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Journal of Preventive Medicine and... Nov 2012Mercury is emitted to the atmosphere from various natural and anthropogenic sources, and degrades with difficulty in the environment. Mercury exists as various species,... (Review)
Review
Mercury is emitted to the atmosphere from various natural and anthropogenic sources, and degrades with difficulty in the environment. Mercury exists as various species, mainly elemental (Hg(0)) and divalent (Hg(2+)) mercury depending on its oxidation states in air and water. Mercury emitted to the atmosphere can be deposited into aqueous environments by wet and dry depositions, and some can be re-emitted into the atmosphere. The deposited mercury species, mainly Hg(2+), can react with various organic compounds in water and sediment by biotic reactions mediated by sulfur-reducing bacteria, and abiotic reactions mediated by sunlight photolysis, resulting in conversion into organic mercury such as methylmercury (MeHg). MeHg can be bioaccumulated through the food web in the ecosystem, finally exposing humans who consume fish. For a better understanding of how humans are exposed to mercury in the environment, this review paper summarizes the mechanisms of emission, fate and transport, speciation chemistry, bioaccumulation, levels of contamination in environmental media, and finally exposure assessment of humans.
Topics: Air Pollutants; Environmental Exposure; Environmental Restoration and Remediation; Food Chain; Humans; Mercury; Methylmercury Compounds; Photolysis; Sulfur-Reducing Bacteria; Water Pollutants, Chemical
PubMed: 23230463
DOI: 10.3961/jpmph.2012.45.6.335 -
Ecotoxicology and Environmental Safety Jul 2024Boreal peatlands are "hotspots" of net methylmercury (MeHg) production and may become drier in the future due to climate change. This study investigates a critical gap...
Boreal peatlands are "hotspots" of net methylmercury (MeHg) production and may become drier in the future due to climate change. This study investigates a critical gap by analyzing the nuanced relationship between soil moisture content and the release of MeHg, inorganic mercury (IHg), sulfate (SO), and dissolved organic matter (DOM) in a laboratory incubation of boreal peat soils. Dried peat soils exhibited heightened releases of IHg, MeHg, and SO during re-wetting events. Both dried and saturated peat soils released more DOM than moist peat soils during re-wetting events, and DOM released from dried soils had higher bioaccessibility than that from the saturated soils (p<0.05). There was an equilibrium of IHg concentrations between peat soils and pore waters, but long-term severe drought may disrupt this equilibrium and then release more IHg to pore waters during re-wetting events. Contrary to expectations, positive relationships between IHg concentrations and SUVA did not exist in all treatments. MeHg and SO were depleted quickly because there was no external input of Hg and SO to this static system. More bioaccessible DOM than aromatic DOM was released from peat soils with different soil moisture contents after 32 weeks during the re-wetting event (p<0.05). These results imply that re-wetting of peat soils after droughts can increase the release of MeHg from peat soils and may also increase net MeHg production due to the release of SO and bioaccessible DOM from peat soils, reshaping our understanding of soil moisture's role in mercury dynamics. This novel insight into soil moisture and MeHg dynamics carries significant implications for mitigating mercury contamination in aquatic ecosystems.
Topics: Methylmercury Compounds; Soil; Mercury; Soil Pollutants; Environmental Monitoring; Water; Climate Change; Water Pollutants, Chemical
PubMed: 38870737
DOI: 10.1016/j.ecoenv.2024.116573 -
Environmental Research Oct 2016Rice ingestion is an important dietary exposure pathway for methylmercury. There are few studies concerning prenatal methylmercury exposure through rice ingestion, yet...
BACKGROUND
Rice ingestion is an important dietary exposure pathway for methylmercury. There are few studies concerning prenatal methylmercury exposure through rice ingestion, yet the health risks are greatest to the developing fetus, and thus should be investigated.
OBJECTIVES
Our main objective was to quantify dietary methylmercury intake through rice and fish/shellfish ingestion among pregnant mothers living in southern China, where rice was a staple food and mercury contamination was considered minimal.
