Spatial distribution of groundwater fluoride and arsenic and its related disease in typical drinking endemic regions

Improved effect of antibiotic treatments on the hippocampal spatial memory dysfunction of mice induced by high fluoride exposure: Insight from assembly processes and co-occurrence networks of gut microbial community

High fluoride exposure was widely demonstrated to be related with brain memory impairment. Since the absorption of F- enters the body mainly through the gastrointestinal tract, studying the effects of excessive intake of fluoride on brain memory function in various gut microbiome states might have profound implications for the prevention of fluorosis because growing evidence revealed the significance of the "microbiota-gut-brain" axis (MGBA). In the present study, we aimed to illustrate the potential mechanism of gut microbiota on high fluoride exposure-induced hippocampal lesions and spatial memory dysfunction in mice by the various intestinal microecological environments, which were constructed by antibiotic treatment. Mice fed with normal (CG1 and Exp1 groups) or sodium-fluoride (CG2 and Exp2 groups; 24 mg/kg sodium fluoride per mouse) by gavage administration with or without antibiotic treatments, a combination of metronidazole (1 g/L) and ciprofloxacin (0.2 g/L) in drinking water. Mice gavaged with excessive sodium fluoride alone exhibited reduced weight gain, hippocampal tissue damages, spatial memory levels dysfunction, impaired intestinal permeability, decreased inflammatory cytokines expression and antioxidant capability in the hippocampal and ileal tissues. In contrast, antibiotic intervention significantly reversed these high fluoride exposure-induced hippocampal and ileal changes.16S rRNA high throughput sequencing found that ileal microbiota were dominated by abundant taxa, which is conducive to constructing microbial interaction networks and module communities, and identifying keystone species targeted by high fluoride exposure compared with colonic microbiome. In addition, the microbial community composition and assembly mechanism of ileal microbiome under the effects of antibiotics were suitable for revealing the characteristics of high fluoride environment. In the later analysis, Lactobacillus, Staphylococcus, Muribaculaceae and Robinsoniella were considered as the keystone species targeted by high fluoride-exposed mice based on the analysis of network node properties and niche overlap of ileal microbes. Spearman rank correlation demonstrated that these keystone species had significant effects on hippocampal memory levels and intestinal health, as well as microbial communities functions. Compared to previous researches, this study further revealed intestinal microbial coummunity mediated the underlying mechanism through antibiotic treatment against high fluoride-induce hippocampal spatial memory impairment.

Hydrochemical fingerprints and health risk assessment of groundwater contamination in the Bohai Sea region, China

Seawater intrusion and human activities have significantly impacted coastal groundwater quality in many regions worldwide. This study systematically assessed groundwater chemistry, its suitability for drinking and irrigation (sample size, n = 3034), and exposure risks (n = 2863) across three key sub-regions of the Bohai Sea area: Bohai Bay, Liaodong Bay, and Laizhou Bay. Significant seasonal variations observed in groundwater chemistry at different depths in Bohai Bay region, with severe contamination from salinity-alkalinity and nitrogen-fluoride. SO₄-Cl-Na type groundwater predominates in Bohai Bay and Laizhou Bay areas, primarily influenced by evaporation dissolution and seawater mixing, while carbonate weathering and reverse ion exchange play secondary roles. In the Liaodong Bay region, SO₄-Cl-Ca-Mg water is dominant, driven primarily by carbonate weathering and reverse ion exchange. Groundwater evolution over time follows a complex sequence: Bohai Bay (mainly freshening) < Liaodong Bay (freshening > intrusion) < Laizhou Bay (freshening ≈ intrusion). Groundwater in the Bohai Sea region exhibits high sodium percentage, sodium adsorption ratio, total hardness, corrosion ratio, and residual sodium carbonate, with exceedance levels ranked as Bohai Bay > Laizhou Bay > Liaodong Bay, while irrigation efficiency follows the opposite trend. Fluoride, nitrogen, and bromine contamination pose significant health risks, particularly to children, and are likely linked to both anthropogenic interventions (such as industrial layout) and natural (geological) factors. Diseases types and incidence rates among residents closely correlate with groundwater pollutant levels, emphasizing the need for targeted pollution reduction and dynamic management strategies.

