Environmental Mercury Exposure Research Articles

Blood mercury concentrations in preschool children and potential risk factors in São Paulo, Brazil

Environmental exposure of preschool children to mercury can elevate blood mercury levels (BML) and negatively affect their health. This study aimed to determine BML in preschool children from Brazil's largest city and explore potential associated risk factors. Blood samples were collected in 2013 from 2,436 children (age 1-5 years) attending 50 daycare centers (DCC) located in São Paulo, Brazil. Parents or guardians answered questionnaires collecting information on sociodemographics and potential risk factors. BML was determined by Cold Vapor Atomic Absorption Spectrophotometry (CV-AAS) and categorized using a cutoff point of 2.77 μg L⁻1, corresponding to the 75th percentile. Multiple logistic regression was performed (p<0.05). Data were georeferenced and associations with air pollution, wind frequency and direction were evaluated. The results showed a geometric mean for BML of 1.65 μg L⁻1 (95%CI: 1.60-1.70), arithmetic mean of 2.15 μg L⁻1 (95%CI: 2.09-2.22), 75th percentile of 2.77 μg L⁻1 (95%CI: 2.67-2.91) and 95th percentile of 5.51 μg L⁻1 (95%CI: 5.18-5.92). DCCs located in the Northwest and East zones (p<0.001) and fish consumption in the past two days (p=0.04) were associated with high BML. The elevated BML observed in children living in the eastern zone might be attributed to the southeasterly winds passing through a petrochemical complex located nearby. The 95th percentile of BML in this study exceeded the U.S. 95th percentile by five times. BML in Sao Paulo preschool children was associated with individual and environmental risk factors. This finding highlights the need to identify and control hot spots in Sao Paulo, Brazil, especially in peripheral and surrounding areas, where individuals are more vulnerable. Further research is needed in Latin America to identify additional sources of urban environmental mercury exposure and guide interventions for protecting the environment and safeguarding children's health.

Association between environmental mercury exposure and allergic disorders in Korean children: Korean National Environmental Health Survey (KoNEHS) cycles 3–4 (2015–2020)

Although previous studies have suggested potential adverse effects of mercury on a child’s immune system, the associations have been inconsistent. We aimed to determine the association between urinary mercury levels and allergic diseases in Korean children with high mercury exposure. Data from 853 and 710 children aged 6–11 years in the Korean National Environmental Health Survey (KoNEHS) cycle 3 (2015–2017) and cycle 4 (2018–2020) were analyzed. We examined the association between mercury exposure and the prevalence of atopic dermatitis (AD), asthma, allergic rhinitis (AR), and allergic multimorbidity. After adjusting for all covariates, the urinary mercury level was positively associated with AD in the 2015–2017 study (OR = 1.34, 95% CI = 1.01, 1.79) and AR in 2018–2020 study (OR = 1.46, 95% CI = 1.01, 2.10). Pooled effects showed OR of 1.34 (95% CI = 1.01, 1.79) for AD and 1.47 (95% CI = 1.01, 2.12) for allergic multimorbidity. The association with allergic multimorbidity was greater in boys (OR = 1.88, 95% CI = 1.01, 3.49) than in girls (OR = 1.25, 95% CI = 0.73, 2.14). These results suggest that environmental mercury exposure may exacerbate symptoms of atopic dermatitis and allergic multimorbidity in children.

Reductions in plasma and urine mercury concentrations following N,N′bis-(2-mercaptoethyl) isophthalamide (NBMI) therapy: a post hoc analysis of data from a randomized human clinical trial

