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International Journal of Environmental... Jun 2023Minamata disease, which happened during the 1950s and 1960s in Minamata, Japan, is a well-known case of food poisoning caused by methylmercury-contaminated fish....
Minamata disease, which happened during the 1950s and 1960s in Minamata, Japan, is a well-known case of food poisoning caused by methylmercury-contaminated fish. Although many children were born, in the affected areas, with severe neurological signs after birth (known as congenital Minamata disease (CMD)), few studies have explored the possible effects of low-to-moderate methylmercury exposure in utero, probably at lower levels than in CMD patients, in Minamata. We, therefore, recruited 52 participants in 2020: 10 patients with known CMD; 15 moderately exposed residents; and 27 non-exposed controls. The average umbilical cord methylmercury concentrations were 1.67 parts per million (ppm) for CMD patients and 0.77 ppm for moderately exposed participants. After conducting four neuropsychological tests, we compared the functions among the groups. Compared with the non-exposed controls, both the CMD patients and moderately exposed residents had worse scores in the neuropsychological tests, although the score decline was more severe in the CMD patients. For example, even after adjusting for age and sex, the CMD patients and moderately exposed residents had 16.77 (95% CI: 13.46 to 20.08) and 4.11 (95% CI: 1.43 to 6.78) lower scores in the Montreal Cognitive Assessment, respectively, than the non-exposed controls. The present study indicates that residents of Minamata who experienced low-to-moderate prenatal methylmercury exposure also have neurological or neurocognitive impairments.
Topics: Animals; Foodborne Diseases; Japan; Mercury Poisoning, Nervous System; Methylmercury Compounds; Neurologic Examination; Humans
PubMed: 37372760
DOI: 10.3390/ijerph20126173 -
International Journal of Molecular... Feb 2023Exposure to chemicals may pose a greater risk to vulnerable groups, including pregnant women, fetuses, and children, that may lead to diseases linked to the toxicants'... (Review)
Review
Exposure to chemicals may pose a greater risk to vulnerable groups, including pregnant women, fetuses, and children, that may lead to diseases linked to the toxicants' target organs. Among chemical contaminants, methylmercury (MeHg), present in aquatic food, is one of the most harmful to the developing nervous system depending on time and level of exposure. Moreover, certain man-made PFAS, such as PFOS and PFOA, used in commercial and industrial products including liquid repellants for paper, packaging, textile, leather, and carpets, are developmental neurotoxicants. There is vast knowledge about the detrimental neurotoxic effects induced by high levels of exposure to these chemicals. Less is known about the consequences that low-level exposures may have on neurodevelopment, although an increasing number of studies link neurotoxic chemical exposures to neurodevelopmental disorders. Still, the mechanisms of toxicity are not identified. Here we review in vitro mechanistic studies using neural stem cells (NSCs) from rodents and humans to dissect the cellular and molecular processes changed by exposure to environmentally relevant levels of MeHg or PFOS/PFOA. All studies show that even low concentrations dysregulate critical neurodevelopmental steps supporting the idea that neurotoxic chemicals may play a role in the onset of neurodevelopmental disorders.
Topics: Child; Humans; Female; Pregnancy; Neural Stem Cells; Neurotoxicity Syndromes; Methylmercury Compounds; Hazardous Substances
PubMed: 36901772
DOI: 10.3390/ijms24054338 -
Brazilian Journal of Medical and... 2022Non-biodegradable metals such as mercury accumulate in living organisms during life (bioaccumulation) and also within trophic webs (biomagnification) and may reach high...
Non-biodegradable metals such as mercury accumulate in living organisms during life (bioaccumulation) and also within trophic webs (biomagnification) and may reach high concentrations in humans. The contamination of humans by mercury in drinking water and food may be common, in particular in riverside communities that have a diet rich in fish. In vitro studies of human cell lines exposed to the cytotoxic and mutagenic effects of methylmercury have shown that prolactin has potential cytoprotective properties and may act as a co-mitogenic factor and inhibitor of apoptosis. The present in vivo study investigated the protective potential of prolactin against the toxic effects of methylmercury in the mammal Mus musculus. Histological and biochemical analyses, together with biomarker of genotoxicity, were used to verify the protective potential of prolactin in mice exposed to methylmercury. The reduction in kidney and liver tissue damage was not significant. However, results of biochemical and genotoxic analyses were excellent. After prolactin treatment, a significant reduction was observed in biochemical parameters and mutagenic effects of methylmercury. The study results therefore indicated that prolactin has protective effects against the toxicity of methylmercury and allowed us to suggest the continuation of research to propose prolactin in the future, as an alternative to prevent the damage caused by mercury, especially in populations that are more exposed.