Geochemical evolution, geostatistical mapping and machine learning predictive modeling of groundwater fluoride: a case study of western Balochistan, Quetta

Around 2.6 billion people are at risk of tooth carries and fluorosis worldwide. Quetta is the worst affected district in Balochistan plateau. Endemic abnormal groundwater fluoride (F - ) lacks spatiotemporal studies. This research integrates geospatial distribution, geochemical signatures, and data driven method for evaluatingF - levels and population at risk. GroundwaterF - ranged from 0 to 3.4 mg/l in (n = 100) with 52% samples found unfit for drinking. Through geospatial IDW tool hotspot areas affected with low and high groundwaterF - levels were identified. Geochemical distribution in geological setups recognized sediment variation leads to highF - (NaHCO3) and lowF - (CaHCO3) water types in low elevation (central plain) and high elevation (mountain foot) respectively. Results of the modified water quality index identified 60% samples to be unsuitable for drinking. Support vector machine (SVM), random forest regression (RFR) and classification and regression tree (CART) machine learning models foundNa + , Salinity andCa + 2 as important contributing variables in groundwaterF - prediction. CART model with R2 value of 0.732 outperformed RFR and SVM in predictingF - . Noncarcinogenic health risk vulnerability fromF - increased from Adults < Teens < Children < Infants. Infants and children with hazard quotient values of 11.3 and 4.2 were the most vulnerable population at risk for consumingF - contaminated groundwater. The research emphasizes on both nutritional need and hazardous effect ofF - , and development of desirable limit forF - .

Enrichment mechanism and probabilistic health risk assessment of high-fluoride groundwater in Gaomi City, China

Fluoride (F) is the most important inorganic pollutant in groundwater that affects human health, and analyzing the causes of high-fluoride groundwater is a prerequisite for protecting the health of residents. To comprehensively understand the enrichment characteristics of groundwater in the high-fluoride areas, this study systematically investigated the concentrations of fluoride in Gaomi City, a typical study area in the Jiaolai Plain and explored the spatiotemporal distribution patterns, enrichment mechanisms, and the probabilistic health risk associated with F-. The results indicate that there is serious fluorine pollution in groundwater, which is mainly concentrated in the alluvial plain in the north and affected by topographical and aquifer characteristics. Favorable runoff conditions effectively improve the fluoride status of shallow groundwater on both sides of rivers and in hilly areas. Hydrogeochemical methods reveal the mechanism of fluoride enrichment. The relative contributions rates of different hydrogeochemical processes to the fluoride enrichment are as follows: dissolution and precipitation (39.02%) > cation exchange (25.25%) > competitive adsorption (19.48%) > seawater intrusion (3.14%) > evaporative and concentration (1.99%). Health risk assessment based on Monte Carlo simulation shows that health risk susceptibilities of different populations are infants (76.07%), children (66.59%), teenagers (44.54%), and adults (5.68%), respectively. In addition, targeted management suggestions are put forward regarding the enrichment mechanisms of fluoride in groundwater and its impact on health. These findings have significant implications for controlling regional diffuse F- contamination in groundwater, protecting public health, and promoting social development in regions with a high risk of groundwater fluoride contamination.

Hydrochemical processes and fluoride enrichment patterns in high-fluoride geothermal water in the Weihe Basin, China

