Evaluation of the cardiovascular effects of methylmercury exposures: current evidence supports development of a dose-response function for regulatory benefits analysis

Improved Mechanistic Modeling on Reproducing Particle-Bound Mercury in the Marine Atmosphere

Mercury (Hg) is a neurotoxic pollutant that is ubiquitous on the planet and receives global concern because of its adverse health effects. Particle-bound HgP formation in the atmosphere stems mainly from the adsorption of reactive gaseous HgII on aerosol particles, particularly sea salt aerosol. However, the observed comparable abundance of HgP over HgII in the marine atmosphere has not been reproduced by traditional statistics-based schemes, which were constructed by continental observations. This study incorporated an improved mechanistic scheme in an atmospheric chemical transport model to simulate SSA-bound HgP cycling processes in the marine atmosphere. Results show that a widely used statistics-based scheme could reproduce atmospheric HgP concentrations over continents but failed to reproduce the concentrations over the ocean. The HgP concentrations particularly relative abundance of HgP over HgII in the marine atmosphere could be successfully reproduced by the process-based scheme. Accordingly, a new global atmospheric Hg cycling budget was constructed, manifesting mainly in the atmospheric burden of 4 Mg, dry deposition of 160 Mg yr-1, and wet deposition of 1410 Mg yr-1 for SSA-bound HgP. The new insight on the global atmospheric Hg budget sheds light on the re-examination of Hg deposition risks in the ocean owing to a transition from previously recognized gaseous HgII deposition to unrecognized particulate HgP deposition over the ocean.

Global mercury dataset with predicted methylmercury concentrations in seafoods during 1995-2022

Mercury exposure poses significant threats to human health, particularly in its organic form, methylmercury (MeHg). Diet is the main pathway for human MeHg exposure, especially through seafood consumption. In this context, numerous studies have established seafood MeHg concentration datasets to assess MeHg-related health risks from seafood consumption. However, existing datasets are limited to specific regions and short-term observations, making it difficult to support continuous and dynamic assessments of global MeHg-related health risks. This study takes a bottom-up approach to construct a global seafood MeHg concentration dataset during 1995-2022. Firstly, it compiles a long-term time series marine-scale dataset of seafood MeHg concentrations, based on the reported seafood mercury concentrations from existing literature and machine learning methods. Subsequently, this study used the seafood catch volumes of each nation in different marine areas as weights to estimate the national-scale seafood MeHg concentrations. This dataset can provide essential data support for environmental impact assessment of mercury and its compounds as mentioned in Articles 12 and 19 of the Minamata Convention on Mercury.

Re-thinking the link between exposure to mercury and blood pressure

Hypertension or high blood pressure (BP) is a prevalent and manageable chronic condition which is a significant contributor to the total global disease burden. Environmental chemicals, including mercury (Hg), may contribute to hypertension onset and development. Hg is a global health concern, listed by the World Health Organization (WHO) as a top ten chemical of public health concern. Most people are exposed to some level of Hg, with vulnerable groups, including Indigenous peoples and small-scale gold miners, at a higher risk for exposure. We published a systematic review and meta-analysis in 2018 showing a dose-response relationship between Hg exposure and hypertension. This critical review summarizes the biological effects of Hg (both organic and inorganic form) on the underlying mechanisms that may facilitate the onset and development of hypertension and related health outcomes and updates the association between Hg exposure (total Hg concentrations in hair) and BP outcomes. We also evaluated the weight of evidence using the Bradford Hill criteria. There is a strong dose-response relationship between Hg (both organic and inorganic) exposure and BP in animal studies and convincing evidence that Hg contributes to hypertension by causing structural and functional changes, vascular reactivity, vasoconstriction, atherosclerosis, dyslipidemia, and thrombosis. The underlying mechanisms are vast and include impairments in antioxidant defense mechanisms, increased ROS production, endothelial dysfunction, and alteration of the renin-angiotensin system. We found additional 16 recent epidemiological studies that have reported the relationship between Hg exposure and hypertension in the last 5 years. Strong evidence from epidemiological studies shows a positive association between Hg exposure and the risk of hypertension and elevated BP. The association is mixed at lower exposure levels but suggests that Hg can affect BP even at low doses when co-exposed with other metals. Further research is needed to develop robust conversion factors among different biomarkers and standardized measures of Hg exposure. Regulatory agencies should consider adopting a 2 µg/g hair Hg level as a cut-off for public health regulation, especially for adults older than child-bearing age.

China's municipal wastewater policies enhanced seafood safety and offset health risks from atmospheric mercury emissions in the past four decades

The neurotoxin methylmercury in seafood threatens food safety worldwide. China has implemented stringent wastewater policies, established numerous treatment facilities and enforced rigorous water quality standards to address pollution in its waterways. However, the impact of these policies on seafood safety and methylmercury exposure remains unknown. Here we developed a process-based model showing that, although mercury reductions from municipal wastewater policies accounted for only 9% of atmospheric mercury emissions during 1980-2022, these measures unexpectedly prevented102,000 - 6,600 + 11,000 mercury-related deaths and counteracted nearly two thirds of potential deaths from those emissions. Furthermore, these policies ensured that146 - 9 + 8 megatonnes of freshwater seafood met the World Health Organization and China's mercury-safety standards, preventing US $ 498 - 29 + 32 billion in economic losses. Finally, we explore how China, as the primary global seafood producer and exporter, could develop municipal wastewater policies at the regional level to reduce aquatic pollutants and unlock the health benefits of seafood consumption.

Tree Rings Mercury Controlled by Atmospheric Gaseous Elemental Mercury and Tree Physiology

Tree rings are an emerging atmospheric mercury (Hg) archive. Questions have arisen, though, regarding their mechanistic controls and reliability. Here, we report contrasting tree-ring Hg records in three collocated conifer species: Norway spruce (Picea abies), Scots pine (Pinus sylvestris), and European larch (Larix decidua), which are from a remote boreal forest. Centennial atmospheric Hg trends at the site, derived from varved lake sediments, peats, and atmospheric monitoring, indicated a steady rise from the 1800s, peaking in the 1970s, and then declining. Prior to ca. 2005, larch and spruce tree rings reproduced the peak in the atmospheric Hg trend, while pine tree rings peaked in the 1930s, likely due to the prolonged sapwood period and ambiguity in the heartwood-sapwood boundary of pine. Since ca. 2005, tree rings from all species showed increasing Hg concentrations in the physiologically active outer rings despite declining atmospheric Hg concentrations. The good agreement between Hg and nitrogen concentrations in active tree-ring cells indicates a similar transport mechanism and cautions against their applicability as atmospheric Hg archives. Our results suggest that tree-ring Hg records are controlled by atmospheric Hg and tree physiology. We provide recommendations for using tree-ring Hg archives that take tree physiology into account.

The duality of sulfate-reducing bacteria: Reducing methylmercury production in rhizosphere but enhancing accumulation in rice plants

Sulfate-reducing bacteria (SRB) are known to alter methylmercury (MeHg) production in paddy soil, but the effect of SRB on MeHg dynamics in rhizosphere and rice plants remains to be fully elucidated. The present study investigated the impact of SRB on MeHg levels in unsterilized and γ-sterilized mercury-polluted paddy soils, with the aim to close this knowledge gap. Results showed that the presence of SRB reduced MeHg production by ∼22 % and ∼17 % in the two soils, but elevated MeHg contents by approximately 55 % and 99 % in rice grains, respectively. Similar trend at smaller scales were seen in roots and shoots. SRB inoculation exerted the most profound impact on amino acid metabolism in roots, with the relative response of L-arginine positively linking to MeHg concentrations in rhizosphere. The SRB-induced enrichment of MeHg in rice plants may be interpreted by the stronger presence of endophytic nitrogen-related microbes (e.g. Methylocaldum, Hyphomicrobium and Methylocystis) and TGA transcription factors interacting with glutathione metabolism and calmodulin. Our study provides valuable insights into the complex effects of SRB inoculation on MeHg dynamics in rice ecosystems, and may help to develop strategies to effectively control MeHg accumulation in rice grains.

Global Distribution of Mercury in Foliage Predicted by Machine Learning

Foliar assimilation of elemental mercury (Hg0) from the atmosphere plays a critical role in the global Hg biogeochemical cycle, leading to atmospheric Hg removal and soil Hg insertion. Recent studies have estimated global foliar Hg assimilation; however, large uncertainties remained due to coarse accounting of observed foliar Hg concentrations, posing a substantial challenge in constraining the global Hg budget. Here, we integrated a comprehensive observation database of foliar Hg concentrations and machine learning algorithms to predict the first spatial distribution of foliar Hg concentrations on a global scale, contributing to the first estimate of global Hg pools in foliage. The global average of foliar Hg concentrations was estimated to be 24.0 ng g-1 (7.5-56.5 ng g-1), and the global total in foliar Hg pools reached 4561.3 Mg (1455.2-9062.8 Mg). The spatial distribution showed the hotspots in tropical regions, including the Amazon, Central Africa, and Southeast Asia. A range of 2268.5-2727.0 Mg yr-1 was estimated for annual foliar Hg assimilation accounting for the perennial continuous assimilation by evergreen vegetation foliage. The first spatial maps of foliar Hg concentrations and Hg pools may aid in understanding the global biogeochemical cycling of Hg, especially in the context of climate change and global vegetation greening.