Environmental mercury exposure possesses a significant risk to many human populations. At present there are no effective treatments for acute mercury toxicity. A new compound, N,N′bis-(2-mercaptoethyl) isophthalamide (NBMI), a lipophilic chelating agent was created to tightly/irreversibly bind mercury. A post hoc dose-dependent analysis of NBMI therapy was undertaken on data from a randomized controlled NBMI human treatment trial on 36 Ecuadorian gold miners with elevated urinary mercury concentrations. Study subjects were randomly assigned to receive 100 milligram (mg) NBMI/day, 300 mg NBMI/day, or placebo for 14 days. For each study subject daily mg NBMI dose/Kilogram (Kg) bodyweight were determined and plasma and urine mercury concentrations (micrograms (µg)/Liter (L)) on study day 1 (pre-NBMI treatment), 15 (after 14 days of NBMI treatment) and 45 (30 days after NBMI treatment) were correlated with NBMI dosing using the linear regression statistic in SAS. Regression revealed significant inverse correlations between increasing per mg NBMI/Kg bodyweight/day and reduced concentrations of urinary and plasma mercury on study day 15 (reduced by in urine = 18–20 µg/L and plasma = 2 µg/L) and study day 30 (reduced by in urine = 15–20 µg/L and plasma = 4 µg/L) and significant correlations between reductions in mercury concentrations in urine and plasma. Significant 30% reductions in urinary mercury concentrations per mg NBMI/Kg bodyweight/day administered for 14 days were observed. This study supports the dose-dependent ability of NBMI therapy to significantly reduce mercury concentrations, particularly in the urine, in an acutely mercury exposed human population. NBMI therapy should be evaluated in other mercury exposed populations.

Prevalence and diversity of malaria parasites (genus Plasmodium) in the imperiled Saltmarsh Sparrow are greater at northern sites

Abstract Malaria parasites (genus Plasmodium) are important agents of infectious disease in birds and multiple factors, including warming temperatures and environmental contamination, may act to increase their geographic and host ranges. Here, we examined the role of geographical variation and environmental mercury exposure in malaria parasite infection dynamics in an imperiled songbird species with high mercury exposition, the Saltmarsh Sparrow (Ammospiza caudacutus). Using polymerase chain reaction (PCR) methods, we screened 280 Saltmarsh Sparrows from across their breeding range for malaria parasite infection. We detected malaria parasites in 17% of sampled birds and a total of 6 Plasmodium lineages. Prevalence of infection and diversity of parasite lineages varied across the breeding range of the Saltmarsh Sparrow and increased at more northern latitudes. Although mercury is a known immunosuppressant and has been documented to alter an individual’s susceptibility to pathogens, we did not find a significant difference in blood mercury levels between infected and not infected birds, perhaps due to sampling methods and/or small sample sizes. As a specialist of coastal wetlands, the Saltmarsh Sparrow is an excellent indicator species for ecological health, and the patterns of malaria parasite infection with host distribution and mercury suggest that birds at northern latitudes are at greater risk of disease and should be priorities for conservation, habitat, and pathogen monitoring.

The Roles of the Moss Layer in Mediating Tree Seedling Environmental Stress, Mercury Exposure, and Regeneration in High-Elevation Conifer Forests

The persistence of future forests depends on the success of tree seedlings which are experiencing increasing physiological stress from changing climate and air pollution. Although the moss layer can serve as an important substrate for tree seedlings, its potential for reducing environmental stress and enhancing the establishment of seedlings remains poorly understood. We tested if the moss layer decreased environmental stress and increased the abundance of balsam fir seedlings dominant in high-elevation forests of northeastern United States that are sensitive to changing climate and mercury deposition. We surveyed balsam fir seedling density by substrate (moss, litter, other) on 120 quadrats (1 × 1 m) in two contrasting canopy environments (in gaps and under canopies), measured seedling stress, and quantified mercury content in seedlings and substrates. We observed that, in both canopy environments, tree seedlings established on moss exhibited (i) increased density, (ii) decreased physiological stress, and (iii) higher potential to recruit into larger size classes, compared to seedlings established in litter. Regardless of canopy environment, seedling foliar mercury levels did not correspond to substrate mercury despite large differences in substrate mercury concentrations (relative to moss, litter concentrations were ~ 4-times greater and soil concentrations were ~ 6-times greater), likely reflecting the dominance of foliar over root uptake of mercury. Because the moss layer appeared to mitigate seedling drought stress, and to increase seedling establishment and recruitment compared to other substrates, these microsite effects should be considered in models predicting forest regeneration and dynamics under increased drought stress associated with the ongoing climate warming.

