Body Burden Of Mercury Research Articles

Characterizing variability in total mercury hair:blood ratio in the general Canadian population

Background/objectivesThe body burden of mercury in humans can be measured through hair or blood biomarkers. To compare results from different studies, it is often required to convert mercury in hair to an equivalent level in blood, using a default hair:blood ratio of 250:1 by the World Health Organization (WHO). However, the actual ratio may vary within and between populations. The objectives of this study were to analyze the hair:blood mercury ratio in the general Canadian population, explore factors associated with higher/lower ratios, and determine if the standard ratio of 250:1 is supported. MethodsThe Canadian Health Measures Survey (CHMS) Cycle 5 (2016–2017) measured total mercury (THg) in both hair and blood of 1168 participants 20–59 years of age. We calculated geometric mean (GM) concentrations of THg for this entire sample and subgroups. The subgroups included biological sex, women of childbearing age, race, hair treatments, categories of blood and hair selenium, urinary arsenobetaine/arsenocholine, categories of blood and hair mercury, and food consumption. We calculated a hair:blood ratio for each participant and determined population-level ratios from the GMs of the distributions. Differences by subgroups, and agreement with the WHO ratio of 250:1, were tested. The combined effect of factors on the THg hair:blood ratio was explored using staged regression analysis. ResultsFor participants with paired hair and blood mercury measurements, the GM of the hair:blood THg ratio was 293 (95%CI:273–316), and significantly >250. In women of childbearing age, the ratio did not differ from 250. The GMs of the ratio were higher (i.e.>300) for second tertile blood selenium (365, 95%CI:307–433), third and fourth quartiles hair mercury (347, 95%CI:308–390 and 376, 95%CI:336–422), and consumers of shellfish (338, 95%CI:308–371). Shellfish consumption was the only statistically significant factor associated with the hair:blood ratio as identified in the regression model. ConclusionsThe mean hair:blood THg ratio among Canadians generally exceeded the default ratio of 250:1. Higher ratios were observed in certain subgroups, such as seafood consumers, and shellfish consumption was the most important variable associated with the ratio. Our results suggest that population-specific hair:blood THg ratios be considered, if possible, when converting mercury levels from hair to blood to better characterize the variation around the conversion.

Dual role of titanium dioxide nanoparticles in the accumulation of inorganic and methyl mercury by crustacean Daphnia magna through waterborne and dietary exposure

Titanium dioxide nanoparticles (nTiO2) are widely used in numerous products, yet their role in the accumulation and transfer of other contaminants in the aquatic food webs is not well understood. The influence of nTiO2 on inorganic (IHg) and monomethyl mercury (MeHg) accumulation in invertebrate Daphnia magna through waterborne and dietary exposure was thus thoroughly investigated. The results showed that nTiO2 led to a substantial decrease of the total mercury body burden (THg) in D. magna in direct waterborne exposure to IHg/MeHg. However, exposure to nTiO2 pre-treated with IHg/MeHg resulted in an increase of the THg body burden in daphnids. The presence of nTiO2 led to a substantial decrease of the THg in D. magna when exposed to IHg/MeHg via algal food. These effects were more pronounced for IHg than that for MeHg due to the higher adsorption capabilities of nTiO2 for IHg. In addition, high concentrations of nTiO2 favored the trophic transfer of IHg/MeHg through feeding on nTiO2 pre-treated with Hg, however lessened it when D. magna were fed on alga pre-treated with IHg/MeHg. Comparable assimilation efficiency (AE), determined as Hg retained in daphnids after depuration, was observed in D. magna when exposed to IHg/MeHg via algal food regardless the absence or presence of 20 mgL−1 nTiO2. By contrast, an increase of the AE of MeHg through feeding on nTiO2 and alga was found in the presence of higher concentration of 200 mgL−1 nTiO2. The present results will help to better understand the role of nTiO2 on bioavailability and trophic transfer of global contaminants, such as mercury, known to bioaccumulate and biomagnify in the aquatic environment.

