A review on fluoride contamination in groundwater and human health implications and its remediation: A sustainable approaches

Contamination of drinking water due to fluoride (F-) is a major concern worldwide. Although fluoride is an essential trace element required for humans, it has severe human health implications if levels exceed 1.5 mg. L-1 in groundwater. Several treatment technologies have been adopted to remove fluoride and reduce the exposure risk. The present article highlights the source, geochemistry, spatial distribution, and health implications of high fluoride in groundwater. Also, it discusses the underlying mechanisms and controlling factors of fluoride contamination. The problem of fluoride-contaminated water is more severe in India's arid and semiarid regions than in other Asian countries. Treatment technologies like adsorption, ion exchange, precipitation, electrolysis, electrocoagulation, nanofiltration, coagulation-precipitation, and bioremediation have been summarized along with case studies to look for suitable technology for fluoride exposure reduction. Although present technologies are efficient enough to remove fluoride, they have specific limitations regarding cost, labour intensity, and regeneration requirements.

An investigation into the present levels of contamination in children's toys and jewelry in different countries: a systematic review

Contamination by heavy metals and toxic elements in children's toys and jewelry is an ongoing challenge in different countries. These contaminants can enter the children's body via oral, dermal, and respiratory routes, leading to adverse health effects. This study aimed to investigate the present levels of contamination in children's toys and jewelry in 15 countries, including UK, Saudi Arabia, Cambodia, China, Kosovo, Nigeria, North American, Kazakhstan, UAE, Pakistan, Iraq, Israel, West Bank/Palestine, Czech Republic, and Turkey. In this review, the legislation and recommendation of the United States (U.S.), the Bureau of Indian Standards (BIS), Turkish Standards Institute (TSE), Canada, and the European Union (E.U.) on toxic elements in toys and jewelry are introduced. Plastic or metallic toys and children's jewelry still have the most severe toxic elements pollution and the existence of lead (Pb), nickel (Ni), cadmium (Cd), arsenic (As), mercury (Hg), chromium (Cr), copper (Cu), selenium (Se), barium (Ba), Zinc (Zn), cobalt (Co), manganese (Mn), bisphenol A, phthalates, parabens, azo dyes, and flame retardants has been regarded as an ongoing challenge in these articles. Finally, this review offers benchmarking of the concentrations of toxic elements in all types of children's toys and jewelry in different nations.

An investigation into the association between suicide mortality rate and lithium levels in potable water: a review study

This study aimed to investigate the association between lithium levels in potable water and suicide mortality rates in the total inhabitants. We systematically searched Embase, PubMed/MEDLINE, Scopus, PubMed Central (PMC), Google Scholar databases, as well as medRxiv using the following keywords: drinking water, lithium, standardized mortality ratio (SMR), tap water, suicide, and ground water. Pearson regression analysis was used to test an association between variables with 95% confidence interval (CI). A value of P < 0.05 was considered significant. A total of 16 eligible articles were identified. Lithium concentrations in drinking water range from 0.4 to 32.9 μg/l. Average rates of suicide mortality (per 100 000 capita) range between 0.790 (±0.198) and 123 (±50). About 16 original studies confirmed the inverse relationship between lithium concentrations in potable water and suicide mortality rates (R = -0.576; R2 = 0.3323; 95% CI, -0.820 to -0.325; β = -0.3.2; P = 0.019). High lithium concentrations in potable water were associated with decreased suicide rates. We concluded that lithium concentration in potable water was inversely associated with suicide mortality rates among a total population. However, further research is required to clarify the relationship between lithium concentrations in drinking water and suicide rate.

Simultaneous removal of fluoride and nitrate from synthetic aqueous solution and groundwater by the electrochemical process using non-coated and coated anode electrodes: A human health risk study

Co-presence of fluoride (F^-) and nitrate (NO₃^-) in water causes numerous health complications. Thus, they should be eliminated by an appropriate method like the EC process. In this research, simultaneous removal of F^- and NO₃^- from synthetic aqueous solution and groundwater has been considered by the EC technique under operational parameters like anode materials (un-coated (Al and Fe) and synthesized coated (Ti/TiRuSnO₂ and Ti/PbO₂)), cathode materials (Cu, St, and Gr), current density (12, 24, and 36 mA/cm²), inter-electrode distance (0.5, 1, and 2 cm), pH (5.5, 7, and 8.5), NaCl concentrations (0.5, 1, and 1.5 g/L), electrolysis time (15, 30, 45, 60, 90, and 120 min), NO₃^- concentrations (75, 150, and 225 mg/L), and F^- concentrations (2, 4, 6, and 8 mg/L) for the first time in this research. The results proved that Al as non-coated anode and Cu as cathode electrodes were more effective in the co-removal of F^- and NO₃^-. The maximum removal efficiencies of 94.19 and 95% were observed at the current density of 36 mA/cm², 1 cm of inter-electrode distance, pH 7, 1 g/L of NaCl, and 90 min electrolysis time by Al-Cu electrode for F^- (2 mg/L) and NO₃^- (75 mg/L), respectively. The higher efficiency of Al-Cu electrodes was due to the simultaneous occurrence of electrocoagulation, electroreduction, and electrooxidation processes. Al-Cu electrode application considerably diminished f- and NO3- concentrations in the groundwater. Health risk assessment proved that HQ of F^- was significantly decreased after treatment by the Al-Cu electrode. Thus, the EC process using an appropriate and effective electrode is a promising technique for treating aqueous solutions containing F^- and NO₃^-.

Nanoarchitectonics and Kinetics Insights into Fluoride Removal from Drinking Water Using Magnetic Tea Biochar

Fluoride contamination in water is a key problem facing the world, leading to health problems such as dental and skeletal fluorosis. So, we used low-cost multifunctional tea biochar (TBC) and magnetic tea biochar (MTBC) prepared by facile one-step pyrolysis of waste tea leaves. The TBC and MTBC were characterized by XRD, SEM, FTIR, and VSM. Both TBC and MTBC contain high carbon contents of 63.45 and 63.75%, respectively. The surface area of MTBC (115.65 m²/g) was higher than TBC (81.64 m²/g). The modified biochar MTBC was further used to remediate the fluoride-contaminated water. The fluoride adsorption testing was conducted using the batch method at 298, 308, and 318 K. The maximum fluoride removal efficiency (E%) using MTBC was 98% when the adsorbent dosage was 0.5 g/L and the fluoride concentration was 50 mg/L. The experiment data for fluoride adsorption on MTBC best fit the pseudo 2nd order, rather than the pseudo 1st order. In addition, the intraparticle diffusion model predicts the boundary diffusion. Langmuir, Freundlich, Temkin, and Dubnin-Radushkevich isotherm models were fitted to explain the fluoride adsorption on MTBC. The Langmuir adsorption capacity of MTBC = 18.78 mg/g was recorded at 298 K and decreased as the temperature increased. The MTBC biochar was reused in ten cycles, and the E% was still 85%. The obtained biochar with a large pore size and high removal efficiency may be an effective and low-cost adsorbent for treating fluoride-containing water.