Occupational and environmental mercury exposure and human reproductive health - a review.

Mercury is a toxic heavy metal. Humans are exposed to mercury through several sources including environmental, occupational, contaminated food and water and from mercury-containing dental amalgam. Mercury exposure is known to harm the nervous system profoundly, and have a negative impact on digestive and immune systems, and other organs. To review and discuss the effect of mercury exposure through environmental or occupational routes on human reproduction, pregnancy, and its outcome. Published information about the potential toxic effects of mercury on human reproduction were collected and summarized. Literature was identified by systematic search using relevant keywords. Literature review revealed a number of negative impacts of mercury on human reproduction. These included effects on semen quality, including reduced sperm count, motility, and changes in morphology that may reduce fertility potential. There may also be an effect in changing reproductive hormone levels. Mercury exposure might also affect pregnancy but the data concerning mercury effects on female reproduction are limited except for some data about mercury exposure and poor pregnancy outcomes. Available data indicate that mercury exposure may have a toxicity effect on reproductive potential, especially in males. Prenatal mercury exposure may affect pregnancy or its outcome and this appears to be dependent upon dose, duration, and timing of exposure. Nutritional status of exposed individual might also influence the impact of mercury.

Low-Level Environmental Mercury Exposure and Thyroid Cancer Risk Among Residents Living Near National Industrial Complexes in South Korea: A Population-Based Cohort Study.

Background: Previous studies suggested that mercury may be linked to thyroid cancer due to its bioaccumulation in the thyroid gland, but no studies have evaluated the association between mercury exposure and thyroid cancer risk. We examined the relationship between mercury exposure and thyroid cancer risk, with the potential modification of hematological parameters. Methods: We performed a secondary analysis of a prospective cohort study among residents living near industrial complexes in South Korea (recruited from 2003 to 2011). Incident thyroid cancer cases (C73, ICD-10 code) were identified from the National Cancer Registry and Statistics Korea. Urinary mercury concentrations were measured using thermal decomposition amalgamation atomic absorption spectrometry (TDA-AAS). Cox proportional hazards regression models (adjusted for age, sex, educational level, smoking status, and employment) were used to estimate the hazard ratio (HR) and confidence interval [CI] between mercury exposure and the incidence of thyroid cancer. Results: We documented 69 cases of thyroid cancer in a total of 5213 participants during follow-up (median 8.7 years). The geometric mean of urinary mercury concentration was 1.8 μg/L for thyroid cancer cases and 1.2 μg/L for noncases (p for difference = 0.001). After adjusting for potential confounders, those in the highest tertile of urinary mercury levels had a twofold higher risk of thyroid cancer (HR = 1.97 [CI 1.03 - 3.80] in the highest tertile vs. the lowest tertile, p for trend = 0.043). This association was stronger for those with lower mean corpuscular volume and mean corpuscular hemoglobin status. Conclusions: Urinary mercury concentration was positively associated with the risk of thyroid cancer among residents living near national industrial complexes, and this association was influenced by red blood cell indices status. These results provide some evidence suggesting the adverse effects of environmental metal pollution in the development of thyroid cancer.

Holistic health risk assessment in an artisanal mercury mining region in Mexico.

Mexico is one of the world's leading mercury producers and exporters. However, mercury mining is carried out using artisanal procedures, which highly impact ecosystems. In the municipality of Pinal de Amoles, Queretaro, Mexico, artisanal mercury mining (AMM) is practiced in a region that has been categorized as a Biosphere Reserve. Therefore, a holistic health risk assessment for mercury was performed in the region, including environmental monitoring (air, water, and soil) and mercury exposure in both humans (children, women, and miners) and biota (plants, rodents, and worms). The atmospheric mercury determination was carried out using the JEROME® J405 analyzer, whereas total mercury in environmental and biological samples was determined by atomic absorption spectrophotometry/cold vapor. Results showed that mercury concentrations in the environmental and biological matrices exceeded their respective reference values. These results demonstrate the direct influence of AMM in the increasing levels of mercury in all the components of the studied ecosystem. Therefore, comprehensive intervention strategies must be implemented to reduce and prevent human health and ecological risks due to the presence of mercury. In this regard, the Minamata Convention for mercury control should include biomonitoring programs not only for humans but also for critical ecological receptors in polluted ecosystems.