Regionally representative hair mercury levels in Canadian First Nations adults living on reserves

ObjectiveThe primary objective of this participatory study was to assess the current body burden of mercury among First Nations adults.MethodsThe First Nations Food, Nutrition and Environment Study (2008–2018) collected regionally representative data from First Nations adults living on reserves south of the 60th parallel. Mercury was analyzed in hair as a preferred biomarker for prolonged exposure. Hair samples, a 5 mm bundle cut from the occipital region, were collected from the participants who gave consent and measured for total mercury concentrations using cold vapor atomic fluorescence spectrophotometry.ResultsIn total, 3404 First Nations adults living in 92 communities provided hair samples. This represents 52.5% of the respondents to the household surveys. The mean hair mercury concentrations were 0.56 μg/g among all participants and 0.34 μg/g among women of childbearing age (WCBA). There were 64 exceedances of Health Canada’s mercury biomonitoring guidelines (44 WCBA, 8 women aged 51+ years, 3 men aged 19–50 years, and 9 men aged 51+ years).ConclusionCurrent mercury exposure no longer presents a significant clinical health risk in most of the First Nations population south of the 60th parallel across Canada. However, mercury exposure continues to be an ongoing environmental public health concern that requires continued monitoring and assessment. Women of childbearing age (19–50 years) and older individuals living in northern ecozones and Quebec have higher mercury exposures, often exceeding Health Canada’s guidelines. Careful risk communication and risk management programs need to focus on northern ecozones and Quebec.

Differential exposure to metallic mercury in children under 5 living in areas of gold mining of Antioquia, Colombia

Background: The department of Antioquia in Colombia has the highest rates of artisanal and small-scale gold mining (ASM) mostly without mining permits. ASM is not a homogeneous process and exposure to metallic mercury can be variable, fetuses and those in early childhood are the most susceptible to its toxicity. Aim: to identify risk factors related to the body burden of mercury among children under 5 years, living, but not working, close to ASM in Colombia.Methods: a base-line for a cohort study was carried out with 240 children in the municipalities of Anzá, Caicedo and Sabanalarga in Colombia. Collection of sociodemographic variables and urine samples for detection of mercury levels was was carried out with the consent of the legal guardian of the child. Levels equal to or greater than 5 μg/g were considered exposedResults: Fifteen (15) children had higher than admissible levels of mercury and of these, three exceeded 30 μg/g and one was above 90 μg/g. In Guintar and Chuscalita in the municipality of Anzá where amalgam burning is performed, the highest levels of mercury were found and, in all children, mercury was detected in urine. In Caicedo, where ASM has been nearly absent for almost 4 years levels of mercury were the lowest. Sabanalarga, where bareboat artisanal mining is practiced with little use of mercury, only one case exceeded 5 μg/g. No differences in mercury level were found when comparing: sex, age, breastfeeding for the first 6 months of life, history of vaccination, median age, and level of schooling of the caregiver.This research revealed an environmental health problem that was not previously identified in these municipalities and points out the need for non-passive epidemiological surveillance and for actions not only with those who seem to be more exposed, but with those most susceptible

Relationship Between Elevated Hair Mercury Levels, Essential Element Status, and Metabolic Profile in Overweight and Obese Adults.