The enrichment of fluoride in the deep geothermal water of the Lantian - Bahe Formation in parts of the Weihe Basin in China is a potential health hazard for the millions of inhabitants of this region. We conducted hydrochemical and hydrogeological analyses of water samples from 31 geothermal wells in the Weihe Basin, with the aims of determining the distribution characteristics, enrichment patterns, hydrochemical processes, and the factors influencing the geochemistry of deep geothermal fluids. We also evaluated the potential health hazards of fluoride ions in these fluids. Our results show that geothermal fluids with high fluoride content are widely distributed in the deep aquifers of the Weihe Basin. The principal hydrochemical types are: HCO3-Na and SO4⋅HCO3⋅Cl-Na. We used hydrodynamic simulation and regression analysis to show that the high proportion of HCO3- in the geothermal water facilitates the precipitation of Ca2+ and the dissolution of fluorine-bearing minerals. The high temperature, alkaline environment, cation exchange reactions, and dissolution and precipitation processes lead to Ca2+ depletion, which facilitates the release of fluoride ions from the surrounding rocks into the geothermal fluids. A human health risk assessment shows that the hazard quotient (HQ) values of geothermal water for adult males, adult females, children, and infants are: 3.96 - 14.41 (median 6.55), 3.32 - 12.08 (median 4.50), 4.63 - 16.84 (median 5.50), and 7.48 - 27.22 (median 9.00), respectively. Infants are the most susceptible to the effects of high fluoride in groundwater due to their physiological characteristics. while the potential health risks of F- for children and adult women/men are relatively low. Therefore, in the process of developing deep geothermal water, it is necessary to prevent it from mixing into shallow drinking water as much as possible. If the fluoride ion content in the shallow water exceeds the standard, it may have an impact on the local environment and residents' health. These findings provide a scientific foundation for the effective management of high fluoride groundwater in the Weihe Basin and analogous regions elsewhere.

Curcumin mitigates sodium fluoride toxicity in Caenorhabditis elegans

Fluoride, a naturally occurring element found in water, soil, food, and atmospheric precipitation, can lead to fluorosis and various health issues when consumed excessively. However, the mechanism of fluorosis is still under investigation. This study utilizes Caenorhabditis elegans as a model organism to investigate the effects of fluoride exposure on biological systems and to explore the mechanisms by which curcumin mitigates fluoride-induced toxicity. Three groups were established: a blank control, a sodium fluoride (NaF) exposure group (concentration 5 mmol/L), and a curcumin intervention group (concentration 25 μmol/L). Physiological parameters, lipofuscin levels, intracellular reactive oxygen species (ROS) levels, mitochondrial membrane potential, and mitochondrial copy numbers were measured to assess the effects of fluoride toxicity and curcumin protection. RNA-seq and qRT-PCR were utilized to investigate the molecular mechanisms underlying fluoride-induced damage and curcumin's mitigating effects. Results indicated that fluoride-exposed nematodes displayed physiological abnormalities, increased ROS production, higher lipofuscin levels, altered mitochondrial membrane potential and mitochondrial copy number, and activated MAPK signaling pathway genes. Curcumin exhibited protective effects on these parameters, suggesting its potential in preventing fluoride-induced harm by modulating oxidative stress and preserving mitochondrial function. This research enhances our understanding of the mechanisms of fluoride toxicity and highlights the potential benefits of curcumin.

Impact of fluorosis on molecular predictors in pathogenesis of type 2 diabetes associated microvascular complications

AIM

This review presents specific insights on the molecular underpinnings of the connection between fluorosis, type 2 diabetes, and microvascular complications, along with the novel biomarkers that are available for early detection.

SUMMARY

Fluoride is an essential trace element for the mineralization of teeth and bones in humans. Exposure to higher concentrations of fluoride has harmful effects that significantly outweigh its advantageous ones. Dental fluorosis and skeletal fluorosis are the common side effects of exposure to fluoride, which affect millions of individuals globally. Alongside, it also causes non-skeletal fluorosis, which affects the population suffering from non-communicable diseases like diabetes by impacting the soft tissues and causing diabetic microvascular complications. Previous studies reported the prevalence range of these diabetic complications of neuropathy (3-65 %), nephropathy (1-63 %), and retinopathy (2-33 %). Fluoride contributes to the development of these complications by causing oxidative stress, cellular damage, degrading the functioning capability of mitochondria, and thickening the retinal vein basement.

CONCLUSION

Early diagnosis is a prompt way of prevention, and for that, biomarkers have emerged as an innovative and useful technique. This allows healthcare practitioners and policymakers in endemic areas to comprehend the molecular complexities involved in the advancement of diabetic microvascular problems in the context of high fluoride exposure.