Topics: Animals; DNA Damage; Fishes; Humans; Mammals; Mercury; Methylmercury Compounds; Mice; Prolactin
PubMed: 35857996
DOI: 10.1590/1414-431X2022e11976 -
Brain Research Apr 2023Exploratory whole-brain studies in patients suffering from methylmercury (MeHg) poisoning have not been conducted. We aimed to evaluate the neuroanatomical differences...
Exploratory whole-brain studies in patients suffering from methylmercury (MeHg) poisoning have not been conducted. We aimed to evaluate the neuroanatomical differences between patients with chronic MeHg poisoning and healthy volunteers via magnetic resonance (MR) imaging. Patients included in this case-control study were divided into three categories based on whether MeHg exposure occurred in utero, under 15 years of age, or over 15 years of age, as fetal-, pediatric-, and adult-type patients, respectively. This study analyzed MR imaging data from 10 patients each of fetal, pediatric, and adult types of chronic MeHg poisoning in Minamata and corresponding 53, 37, and 15 age- and sex-matched healthy volunteers. Whole-brain voxel-based morphometry (VBM) analysis was used to determine the volumetric gray and white matter (GM and WM) differences in patients with chronic MeHg poisoning. Compared to healthy individuals, VBM revealed a significant reduction in GM in the cerebellar and calcarine areas in pediatric- and adult-type cases and in the thalamus of fetal-type cases. A significant reduction in WM volume was also noted in the cerebral and the cerebellar regions, especially in pediatric-type cases. Patients with chronic MeHg poisoning develop structural differences in the GM of the calcarine, the cerebellum, and the thalamus and in the WM of the cerebrum and cerebellum. These changes can appear, depending on the timing of MeHg exposure.
Topics: Adult; Humans; Child; Adolescent; Methylmercury Compounds; Case-Control Studies; Brain; Gray Matter; Cerebral Cortex; Magnetic Resonance Imaging
PubMed: 36775085
DOI: 10.1016/j.brainres.2023.148278 -
Environmental Pollution (Barking, Essex... Oct 2022Forest management can alter the mobilization of mercury (Hg) into headwater streams and its conversion to methylmercury (MeHg), the form that bioaccumulates in aquatic...
Forest management can alter the mobilization of mercury (Hg) into headwater streams and its conversion to methylmercury (MeHg), the form that bioaccumulates in aquatic biota and biomagnifies through food webs. As headwater streams are important sources of organic materials and nutrients to larger systems, this connectivity may also increase MeHg in downstream biota through direct or indirect effects of forestry on water quality or food web structure. In this study, we collected water, seston, food sources (biofilm, leaves, organic matter), five macroinvertebrate taxa and fish (slimy sculpin; Cottus cognata) at 6 sites representing different stream orders (1-5) within three river basins with different total disturbances from forestry (both harvesting and silviculture). Methylmercury levels were highest in water and some food sources from the basin with moderate disturbance (greater clearcutting but less silviculture). Water, leaves, stoneflies and fish increased in MeHg or total Hg along the river continuum in the least disturbed basin, and there were some dissipative effects of forest management on these spatial patterns. Trophic level (δN) was a significant predictor of MeHg (and total Hg in fish) within food webs across all 18 sites, and biomagnification slopes were significantly lower in the basin with moderate total disturbance but not different in the other two basins. The elevated MeHg in lower trophic levels but its reduced trophic transfer in the basin with moderate disturbance was likely due to greater inputs of sediments and of dissolved organic carbon that is more humic, as these factors are known to both increase transport of Hg to streams and its uptake in primary producers but to also decrease MeHg bioaccumulation in consumers. Overall, these results suggest that the type of disturbance from forestry affects MeHg bioaccumulation and trophic transfer in stream food webs and some longitudinal patterns along a river continuum.
Topics: Animals; Bioaccumulation; Environmental Monitoring; Fishes; Food Chain; Forests; Insecta; Mercury; Methylmercury Compounds; Water Pollutants, Chemical
PubMed: 35940481
DOI: 10.1016/j.envpol.2022.119810 -
The Science of the Total Environment Feb 2021Among populations living in close connection with the sea, rivers and lakes for subsistence, diet varies according to local monthly wildlife species availability and...