The objective of the present study was to evaluate hair essential and trace element levels and metabolic risk markers in overweight and obese subjects in relation to body mercury burden. According to 2 × 2 factorial design a total of 440 adults were distributed to four groups: (i) low-Hg normal-weight subjects (n = 114); (ii) high-Hg normal weight subjects (n = 113); (iii) low-Hg overweight (BMI > 25) subjects (n = 110); (iv) high-Hg overweight (BMI > 25) subjects (n = 110). Hg-exposed groups consisted of subjects characterized by frequent seafood consumption (> 4 times/week) subsequently evaluated by hair analysis (> 0.58μg/g). Dietary-exposed subjects were characterized by a more than 3-fold higher hair Hg content irrespectively of body weight values. Both low-Hg and high-Hg overweight subjects were characterized by significantly higher ALT activity, as well as elevated serum glucose, LDL, and triglyceride levels as compared to the respective groups of normal weight subjects. High Hg body burden had a more significant effect on metabolic parameters in overweight and obese adults. Particularly, high-Hg overweight subjects were characterized by significantly higher serum creatinine and uric acid levels, as well as increased GGT and CK activity as compared to low-Hg overweight counterparts. In addition, hair Mg, Mn, and Sr content in high-Hg overweight subjects was significantly lower than that in low-Hg normal weight and overweight examinees. In turn, high Hg levels in overweight subjects were associated with significantly higher hair Se and Zn levels when compared to unexposed overweight adults. Generally, the obtained data demonstrate that increased hair Hg levels in overweight and obese subjects is associated with adverse metabolic profile. It is proposed that observed metabolic alterations may be at least partially mediated by Hg-associated disturbances in essential trace element and mineral metabolism.

Following up mercury pollution in the Ebro Delta (NE Spain): Audouin’s gull fledglings as model organisms to elucidate anthropogenic impacts on the environment

As top-predators in marine ecosystems, seabirds are regarded as appropriate bioindicator species for a variety of contaminants. Mercury (Hg) is a global pollutant, which can biomagnify along marine and freshwater food webs. Therefore, mercury body burden in seabirds, such as gulls, will integrate information about pollution in the environment. In the Ebro Delta (NE Spain), legacy mercury pollution from a chlor-alkali industry located ca. 100 km upstream of the Ebro river mouth has been affecting the delta environment. We have analyzed a 15-year temporal series (2004–2019) of Hg in birds from a breeding colony of Audouin’s gull (Ichthyaetus audouinii) in the Ebro Delta to understand how fluctuations in Hg levels are coupled to human activities in the industrial area in the upstream region of the river. Stable isotopic signatures of C and N (δ13Cbulk and δ15Nbulk) are determined to characterize the trophic ecology of the species. Since only δ13Cbulk but not δ15Nbulk was associated with THg levels, we used compound-specific stable nitrogen isotope analysis of amino acids (AA-CSIA) to evaluate the causes of variation in δ15Nbulk to further investigate the idea of a decoupling of δ15Nbulk and THg over time. We found Audouin’s gull to be sensitive to Hg variations in the environment due to anthropogenic changes and to be a good indicator species for this contaminant in the Ebro Delta.

Artisanal and small-scale gold mining: A cross-sectional assessment of occupational mercury exposure and exposure risk factors in Kadoma and Shurugwi, Zimbabwe

In artisanal and small-scale gold mining (ASGM) the toxic metal mercury is used for gold extraction. The objective of this cross-sectional study was to assess mercury concentrations in urine and blood and mercury-related symptoms of participants identifying themselves as miners from Kadoma and Shurugwi, Zimbabwe. Moreover, we aimed to explore possible risk factors influencing mercury body burden. In 2019, urine and blood samples of 207 participants were collected and analyzed for mercury using atomic absorption spectroscopy. All participants answered questions regarding their exposure risks. The median urine mercury value was 4.75 μg/L with a maximum of 612 μg/L. Median mercury concentration in creatinine corrected urine values was 3.98 μg/g with a maximum value of 478 μg/g. The median blood mercury value was 2.70 μg/L with a maximum of 167 μg/L. Correlations between exposure risks factors such as the lack of retort use and elevated mercury values were demonstrated. ASGM is very common in Zimbabwe. Thus, mercury exposure is a major occupational health risk for miners. Moreover, this study emphasizes the impact of exposure risk factors on the mercury body burden.

Contaminant Concentrations in Sediments, Aquatic Invertebrates, and Fish in Proximity to Rail Tracks Used for Coal Transport in the Pacific Northwest (USA): A Baseline Assessment.