Natural background level, source apportionment and health risk assessment of potentially toxic elements in multi-layer aquifers of arid area in Northwest China

Groundwater contaminated by potentially toxic elements has become an increasing global concern for human health. Therefore, it is crucial to identify the sources and health risks of potentially toxic elements, especially in arid areas. Despite the necessity, there is a notable research gap concerning the sources and risks of these elements within multi-layer aquifers in such regions. To address this gap, 54 phreatic and 24 confined groundwater samples were collected from an arid area in Northwest China. This study aimed to trace the sources and evaluate the human health risks of potentially toxic elements by natural background level (NBL), positive matrix factorization (PMF) model, and health risk model. Findings revealed exceeding levels of potentially toxic elements existed in phreatic and confined aquifers. Source apportionment and NBL results indicated that mineral dissolution, evaporation, redox reactions, and human activities were the main factors for elevated concentrations of potentially toxic elements. High Fe and Mn concentrations were attributed to reduction environments, while F accumulation resulted from slow runoff, and irrigation from the Yellow River. Due to high F levels, more than one-third of groundwater samples (phreatic: 33.14 %, confined: 56.22 %) posed non-carcinogenic health risks to population groups. Adults displayed higher carcinogenic risks (phreatic: 19.47 %, confined: 34.16 %) than infants (phreatic: 0 %, confined: 0 %) and children (phreatic: 1.26 %, confined: 7.97 %) owing to the toxic elements of Cr. The confined aquifer presented greater health risks than the phreatic aquifer. Consequently, controlling the levels of F and Cr in multi-layered aquifers is key to reducing health risks. These findings provide valuable insights into protecting groundwater from contamination by potentially toxic elements in multi-layered aquifers worldwide.

Development of modified MgO/biochar composite for chemical adsorption enhancement to cleanup fluoride-contaminated groundwater

Fluoride contamination in groundwater has become a global environmental issue. Magnesium oxide (MgO) has demonstrated effectiveness as an adsorbent in treating fluoride pollution in groundwater. However, its use in powder and fine granular form often results in losses during the adsorption process, posing challenges for post-treatment recovery and potentially causing secondary environmental pollution. In this study, two novel fluoride adsorbents [rice husk (RH) and spent coffee grounds (SCG)-based magnesium oxide (MgO) biochar composites (MgO/RH and MgO/SCG)] were developed to cleanup fluoride-polluted groundwater. During the adsorbent synthesis process, RH and SCG biochar were pyrolyzed at 500 °C and modified by calcination using MgO. Both MgO/RH and MgO/SCG surfaces exhibited abundant pore structures and formed MgO crystal phases. Batch experiments results show that when the MgO/RH and MgO/SCG material dosages were 1 g/L, fluoride removal rates reached 80% and 86% respectively. The isotherms and kinetics of fluoride adsorption with MgO/RH and MgO/SCG followed the Langmuir isotherm equation and pseudo-second-order kinetic model. The maximum fluoride adsorption capacities of MgO/RH and MgO/SCG were 63.47 mg/g and 141.98 mg/g, respectively, indicating these materials used mono-layer adsorption mechanism for fluoride adsorption. The addition of MgO into the pores of porous adsorbent materials effectively increased their reactive sites and enhanced the adsorption performance of carbon materials. Particularly, SCG biochar had a richer pore structure than RH biochar, providing a larger contact surface area, facilitating the effective dispersion and doping of MgO into the pores. Therefore, MgO/SCG composite exhibited excellent fluoride adsorption properties in water, indicating the potential for developing a new type of MgO-modified SCG adsorbent material with green prospects. This composite effectively mitigated fluoride contamination, reducing the fluoride concentration in groundwater. Both RH and SCG are agricultural and food waste by-products, thus offering the opportunity to significantly reduce production, operation, and maintenance costs.