Role of MT1A Polymorphism and Environmental Mercury Exposure on the Montreal Cognitive Assessment (MoCA).

PurposeMany age-related structural and functional changes in the brain have important consequences. Long-term exposure to mercury and the impact of functional polymorphisms of metal-regulating proteins such as metallothioneins (MTs) can result in neurological-neurobehavioral effects in elderly individuals. Therefore, the aims of this study are to examine the associations between biomarkers of mercury exposure and cognitive impairment and to investigate the effect of the rs8052394 single nucleotide polymorphism (SNP) of the potential modifier gene MT1A on different domains of the Montreal Cognitive Assessment (MoCA).Materials and MethodsWe studied 436 participants aged ≥55 years from the Electricity Generating Authority of Thailand study. They underwent a physical examination, an extensive cognitive assessment with the MoCA (cutoff <26 points), and a biochemical analysis related to diabetes and dyslipidemia. The blood mercury level was determined by inductively coupled plasma mass spectrometry. Genotyping of the MT1A rs8052394 SNP was performed by the restriction fragmentation length polymorphism method.ResultsThe mean age of the study population was 58.8±3.01 years, and most had ≥12 years of education (75.7%). The primary study finding was that the prevalence of mild cognitive impairment (MCI) in older Thai adults was 39.7%. The frequency distributions of the G allele of the rs8052394 SNP of the MT1A gene were significantly associated with the total and sub-domain MoCA scores. The prevalence of MCI was significantly associated with increased age, hypertriglyceridemia, hyperhomocysteinemia, the third tertile of blood mercury concentration, and the rs8052394 variant genotype of MT1A (P values for all odds ratios <0.05).ConclusionThese findings suggested that neurocognitive effects associate with mercury exposure and genetic susceptibility in toxicokinetics. Public health strategies can be used to implement as a comprehensive action plan to educate vulnerable populations on how to reduce mercury exposure. Concurrently, impact of such genetic predisposition requires replication for identifying and protecting susceptible individuals from mercury toxicity.

Impact of environmental mercury exposure on the blood cells oxidative status of fishermen living around Mundaú lagoon in Maceió – Alagoas (AL), Brazil

Mercury in the aquatic environment can lead to exposure of the human population and is a known toxic metal due to its capacity for accumulation in organs. We aimed to evaluate the mercury level in the blood and urine of fishermen and correlate it with the level of oxidative stress in blood cells. We show in this case-control study that the fishermen of the exposed group (case) of Mundaú Lagoon (Maceió - Alagoas, Brazil) have higher concentrations of total mercury in the blood (0.73–48.38 μg L−1) and urine (0.430–10.2 μg L−1) than the total mercury concentrations in blood (0.29–17.30 μg L−1) and urine (0.210–2.65 μg L−1) of the control group. In the blood cells of fishermen, we observed that the lymphomononuclear cells produced high levels of reactive oxygen species (61.7%), and the erythrocytes presented increased lipid peroxidation (151%) and protein oxidation (41.0%) and a decrease in total thiol (36.5%), GSH and the REDOX state (16.5%). The activity of antioxidant system enzymes (SOD, GPx, and GST) was also reduced in the exposed group by 26.9%, 28.3%, and 19.0%, respectively. Furthermore, hemoglobin oxygen uptake was decreased in the exposed group (40.0%), and the membrane of cells presented increased osmotic fragility (154%) compared to those in the control group. These results suggest that mercury in the blood of fishermen can be responsible for causing impairments in the oxidative status of blood cells and is probably the cause of the reduction in oxygen uptake capacity and damage to the membranes of erythrocytes.