Railway transport of coal poses an environmental risk, because coal dust contains polycyclic aromatic hydrocarbons (PAHs), mercury, and other trace metals. In the Pacific Northwest of the United States, proposed infrastructure projects could result in an increase in coal transport by train through the Columbia River corridor. Baseline information is needed on current distributions, levels, and spatial patterns of coal dust-derived contaminants in habitats and organisms adjacent to existing coal transport lines. To that end, we collected aquatic surface sediments, aquatic insects, and juvenile fish in 2014 and 2015 from Horsethief Lake State Park and Steigerwald National Wildlife Refuge, both located in Washington state close to the rail line and within the Columbia River Gorge National Scenic Area. Two subsites in each area were selected: one close to the rail line and one far from the rail line. Detected PAH concentrations were relatively low compared with those measured at more urbanized areas. Some contaminants were measured at higher concentrations at the subsites close to the rail line, but it was not possible to link the contaminants to a definitive source. Trace metal concentrations were only slightly higher than background concentrations, but a few of the more sensitive benchmarks were exceeded, including those for arsenic, lead, and selenium in fish tissue and fluoranthene, cadmium, copper, manganese, nickel, zinc, iron, and arsenic in sediments. At Horsethief Lake, Chinook salmon and yellow perch showed lower total mercury body burdens than other species, but PAH body burdens did not differ significantly among species. Differences in the species caught among subsites and the low number of invertebrate samples rendered food web comparisons difficult, but these data show that the PAHs and trace metals, including mercury, are accumulating in these wetland sites and in some resident organisms.

Incidence of attention-deficit and hyperactivity disorder among school children in Riyadh city and its association with body burden of mercury leached from dental amalgam fillings: A cross-sectional study

Objectives: The objectives of this study are to determine the association between the incidence of attention-deficit and hyperactivity disorder (ADHD) in children of mothers with and without amalgam fillings. Design: The study design was a cross-sectional descriptive study. Setting: The study was conducted at a dental college's clinic in Riyadh, Saudi Arabia. Participants: In total, 869 children (512 males and 357 females) aged 6–12 years and 796 mothers were included. Children suffering from hearing impairment, language impairment, or learning disabilities or those diagnosed with mental health problems were excluded from the study. Primary and Secondary Outcome Measures: The primary outcome measures included the results of the Vanderbilt scale used for ADHD diagnosis in children and the mercury concentration in 1 ml saliva samples obtained from both the mother and the children. The secondary outcome measures included the number of dental amalgam restorations in the oral cavity determined through a dental examination of children and their mothers. Methodology: A consent form was signed by the mothers who agreed to participate in our study, they were all examined for amalgam presence and a saliva samples were collected and digested. Results: Children with ADHD showed significantly higher levels of mercury in saliva than did children without ADHD. The mothers who had dental amalgam fillings during pregnancy had significantly higher mercury levels than did the mothers who did not have dental amalgam fillings. Conclusion: Prenatal mercury exposure is associated with a higher risk of ADHD behavior. Further research can be carried out to identify the toxic effects of mercury on different body organs owing to dental amalgam fillings. The study scale can be further increased to obtain a more accurate percentage of ADHD cases in Saudi Arabia.

Histology of Sculpin spp. in East Greenland. II. Histopathology and trace element concentrations

For many years, the sculpin has been utilized as a sentinel monitoring species for anthropogenic impacts on the marine environment. To further develop its potential as a screening model body burden of several trace elements, including cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb) and selenium (Se), were investigated. In addition, histopathology in shorthorn sculpins (Myoxocephalus scorpius; n = 20) and fourhorn sculpins (Myoxocephalus quadricornis; n = 10) were examined at three sites around the Scoresby Sound settlement in Central East Greenland. Fourhorn sculpins caught at the most distant site from the settlement, contained significantly higher hepatic Cu and Cd concentrations as well as significantly elevated gill Pb levels compared to the shorthorn sculpins collected at two other sites closer to the settlement. Histological examinations showed that fish with significantly higher concentrations of hepatic Cd and Se exhibited greater nuclear alterations, interstitial hyperplasia/hypertrophy, interstitial mononuclear infiltrations and granulomas. Further, fish with higher Cd and Cu gill tissue levels displayed a significantly higher number of cytoplasmic alterations and lamellar epithelium lifting, hypertrophic and hyperplastic epithelium along with mucus cell hyperplasia. While the presence of liver lesions were not species or sex-specific, the presence of gill lesions decreased in the order female fourhorn sculpins > female shorthorn sculpins > male fourhorn sculpins > male shorthorn sculpins. Hepatic Hg concentrations exceeded known lowest observable effect doses (LOED) for fish (0.1–0.5 μg g−1 ww) in 27% of fish, while liver Cd residues in 80% exceeded LOED (0.42–1.8 μg g−1 ww). Based upon these results, data suggest that using the sculpin as a valuable sentinel fish species histopathology may serve as a reliable tool for assessing marine ecosystem exposure to trace metals. However, confounding physiological and ecological factors also need to be considered.