Economic benefit of ecological remediation of mercury pollution in southwest China 2007-2022

Methylmercury (MeHg) exposure via rice consumption poses health risk to residents in mercury contaminated areas, such as the Wanshan Hg mining area (WSMA) in southwest China. Making use of the published data for WSMA, this study developed a database of rice MeHg concentrations for different villages in this region for the years of 2007, 2012, 2017, and 2019. The temporal changes of human MeHg exposure, health effects, and economic benefits under different ecological remediation measures were then assessed. Results from this study revealed a decrease of 3.88 μg/kg in rice MeHg concentration and a corresponding reduction of 0.039 μg/kg/d in probable daily intake of MeHg in 2019 compared to 2007 on regional average in the WSMA. Ecological remediation measures in this region resulted in the accumulated economic benefits of $38.7 million during 2007-2022, of which 84 % was from pollution source treatment and 16 % from planting structure adjustment. However, a flooding event in 2016 led to an economic loss of $2.43 million (0.38 % of regional total Gross Domestic Product). Planting structure adjustment generates the greatest economic benefits in the short term, whereas pollution source treatment maximizes economic benefits in the long term and prevents the perturbations from flooding event. These findings demonstrate the importance of ecological remediation measures in Hg polluted areas and provide the foundation for risk assessment of human MeHg exposure via rice consumption.

Influence of genetic polymorphisms of Hg metabolism and DNA repair on the frequencies of micronuclei, nucleoplasmic bridges, and nuclear buds in communities living in gold mining areas

Fishing communities living near gold mining areas are at increased risk of mercury (Hg) exposure via bioaccumulation of methylmercury (MeHg) in fish. This exposure has been linked to health effects that may be triggered by genotoxic events. Genetic polymorphisms play a role in the risk associated with Hg exposure. This study evaluated the effect of single nucleotide polymorphisms (SNPs) in metabolic and DNA repair genes on genetic instability and total hair Hg (T-Hg) levels in 78 individuals from "La Mojana" in northern Colombia and 34 individuals from a reference area. Genetic instability was assessed by the frequency of micronuclei (MNBN), nuclear buds (NBUDS), and nucleoplasmic bridges (NPB). We used a Poisson regression to assess the influence of SNPs on T-Hg levels and genetic instability, and a Bayesian regression to examine the interaction between Hg detoxification and DNA repair. Among exposed individuals, carriers of XRCC1Arg399Gln had a significantly higher frequency of MNBN. Conversely, the XRCC1Arg194Trp and OGG1Ser326Cys polymorphisms were associated with lower frequencies of MNBN. XRCC1Arg399Gln, XRCC1Arg280His, and GSTM1Null carriers showed lower NPB frequencies. Our results also indicated that individuals with the GSTM1Nulland GSTT1null polymorphisms had a 1.6-fold risk for higher T-Hg levels. The Bayesian model showed increased MNBN frequencies in carriers of the GSTM1Null polymorphism in combination with XRCC1Arg399Gln and increased NBUDS frequencies in the GSTM1Null carriers with the XRCC3Thr241Met and OGG1Ser326Cys alleles. The GSTM1+ variant was found to be a protective factor in individuals carrying OGG1Ser326Cys (MNBN) and XRCC1Arg280His (NPB); the GSTT1+ polymorphism combined with XRCCArg194Trp also modulated lower MNBN frequencies, while GSTT1+ carriers with the XRCC1Arg399Gln allele showed lower NPB frequencies. Consistent with GSTM1, GSTT1Null carriers with XRCC3Thr241Met showed increased NBUDS frequency. With the rise of gold mining activities, these approaches are vital to identify and safeguard populations vulnerable to Hg's toxic effects.

Addressing the Missing Links in Cardiovascular Aging

The aim of this manuscript is to provide a review of available options to enhance cardiovascular health and prevent cardiovascular disease (CVD) in the aging population using a systems-biology approach. These include the role of the gut microbiome, the early identification and removal of environmental toxins, and finally age related sex hormones and supplement replacement which all influence aging. Implementing such a comprehensive approach has the potential to facilitate earlier risk assessment, disease prevention, and even improve mortality. Further study in these areas will continue to advance our understanding and refine therapeutic interventions for a healthier cardiovascular aging process.

Methylmercury induces inflammatory response and autophagy in microglia through the activation of NLRP3 inflammasome

Methylmercury (MeHg) is a global environmental pollutant with neurotoxicity, which can easily crosses the blood-brain barrier and cause irreversible damage to the human central nervous system (CNS). CNS inflammation and autophagy are known to be involved in the pathology of neurodegenerative diseases. Meanwhile, MeHg has the potential to induce microglia-mediated neuroinflammation as well as autophagy. This study aims to further explore the exact molecular mechanism of MeHg neurotoxicity. We conducted in vitro studies using BV2 microglial cell from the central nervous system of mice. The role of inflammation and autophagy in the damage of BV2 cells induced by MeHg was determined by detecting cell viability, cell morphology and structure, reactive oxygen species (ROS), antioxidant function, inflammatory factors, autophagosomes, inflammation and autophagy-related proteins. We further investigated the relationship between the inflammatory response and autophagy induced by MeHg by inhibiting them separately. The results indicated that MeHg could invade cells, change cell structure, activate NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome and autophagosome, release a large amount of inflammatory factors and trigger the inflammatory response and autophagy. It was also found that MeHg could disrupt the antioxidant function of cells. In addition, the inhibition of NLRP3 inflammasome alleviated both cellular inflammation and autophagy, while inhibition of autophagy increased cellular inflammation. Our current research suggests that MeHg might induce BV2 cytotoxicity through inflammatory response and autophagy, which may be mediated by the NLRP3 inflammasome activated by oxidative stress.

Early exposure to mercury and cardiovascular function of seven-year old children in Guadeloupe (French West Indies)

BACKGROUND

The cardiotoxicity of prenatal exposure to mercury has been suggested in populations having regular contaminated seafood intake, though replications in the literature are inconsistent.

METHODS

The Timoun Mother-Child Cohort Study was set up in Guadeloupe, an island in the Caribbean Sea where seafood consumption is regular. At seven years of age, 592 children underwent a medical examination, including cardiac function assessment. Blood pressure (BP) was taken using an automated blood pressure monitor, heart rate variability (HRV, 9 parameters) and electrocardiogram (ECG) characteristics (QT, T-wave parameters) were measured using Holter cardiac monitoring during the examination. Total mercury concentrations were measured in cord blood at birth (median = 6.6 μg/L, N = 399) and in the children's blood at age 7 (median = 1.7 μg/L, N = 310). Adjusted linear and non-linear modelling was used to study the association of each cardiac parameter with prenatal and childhood exposures. Sensitivity analyses included co-exposures to lead and cadmium, adjustment for maternal seafood consumption, selenium and polyunsaturated fatty acids (n3-PUFAs), and for sporting activity.

RESULTS

Higher prenatal mercury was associated with higher systolic BP at 7 years of age (βlog2 = 1.02; 95% Confidence Interval (CI) = 0.10, 1.19). In boys, intermediate prenatal exposure was associated with reduced overall HRV and parasympathetic activity, and longer QT was observed with increasing prenatal mercury (βlog2 = 4.02; CI = 0.48, 7.56). In girls, HRV tended to increase linearly with prenatal exposure, and no association was observed with QT-wave related parameters. Mercury exposure at 7 years was associated with decreased BP in girls (βlog2 = -1.13; CI = -2.22, -0.004 for diastolic BP). In boys, the low/high-frequency (LF/HF) ratio increased for intermediate levels of exposure.

CONCLUSION

Our study suggests sex-specific and non-monotonic modifications in some cardiac health parameters following prenatal exposure to mercury in pre-pubertal children from an insular fish-consuming population.