Blood lead and mercury levels are associated with low resting heart rate in community adolescent boys.

While the neurotoxic effects of heavy metals at even low levels have been well-studied, few studies have examined the cardiovascular effects of heavy metals on resting heart rate and these have focused on adult populations. The present study aimed to examine the association between low-level environmental lead and mercury exposure and resting heart rate in community adolescents. As part of the China Jintan Cohort Study, 532 adolescents aged 12 years (SD=0.6) were tested for blood levels of lead (BLL) and mercury (BML) and resting heart rate (RHR). Generalized linear models were conducted to test the relationship between BLL and BML and RHR, controlling for children's sex, age, and socioeconomic status. Analyses were clustered at the preschool level when the children were recruited to adjust for standard error. The mean (SD) BLL and BML were 3.14 (SD=1.19) μg/dL and 1.26 (SD=0.68) μg/L at age 12 years, respectively. After adjusting for confounders, we found a significant interaction between BML and BLL in predicting RHR in boys (B=-1.27, SE=0.49, p<0.01, n=289). We created BLL and BML groups in boys based on median cut-offs. Boys in the High BLL/High BML group had significantly lower RHR (mean=84.22 beats per minute [bpm], SD=8.77, n=61) than boys in the Low BLL/Low BML group (mean=89.03 bpm, SD=10.75, n=69; p<0.05). BML and BLL did not interact to predict RHR in girls (B=-0.18, SE=0.88, p>0.05, n=242). Combined high BLL and BML were associated with low RHR in community adolescent boys. Low RHR is an indication of chronic under-arousal and has been implicated in psychopathology, particularly for externalizing behavior. Our findings may stimulate further communication and research in this area.

A synthesis of patterns of environmental mercury inputs, exposure and effects in New York State

Mercury (Hg) pollution is an environmental problem that adversely affects human and ecosystem health at local, regional, and global scales—including within New York State. More than two-thirds of the Hg currently released to the environment originates, either directly or indirectly, from human activities. Since the early 1800s, global atmospheric Hg concentrations have increased by three- to eight-fold over natural levels. In the U.S., atmospheric emissions and point-source releases to waterways increased following industrialization into the mid-1980s. Since then, water discharges have largely been curtailed. As a result, Hg emissions, atmospheric concentrations, and deposition over the past few decades have declined across the eastern U.S. Despite these decreases, Hg pollution persists. To inform policy efforts and to advance public understanding, the New York State Energy Research and Development Authority (NYSERDA) sponsored a scientific synthesis of information on Hg in New York State. This effort includes 23 papers focused on Hg in atmospheric deposition, water, fish, and wildlife published in Ecotoxicology. New York State experiences Hg contamination largely due to atmospheric deposition. Some landscapes are inherently sensitive to Hg inputs driven by the transport of inorganic Hg to zones of methylation, the conversion of inorganic Hg to methylmercury, and the bioaccumulation and biomagnification along food webs. Mercury concentrations exceed human and ecological risk thresholds in many areas of New York State, particularly the Adirondacks, Catskills, and parts of Long Island. Mercury concentrations in some biota have declined in the Eastern Great Lakes Lowlands and the Northeastern Highlands over the last four decades, concurrent with decreases in water releases and air emissions from regional and U.S. sources. However, widespread changes have not occurred in other ecoregions of New York State. While the timing and magnitude of the response of Hg levels in biota varies, policies expected to further diminish Hg emissions should continue to decrease Hg concentrations in food webs, yielding benefits to the fish, wildlife, and people of New York State. Anticipated improvements in the Hg status of aquatic ecosystems are likely to be greatest for inland surface waters and should be roughly proportional to declines in atmospheric Hg deposition. Efforts that advance recovery from Hg pollution in recent years have yielded significant progress, but Hg remains a pollutant of concern. Indeed, due to this extensive compilation of Hg observations in biota, it appears that the extent and intensity of the contamination on the New York landscape and waterscape is greater than previously recognized. Understanding the extent of Hg contamination and recovery following decreases in atmospheric Hg deposition will require further study, underscoring the need to continue existing monitoring efforts.