Mercury Exposure, Blood Pressure, and Hypertension: A Systematic Review and Dose-response Meta-analysis.

Background:Body burden of mercury has been linked to hypertension in populations exposed to high mercury levels.Objectives:We summarized, extracted, and pooled the results of published studies that investigated mercury biomarkers and hypertension or blood pressure (BP) measurements to examine this potential relationship.Methods:We searched PubMed, Embase, and TOXLINE and selected studies according to a priori defined inclusion criteria. Study quality was assessed by the Newcastle-Ottawa scale for cohort and case–control studies and the Quality Assessment Tool for cross-sectional studies. Study estimates were pooled using inverse-variance weighted random-effects models. Dose–response meta-analysis was performed with studies reporting hypertension and systolic BP for at least three mercury categories.Results:A total of 29 studies were included in the meta-analysis. The pooled odds ratio (OR) for hypertension, comparing the highest and lowest mercury exposure categories, was 1.35 [95% confidence interval (CI): 0.99, 1.83] for populations with hair mercury in comparison with the OR of 1.12 (95% CI: 0.82, 1.52) for populations with hair mercury . Positive associations were also observed for highest versus lowest mercury exposure categories on systolic and diastolic BP. Heterogeneity was observed for mercury species and exposure groups across different studies. Associations estimated using different mercury biomarkers generally agree with each other in the same study. A nonlinear dose–response relationship with an inflection point at was identified, for both hypertension and systolic BP.Conclusions:A significant positive association between mercury and hypertension and between mercury and BP was identified. The exposure dose is an important factor in determining the toxic effects of mercury on hypertension. https://doi.org/10.1289/EHP2863

Retention and distribution of methylmercury administered in the food in marine invertebrates: Effect of dietary selenium

Methylmercury is transported along aquatic food chains from the lower trophic levels and selenium modulates the biokinetics of mercury in organisms in complex ways. We investigated the retention of orally administered methylmercury in various marine invertebrates and the effect of selenium hereon. Shrimps (Palaemon adpersus and P. elegans), blue mussels (Mytilus edulis), shore crabs (Carcinus maenas) and sea stars (Asterias rubens) eliminated methylmercury slowly (t½ = ½ to >1 year) and the copepod (Acartia tonsa) faster (t½ ∼ 12–24 h). Orally administered selenite augmented elimination of methylmercury in the copepod (in one of two experiments) and blue mussels, but not in shrimps, crabs and sea stars. Selenium generally alters the distribution of the body burden of mercury, leaving more mercury in muscle and less mercury in digestive glands or rest of the body – also in the species where total body retention is not affected.

Association Study Between Metallothionein-3 Protein Polymorphisms and Autism.

Genetic susceptibility to high mercury body burden has been suggested as an autism risk factor in children. Metallothionein III (MT3) is the brain-specific form of the metallothionein family, which plays a key role in metal metabolism. We therefore looked for genetic variations in the MT3 gene that might increase the predisposition to autism. DNA was extracted from 132 autistic children and 132 age and gender-matched unrelated controls. All the samples were analyzed for nine single nucleotide polymorphisms (SNPs) with minor allele frequency > 10% in the MT3 gene. The mRNA levels of MT3 in white blood cells were evaluated by real-time PCR. We did not detect any association between these MT3 polymorphisms and the mRNA levels of MT3. We did not detect any association between MT3 polymorphisms and autism risk. However, we detected four novel MT3 SNPs that are not in the human SNP database. The clinical importance of these SNPs needs further investigation. Our data suggest that MT3 gene polymorphisms are not associated with autism.