Anthropogenic short-lived halogens increase human exposure to mercury contamination due to enhanced mercury oxidation over continents

Mercury (Hg) is a contaminant of global concern, and an accurate understanding of its atmospheric fate is needed to assess its risks to humans and ecosystem health. Atmospheric oxidation of Hg is key to the deposition of this toxic metal to the Earth's surface. Short-lived halogens (SLHs) can provide halogen radicals to directly oxidize Hg and perturb the budget of other Hg oxidants (e.g., OH and O3). In addition to known ocean emissions of halogens, recent observational evidence has revealed abundant anthropogenic emissions of SLHs over continental areas. However, the impacts of anthropogenic SLHs emissions on the atmospheric fate of Hg and human exposure to Hg contamination remain unknown. Here, we show that the inclusion of anthropogenic SLHs substantially increased local Hg oxidation and, consequently, deposition in/near Hg continental source regions by up to 20%, thereby decreasing Hg export from source regions to clean environments. Our modeling results indicated that the inclusion of anthropogenic SLHs can lead to higher Hg exposure in/near Hg source regions than estimated in previous assessments, e.g., with increases of 8.7% and 7.5% in China and India, respectively, consequently leading to higher Hg-related human health risks. These results highlight the urgent need for policymakers to reduce local Hg and SLHs emissions. We conclude that the substantial impacts of anthropogenic SLHs emissions should be included in model assessments of the Hg budget and associated health risks at local and global scales.

Catchment land use effect on mercury concentrations in lake sediments: A high-resolution study of Qinghai Lake

Mercury (Hg) contamination in aquatic environments presents a significant ecological and human health concern. This study explored the relationship between catchment land use and Hg concentrations within Qinghai Lake sediment, the largest lake in China, situated on the Qinghai-Tibet plateau. The study entailed detailed mapping of Hg sediment concentrations and a subsequent environmental risk assessment. Considering the complex nature of the plateau landform and surface vegetation, the study area was delineated at a 100 km radius centered on Qinghai Lake, which was divided into 30 sectors to quantify relationships between land use and the sediment Hg concentration. The results revealed a mean sediment Hg concentration of 29.91 μg/kg, which was elevated above the background level. Kendall's correlation analysis revealed significant but weak associations between sediment Hg concentrations and three land use types: grassland (rangeland and trees) (rs = 0.27, p < 0.05), crops (rs = -0.37, p < 0.05), and bare ground (rs = -0.25, p < 0.1), suggesting that growing areas of grassland correlated with higher Hg levels in the lake sediment, in contrast to bare ground or crops area, which correlated with lower Hg concentrations. Multiple linear regression models also observed weak negative relationships between bare ground and crops with sediment Hg concentration. This research methodology enhances our understanding of the impact of land use on Hg accumulation in lake sediments and underscores the need for integrated watershed management strategies to mitigate Hg pollution in Qinghai Lake.

Dietary shifts drive the slowdown of declining methylmercury related health risk in China

Chinese population suffers severe health risk from dietary methylmercury (MeHg) exposure. However, the temporal change of such risk and socioeconomic driving factors remain unknown. This study investigates this issue by compiling time-series inventory of China's MeHg-related health risk at the provincial scale and revealing critical socioeconomic influencing factors through structural decomposition analysis. Results show that the per-fetus IQ decrements from dietary MeHg exposure have declined by 60% nationally during 2004-2019. Such decline results from the joint effects of dietary shifts (contributing 44%) and the decrease of MeHg concentrations in foods consumed (contributing 56%). However, the declining trend has slowed down since 2014 and even leveled off after 2016, which is mainly affected by dietary pattern changes. Especially, the increased intake level and proportion of fishes in underdeveloped provinces of China have dominated the slowdown of declining trend after 2016. Moreover, the affluence and education levels have significantly negative associations with per-fetus IQ decrements. Rich and well-educated people have higher ability of risk perception, which indicates the importance of rational consumption patterns. Our findings can help develop socioeconomic regulatory policies on reducing per-fetus IQ decrements from dietary MeHg exposure in China.

Estimation of mercury uptake and distinction of corn cultivation in China

Corn cultivation potentially plays a vital role in the global mercury (Hg) biogeochemical cycle. Nevertheless, there have been limited studies quantifying the Hg mass flow during corn cultivation. This study focuses on Hg uptake by corn plants in China, integrating data from both sample collection and prior studies, resulting in 400 datasets. The findings reveal that the Hg in corn plants is mainly incorporated in leaves (45.5 %-47.5 %) and husks (14.5 %-15.7 %). Despite a decrease in total gaseous Hg (TGM) concentrations in the atmosphere over time, annual Hg uptake by corn cultivation in China has risen from 72.0 (ranging from 47.6 to 96.3) tons (2009-2014) to 84.3 (ranging from 51.9 to 109.6) tons (2015-2020) due to the increasing in corn kernel production. Spatial analysis demonstrates regional disparities in Hg uptake, primarily influenced by corn kernel production, TGM levels, and soil Hg content. Furthermore, temporal analysis reveals a shift in the fate of Hg in corn plants, which can be attributed to variations in corn straw treatment policy or methods. From 2009 to 2014, a substantial amount of absorbed Hg by corn plants was re-released into the atmosphere (48.9 %) due to corn residues burning, whereas, between 2015 and 2020, a greater proportion of Hg ended up accumulating in the soil (51.1 %) after the imposition of the straw burning ban in China. Prior to the ban (2009-2014), corn cultivation contributed approximately 7.7 tons of Hg input to soil annually, with a range from 1.7 to 13.5. However, following the ban (2015-2020), Hg input into the soil increased by approximately 4.5 times, reaching 34.5 (ranging from 17.5 to 52.6) tons per year. These findings emphasize the significant risks associated with soil Hg pollution caused by corn cultivation due to the straw burning ban.

A high spatial resolution dataset for methylmercury exposure in Guangdong-Hong Kong-Macao Greater Bay Area

Dietary methylmercury (MeHg) exposure increases the risk of many human diseases. The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is the world's most populous bay area and people there might suffer a high risk of dietary MeHg exposure. However, there lacks a time-series high spatial resolution dataset for dietary MeHg exposure in the GBA. This study constructs a high spatial resolution (1 km × 1 km) dataset for dietary MeHg exposure in the GBA during 2009-2019. It first constructs the dietary MeHg exposure inventory for each county/district of the GBA, based on MeHg concentrations of foods (i.e., rice and fish in this study) and per capita rice and fish intake. Subsequently, this study spatializes the dietary MeHg exposure inventory at 1 km × 1 km scale, using gridded data for food consumption expenditure as the proxy. This dataset can describe the spatially explicit hotspots, distribution patterns, and variation trend of dietary MeHg exposure in the GBA. This dataset can support spatially explicit evaluation of MeHg-related health risks in the GBA.

Circumpolar assessment of mercury contamination: the Adélie penguin as a bioindicator of Antarctic marine ecosystems

Due to its persistence and potential ecological and health impacts, mercury (Hg) is a global pollutant of major concern that may reach high concentrations even in remote polar oceans. In contrast to the Arctic Ocean, studies documenting Hg contamination in the Southern Ocean are spatially restricted and large-scale monitoring is needed. Here, we present the first circumpolar assessment of Hg contamination in Antarctic marine ecosystems. Specifically, the Adélie penguin (Pygoscelis adeliae) was used as a bioindicator species, to examine regional variation across 24 colonies distributed across the entire Antarctic continent. Mercury was measured on body feathers collected from both adults (n = 485) and chicks (n = 48) between 2005 and 2021. Because penguins' diet represents the dominant source of Hg, feather δ13C and δ15N values were measured as proxies of feeding habitat and trophic position. As expected, chicks had lower Hg concentrations (mean ± SD: 0.22 ± 0.08 μg·g‒1) than adults (0.49 ± 0.23 μg·g‒1), likely because of their shorter bioaccumulation period. In adults, spatial variation in feather Hg concentrations was driven by both trophic ecology and colony location. The highest Hg concentrations were observed in the Ross Sea, possibly because of a higher consumption of fish in the diet compared to other sites (krill-dominated diet). Such large-scale assessments are critical to assess the effectiveness of the Minamata Convention on Mercury. Owing to their circumpolar distribution and their ecological role in Antarctic marine ecosystems, Adélie penguins could be valuable bioindicators for tracking spatial and temporal trends of Hg across Antarctic waters in the future.

Sociodemographic Disparities in Mercury Exposure from United States Coal-Fired Power Plants

Hazardous air pollutants emitted by United States (U.S) coal-fired power plants have been controlled by the Mercury and Air Toxics Standards (MATS) since 2012. Sociodemographic disparities in traditional air pollutant exposures from U.S. power plants are known to occur but have not been evaluated for mercury (Hg), a neurotoxicant that bioaccumulates in food webs. Atmospheric Hg deposition from domestic power plants decreased by 91% across the contiguous U.S. from 6.4 Mg in 2010 to 0.55 Mg in 2020. Prior to MATS, populations living within 5 km of power plants (n = 507) included greater proportions of frequent fish consumers, individuals with low annual income and less than a high school education, and limited English-proficiency households compared to the US general population. These results reinforce a lack of distributional justice in plant siting found in prior work. Significantly greater proportions of low-income individuals lived within 5 km of active facilities in 2020 (n = 277) compared to plants that retired after 2010, suggesting that socioeconomic status may have played a role in retirement. Despite large deposition declines, an end-member scenario for remaining exposures from the largest active power plants for individuals consuming self-caught fish suggests they could still exceed the U.S. Environmental Protection Agency reference dose for methylmercury.