Among populations living in close connection with the sea, rivers and lakes for subsistence, diet varies according to local monthly wildlife species availability and food preferences. This may lead to variations in methylmercury (MeHg) exposure over a year, although no biomonitoring studies have documented this issue in Circumpolar populations, the most exposed to international Hg emissions. Our aim was to characterize seasonal variations in MeHg exposure among pregnant Inuit women from Nunavik and to identify country foods responsible for these variations. Between October 2016 and March 2017, 97 participants were recruited. Blood mercury (Hg) was tested and hair Hg was measured by centimeter as a surrogate for monthly MeHg exposure over the past year. Latent class growth analysis was conducted to identify groups of pregnant women with similar hair Hg monthly trajectories. Country foods consumption was documented by season. Seasonal daily intakes of MeHg were estimated based on concentrations in country foods. Retrospective monthly hair Hg analyses revealed that MeHg exposure was lowest in winter, and highest in summer and early fall months. Three latent classes (groups) of pregnant women with similar trajectories of monthly hair Hg variations were identified: high (n = 20, 21%), moderate (n = 38, 41%) and low variation (n = 35, 38%). Beluga meat was the country food contributing to most of daily MeHg intake, primarily during summer and fall, and was the only one associated with the odds of being classified into moderate and high variation groups (OR 95% CI: 1.19 [1.01-1.39] and 1.25 [1.04-1.50]). These findings underscore the importance of monthly variations in exposure to MeHg due to the seasonality of local foods consumed and responsible for elevated MeHg exposure. Further studies critically need to understand local diet fluctuations over a year to adequately assess MeHg exposure, adopt timely preventive interventions and evaluate the effectiveness of the Minamata Convention.
Topics: Canada; Diet; Environmental Exposure; Female; Humans; Inuit; Mercury; Methylmercury Compounds; Pregnancy; Pregnant Women; Retrospective Studies; Seasons
PubMed: 33183817
DOI: 10.1016/j.scitotenv.2020.143196 -
International Journal of Environmental... Jan 2022This study measures total mercury (THg), methylmercury (MeHg) and selenium (Se) concentrations in elasmobranch fish from an Italian market with the aim of evaluating the...
This study measures total mercury (THg), methylmercury (MeHg) and selenium (Se) concentrations in elasmobranch fish from an Italian market with the aim of evaluating the risk-benefit associated with their consumption, using estimated weekly intake (EWI), permissible safety level (MeHg), selenium health benefit value (HBV) and monthly consumption rate limit (CR) for each species. THg and Se were analysed by atomic absorption spectrometry, while MeHg was determined by HrGc/Ms. THg and MeHg concentrations ranged from 0.61 to 1.25 μg g w.w. and from 0.57 to 0.97 μg g w.w., respectively, whereas Se levels were 0.49-0.65 μg g w.w. In most samples European Community limits for THg were surpassed, while for MeHg none of the fish had levels above the limit adopted by FAO/WHO. EWIs for THg and MeHg in many cases were above the provisional tolerable weekly intakes (PTWIs). MeHg estimate showed that fish should contain approximately 50% of the concentration measured to avoid exceeding the PTWI. Nevertheless, the HBV index indicated that solely skates were safe for human consumption (HBV = 3.57-6.22). Our results highlight the importance of a constant monitoring of THg and MeHg level in fish, especially in apex predators, to avoid the risk of overexposure for consumers.
Topics: Animals; Elasmobranchii; Environmental Monitoring; Fishes; Humans; Mercury; Methylmercury Compounds; Seafood; Selenium; Water Pollutants, Chemical
PubMed: 35055610
DOI: 10.3390/ijerph19020788 -
Scientific Reports Feb 2020Developmental neurotoxic compounds impair the developing human nervous system at lower doses than those affecting adults. Standardized test methods for assessing...
Developmental neurotoxic compounds impair the developing human nervous system at lower doses than those affecting adults. Standardized test methods for assessing developmental neurotoxicity (DNT) require the use of high numbers of laboratory animals. Here, we use a novel assay that is based on the development of an intact insect embryo in serum-free culture. Neural pathways in the leg of embryonic locusts are established by a pair of afferent pioneer neurons, extending axons along a well-defined pathway to the central nervous system. After exposure to test chemicals, we analyze pioneer neuron shape with conventional fluorescence microscopy and compare it to 3D images, obtained by scanning laser optical tomography (SLOT) and processed by a segmentation algorithm. The segmented SLOT images resolve the 3D structure of the pioneers, recognize pathfinding defects and are thus advantageous for detecting DNT-positive compounds. The defects in axon elongation and pathfinding of pioneer axons caused by two DNT-positive reference compounds (methylmercury chloride; sodium(meta)arsenite) are compared to the biochemically measured general viability of the embryo. Using conventional fluorescence microscopy to establish concentration-response curves of axon elongation, we show that this assay identifies methylmercury chloride and the pro-apoptotic compound staurosporine as developmental neurotoxicants.