Editor's Highlight: Variation in Methylmercury Metabolism and Elimination Status in Humans Following Fish Consumption.

Evaluating the potential for methylmercury (MeHg) toxicity relies on accurately predicting the mercury (Hg) body burden that results from eating fish. Hg body burden is directly determined by the slow elimination kinetics of MeHg in the human body (kel = 0.014 days-1 or t1/2 =50 days). Existing studies on MeHg half-life in humans demonstrate a wide range values (t1/2 = 30 to >150 days) and has lead to uncertainty in the derivation of a regulatory standard for acceptable daily oral intake. The causes of variation in MeHg toxicokinetics in humans remain little explored. Here we characterize variation in human MeHg metabolism and elimination rate (kel) in 37 adult volunteers who consumed 3 fish meals. We determined MeHg elimination rates via longitudinal Hg analysis in single hairs using laser ablation inductively coupled plasma mass spectrometry. We also measured MeHg metabolism (biotransformation) via speciation of fecal Hg. We find an average kel = 0.0157 days-1 (t1/2 = 44 days) amongst a more than 2-fold variation in kel across the cohort (0.0248-0.0112 days-1; t1/2 = 28-62 days). Although MeHg biotransformation varied widely between individuals, it showed a positive association with elimination rates across the cohort. A more than 2-fold change in kel over a period of 2 years was seen in some individuals. In 2 individuals, who received antibiotic for unrelated health issues, elimination rate was seen to slow significantly. Associations of kel with age, body mass index, gender, and fish eating habits were not observed. We establish that a measure of methylmercury metabolism and eliminaiton status (MerMES) can reduce uncertainty in determining an individual's MeHg toxicokinetics subsequent to eating fish.

Mercury alters initiation and construction of nests by zebra finches, but not incubation or provisioning behaviors.

Mercury is an environmental contaminant that impairs avian reproduction, but the behavioral and physiological mechanisms underlying this effect are poorly understood. The objective of this study was to determine whether lifetime dietary exposure to mercury (1.2 µg/g wet weight in food) impacted avian parental behaviors, and how this might influence reproductive success. To distinguish between the direct effects of mercury on parents and offspring, we created four treatment groups of captive-bred zebra finches (Taeniopygia guttata), with control and mercury-exposed adults raising cross-fostered control or mercury-exposed eggs (from maternal transfer). Control parents were 23% more likely to fledge young than parents exposed to mercury, regardless of egg exposure. Mercury-exposed parents were less likely to initiate nests than controls and spent less time constructing them. Nests of mercury-exposed pairs were lighter, possibly due to an impaired ability to bring nest material into the nestbox. However, nest temperature, incubation behavior, and provisioning rate did not differ between parental treatments. Unexposed control eggs tended to have shorter incubation periods and higher hatching success than mercury-exposed eggs, but there was no effect of parental exposure on these parameters. We accidentally discovered that parent finches transfer some of their body burden of mercury to nestlings during feeding through secretion in the crop. These results suggest that, in mercury-exposed songbirds, pre-laying parental behaviors, combined with direct exposure of embryos to mercury, likely contribute to reduced reproductive success and should be considered in future studies. Further research is warranted in field settings, where parents are exposed to greater environmental challenges and subtle behavioral differences might have more serious consequences than were observed in captivity.