Global change effects on biogeochemical mercury cycling

Past and present anthropogenic mercury (Hg) release to ecosystems causes neurotoxicity and cardiovascular disease in humans with an estimated economic cost of $117 billion USD annually. Humans are primarily exposed to Hg via the consumption of contaminated freshwater and marine fish. The UNEP Minamata Convention on Hg aims to curb Hg release to the environment and is accompanied by global Hg monitoring efforts to track its success. The biogeochemical Hg cycle is a complex cascade of release, dispersal, transformation and bio-uptake processes that link Hg sources to Hg exposure. Global change interacts with the Hg cycle by impacting the physical, biogeochemical and ecological factors that control these processes. In this review we examine how global change such as biome shifts, deforestation, permafrost thaw or ocean stratification will alter Hg cycling and exposure. Based on past declines in Hg release and environmental levels, we expect that future policy impacts should be distinguishable from global change effects at the regional and global scales.

Health risk assessment of methyl mercury from fish consumption in a sample of adult Qatari residents

Fish constitutes an essential source of high-quality protein and is, at the same time, the source of exposure to many hazardous contaminants, namely mercury and methyl mercury (MeHg). This study aims at assessing the risk that MeHg poses to the health of adult Qatari residents through fish consumption. Data on fish consumption were collected using a self-administered online survey composed of three sections that collected information about the fish-eating patterns of the participants. The fish species that were reported to be consumed by ≥ 3% of the respondents were sampled and analyzed for their total mercury (T-Hg) content levels. MeHg concentrations were derived from T-Hg content levels using a scenario-based approach. Disaggregated fish consumption and contamination data were combined using the deterministic approach to estimate MeHg intakes. The average, 75th, and 95th percentiles of the MeHg intake estimates were determined and compared to the tolerable weekly intake (TWI) set by the European Food Safety Agency (EFSA) (1.3 μg·kg^-1·w^-1). All fish samples contained T-Hg at levels ˂ 0.3-0.5 µg/g with a mean value of 0.077 µg/g. The study population had an average fish consumption of 736.0 g/week. The average estimated weekly intakes of MeHg exceeded TWI for some fish consumers including females of childbearing age and those following a high-protein diet. Our study highlights the need to establish regulatory guidelines and dietary advice based on risk/benefit ratio.

Elevated methylmercury in Antarctic surface seawater: The role of phytoplankton mass and sea ice

Methylmercury is a neurotoxin that is biomagnified in marine food webs. Its distribution and biogeochemical cycle in Antarctic seas are still poorly understood due to scarce studies. Here, we report the total methylmercury profiles (up to 4000 m) in unfiltered seawater (MeHg_T) from the Ross Sea to the Amundsen Sea. We found high MeHg_T levels in oxic unfiltered surface seawater (upper 50 m depth) in these regions. It was characterized by an obviously higher maximum concentration level of MeHg_T (up to 0.44 pmol/L, at a depth of 3.35 m), which is higher than other open seas (including the Arctic Ocean, the North Pacific Ocean and the equatorial Pacific), and a high MeHg_T average concentration in the summer surface water (SSW, 0.16 ± 0.12 pmol/ L). Further analyses suggest that the high phytoplankton mass and sea-ice fraction are important drivers of the high MeHg_T level that we observed in the surface water. For the influence of phytoplankton, the model simulation showed that the uptake of MeHg by phytoplankton would not fully explain the high levels of MeHg_T, and we speculated that high phytoplankton mass may emit more particulate organic matter as microenvironments that can sustain Hg in-situ methylation by microorganisms. The presence of sea-ice may not only harbor a microbial source of MeHg to surface water but also trigger increased phytoplankton mass, facilitating elevation of MeHg in surface seawater. This study provides insight into the mechanisms that impact the content and distribution of MeHg_T in the Southern Ocean.

Emerging mercury and methylmercury contamination from new artisanal and small-scale gold mining along the Nile Valley, Egypt

The past decade witnessed the initiation and boom of the Artisanal and Small-scale Gold Mining (ASGM) activities in the hyper-arid southern Egypt. The ores are mined in the Eastern Desert and then transported to the densely populated farming communities in the Nile Valley, where the river provides the water resources needed for ore processing. In search for economic benefits, the poorly educated farmers with limited technical resources transformed their cultivated lands into ASGM operations, exposing themselves, their families, the residents, and the Nile ecosystems to several environmental and occupational health problems. Using integrated remote sensing, field, geochemical, and isotopic analyses, we report the first inventory of ASGM-related total mercury (THg) and methylmercury (MeHg) levels in tailings, amalgamation-tailing ponds, and surface and groundwater with emphasis on the Edfu city and its surroundings. The field and remote sensing-based mapping of ASGM activities reveals clustering around the Nile waterways and suggests interaction of Hg contamination sources with their surrounding receptors. Common ASGM practices include release of contaminated water from unlined amalgamation-tailing ponds into irrigation and drainage canals, and spreading of tailings over cultivated soils. In a short period (10 years), the released Hg contaminated multiple media, including the surface water, the shallow and deep aquifers, and possibly the soil, crops, and livestock. THg levels in amalgamation-tailing ponds (1200-8470 ng/L) are fourfold higher than US EPA and eightfold the WHO thresholds. The contaminated waters released from amalgamation-tailing ponds raised THg levels in surface water (irrigation canals: 50-100 ng/L; drainage canals: THg: > 200 ng/L) and groundwater (shallow and deep aquifers: 80-500 ng/L). Our findings highlight the need to extend the adopted approach to cover the entire length of the Nile River and its valley and the importance of conducting awareness campaigns to educate residents and health care providers about potential ASGM-related environmental and health hazards.

Synergistic soil-less medium for enhanced yield of crops: a step towards incorporating genomic tools for attaining net zero hunger

Globally, industrial farming endangers crucial ecological mechanisms upon which food production relies, while 815 million people are undernourished and a significant number are malnourished. Zero Hunger aims to concurrently solve global ecological sustainability and food security concerns. Recent breakthroughs in molecular tools and approaches have allowed scientists to detect and comprehend the nature and structure of agro-biodiversity at the molecular and genetic levels, providing us an advantage over traditional methods of crop breeding. These bioinformatics techniques let us optimize our target plants for our soil-less medium and vice versa. Most of the soil-borne and seed-borne diseases are the outcomes of non-treated seed and growth media, which are important factors in low productivity. The farmers do not consider these issues, thereby facing problems growing healthy crops and suffering economic losses. This study is going to help the farmers increase their eco-friendly, chemical residue-free, quality yield of crops and their economic returns. The present invention discloses a synergistic soil-less medium that consists of only four ingredients mixed in optimal ratios by weight: vermicompost (70-80%), vermiculite (10-15%), coco peat (10-15%), and Rhizobium (0-1%). The medium exhibits better physical and chemical characteristics than existing conventional media. The vermiculite to coco peat ratio is reduced, while the vermicompost ratio is increased, with the goals of lowering toxicity, increasing plant and water holding capacity, avoiding drying of the media, and conserving water. The medium provides balanced nutrition and proper ventilation for seed germination and the growth of seedlings. Rhizobium is also used to treat the plastic bags and seeds. The results clearly show that the current synergistic soil-less environment is best for complete plant growth. Securing genetic advantages via sexual recombination, induced random mutations, and transgenic techniques have been essential for the development of improved agricultural varieties. The recent availability of targeted genome-editing technology provides a new path for integrating beneficial genetic modifications into the most significant agricultural species on the planet. Clustered regularly interspaced short palindromic repeats and associated protein 9 (CRISPR/Cas9) has evolved into a potent genome-editing tool for imparting genetic modifications to crop species. In addition, the integration of analytical methods like population genomics, phylogenomics, and metagenomics addresses conservation problems, while whole genome sequencing has opened up a new dimension for explaining the genome architecture and its interactions with other species. The in silico genomic and proteomic investigation was also conducted to forecast future investigations for the growth of French beans on a synergistic soil-less medium with the purpose of studying how a blend of vermicompost, vermiculite, cocopeat, and Rhizobium secrete metal ions, and other chemical compounds into the soil-less medium and affect the development of our target plant as well as several other plants. This interaction was studied using functional and conserved region analysis, phylogenetic analysis, and docking tools.