Environmental mercury exposure and health effects

Mercury is a heavy metal and one of the major public health concern chemicals. Mercury is spread to the environment due to natural and human activities. Industrial processes such as coal-fired thermal power plants, coal-fired activities for heating, waste incineration and metal mining, and scrap metal processing are man-made activities that cause mercury in the environment. Exposure to mercury causes significant health effects. These health effects may vary depending on the type of mercury being exposed, dose, time, route, age and developmental status of the subject. Mercury has many health negative effects, particularly kidney toxicity and neurotoxic effects. In this review health effects of environmental mercury exposure are examined.

Infants and mothers levels of mercury in breast milk, urine and hair, data from an artisanal and small-scale gold mining area in Kadoma / Zimbabwe

In Kadoma (Zimbabwe) gold is extracted from ore based on a simple technology using mercury. Women are exposed whilst living in an exposed area, or even more working directly with mercury. Breast fed infants are exposed via mercury contaminated milk and the general environmental mercury exposure. The aim of the study was to measure infants and mothers levels of mercury in urine and hair, as well as in breast milk. In 2006, an environmental epidemiological field study with 120 mother – child pairs was conducted. A non exposed control group (n = 42) was compared with a medium exposed group (n = 51) and a high exposed group (occupational exposure, n = 27). Urine and hair samples from mother and infants plus breast milk samples were analyzed for total mercury. 120 breast milk samples were analyzed, median (maximum) concentrations [μg Hg/l] were (i) control group < 0.50 (1.55), (ii) medium exposed group 1.10 (10.48), (iii) high exposed group 1.20 (24.80) (p < 0,001). Urine and hair results were distributed similarly for infants and mothers, with higher levels according to the exposure subgroup. All specimen results correlated very well with another, indicating there is a pathway between breast milk and infant's level of mercury. The daily uptake of mercury via breast milk was calculated. The reference dose of 0.3°[μg Hg/kg BW/d] was used to compare the burden of the infants. No infant from the control group, but 17.6% of the medium and 18.5% of the high exposed group were above the reference dose. Mercury in breast milk is generally higher in artisanal and small scale gold mining areas. Breast fed infants were burdened with toxic mercury via breast milk and via the general environment, both are important public health issues.

Associations between mercury exposure and the risk of nonalcoholic fatty liver disease (NAFLD) in US adolescents.

Little is known regarding the effects of environmental mercury (Hg) exposure on liver dysfunction in adolescents. We aimed to explore the association between Hg exposure and the risk of nonalcoholic fatty liver disease (NAFLD) in the adolescent population. The cross-sectional associations between blood Hg concentrations and serum alanine aminotransferase (ALT) levels, a surrogate for suspected NAFLD, were evaluated using data from adolescents (aged 12-17 years old) who participated in the National Health and Nutrition Examination Survey (NHANES), 1999-2014. A final sample of 6389 adolescents was analysed. Elevated ALT was defined as > 25 IU/L and > 22 IU/L for boys and girls ≤ 17 years old, respectively. Odds ratios (ORs) of Hg levels in association with serum ALT levels were estimated using a logistic regression after adjusting for gender, age, ethnicity, serum cotinine, body mass index, the poverty income ratio, and NHANES cycles. The median blood Hg level was 0.73 ± 0.91 μg/L amongst US adolescents. In the adjusted model, the ORs of elevated ALT levels of those in the 4th quartile were higher amongst non-Hispanic white adolescents (OR = 1.76, 95% CI 1.20, 2.59; P = 0.035) and those who were normal or underweight (OR = 1.41, 95% CI 1.08, 1.85; P = 0.020). No association was observed for the other variables. Our results indicate that the positive association between blood Hg exposure and the risk of NAFLD in US adolescents is the highest amongst non-Hispanic white and those who are normal or underweight, regardless of ethnicity. More research is necessary to confirm this association and to clarify the potential mechanisms.