Reductions in fish-community contamination following lowhead dam removal linked more to shifts in food-web structure than sediment pollution

Recent increases in dam removals have prompted research on ecological and geomorphic river responses, yet contaminant dynamics following dam removals are poorly understood. We investigated changes in sediment concentrations and fish-community body burdens of mercury (Hg), selenium (Se), polychlorinated biphenyls (PCB), and chlorinated pesticides before and after two lowhead dam removals in the Scioto and Olentangy Rivers (Columbus, Ohio). These changes were then related to documented shifts in fish food-web structure. Seven study reaches were surveyed from 2011 to 2015, including controls, upstream and downstream of the previous dams, and upstream restored vs. unrestored. For most contaminants, fish-community body burdens declined following dam removal and converged across study reaches by the last year of the study in both rivers. Aldrin and dieldrin body burdens in the Olentangy River declined more rapidly in the upstream-restored vs. the upstream-unrestored reach, but were indistinguishable by year three post dam removal. No upstream-downstream differences were observed in body burdens in the Olentangy River, but aldrin and dieldrin body burdens were 138 and 148% higher, respectively, in downstream reaches than in upstream reaches of the Scioto River following dam removal. The strongest relationships between trophic position and body burdens were observed with PCBs and Se in the Scioto River, and with dieldrin in the Olentangy River. Food-chain length – a key measure of trophic structure – was only weakly related to aldrin body burdens, and unrelated to other contaminants. Overall, we demonstrate that lowhead dam removal may effectively reduce ecosystem contamination, largely via shifts in fish food-web dynamics versus sediment contaminant concentrations. This study presents some of the first findings documenting ecosystem contamination following dam removal and will be useful in informing future dam removals.

Developmental Methylmercury Exposure Affects Swimming Behavior and Foraging Efficiency of Yellow Perch (Perca flavescens) Larvae.

Methylmercury (MeHg) is a pervasive and ubiquitous environmental neurotoxicant within aquatic ecosystems, known to alter behavior in fish and other vertebrates. This study sought to assess the behavioral effects of developmental MeHg exposure on larval yellow perch (Perca flavescens)—a nonmodel fish species native to the Great Lakes. Embryos were exposed to MeHg (0, 30, 100, 300, and 1000 nM) for 20 h and then reared to 25 days post fertilization (dpf) for analyses of spontaneous swimming, visual motor response (VMR), and foraging efficiency. MeHg exposures rendered total mercury (THg) body burdens of 0.02, 0.21, 0.95, 3.14, and 14.93 μg/g (wet weight). Organisms exposed to 1000 nM exhibited high mortality; thus, they were excluded from downstream behavioral analyses. All MeHg exposures tested were associated with a reduction in spontaneous swimming at 17 and 25 dpf. Exposure to 30 and 100 nM MeHg caused altered locomotor output during the VMR assay at 21 dpf, whereas exposure to 100 nM MeHg was associated with decreased foraging efficiency at 25 dpf. For the sake of comparison, the second-lowest exposure tested here rendered a THg burden that represents the permissible level of consumable fish in the United States. Moreover, this dose is reported in roughly two-thirds of consumable fish species monitored in the United States, according to the Food and Drug Administration. Although the THg body burdens reported here were higher than expected in the environment, our study is the first to analyze the effects of MeHg exposure on fundamental survival behaviors of yellow perch larvae and advances in the exploration of the ecological relevance of behavioral end points.

Signs and symptoms of mercury-exposed gold miners.