Perinatal Metal and Metalloid Exposures and Offspring Cardiovascular Health Risk

PURPOSE OF REVIEW

Toxic metal exposures have been associated with cardiovascular disease in adults and growing evidence suggests metal exposures also adversely affect cardiovascular phenotypes in childhood and adolescence. However, to our knowledge, the influence of perinatal metals exposure, particularly metal mixtures, in relation to cardiovascular-related outcomes have not been comprehensively reviewed.

RECENT FINDINGS

We summarized 17 contemporary studies (2017-2021) that investigated the impact of perinatal metal exposures on measures of cardiovascular health in children. Accumulating evidence supports a potential adverse impact of perinatal Pb exposure on BP in children. Fewer recent studies have focused on perinatal As, Hg, and Cd; thus, the cardiovascular impacts of these metals are less clear. Studies of metal mixtures demonstrate that interactions between metals may be complex and have identified numerous understudied elements and essential metals, including Mo, Co, Ni, Se, Zn, and Mn, which may influence cardiovascular risk. A key question that remains is whether perinatal metals exposure influences cardiovascular health into adulthood. Comparisons across studies remain challenging due to several factors, including differences in the timing of exposure/outcome assessments and exposure biomarkers, as well as variability in exposure levels and mixture compositions across populations. Future studies longitudinally investigating trajectories of cardiovascular outcomes could help determine the influence of perinatal metals exposure on long-term effects of clinical relevance in later life and whether interventions, which reduce metals exposures during this key developmental window, could alter disease development.

Effects of physical disturbance of sediment on the cycling of mercury in coastal regions

Mercury (Hg) is a global pollutant of health concern due to formation and bioaccumulation of methylmercury (MeHg) during its biogeochemical cycle. Coastal areas are important regions in the biogeochemical cycling of Hg (Liu et al., 2017), where often-occurring natural and anthropogenic perturbations affect Hg transport and transformation and the associated health risk from Hg. The rapidly growing mariculture associated with the rising global demand for food may have a profound effect on coastal Hg cycling, due to the environmental alterations (e.g., resuspension and sedimentation) caused by maricultural activities (e.g., bottom sowing and harvesting). Through simulating the effect of water scouring, a common harvesting method, this study investigated Hg migration and distribution in particulate and dissolved phases in Laizhou Bay of Bohai Sea, China, where mariculture exists extensively. Particulate total and methyl Hg (PTHg and PMeHg) in water (expressed as ng/L) increased sharply due to the resuspension of sediment, but decreased rapidly after a one-off scouring event. When normalized by particle mass, PTHg and PMeHg (ng/g) in suspended sediment particles were significantly higher than that in the initial sediment, suggesting a higher distribution coefficient and higher affinity to bind Hg in the suspended particles. This may be due to the smaller particle sizes, and higher contents of organic matter and Fe/Mn of suspended sediments compared to the initial sediment. While the concentrations of dissolved THg (DTHg) in water column showed minimum changes or decreased, dissolved MeHg (DMeHg) concentrations increased sharply after the perturbation, due to the possible release of MeHg from porewater and potential Hg methylation during the event. These results provide fundamental information needed for ecological and health risk assessment of Hg in mariculture, and highlights the increased mobility and bioaccumulation of MeHg during anthropogenic perturbations in these areas.

Hair methylmercury levels are inversely correlated with arterial stiffness

BACKGROUND AND AIMS

Cardiovascular diseases (CVD), including coronary heart disease, are the leading cause of death worldwide. Several studies investigating the relationship between fish intake, methylmercury exposure, and CVDs in adults have reported inconsistent results. This study aimed to determine the association between hair methylmercury levels and arterial stiffness using brachial-ankle pulse wave velocity (baPWV).

METHODS

This cross-sectional study included 891 seemingly healthy Korean adults (418 men and 473 women). The anthropometric and biochemical profiles, including methylmercury levels in the hair, were measured. Arterial stiffness was measured using baPWV, wherein high baPWV was defined as >1375 cm/s (>75th percentile). The odds ratios for high baPWVs were examined using multivariable logistic regression analysis after adjusting for potential confounders across the quintiles of hair methylmercury levels (Q1 = ≤0.6, Q2 = 0.6-0.8, Q3 = 0.8-1.1, Q4 = 1.1-1.5, and Q5=>1.5 μg/g).

RESULTS

After adjusting for multiple confounders-age, sex, height, body weight, smoking status, weekly alcohol consumption, total metabolic equivalent of task, mean arterial blood pressure, resting heart rate, triglycerides, low density lipoprotein cholesterol, fasting plasma glucose, uric acid and white blood cell count-the odds ratios (95% confidence intervals) for high baPWVs in each quintile of hair methylmercury levels were 1.00, 0.36 (0.17-0.76), 0.38 (0.20-0.76), 0.28 (0.13-0.61), and 0.49 (0.24-0.99), respectively.

CONCLUSIONS

Within non-toxic low levels, higher hair methylmercury levels are independently associated with lower arterial stiffness in seemingly healthy Korean adults regardless of classical cardiovascular risk factors.

Global Health Impact of Atmospheric Mercury Emissions from Artisanal and Small-Scale Gold Mining

Artisanal and small-scale gold mining (ASGM) is the leading source of mercury (Hg), a global neurotoxin. Past research has focused on the health impacts on miners and nearby residents; here, we estimate the risk for global general populations by employing a comprehensive atmosphere-land-ocean-ecosystem and exposure-risk-valuation model framework. Our results suggest that ASGM sources contribute 12%, 10%, and 0.63% to the atmospheric Hg deposition, plankton methylmercury concentrations, and soil total Hg concentrations at present day, respectively, and cause 5.8×10⁵ points of intelligence quotient decrements and 1,430 deaths for global general populations per year. The monetized global health impact of ASGM ($154 billion) is 1.5 times its local impact and accounts for half of the total revenue of ASGM ($319 billion). A major spatial decoupling between the health impact and economic gains is also revealed, suggesting that intervention measures such as awareness-raising, capacity-building, and technology transfer funded by the Global North are cost-effective.

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Contributions of ASGM to MeHg concentrations in different organisms are calculated

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The global health impact of atmospheric Hg from ASGM is first revealed

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The health impacts and economic gains of ASGM are compared

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Intervention measures for ASGM are proved to be cost-effective

Source Apportionment of Speciated Mercury in Chinese Rice Grain Using a High-Resolution Model

Rice grain consumption is a primary pathway of human mercury exposure. To trace the source of rice grain mercury in China, we developed a rice paddy mercury transport and transformation model with a grid resolution of 1 km × 1 km by using the unit cell mass conservation method. The simulated total mercury (THg) and methylmercury (MeHg) concentrations in Chinese rice grain ranged from 0.08 to 243.6 and 0.03 to 238.6 μg/kg, respectively, in 2017. Approximately, 81.3% of the national average rice grain THg concentration was due to atmospheric mercury deposition. However, soil heterogeneity, especially the variation in soil mercury, led to the wide rice grain THg distribution across grids. Approximately, 64.8% of the national average rice grain MeHg concentration was due to soil mercury. In situ methylation was the main pathway via which the rice grain MeHg concentration was increased. The coupled impact of high mercury input and methylation potential led to extremely high rice grain MeHg in partial grids among Guizhou province and junctions with surrounding provinces. The spatial variation in soil organic matter significantly impacted the methylation potential among grids, especially in Northeast China. Based on the high-resolution rice grain THg concentration, we identified 0.72% of grids as heavily polluted THg grids (rice grain THg > 20 μg/kg). These grids mainly corresponded to areas in which the human activities of nonferrous metal smelting, cement clinker production, and mercury and other metal mining were conducted. Thus, we recommended measures that are targeted at the control of heavy pollution of rice grain by THg according to the pollution sources. In addition, we observed a wide spatial variation range of MeHg to THg ratios not only in China but also in other regions of the world, which highlights the potential risk of rice intake.

The impact of mercury contamination on human health in the Arctic: A state of the science review

The 2021 Arctic Monitoring and Assessment Programme (AMAP) Mercury (Hg) Assessment is motivated by Arctic populations, and most notably Indigenous Peoples in the region, who are particularly vulnerable to Hg pollution. The objective of this review paper is to answer the following AMAP policy-relevant question: what is the human health impact of Hg pollution in the Arctic? In doing so, this state of the science review paper builds on information published 10 years ago in the last AMAP Hg assessment. The synthesized results demonstrate that: a) global influences (e.g., sources and transport pathways, biogeochemical processes, climate change, globalization) drive Hg exposures into human communities; b) Hg exposures are realized through dietary intake of certain country food items, and that new exposure science approaches are helping to deepen understandings; c) the nutritional and cultural benefits of country foods are immense, though a dietary transition is underway raising concerns over metabolic syndrome and broader issues of food security as well as cultural and social well-being; d) blood Hg measures are among the highest worldwide based on the results of human biomonitoring studies; e) Hg exposures are associated with adverse health outcomes across life stages (e.g., neurodevelopmental outcomes in young children to cardiovascular disease in adults); and f) risk communication needs to be balanced, targeted and clear, culturally appropriate, and be done collaboratively. These synthesized findings are particularly timely and policy-relevant given that the Minamata Convention entered into legal force worldwide in 2017 as a regulatory scheme to reduce the use and environmental release of Hg in order to protect human health and the environment. The Convention was influenced by health concerns raised by northern populations as indicated in the preamble text which makes reference to "the particular vulnerabilities of Arctic ecosystems and Indigenous communities".