Environmental mercury exposure and selenium-associated biomarkers of antioxidant status at molecular and biochemical level. A short-term intervention study

Mercury (Hg) is a potent toxicant. In the field of public health a chronic-low-level environmental Hg exposure resulting from fish consumption in general population is still being discussed. The objective of the study was to assess the influence of real Hg exposure on biomarkers of selenium (Se) status and selected biomarkers of pro-oxidant/anti-oxidant effects in healthy men (n = 67) who participated in the short-term intervention study consisting in daily fish consumption for two weeks. The analysis included Se level, Se-associated antioxidants at molecular (profile of 7 genes encoding selected proteins related to antioxidant defense) and biochemical levels (Se-dependent glutathione peroxidases activities and plasma selenoprotein P concentration). A pro-oxidant/anti-oxidant balance was explored using a biomarker of plasma lipid peroxidation and total antioxidant activity. The study revealed significant correlations (p < 0.05) between the biomarkers of exposure to Hg, Se level and Se-dependent antioxidants. Even though the risk of adverse effects of Hg for volunteers was substantially low, biomarkers of Hg altered levels of circulation selenoproteins and their genes expression. Changes in genes expression during study differed between the main enzymes involved in two systems: downregulation of thioredoxin reductase1 and upregulation of glutathione peroxidases. Hg exposure caused imbalance between the biomarkers of pro-oxidant/anti-oxidant effects.

Distribution of organic and inorganic mercury across the pelts of Canadian river otter (Lontra canadensis)

Fur is a common biomarker of environmental mercury (Hg) exposure. Further, there are well-established relationships between total mercury (THg) in fur and organs. However, these models assumed that THg is uniformly distributed across the fur in a pelt. In this study, we assess the distribution of THg and methylmercury (MeHg) across the pelts of four river otters (Lontra canadensis). THg concentrations were measured in the topcoat (n = 95) and undercoat fur (n = 95). MeHg was measured in a subset of these samples (n = 10). Patterns of THg and MeHg were explored using cluster analyses and ANOVAs. Significant differences existed between THg in topcoat and undercoat and between anatomical region (head/body/tail/legs) and fur regions (dorsal/ventral/furline). The cluster analysis showed significant THg clusters in undercoat fur and to a lesser extent topcoat fur. Further, the error rate for predicting internal THg is lowest in the forebody region of the topcoat, thus, making this the optimal region to sample for biomonitoring. Fur samples taken outside of this region could result in prediction error as high as 140% when estimating internal organ THg. The ratio of MeHg in THg in topcoat fur was measured at 95.7 ± 3.4% indicating THg concentrations can be used to assess MeHg exposure.

Mercury pollution in modern times and its socio-medical consequences

Mercury plays a critical role in serious health problems due to environmental or occupational exposures. Aquatic ecosystems are an essential component of the global biogeochemical cycle of mercury, as inorganic mercury can be converted to toxic methyl mercury in these environments and reemissions of elemental mercury rival anthropogenic mercury releases on a global scale.The history of the Minamata disease, a typical example of industrial pollution, has shown how corporate secrecy and ignorance on part of the health authorities may influence the devastating spread of environmental contamination and the progress of disease. While the Minamata Convention, in place since 2017, is aiming to lower mercury exposure and to prevent adverse effects, there are still knowledge gaps in the areas of global environmental mercury exposure. Areas of uncertainty in the global biogeochemical cycle of mercury include oxidation processes in the atmosphere, land-atmosphere and ocean-atmosphere cycling, and methylation processes in the ocean. Pollution related to climate change (especially in boreal and arctic regions), bioaccumulation and biomagnification of methyl mercury in the food chain, especially in fish and marine mammals, needs to be addressed in more detail. Information is lacking on numerous hidden contaminant exposures i.e. from globally applied traditional medicine, mercury containing skin creams and soaps, dental amalgam, ethyl mercury containing vaccines and latex paint additives, as well as on mercury releases from power plants, e-waste/fluorescent lamps, wildfire emissions, and global artisanal small-scale gold mining activities.Mercury occurs in various forms with different levels of toxicity. While much is already known and documented on the health effects of mercury, present knowledge and translation into preventive actions is still incomplete. Risks for long term health effects trough prolonged low dose exposure and trough cumulative exposures of various mercury forms should be further addressed. Preventive actions should include adequate human biomonitoring programs. Research data should be translated swiftly into management tools for local policy makers and health professionals, also paying attention at the major differences in mercury contamination across the globe.