Gold miners use mercury to extract gold from ore adding liquid mercury to the milled gold-containing ore. This results in a mercury-gold compound, called amalgam. Miners smelt this amalgam to obtain gold, vaporizing it and finally inhaling the toxic mercury fumes. The objective was to merge and analyze data from different projects, to identify typical signs and symptoms of chronic inorganic mercury exposure. Miners and community members from various artisanal small-scale gold mining areas had been examined (Philippines, Mongolia, Tanzania, Zimbabwe, Indonesia). Data of several health assessments were pooled. Urine, blood and hair samples were analyzed for mercury (N = 1252). Questionnaires, standardized medical examinations and neuropsychological tests were used. Participants were grouped into: Controls (N = 209), living in an exposed area (N = 408), working with mercury as panners (N = 181), working with mercury as amalgam burners (N = 454). Chi2 test, linear trend test, Mann-Whitney test, Kruskal-Wallis test, correlation coefficient, Spearman's rho, and analysis of variance tests were used. An algorithm was used to define participants with chronic mercury intoxication. Mean mercury concentrations in all exposed subgroups were elevated and above threshold limits, with amalgam burners showing highest levels. Typical symptoms of chronic metallic mercury intoxication were tremor, ataxia, coordination problems, excessive salivation and metallic taste. Participants from the exposed groups showed poorer results in different neuropsychological tests in comparison to the control group. Fifty-four percent of the high-exposed group (amalgam burners) were diagnosed as being mercury-intoxicated, compared to 0% within the control group (Chi2 p < 0.001). Chronic mercury intoxication, with tremor, ataxia and other neurological symptoms together with a raised body burden of mercury was clinically diagnosed in exposed people in artisanal small-scale mining areas. The mercury exposure needs to be urgently reduced. Health care systems need to be prepared for this emerging problem of chronic mercury intoxication among exposed people. Int J Occup Med Environ Health 2017;30(2):249-269.

Leaching of mercury from seal carcasses into Antarctic soils.

More than 400 seal mummies and skeletons are now mapped in the northern part of James Ross Island, Antarctica. Decomposing carcasses represent a rare source of both organic matter and associated elements for the soil. Owing to their high trophic position, seals are known to carry a significant mercury body burden. This work focuses on the extent of the mercury input from seal carcasses and shows that such carcasses represent locally significant sources of mercury and methylmercury for the environment. Mercury contents in soil samples from the surrounding areas were determined using a single-purpose AAS mercury analyzer. For the determination of methylmercury, an ultra-sensitive isotopic dilution HPLC-ICP-MS technique was used. In the soils lying directly under seal carcasses, mercury contents were higher, with levels reaching almost 40μg/kg dry weight of which methylmercury formed up to 2.8% of the total. The spatial distribution implies rather slow vertical transport to the lower soil layers instead of a horizontal spread. For comparison, the background level of mercury in soils of the investigated area was found to be 8μg/kg dry weight, with methylmercury accounting for less than 0.1%. Apart from the direct mercury input, an enhanced level of nutrients in the vicinity of carcasses enables the growth of lichens and mosses with accumulative ability with respect to metals. The enhanced capacity of soil to retain mercury is also anticipated due to the high content of total organic carbon (from 1.6 to 7.5%). According to the results, seal remains represent a clear source of mercury in the observed area.

Factors influencing aquatic-to-terrestrial contaminant transport to terrestrial arthropod consumers in a multiuse river system

Emerging aquatic insects are important vectors of contaminant transfer from aquatic to terrestrial food webs. However, the environmental factors that regulate contaminant body burdens in nearshore terrestrial consumers remain largely unexplored. We investigated the relative influences of riparian landscape composition (i.e., land use and nearshore vegetation structure) and contaminant flux via the emergent aquatic insect subsidy on selenium (Se) and mercury (Hg) body burdens of riparian ants (Formica subsericea) and spiders of the family Tetragnathidae along 11 river reaches spanning an urban-rural land-use gradient in Ohio, USA. Model-selection results indicated that fine-scale land cover (e.g., riparian zone width, shrub cover) in the riparian zone was positively associated with reach-wide body burdens of Se and Hg in both riparian F. subsericea and tetragnathid spiders (i.e., total magnitude of Hg and Se concentrations in ant and spider populations, respectively, for each reach). River distance downstream of Columbus, Ohio – where study reaches were impounded and flow through a large urban center – was also implicated as an important factor. Although stable-isotope analysis suggested that emergent aquatic insects were likely vectors of Se and Hg to tetragnathid spiders (but not to F. subsericea), emergent insect contaminant flux did not emerge as a significant predictor for either reach-wide body burdens of spider Hg or Se. Improved understanding of the pathways and influences that control aquatic-to-terrestrial contaminant transport will be critical for effective risk management and remediation.