fluorescence spectrometry was used for MeHg which can also speciate EtHg in biological matrices.
In 20 samples of infants' hair, all but two samples showed variable amounts of MeHg (10.3 to 668ng/g), while precise and reliable concentrations of EtHg (3.7 to 65.0ng/g) were found in 15 of the 20 samples. A statistically significant inverse association (r=−05572; p=0.0384) was found between hair-EtHg concentrations and the time elapsed after the last TCV shot.
The analytical method proved sensitive enough to quantify EtHg in babies' hair after acute exposure to thimerosal in vaccine shots. Provided that the mass of hair was above 10mg, organic-mercury exposure during early life can be speciated, and quantified in babies' first hair, thus opening opportunities for clinical and forensic studies.
The exposome paradigm through an integrated approach to investigating the impact of perinatal exposure to metals on child neurodevelopment in two cohorts carried out in Slovenia (PHIME cohort) and ...Greece (HERACLES cohort) respectively, is presented herein. Heavy metals are well-known neurotoxicants with well-established links to impaired neurodevelopment. The links between in
and early-life exposure to metals, metabolic pathway dysregulation, and neurodevelopmental disorders were drawn through urinary and plasma untargeted metabolomics analysis, followed by the combined application of
and biostatistical methods. Heavy metal prenatal and postnatal exposure was evaluated, including parameters indirectly related to exposure and health adversities, such as sociodemographic and anthropometric parameters and dietary factors. The primary outcome of the study was that the identified perturbations related to the TCA cycle are mainly associated with impaired mitochondrial respiration, which is detrimental to cellular homeostasis and functionality; this is further potentiated by the capacity of heavy metals to induce oxidative stress. Insufficient production of energy from the mitochondria during the perinatal period is associated with developmental disorders in children. The HERACLES cohort included more detailed data regarding diet and sociodemographic status of the studied population, allowing the identification of a broader spectrum of effect modifiers, such as the beneficial role of a diet rich in antioxidants such as lycopene and ω-3 fatty acids, the negative effect the consumption of food items such as pork and chicken meat has or the multiple impacts of fish consumption. Beyond diet, several other factors have been proven influential for child neurodevelopment, such as the proximity to pollution sources (e.g., waste treatment site) and the broader living environment, including socioeconomic and demographic characteristics. Overall, our results demonstrate the utility of exposome-wide association studies (EWAS) toward understanding the relationships among the multiple factors that determine human exposure and the underlying biology, reflected as omics markers of effect on neurodevelopment during childhood.
Wet deposition is the main source of mercury (Hg) from the atmosphere to the Earth’s surface. However, the processes that govern the dispersion of deposited Hg in seawater are currently not well ...understood. To address this issue, total mercury (THg) concentrations in surface seawaters and precipitation were determined on a monthly basis in the Bay of Kaštela (Central Adriatic Sea). Following the assumption that deposited THg is diluted in the seawater bulk due to mixing processes, an exponential decay-like model was developed and the wet deposition of THg was normalized based on periods between precipitation events and seawater sampling. Normalized wet deposition of THg showed significant correlation with the THg gradient in surface seawater after removal of an outlier. To explain the observed outlier, further data normalization included wind data to account for enhanced seawater mixing due to strong winds. Wind-normalized THg deposition of all datapoints showed significant correlation with the THg gradient in surface seawater. The correlation showed that the THg gradient in surface seawater of 0.378 pg L−1 m−1 corresponds to THg wet deposition of 1 ng m−2 after including the influence of wind speed on seawater mixing.
A summary of data recently obtained for mercury analysis and speciation (reactive Hg, total Hg and monomethylmercury (MMHg)) in filtered and non-filtered seawater samples, dissolved gaseous mercury ...(DGM) and dimethylmercury (DMHg) in open and coastal waters of the Mediterranean Sea is presented. The majority of the results were obtained during an oceanographic cruise aboard the research vessel Urania from 14 July to 9 August, 2000, as part of the MED-OCEANOR Project funded by the National Research Council of Italy. The results are compared with those obtained in contaminated coastal environments of the Adriatic (The Gulf of Trieste and Kaštela Bay) and non-contaminated coastal waters of the eastern Adriatic coast obtained in 1998. Total mercury concentrations in surface ocean waters are relatively low with an average of 0.81
pM (0.49–1.91
pM). Reactive Hg represents a substantial part with an average of 57% of total Hg (15–97%). Most mercury in open ocean waters was present in the dissolved form (32–95%, av. 70%), which is mainly due to the low abundance of particulate matter, a phenomenon well known for the Mediterranean open ocean waters. On average the percentage of Hg as MMHg was about 20%, of which about 66% was present in the dissolved form. The percentage of DGM in the surface ocean waters represents about 9% of total Hg (2.5–24.5%) and may originate from photochemical, biologically mediated mechanisms or diffusion from deeper layer either due to biological and/or to tectonic activity which is typical of the Mediterranean region. The presence of DMHg was confirmed only in waters below 20
m (up to 12
fM), while in surface waters DMHg was below the limit of detection (<0.1
fM). Surface concentrations of Hg in the eastern and western parts are comparable, except for DGM which shows significantly higher concentrations in the eastern part (mean value: 0.22
pM) as compared to the western Mediterranean (mean value: 0.09
pM). The distribution of Hg species with depth was only measured at two stations, and indicated variability comparing the eastern and the western leg of the Urania cruise. The depth profile pattern confirms the importance of dynamic processes at the surface layers, while deep water continuously supplies DGM to the surface layer. The importance of analytical quality control is also discussed in this paper.