Using Geospatial Methods to Quantify the Co-Dispersion of Mercury Sources and Exposures in River Otter (Lontra Canadensis) for Risk Prediction

Mercury is an environmental contaminant of concern due to the established effects of methylated mercury (MeHg) on neurological functioning. Sentinel species such as the river otter (Lontra canadensis) are commonly used to monitor environmental mercury concentrations. Fur mercury has proven to be a reliable and cost-effective measure of exposure to MeHg in river otters and is a good proxy for assessing environmental mercury concentrations. A total of 311 geolocated fur samples were obtained from wildlife biomonitoring programs at Environment and Climate Change Canada and from the North American Fur Auction. These samples represent 131 unique locations throughout Canada collected between 2013 and 2016. Total mercury (THg) was measured on a MA-3000. Clustering of high THg was assessed using Getis and Ord&amp;#8217;s Gi*. The association between fur THg and mercury sources was assessed using linear regression modelling alongside spatial regression methods such as geographically weighted regression. A cluster of low fur THg concentrations was observed in Alberta, and clusters of high fur THg concentrations were observed in northeastern Ontario, New Brunswick, and Nova Scotia. There is a statistically significant (p&amp;lt;0.05) negative relationship between fur THg and proximity to dam reservoir water, and pH of soil. There was also a statistically significant interaction between proximity to dam reservoir water and the pH of the soil. Otters that live closer to the reservoir water of dams have higher fur THg concentrations. This effect is enhanced if the soil pH surrounding the reservoir is also low. Using a geographically weighted regression these variables explain up to 35% of the variance. Results from this research are important for assessing the impact of future hydroelectric dam development on aquatic ecosystems. This research also further supports the use of river otter fur as a biomonitoring tool for environmental mercury exposure.

8. Does Oxidative Stress Function as a Biomarker of Environmental Mercury Contamination in Double-Crested Cormorant?

Mercury is a widespread contaminant that has been shown to induce a wide range of adverse health effects in several animal species including changes in gene expression. This study was undertaken to explore the relationship between environmental mercury exposure and oxidative stress induction in the blood of double-crested cormorants (Phalacrocorax auritus). Blood was sampled at five sites across Central and Southern Ontario ranging from low to high risk of mercury contamination and was analyzed for total mercury concentration. To assess cellular oxidative stress, the expression of glutathione peroxidases 1 and 3, glutathione S-transferase µ3, superoxide dismutase 1 and heat-shock protein 70 kd-8 were measured in whole blood samples. Preliminary results indicate that erythrocyte mercury concentrations ranged from 5.0 to 27.3 µg/g dry weight. Mean (± standard error) site-specific erythrocyte mercury concentrations ranged from 9.0 ± 3.6 µg/g dry weight in Lake Erie to 17.5 ± 4.2 µg/g dry weight in Lake Nipissing. Approximately 27% of the birds exceeded the threshold concentration for adverse effects in another piscivorous bird, the common loon (Gavia immer). Results of gene expression analysis will be discussed in relation to mercury concentration. Our study will help to develop an understanding of the interactions of environmental mercury exposure and oxidative stress-related gene expression and will contribute to the development of sub lethal biomarkers for mercury toxicity in wild aquatic piscivorous birds.