Mercury, selenium, and fatty acids in the axial muscle of largemouth bass: evaluating the influence of seasonal and sexual changes in fish condition and reproductive status

Largemouth bass (LMB, 265-475 mm) were collected to document whether changes in fish condition and reproductive status influenced the concentration of total mercury (Hg) and selenium (Se) in axial muscle by season and sex. The fatty acid (FA) composition of fish was also examined to describe seasonal and sexual differences and identify whether arachidonic acid (ARA) could be used as a biomarker of Hg toxicity. There was a trend for females to have lower (p < 0.062) Se concentrations than males. The concentration of Se for females during spring (mean ± SD, 686 ± 51 ng/g dw) was 15% lower than males (806 ± 67 ng/g dw). Lower Se concentrations in females than males continued through summer and fall. Concentration of Hg for females during spring (152 ± 39 ng/g ww) was also 59% lower than males (373 ± 303 ng/g ww), but the difference was not significant (p > 0.2). The percent of lipids was greatest in fall and winter (3%) and comprised primarily of omega-3 fatty acids (35 g/100 g lipid). Fish condition as measured by percent lipids and relative weight was negatively (p < 0.02) related to Hg concentration for females and males. Lipid content for both sexes was also positively (p < 0.05) related to the Se:Hg ratio. Relative weight was positively related to the Se:Hg ratio for females during all seasons (p = 0.014), but only during spring and summer for males (p < 0.007). A low Se:Hg value was associated with an elevation in ARA for both sexes and a reduced hepatosomatic index in males. Data suggested that females transferred muscle stores of Se and Hg to developing oocytes during spring. This study generates hypotheses regarding the physiological drivers of seasonal and sexual variability in Hg, Se, and FA in LMB that may be applicable to other species and have implications for fisheries health and management.

Impact of dissolved organic matter and environmental factors on methylmercury concentrations across aquatic ecosystems inferred from a global dataset

Mercury (Hg) input into ecosystems is estimated to have increased by twofold to fivefold since the industrial revolution. In aquatic ecosystems, methylmercury (MeHg) receives the most attentions of all the Hg species due to its neurotoxicity and strong bioaccumulation capacity in food chain. Dissolved organic matter (DOM) is crucial in impacting aquatic Hg transformation. However, only few spatially constrained studies have attempted to quantify the relative importance of DOM and other factors (e.g., Hg availability, temperature, pH, and land-use type) on MeHg concentration. In this study, we collected data of 585 water samples at 373 sites globally, including lakes, rivers, estuaries, and wetlands, and characterized the global pattern of MeHg distribution and environmental drivers of aquatic MeHg concentration. Our results showed that MeHg concentrations ranged from detection limits to 11 (geometric mean 0.11 and average 0.29) ng/L, and the highest MeHg concentration and Hg methylation potential were observed in wetlands. A positive relationship was observed between MeHg fraction in the total mercury (THg) and DOM for all the aquatic ecosystems. Using the structural equation modeling, we found that Hg availability was a dominant factor in impacting water MeHg concentration followed by DOM. According to 129 samples of specific DOM source information, we found that the percentage of THg as MeHg (%MeHg) in water dominated by the autochthonous DOM was higher than that dominated by the allochthonous DOM. Our results could advance understanding of aquatic Hg cycling and their environmental drivers, which are fundamental for predicting and mitigating MeHg productions and its potential health risks for humans.

Mediterranean Mercury Assessment 2022: An Updated Budget, Health Consequences, and Research Perspectives

Mercury (Hg) and especially its methylated species (MeHg) are toxic chemicals that contaminate humans via the consumption of seafood. The most recent UNEP Global Mercury Assessment stressed that Mediterranean populations have higher Hg levels than people elsewhere in Europe. The present Critical Review updates current knowledge on the sources, biogeochemical cycling, and mass balance of Hg in the Mediterranean and identifies perspectives for future research especially in the context of global change. Concentrations of Hg in the Western Mediterranean average 0.86 ± 0.27 pmol L^-1 in the upper water layer and 1.02 ± 0.12 pmol L^-1 in intermediate and deep waters. In the Eastern Mediterranean, Hg measurements are in the same range but are too few to determine any consistent oceanographical pattern. The Mediterranean waters have a high methylation capacity, with MeHg representing up to 86% of the total Hg, and constitute a source of MeHg for the adjacent North Atlantic Ocean. The highest MeHg concentrations are associated with low oxygen water masses, suggesting a microbiological control on Hg methylation, consistent with the identification of hgcA-like genes in Mediterranean waters. MeHg concentrations are twice as high in the waters of the Western Basin compared to the ultra-oligotrophic Eastern Basin waters. This difference appears to be transferred through the food webs and the Hg content in predators to be ultimately controlled by MeHg concentrations of the waters of their foraging zones. Many Mediterranean top-predatory fish still exceed European Union regulatory Hg thresholds. This emphasizes the necessity of monitoring the exposure of Mediterranean populations, to formulate adequate mitigation strategies and recommendations, without advising against seafood consumption. This review also points out other insufficiencies of knowledge of Hg cycling in the Mediterranean Sea, including temporal variations in air-sea exchange, hydrothermal and cold seep inputs, point sources, submarine groundwater discharge, and exchanges between margins and the open sea. Future assessment of global change impacts under the Minamata Convention Hg policy requires long-term observations and dedicated high-resolution Earth System Models for the Mediterranean region.

Role of environmental toxicants in the development of hypertensive and cardiovascular diseases

The incidence of hypertension with diabetes mellitus (DM) as a co-morbid condition is on the rise worldwide. In 2000, an estimated 972 million adults had hypertension, which is predicted to grow to 1.56 billion by 2025. Hypertension often leads to diabetes mellitus that strongly puts the patients at an increased risk of cardiovascular, kidney, and/or atherosclerotic diseases. Hypertension has been identified as a major risk factor for the development of diabetes; patients with hypertension are at two-to-three-fold higher risk of developing diabetes than patients with normal blood pressure (BP). Causes for the increase in hypertension and diabetes are not well understood, environmental factors (e.g., exposure to environmental toxicants like heavy metals, organic solvents, pesticides, alcohol, and urban lifestyle) have been postulated as one of the reasons contributing to hypertension and cardiovascular diseases (CVD). The mechanism of action(s) of these toxicants in developing hypertension and CVDs is not well defined. Research studies have linked hypertension with the chronic consumption of alcohol and exposure to metals like lead, mercury, and arsenic have also been linked to hypertension and CVD. Workers chronically exposed to styrene have a higher incidence of CVD. Recent studies have demonstrated that exposure to particulate matter (PM) in diesel exhaust and urban air contributes to increased CVD and mortality. In this review, we have imparted the role of environmental toxicants such as heavy metals, organic pollutants, PM, alcohol, and some drugs in hypertension and CVD along with possible mechanisms and limitations in extrapolating animal data to humans.

Looping Mercury Cycle in Global Environmental-Economic System Modeling

The Minamata Convention on Mercury calls for Hg control actions to protect the environment and human beings from the adverse impacts of Hg pollution. It aims at the entire life cycle of Hg. Existing studies on the Hg cycle in the global environmental-economic system have characterized the emission-to-impact pathway of Hg pollution. That is, Hg emissions/releases from the economic system can have adverse impacts on human health and ecosystems. However, current modeling of the Hg cycle is not fully looped. It ignores the feedback of Hg-related environmental impacts (including human health impacts and ecosystem impacts) to the economic system. This would impede the development of more comprehensive Hg control actions. By synthesizing recent information on Hg cycle modeling, this critical review found that Hg-related environmental impacts would have feedbacks to the economic system via the labor force and biodiversity loss. However, the interactions between Hg-related activities in the environmental and economic systems are not completely clear. The cascading effects of Hg-related environmental impacts to the economic system throughout global supply chains have not been revealed. Here, we emphasize the knowledge gaps and propose possible approaches for looping the Hg cycle in global environmental-economic system modeling. This progress is crucial for formulating more dynamic and flexible Hg control measures. It provides new perspectives for the implementation of the Minamata Convention on Mercury.