METHODS
A total of 398 mothers were recruited at parturition, who donated scalp hair and blood samples. Total mercury and/or methylmercury concentrations were measured in biomarkers, in rice samples from each participant's home, and in fish tissue purchased from local markets. Additional fish/shellfish mercury concentrations were obtained from a literature search. Dietary methylmercury intake during the third trimester was equivalent to the ingestion rate for rice (or fish/shellfish)×the respective methylmercury concentration.
RESULTS
Dietary methylmercury intake from both rice and fish/shellfish ingestion averaged 1.2±1.8µg/day (median=0.79µg/day, range=0-22µg/day), including on average 71% from rice ingestion (median: 87%, range: 0-100%), and 29% from fish/shellfish consumption (median 13%, range: 0-100%). Median concentrations of hair total mercury, hair methylmercury, and blood total mercury were 0.40µg/g (range: 0.08-1.7µg/g), 0.28µg/g (range: 0.01-1.4µg/g), and 1.2µg/L (range: 0.29-8.6µg/L), respectively, and all three biomarkers were positively correlated with dietary methylmercury intake through rice ingestion (Spearman's rho=0.18-0.21, p≤0.0005), although the correlations were weak. In contrast, biomarkers were not correlated with fish/shellfish methylmercury intake (Spearman's rho=0.04-0.08, p=0.11-0.46).
CONCLUSIONS
Among pregnant mothers living in rural inland China, rice ingestion contributed to prenatal methylmercury exposure, more so than fish/shellfish ingestion.
Topics: Adult; Animals; China; Environmental Monitoring; Environmental Pollutants; Female; Fishes; Food Contamination; Hair; Humans; Maternal Exposure; Mercury; Methylmercury Compounds; Mothers; Oryza; Pregnancy; Rural Population; Shellfish; Young Adult
PubMed: 27423706
DOI: 10.1016/j.envres.2016.06.038 -
Environmental Health Perspectives Aug 1996
Comparative Study
Topics: Animals; Brain Diseases; Environmental Pollutants; Food Contamination; Humans; Mercury; Methylmercury Compounds; Risk Assessment; Seafood; United States; United States Environmental Protection Agency; United States Food and Drug Administration
PubMed: 8875154
DOI: 10.1289/ehp.96104826 -
Environmental Health : a Global Access... Jan 2013In their new paper, Bellanger and coauthors show substantial economic impacts to the EU from neurocognitive impairment associated with methylmercury (MeHg) exposures....
In their new paper, Bellanger and coauthors show substantial economic impacts to the EU from neurocognitive impairment associated with methylmercury (MeHg) exposures. The main source of MeHg exposure is seafood consumption, including many marine species harvested from the global oceans. Fish, birds and other wildlife are also susceptible to the impacts of MeHg and already exceed toxicological thresholds in vulnerable regions like the Arctic. Most future emissions scenarios project a growth or stabilization of anthropogenic mercury releases relative to present-day levels. At these emissions levels, inputs of mercury to ecosystems are expected to increase substantially in the future, in part due to growth in the legacy reservoirs of mercury in oceanic and terrestrial ecosystems. Seawater mercury concentration trajectories in areas such as the North Pacific Ocean that supply large quantities of marine fish to the global seafood market are projected to increase by more than 50% by 2050. Fish mercury levels and subsequent human and biological exposures are likely to also increase because production of MeHg in ocean ecosystems is driven by the supply of available inorganic mercury, among other factors. Analyses that only consider changes in primary anthropogenic emissions are likely to underestimate the severity of future deposition and concentration increases associated with growth in mercury reservoirs in the land and ocean. We therefore recommend that future policy analyses consider the fully coupled interactions among short and long-lived reservoirs of mercury in the atmosphere, ocean, and terrestrial ecosystems. Aggressive anthropogenic emission reductions are needed to reduce MeHg exposures and associated health impacts on humans and wildlife and protect the integrity of one of the last wild-food sources globally. In the near-term, public health advice on safe fish consumption choices such as smaller species, younger fish, and harvests from relatively unpolluted ecosystems is needed to minimize exposure risks.
Topics: Environmental Exposure; Environmental Pollutants; Female; Hair; Humans; Methylmercury Compounds; Neurotoxicity Syndromes; Pregnancy
PubMed: 23289850
DOI: 10.1186/1476-069X-12-2 -
Chemosphere Jan 2021Methylmercury (MeHg) is a ubiquitous contaminant largely found in aquatic environments, especially in species at high trophic level such as salmonids. The aim of this...