Mobilization mechanisms and spatial distribution of arsenic in groundwater of western Bangladesh: Evaluating water quality and health risk using EWQI and Monte Carlo simulation

Arsenic (As) contamination in groundwater is emerging as a significant global concern, posing serious risks to the safety of drinking water and public health. To understand the release mechanisms, mobilization processes, spatial distribution, and probabilistic health risks of As in western Bangladesh, forty-seven samples were collected and analyzed using an atomic absorption spectrometer (AAS). The As concentrations in groundwater ranged from 1.97 to 697.4 μg L⁻1 (mean: 229.9), significantly exceeding recommended levels. The dominant hydrochemistry of As-enriched groundwater was Ca-Mg-HCO₃, with the primary sources of arsenic in groundwater being the dissolution of arsenic-bearing minerals in sediment and the recharge of aquifers from the Ganges River Basin. The assessment using the Entropy Water Quality Index revealed that the groundwater is unsuitable for drinking, with 89.36% (n = 42) of the samples surpassing the WHO's limit for arsenic. Rock-water interactions, including calcite dissolution and silicate weathering within the confined aquifer, predominantly influenced hydrochemical properties. The significant relationships among Fe, Mn, and As indicate that the reductive dissolution of FeOOH and/or MnOOH considerably contributes to the release of As from sediment into groundwater. Geochemical modeling analysis revealed that siderite and rhodochrosite precipitate into aquifer solids, suggesting a weak to moderate relationship among As, Fe, and Mn. The long residence time of groundwater, combined with the presence of a clayey aquitard, likely controls the mobilization of arsenic in the aquifer. For the first time, Monte Carlo simulations have been used in arsenic-prone areas to assess the severity of arsenic contamination in western Bangladesh. The analysis indicates that out of 100,000 people, 10 may develop cancer as a result of drinking arsenic-contaminated water, with children being more susceptible than adults.

Fluoride exposure during puberty induces testicular impairment via ER stress-triggered apoptosis in mice

Fluoride, a ubiquitous environmental compound, carries significant health risks at excessive levels. This study investigated the reproductive toxicity of fluoride exposure during puberty in mice, focusing on its impact on testicular development, spermatogenesis, and underlying mechanisms. The results showed that fluoride exposure during puberty impaired testicular structure, induced germ cell apoptosis, and reduced sperm counts in mice. Additionally, the SOD activity and GSH content were significantly decreased, while MDA content was significantly elevated in the NaF group. Immunohistochemistry showed an increase in the number of cells positive for GRP78, a key ER stress marker. Moreover, qRT-PCR and Western blot analyses confirmed the upregulation of both Grp78 mRNA and protein expression, as well as increased mRNA expression of other ER stress-associated genes (Grp94, chop, Atf6, Atf4, and Xbp1) and enhanced protein expression of phosphorylated PERK, IRE1α, eIF2α, JNK, XBP-1, ATF-6α, ATF-4, and CHOP. In conclusion, our findings demonstrate that fluoride exposure during puberty impairs testicular structure, induces germ cell apoptosis, and reduces sperm counts in mice. ER stress may participate in testicular cell apoptosis, and contribute to the testicular damage and decreased sperm counts induced by fluoride.

Industrial fluoride emissions and their spatial characteristics in the Nansi Lake Basin, Eastern China

Excessive fluoride emissions threaten ecological stability and human health. Previous studies have noted that industrial sources could be significant. However, quantifying industrial fluoride emissions has not been yet reported. In this study, both bottom-up and top-down approaches were used to estimate the fluoride emissions in the Nansi Lake Basin. Global and local spatial autocorrelation were adopted to reveal the spatial agglomeration effects. The fluoride emissions calculated by the bottom-up approach were larger than those calculated by the top-down method. The highest fluoride input mainly occurred in Zoucheng and Mudan. The highest fluoride emissions mainly occurred in Zoucheng and Rencheng using the bottom-up approach. The highest fluoride emissions mainly occurred in Zoucheng and Yanzhou using the top-down approach. Mining and washing of bituminous coal and anthracite (BAW) was the most significant source of fluoride input and emissions. A significant spatial agglomeration effect of fluoride emissions was found. These findings could provide a method for accurate industrial fluoride emission estimation, complement the critical data on the fluoride emissions of main industrial sectors, and provide a scientific basis for tracing fluoride sources.