Noninvasive Dual-Modality Photoacoustic-Ultrasonic Imaging to Detect Mammalian Embryo Abnormalities after Prenatal Exposure to Methylmercury Chloride (MMC): A Mouse Study

BACKGROUND

Severe environmental pollution and contaminants left in the environment due to the abuse of chemicals, such as methylmercury, are associated with an increasing number of embryonic disorders. Ultrasound imaging has been widely used to investigate embryonic development malformation and dysorganoplasia in both research and clinics. However, this technique is limited by its low contrast and lacking functional parameters such as the ability to measure blood oxygen saturation (SaO 2 ) and hemoglobin content (HbT) in tissues, measures that could be early vital indicators for embryonic development abnormality. Herein, we proposed combining two highly complementary techniques into a photoacoustic-ultrasound (PA-US) dual-modality imaging approach to noninvasively detect early mouse embryo abnormalities caused by methylmercury chloride (MMC) in real time.

OBJECTIVES

This study aimed to assess the use of PA-US dual-modality imaging for noninvasive detection of embryonic toxicity at different stages of growth following prenatal MMC exposure. Additionally, we compared the PA-US imagining results to traditional histological methods to determine whether this noninvasive method could detect early developmental defects in utero.

METHODS

Different dosages of MMC were administrated to pregnant mice by gavage to establish models of different levels of embryonic malformation. Ultrasound, photoacoustic signal intensity (PSI), blood oxygen saturation (SaO 2 ), and hemoglobin content (HbT) were quantified in all experimental groups. Furthermore, the embryos were sectioned and examined for pathological changes.

RESULTS

Using PA-US imaging, we detected differences in PSI, SaO 2 , HbT, and heart volume at embryonic day (E)14.5 and E11.5 for low and high dosages of MMC, respectively. More important, our results showed that differences between control and treated embryos identified by in utero PA-US imaging were consistent with those identified in ex vivo embryos using histological methods.

CONCLUSION

Our results suggest that noninvasive dual-modality PA-US is a promising strategy for detecting developmental toxicology in the uterus. Overall, this study presents a new approach for detecting embryonic toxicities, which could be crucial in clinics when diagnosing aberrant embryonic development. https://doi.org/10.1289/EHP8907.

Unravelling the interactive effect of soil and atmospheric mercury influencing mercury distribution and accumulation in the soil-rice system

Mercury (Hg) accumulation in rice is an emerging health concern worldwide. However, sources and interactions responsible for Hg species accumulation in different rice tissues are still uncertain. Four experimental plots were carefully designed at an artisanal Hg mining site and a control site to evaluate the effect of atmospheric and soil Hg contents on Hg accumulation in rice. We showed that inorganic Hg (IHg) contents in rice tissues grown either in contaminated or control site soil (non-contaminated soil) were higher at Hg artisanal mining site than those at the control site. Elevated total gaseous mercury (TGM) levels in ambient air were the predominant source of IHg to rice at the Hg mining area. Methylmercury (MeHg) concentrations in rice plant tissues increased in proportionality with MeHg contents in paddy soil. Our results suggest that both atmosphere and soil Hg sources have been impacted the IHg accumulation in rice. Above ground rice tissues, grains, leaves, and stalk accumulated IHg from both atmosphere and soil to varying degrees. Nonetheless, the study also provides the first direct evidence that atmospheric Hg accumulated by above-ground rice tissues could be translocated to below-ground tissues (roots). However, the extent to which atmosphere or soil Hg contributes to IHg in rice tissues may vary with each source's concentration gradient at the given site. No evidence of in planta Hg methylation was found during the current study. Hence, paddy fields are potential MeHg production sites, whereas paddy soil is a unique MeHg accumulation source in rice plants. This study expands and clarifies the contribution of various sources involved in Hg accumulation in the soil rice system. The findings here provide the basis for future research strategies to deal with the global issue of Hg contaminated rice.

Economic Impacts on Human Health Resulting from the Use of Mercury in the Illegal Gold Mining in the Brazilian Amazon: A Methodological Assessment

Artisanal small-scale gold mining (ASGM) in the Amazon results in the dumping of tons of mercury into the environment annually. Despite consensus on the impacts of mercury on human health, there are still unknowns regarding: (i) the extent to which mercury from ASGM can be dispersed in the environment until it becomes toxic to humans; and (ii) the economic value of losses caused by contamination becomes evident. The main objective of this study is to propose a methodology to evaluate the impacts of ASGM on human health in different contexts in the Brazilian Amazon. We connect several points in the literature based on hypotheses regarding mercury dispersion in water, its transformation into methylmercury, and absorption by fish and humans. This methodology can be used as a tool to estimate the extent of environmental damage caused by artisanal gold mining, the severity of damage to the health of individuals contaminated by mercury and, consequently, can contribute to the application of fines to environmental violators. The consequences of contamination are evaluated by dose-response functions relating to mercury concentrations in hair and the development of the following health outcomes: (i) mild mental retardation, (ii) acute myocardial infarction, and (iii) hypertension. From disability-adjusted life years and statistical life value, we found that the economic losses range from 100,000 to 400,000 USD per kilogram of gold extracted. A case study of the Yanomami indigenous land shows that the impacts of mercury from illegal gold mining in 2020 totaled 69 million USD, which could be used by local authorities to compensate the Yanomami people.

Xin-Ji-Er-Kang protects myocardial and renal injury in hypertensive heart failure in mice

BACKGROUND

Xin-Ji-Er-Kang (XJEK) as a herbal formula of traditional Chinese medicine (TCM) has shown the protective effects on myocardial function as well as renal function in mouse models of myocardial infarction.

HYPOTHESIS/PURPOSE

We investigated the effects of XJEK on cardiovascular- and renal-function in a heart failure mouse model induced by high salt (HS) and the associated mechanisms.

STUDY DESIGN

For the purpose of assessing the effects of XJEK on a hypertensive heart failure model, mice were fed with 8% high salt diet. XJEK was administered by oral gavage for 8 weeks. Cardiovascular function parameters, renal function associated biomarkers and XJEK's impact on renin-angiotensin-aldosterone system (RAAS) activation were assessed. To determine the underlying mechanism, the calpain1/junctophilin-2 (JP2)/sarcoplasmic reticulum Ca²⁺ ATPase (SERCA2a) pathway was further studied in AC16 cells after angiotensin II-challenge or after calpastatin small interfering RNA (siRNA) transfection.

RESULTS

Mice on HS-diet exhibited hypertensive heart failure along with progressive kidney injury. Similar to fosinopril, XJEK ameliorated hypertension, cardiovascular-and renal- dysfunction in mice of HS-diet group. XJEK inhibited HS-induced activation of RAAS and reversed the abnormal expression pattern of calpain1and JP2 protein in heart tissues. XJEK significantly improved cell viability of angiotensin II-challenged AC16 cells. Moreover, XJEK's impact on calpain1/JP2 pathway was partly diminished in AC16 cells transfected with calpastatin siRNA.

CONCLUSION

XJEK was found to exert cardiovascular- and renal protection in HS-diet induced heart failure mouse model. XJEK inhibited HS-diet induced RAAS activation by inhibiting the activity and expression of calpain1 and protected the junctional membrane complex (JMC) in cardiomyocytes.

Prenatal methylmercury exposure is associated with decrease heart rate variability in children

BACKGROUND

Although several epidemiological studies have suggested mercury (Hg) might be associated with cardiotoxicity, the impact of Hg exposure on cardiac autonomic activity and blood pressure in children has not been investigated at Hg exposure levels equivalent to the Environmental Protection Agency (EPA) reference dose.

OBJECTIVE

To investigate the association between low dose prenatal and recent methylmercury (MeHg) exposures and cardiac autonomic function and blood pressure with adjustment for factors such as fish consumption among children from a high fish consumption coastal city.

METHODS

Children aged 7-8 years were recruited from the birth cohort of our previous study. Heart rate variability (HRV), resting heart rate (RHR) and blood pressure were measured as surrogate markers of cardiac autonomic function. Cord blood and current whole blood Hg concentration were used as biomarkers of prenatal and recent MeHg exposure, respectively. Recent fish consumption information was estimated with a food frequency questionnaire.

RESULTS

Among 604 children, median cord blood and whole blood Hg concentrations were 45.9 nmol/L (IQR: 32.8-65.03 nmol/L) and 13.57 nmol/L (IQR: 9.29-19.72 nmol/L), respectively. Our results demonstrated that prenatal MeHg exposure was associated with decreased HRV (i.e. low CVRR, SDRR, and RMSSD), reflecting reduced parasympathetic activity (i.e. low CCV_HF and HF), and a sympathovagal balance shift toward sympathetic predominance (i.e. high %LF and LF/HF ratio). Adjustment of recent fish consumption further increased the significance and magnitude of the adverse associations of MeHg.