Methylmercury (MeHg) is a ubiquitous contaminant largely found in aquatic environments, especially in species at high trophic level such as salmonids. The aim of this study was to evaluate the effects of MeHg on adipocyte differentiation and lipid metabolism in rainbow trout. Primary cultured preadipocytes were exposed to increasing concentrations of MeHg during six days with or without a hormonal cocktail. Main results showed a dose-dependent intracellular accumulation of neutral lipids with a preferential uptake of n-3 polyunsaturated fatty acids. Interestingly, this accumulation occurred after a fairly low uptake of MeHg by preadipocytes and was maintained after the cellular exposure to MeHg. In membrane phospholipids, arachidonic acid (20:4 n-6) was released in a dose-dependent manner. At the transcriptional level, the expression of several adipocyte-specific genes (perilipin 2 and apolipoprotein Eb) as well as lipid-related genes (fatty acid synthase and fatty acid binding protein 11a) was up-regulated in preadipocytes exposed to MeHg. These results highlight for the first time the disrupting effect of MeHg in trout adipocyte metabolism, providing new insights regarding the role of environmental pollutants in adipose tissue dysfunction and related pathologies.
Topics: Adipocytes; Adipogenesis; Animals; Lipid Metabolism; Methylmercury Compounds; Oncorhynchus mykiss
PubMed: 33297014
DOI: 10.1016/j.chemosphere.2020.127917 -
Ecotoxicology and Environmental Safety Jun 2023By studying the dynamic characteristics of and key growth stages for mercury (Hg) enrichment in rice, the Hg migration and translocation processes in this species can be...
By studying the dynamic characteristics of and key growth stages for mercury (Hg) enrichment in rice, the Hg migration and translocation processes in this species can be better understood. In this study, a pot experiment was conducted, wherein two rice cultivars, Tianyouhuazhan (TYHZ, indica) and Zhendao 18 (ZD18, japonica), were selected and planted for analysing the Hg accumulation kinetic characteristics in rice plants. The plants were sampled at each growth stage, and the biomass and total Hg (THg) and methylmercury (MeHg) concentrations of each tissue were measured. The relative Hg contribution rates (CRs) in whole rice plants and rice grains were calculated, and the growth stage with the highest relative contribution was identified as the key growth stage for Hg accumulation. The results indicated that in rice, the MeHg translocation capability was stronger than the THg translocation capability. Significant differences in the kinetic characteristics of Hg accumulation were found between the two rice cultivars, and the TYHZ rice grains had a stronger Hg accumulation ability than the ZD18 rice grains. The key growth stages for THg accumulation in whole rice plants of both cultivars were the tillering and booting stages, while that for MeHg accumulation was the tillering stage. The key period for Hg accumulation in rice grains was the grain filling stage for both cultivars. The insights from this study could provide scientific guidance for the safe production of rice in Hg-contaminated soil.
Topics: Mercury; Oryza; Soil; Soil Pollutants; Environmental Monitoring; Methylmercury Compounds
PubMed: 37137260
DOI: 10.1016/j.ecoenv.2023.114968 -
Critical Reviews in Toxicology 2008In observational studies, the presence of confounding [corrected] can distort the true association between an exposure and a toxic-effect outcome, if the confounding... (Review)
Review
In observational studies, the presence of confounding [corrected] can distort the true association between an exposure and a toxic-effect outcome, if the confounding variable is not controlled for in the study design or analysis phase. While confounding is often assumed to occur in the same direction as the toxicant exposure, the relationship between the benefits and risks associated with fish and seafood consumption is a classic example of negative confounding: the exposure to methylmercury occurs with fish and seafood, which are also associated with beneficial nutrients, and the signs of mercury toxicity [corrected] Mercury and nutrients may affect the same epidemiological outcomes, but most studies addressing one of them have ignored the potential for negative confounding by the other. This article reviews the existing evidence of effects of both nutrient and contaminant intakes as predictors of neurodevelopmental and cardiovascular outcomes. Substantial underestimation of the effects of mercury toxicity and of fish benefits occurs from the lack of confounder adjustment and imprecision of the exposure parameters. Given this inherent bias in observational studies, regulatory agencies should reconsider current dietary advice in order to provide better guidance to consumers in making prudent choices to maintain a nutritious diet with seafood that is low in mercury concentrations. Attention should also be paid to the occurrence of negative confounding in other connections.