Topics: Animals; Embryo, Nonmammalian; Female; Grasshoppers; Lasers; Neural Pathways; Neurons; Neurotoxins; Tomography, Optical; Toxicity Tests
PubMed: 32060340
DOI: 10.1038/s41598-020-59562-7 -
The ISME Journal Oct 2023Brownlee Reservoir is a mercury (Hg)-impaired hydroelectric reservoir that exhibits dynamic hydrological and geochemical conditions and is located within the Hells...
Brownlee Reservoir is a mercury (Hg)-impaired hydroelectric reservoir that exhibits dynamic hydrological and geochemical conditions and is located within the Hells Canyon Complex in Idaho, USA. Methylmercury (MeHg) contamination in fish is a concern in the reservoir. While MeHg production has historically been attributed to sulfate-reducing bacteria and methanogenic archaea, microorganisms carrying the hgcA gene are taxonomically and metabolically diverse and the major biogeochemical cycles driving mercury (Hg) methylation are not well understood. In this study, Hg speciation and redox-active compounds were measured throughout Brownlee Reservoir across the stratified period in four consecutive years (2016-2019) to identify the location where and redox conditions under which MeHg is produced. Metagenomic sequencing was performed on a subset of samples to characterize the microbial community with hgcA and identify possible links between biogeochemical cycles and MeHg production. Biogeochemical profiles suggested in situ water column Hg methylation was the major source of MeHg. These profiles, combined with genome-resolved metagenomics focused on hgcA-carrying microbes, indicated that MeHg production occurs in this system under nitrate- or manganese-reducing conditions, which were previously thought to preclude Hg-methylation. Using this multidisciplinary approach, we identified the cascading effects of interannual variability in hydrology on the redox status, microbial metabolic strategies, abundance and metabolic diversity of Hg methylators, and ultimately MeHg concentrations throughout the reservoir. This work expands the known conditions conducive to producing MeHg and suggests that the Hg-methylation mitigation efforts by nitrate or manganese amendment may be unsuccessful in some locations.
Topics: Animals; Methylmercury Compounds; Nitrates; Manganese; Mercury; Archaea; Water Pollutants, Chemical
PubMed: 37495676
DOI: 10.1038/s41396-023-01482-1 -
Toxicological Sciences : An Official... Nov 2021Methylmercury (MeHg) is a developmental toxicant capable of eliciting neurocognitive and neuromuscular deficits in children with in utero exposure. Previous research in...
Methylmercury (MeHg) is a developmental toxicant capable of eliciting neurocognitive and neuromuscular deficits in children with in utero exposure. Previous research in Drosophila melanogaster uncovered that developmental MeHg exposure simultaneously targets the developing musculature and innervating motor neuron in the embryo, along with identifying Drosophila neuroligin 1 (nlg1) as a gene associated with developmental MeHg sensitivity. Nlg1 and its transsynaptic partner neurexin 1 (Nrx1) are critical for axonal arborization and NMJ maturation. We investigated the effects of MeHg exposure on indirect flight muscle (IFM) morphogenesis, innervation, and function via flight assays and monitored the expression of NMJ-associated genes to characterize the role of Nlg1 mediating the neuromuscular toxicity of MeHg. Developmental MeHg exposure reduced the innervation of the IFMs, which corresponded with reduced flight ability. In addition, nlg1 expression was selectively reduced during early metamorphosis, whereas a subsequent increase was observed in other NMJ-associated genes, including nrx1, in late metamorphosis. Developmental MeHg exposure also resulted in persistent reduced expression of most nlg and nrx genes during the first 11 days of adulthood. Transgenic modulation of nlg1 and nrx1 revealed that developing muscle is particularly sensitive to nlg1 levels, especially during the 20-36-h window of metamorphosis with reduced nlg1 expression resulting in adult flight deficits. Muscle-specific overexpression of nlg1 partially rescued MeHg-induced deficits in eclosion and flight. We identified Nlg1 as a muscle-specific, NMJ structural component that can mediate MeHg neuromuscular toxicity resulting from early life exposure.
Topics: Animals; Cell Adhesion Molecules, Neuronal; Drosophila melanogaster; Methylmercury Compounds; Muscle Development
PubMed: 34546366
DOI: 10.1093/toxsci/kfab114