CONCLUSION

The results of this study suggest that prenatal MeHg exposure is associated with decreased parasympathetic modulation of cardiac autonomic function in children.

Distribution and bioavailability of mercury in the surface sediments of the Baltic Sea

The study aimed to determine the level of mercury (Hg) and its labile and stable forms in the surface sediments of the Baltic Sea. The work considers the impact of current and historical sources of Hg on sediment pollution, together with the influence of different environmental parameters, including water inflows from the North Sea. Surface sediments (top 5 cm) were collected in 2016-2017 at 91 stations located in different areas of the Baltic Sea, including Belt Sea, Arkona Basin, Bornholm Basin, Gdańsk Basin, West Gotland Basin, East Gotland Basin, and the Bothnian Sea. Besides, the particulate matter suspended in the surface and near-bottom water was also collected. The analysis of total Hg concentration and individual Hg forms in collected samples was carried out using a 5-step thermodesorption method. This method allows for the identification of three labile and thus biologically available, fractions of Hg, which are mercury halides, organic Hg, mercury oxide and sulphate. Two stable fractions, mercury sulphide and residual Hg, were also determined. The highest Hg concentrations, reaching 341 ng g-1, were measured in the highly industrialised Kiel Bay, which was additionally a munition dumping site during and after World War II. High Hg level, ranging from 228 to 255 ng g-1, was also recorded in the surface sediments of the Arkona Basin, which was a result of the cumulative effect of several factors, such as deposition of Hg-rich riverine matter, favourable hydrodynamic conditions and military activities in the past. The relatively elevated Hg concentrations, varying from 60 to 264 ng g-1, were found in the Gdańsk Basin, a region under strong anthropopressure and dominated by soft sediments. The sum of labile Hg in sediments was high and averaged 67% (with the domination of organic Hg compounds), which means that a large part of Hg can be released to the water column. It was found that the water inflows from the North Sea intensify the remobilisation of Hg and its transformation into bioavailable labile forms. As a consequence, the load of Hg introduced into the trophic chain can increase. Despite the significant reduction of Hg emission into the Baltic in the last decades, surface sediments can be an important secondary Hg source in the marine ecosystem. This is especially dangerous in the case of the western Baltic Sea.

Global health effects of future atmospheric mercury emissions

Mercury is a potent neurotoxin that poses health risks to the global population. Anthropogenic mercury emissions to the atmosphere are projected to decrease in the future due to enhanced policy efforts such as the Minamata Convention, a legally-binding international treaty entered into force in 2017. Here, we report the development of a comprehensive climate-atmosphere-land-ocean-ecosystem and exposure-risk model framework for mercury and its application to project the health effects of future atmospheric emissions. Our results show that the accumulated health effects associated with mercury exposure during 2010-2050 are $19 (95% confidence interval: 4.7-54) trillion (2020 USD) realized to 2050 (3% discount rate) for the current policy scenario. Our results suggest a substantial increase in global human health cost if emission reduction actions are delayed. This comprehensive modeling approach provides a much-needed tool to help parties to evaluate the effectiveness of Hg emission controls as required by the Minamata Convention.

Plasma and red blood cells distribution of total mercury, inorganic mercury, and selenium in maternal and cord blood from a group of Japanese women

Fetuses are a high-risk group for methylmercury (MeHg) exposure. The main objective of this study was to compare the characteristic profiles of total mercury (THg), inorganic mercury (IHg), MeHg, and selenium in plasma and red blood cells (RBCs) between maternal and cord blood at parturition collected from a group of Japanese women. Furthermore, correlations of THg in RBCs, which is a biomarker of MeHg, and THg in plasma, which is an IHg exposure biomarker, were examined in maternal and cord blood. Fifty-five pairs of maternal and cord blood samples obtained at parturition were collected from pregnant women in Fukuoka, Japan. THg in RBCs and plasma were significant correlated between maternal and cord blood. THg in RBCs was 13.9 ng/mL for cord and 9.16 ng/mL for maternal blood, with a cord:maternal RBCs ratio for THg of 1.58, suggesting that MeHg is actively transferred from the mother to the fetus via the placenta. THg in plasma showed a positive correlation with THg in RBCs for maternal and cord blood. This result suggests that measuring THg in plasma can overestimate the exposure level to IHg in fish-eating populations. The percentages of IHg in cord plasma and RBCs were 31% and 1.7%, respectively, and those in maternal plasma and RBCs were 46% and 5.9%, respectively. These results suggest that cord blood is rich in MeHg and can easily transfer to the fetal brain. Selenium in cord plasma was 67 ng/mL and that in maternal plasma was 97 ng/mL, with a cord:maternal plasma ratio for Se of 0.69, suggesting that the protective effects of Se against MeHg toxicity in fetuses may be weaker than those expected in adult mothers.

Mercury interactions with selenium and sulfur and the relevance of the Se:Hg molar ratio to fish consumption advice

Eating fish is often recommended as part of a healthful diet. However, fish, particularly large predatory fish, can contain significant levels of the highly toxic methylmercury (MeHg). Ocean fish in general also contain high levels of selenium (Se), which is reported to confer protection against toxicity of various metals including mercury (Hg). Se and Hg have a high mutual binding affinity, and each can reduce the toxicity of the other. This is an evolving area of extensive research and controversy with variable results in the animal and epidemiologic literature. MeHg is toxic to many organ systems through high affinity for -SH (thiol) ligands on enzymes and microtubules. Hg toxicity also causes oxidative damage particularly to neurons in the brain. Hg is a potent and apparently irreversible inhibitor of the selenoenzymes, glutathione peroxidases (GPX), and thioredoxin reductases (TXNRD) that are important antioxidants, each with a selenocysteine (SeCys) at the active site. Hg binding to the SeCys inhibits these enzymes, accounting in part for the oxidative damage that is an important manifestation of Hg toxicity, particularly if there is not a pool of excess Se to synthesize new enzymes. A molar excess of Se reflected in an Se:Hg molar ratio > 1 is often invoked as evidence that the Hg content can be discounted. Some recent papers now suggest that if the Se:Hg molar ratio exceeds 1:1, the fish is safe and the mercury concentration can be ignored. Such papers suggested that the molar ratio rather than the Hg concentration should be emphasized in fish advisories. This paper examines some of the limitations of current understanding of the Se:Hg molar ratio in guiding fish consumption advice; Se is certainly an important part of the Hg toxicity story, but it is not the whole story. We examine how Hg toxicity relates also to thiol binding. We suggest that a 1:1 molar ratio cannot be relied on because not all of the Se in fish or in the fish eater is available to interact with Hg. Moreover, in some fish, Se levels are sufficiently high to warrant concern about Se toxicity.

Linking metal (Pb, Hg, Cd) industrial air pollution risk to blood metal levels and cardiovascular functioning and structure among children in Syracuse, NY

BACKGROUND

Exposure to air pollution has been linked to individual health effects in occupational environments and communities proximate to air pollution sources. Use of estimated chemical concentrations from the Risk Screening Environmental Indicators (RSEI) model, derived from the Toxics Release Inventory, can help approximate some contributions to individual lifetime exposure to risk from air pollution and holds potential for linkages with specific health outcome data.

OBJECTIVES

Our objectives were: (1) use regression modeling to test for associations between observed blood metal concentrations in children and RSEI total air concentrations of the same metals released from proximate manufacturing facilities; (2) determine the relative contribution of RSEI air pollution to blood metal concentrations; and (3) examine associations between chronic metal exposure and cardiovascular functioning and structure in study participants.

METHODS

Using data synthesis methods and regression modeling we linked individual blood-based levels of lead, mercury, and cadmium(Pb, Hg, Cd) and cardiovascular functioning and structure to proximate industrial releases of the same metals captured by the Environmental Protection Agency's (EPA) RSEI geographic microdata.

RESULTS

We found that RSEI-derived ground-level ambient air concentrations of Hg and Cd were a significant predictor of blood metal levels, when controlling for covariates and other exposure variables. In addition to associations with blood metal findings, RSEI concentrations also predicted cardiovascular dysfunction and risk including changes in left-ventricular mass, blood pressure, and heart rate.

DISCUSSION

Right-to-know data, such as EPA's RSEI, can be linked to objective health outcomes, rather than simply serving as a non-specific risk estimate. These data can serve as a proxy for hazard exposure and should be used more widely to understand the dynamics of environmental exposure. Furthermore, since these data are both a product of and contribute to regulatory decision making, they could serve as an important link between disease risk and translation-orientated national environmental health policy.