Topics: Animals; Fish Oils; Fishes; Food Contamination; Humans; Methylmercury Compounds; Risk Assessment; Seafood; Water Pollutants, Chemical
PubMed: 19012089
DOI: 10.1080/10408440802273164 -
Neurotoxicology and Teratology 2014Methylmercury, a worldwide contaminant of fish and seafood, can cause adverse effects on the developing nervous system. However, long-chain n-3 polyunsaturated fatty...
BACKGROUND
Methylmercury, a worldwide contaminant of fish and seafood, can cause adverse effects on the developing nervous system. However, long-chain n-3 polyunsaturated fatty acids in seafood provide beneficial effects on brain development. Negative confounding will likely result in underestimation of both mercury toxicity and nutrient benefits unless mutual adjustment is included in the analysis.
METHODS
We examined these associations in 176 Faroese children, in whom prenatal methylmercury exposure was assessed from mercury concentrations in cord blood and maternal hair. The relative concentrations of fatty acids were determined in cord serum phospholipids. Neuropsychological performance in verbal, motor, attention, spatial, and memory functions was assessed at 7 years of age. Multiple regression and structural equation models (SEMs) were carried out to determine the confounder-adjusted associations with methylmercury exposure.
RESULTS
A short delay recall (in percent change) in the California Verbal Learning Test (CVLT) was associated with a doubling of cord blood methylmercury (-18.9, 95% confidence interval [CI]=-36.3, -1.51). The association became stronger after the inclusion of fatty acid concentrations in the analysis (-22.0, 95% confidence interval [CI]=-39.4, -4.62). In structural equation models, poorer memory function (corresponding to a lower score in the learning trials and short delay recall in CVLT) was associated with a doubling of prenatal exposure to methylmercury after the inclusion of fatty acid concentrations in the analysis (-1.94, 95% CI=-3.39, -0.49).
CONCLUSIONS
Associations between prenatal exposure to methylmercury and neurobehavioral deficits in memory function at school age were strengthened after fatty acid adjustment, thus suggesting that n-3 fatty acids need to be included in analysis of similar studies to avoid underestimation of the associations with methylmercury exposure.
Topics: Attention; Child; Cohort Studies; Denmark; Fatty Acids, Essential; Fatty Acids, Omega-3; Female; Fetal Blood; Food Contamination; Humans; Infant, Newborn; Male; Mental Recall; Methylmercury Compounds; Neuropsychological Tests; Neurotoxins; Pregnancy; Prenatal Exposure Delayed Effects; Seafood
PubMed: 24561639
DOI: 10.1016/j.ntt.2014.02.003 -
Nature Communications Feb 2017A detailed understanding of the formation of the potent neurotoxic methylmercury is needed to explain the large observed variability in methylmercury levels in aquatic...
A detailed understanding of the formation of the potent neurotoxic methylmercury is needed to explain the large observed variability in methylmercury levels in aquatic systems. While it is known that organic matter interacts strongly with mercury, the role of organic matter composition in the formation of methylmercury in aquatic systems remains poorly understood. Here we show that phytoplankton-derived organic compounds enhance mercury methylation rates in boreal lake sediments through an overall increase of bacterial activity. Accordingly, in situ mercury methylation defines methylmercury levels in lake sediments strongly influenced by planktonic blooms. In contrast, sediments dominated by terrigenous organic matter inputs have far lower methylation rates but higher concentrations of methylmercury, suggesting that methylmercury was formed in the catchment and imported into lakes. Our findings demonstrate that the origin and molecular composition of organic matter are critical parameters to understand and predict methylmercury formation and accumulation in boreal lake sediments.
Topics: Ecosystem; Geologic Sediments; Lakes; Methylation; Methylmercury Compounds; Models, Theoretical; Principal Component Analysis
PubMed: 28181492
DOI: 10.1038/ncomms14255