Mercury in air over the Idrija region, where the world's second largest mercury (Hg) mine is located, decreased significantly in the last decade, from more than 20,000
ng
m
−3 in the early 1970s to ...values below 100
ng
m
−3 in the 1980s, and finally reached a level of 10
ng
m
−3 or even lower at the summer of the year 2004.
The air concentration of Hg was continuously monitored after closure of the Hg mine. Hg
0 in air was mapped in November 2003 at over 100 locations in the Idrija region during a 3-day period under different weather conditions, and the concentrations found were between 2.5 to over 2000
ng
m
−3. The Hg concentration in air was mostly below 10
ng
m
−3. The highest values were observed in the near vicinity of the former smelting plant, as well under its chimney. Elevated concentrations were also observed at some other locations in Idrija town. Mercury evaporation from topsoil was measured continuously for a 24
h period at two heavily polluted locations in Idrija and 50
km downstream the River Idrijca at Bača pri Modreju. The average Hg concentration in air at Bača pri Modreju was 5.5
ng
m
−3, with an average Hg flux from soil to atmosphere of 34
ng
m
−2
h
−1. At the site in Idrija the average Hg concentration in air was 11
ng
m
−3 with an average Hg flux from soil to the atmosphere of 84.4
ng
m
−2
h
−1.
500 years of mercury (Hg) mining in the town of Idrija has caused severe pollution in Idrija and its surroundings. Following the closure of the mine in 1995, the environment remains contaminated with ...Hg. Sources of elemental-, inorganic- and methyl Hg exposure were identified, potential environmental level of exposure to Hg was evaluated and actual internal exposure to Hg was assessed in selected susceptible population groups comprising school-age children and pregnant women living in Idrija and in control groups from rural and urban environments. The study of pregnant women (n=31) was conducted between 2003 and 2008, and the study of school-age children (n=176) in 2008. Potential interaction of Hg with selenium (Se) in plasma was assessed in both study populations, while in pregnant women antioxidative enzyme activity (glutathione peroxidase, superoxide dismutase and catalase) in erythrocytes of maternal and cord blood was also assessed. Actual exposure to Hg as indicated by levels of Hg in children's blood (geometric mean (GM) 0.92µg/L), mother's blood (GM 1.86µg/L), children's urine (GM 1.08µg/g crea.), mother's urine (GM 2.51µg/L), children's hair (GM 241ng/g) and mother's hair (GM 251ng/g) was higher in the two study groups from Idrija than in the control groups from rural areas, but was still at the level of a “normal” population and reflects mainly exposure to elemental Hg (Hg°) from dental amalgam and, to a certain extent atmospheric Hg°. Furthermore, the internal doses of Hg received during pregnancy did not decrease the bioavailability of Se. Based on observation in children, the increase in Se protein expression is suggested to be a consequence of moderately elevated exposure to Hg°. The observed changes in activity of antioxidative enzymes, as biomarkers of oxidative stress, appear to be mainly associated with pregnancy per se and not with an increased exposure to Hg. In view of the continuing increased potential for Hg exposure and the low number of pregnant women studied, the results warrant a further longitudinal study of a larger group of pregnant women residing in the area of the former mercury mine.
•Estimated environmental Hg exposure in the town of Idrija still poses a potential risk to susceptible groups of inhabitants.•Actual internal exposure reflects mainly exposure to Hg° from dental amalgam and, to a certain extent atmospheric Hg°.•The internal doses of Hg received in the Idrija children and pregnant women did not decrease the bioavailability of Se.•Changes in activity of antioxidative enzymes were not associated with exposure to Hg in the town of Idrija.
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