Excess fluoride concentration in drinking water is a global issue, as this has an adverse effect on human health. Several adsorbents have been synthesized from natural raw material to remove fluoride from water. Reported adsorbents have some problems with the leaching of metal ions, fewer adsorption sites, and low adsorption capacity. Therefore, to address this, an effective biomaterial derived from the Luffa cylindrica (LC), containing many active sites, was integrated with a nano form of cerium oxide to form a robust, biocompatible, highly porous, and reusable LC–Ce adsorbent. This synthesized biosorbent offers better interaction between the active sites of LC–Ce and fluoride, resulting in higher adsorption capacity. Several factors, influence the adsorption process, were studied by a central composite design (CCD) model of statistical analysis. Langmuir’s and Freundlich’s models well describe the adsorption and kinetics governed by the pseudo–second–order model. The maximum monolayer adsorption capacity was found to be 212 and 52.63 mg/g for LC–Ce and LC, respectively determined by the Langmuir model. Detailed XPS and FTIR analyses revealed the underlying mechanism of fluoride adsorption via ion-exchange, electrostatic interaction, H–bonding, and ion-pair formation. All the results indicate that LC–Ce could serve as a suitable adsorbent for efficient fluoride removal (80–85%).

CuFeO₂/CeO₂ as a novel catalyst was synthesized and its catalytic performance was evaluated for electro-Fenton degradation of acid orange 7 (AO7). It was demonstrated from the characterization results that the rhombohedral structure of CuFeO₂ and face-centered cubic fluorite structure of CeO₂ remained stable after nanocomposite construction. The impact of such operating parameters as pH, current intensity and, catalyst amount was investigated and the optimum conditions (100 mgL⁻¹ AO7, pH 3, 150 mgL⁻¹ CuFeO₂/CeO₂, I: 150 mA) determination led to 99.3% AO7 removal and 79.1% COD removal in 60 min. The introduction of CeO₂ as non-inert support had a significant impact on H₂O₂ electro-generation as an important step in AO7 removal. CuFeO₂/CeO₂ presented negligible metal leaching (iron 4.13%, copper 2.4%, and cerium 0.33%) which could be due to the strong interaction between active species and support. The nanocomposite performed efficiently in salty systems and two samples of real wastewaters due to Brønsted acidity character of ceria, which makes it a potential choice in industrial applications. The good performance of nanocomposite could be the result of the synergistic effect between Fe, Cu, and Ce. Regarding scavenging measurements results, the electro-Fenton process followed the Haber-Weiss mechanism. The by-products detection was performed using GC-MS analysis to propose an acceptable pathway for EF degradation of AO7. The BMG kinetics model (1/b = 0.969 (min) and 1/m = 0.269 (min⁻¹)) was matched with the experimental data and described the kinetics of reaction very well. The catalytic activity of CuFeO₂/CeO₂ almost remained after six cycles. Based on the obtained results, CuFeO₂/CeO₂ using the benefit of the synergistic effect of Ce³⁺ with Fe²⁺ and Cu⁺can be introduced as a promising novel catalyst for the electro-Fenton reaction in wastewater treatment.

There is a lack of appropriate models to delineate the toxicity of rare earth elements (REEs) while taking into account the factors that affect bioavailability. Here, standardized wheat (Triticum aestivum L.) root elongation tests were conducted to examine the impact of exposure conditions (i.e., varying Ca, Mg, Na, K and pH levels) on Y and Ce toxicity. Cation competition and electrostatic theory were examined for their applicability in explaining the observed variations in toxicity. Only Ca2+ and Mg2+ significantly alleviated the toxicity of Y3+ and Ce3+, while Na+, K+ and H+ showed no significant effects. Based on the cation competition, the derived binding constants for the hypothetical biotic ligands of wheat logKCaBL, logKMgBL, logKYBL, and logKCeBL were 3.87, 3.59, 6.70, and 6.48, respectively. The biotic ligand model (BLM) succeeded in predicting toxicities of Y and Ce, with more than 93% of the variance in toxicity explained. Given the BLM requires large data sets for deriving model parameters, attempts were further made to explore a simpler electrostatic based model to quantify REEs toxicity. The results demonstrated that the predictive capacity of the electrostatic approach, which considers ion activities at the plasma membrane surface, was comparable to that of BLM with at least 87% of the variations in toxicity explained. This suggested that the electrostatic theory can serve as a surrogate to BLM in modeling Y and Ce toxicities. Therefore, we recommend the BLM and electrostatic-based model as effective approaches to incorporate bioavailability in quantifying REEs toxicity in the presence of various levels of other major cations.

Rare earth elements (REEs) have many applications in industry, agriculture, and medicine, resulting in occupational and environmental exposure and concerns regarding REE-associated health effects. However, few epidemiological studies have examined the adverse effects of REEs on pregnancy outcomes. Therefore, this study examined the relationship between the REE concentrations in maternal hair growing during early pregnancy and the risk of neural tube defects (NTDs) in offspring. We included 191 women with NTD-affected pregnancies (cases) and 261 women delivering healthy infants (controls). The cases were divided into three subtypes: anencephaly, spina bifida, and encephalocele. Four REEs in maternal hair were analyzed by inductively coupled plasma-mass spectrometry: lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd). A questionnaire was used to collect information about maternal sociodemographic characteristics and dietary habits. The median concentrations of Ce and Pr in the NTD group were higher than those in the control group, whereas there were no significant differences for La and Nd. The adjusted odds ratios (ORs) for the four REE concentrations above the median in the case groups were not significantly > 1. An increasing frequency of the consumption of beans or bean products and fresh fruit was negatively correlated with the four REE concentrations. Our results did not suggest that the concentrations of REEs in maternal hair were associated with the risk of NTDs or any subtype of NTDs in the general population.

Studies have shown that residents living near rare earth mining areas have high concentrations of rare earth elements (REEs) in their hair. However, the adverse effects of REEs on human health have rarely been the focus of epidemiological studies. The goal of this study was to evaluate the relationship between REEs in hair and the risk of hypertension in housewives. We recruited 398 housewives in Shanxi Province, China, consisting of 163 women with hypertension (cases) and 235 healthy women without hypertension (controls). We analyzed 15 REEs (lanthanum (La), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), Yttrium (Y), cerium (Ce), praseodymium (Pr), and neodymium (Nd)) and calcium (Ca) accumulated in housewives hair over a period of two years. The results revealed that, with the exception of Eu, concentrations of the REEs in hair were higher in the cases than in the controls. The univariate odds ratios (ORs) of the 14 REEs were >1, and four of the REEs (Dy, Tm, Yb, and Y) also had adjusted ORs > 1. The increasing dose-response trends of the four REEs further indicated the potential for increased hypertension risk. Moreover, the REEs were negatively correlated with Ca content in hair. These results might suggest an antagonistic effect of REEs on Ca in the human body. It was concluded that high intake of REEs might increase the risk of hypertension among housewives.

Information regarding chemical pollutant levels in farmed fish and shellfish, along with the risks associated with their consumption is still scarce. This study was designed to assess levels of exposure to 21 trace elements in fish (Dicentrarchus labrax), mussels (Mytilus galloprovincialis) and oysters (Crassostrea gigas) collected from aquaculture marine ecosystems of the northwestern Mediterranean Sea. Metal concentrations showed great variability in the three species; the highest values of the nonessential elements As and Cd were found in oysters while the highest levels of Al, Pb and V were found in mussels. The essential elements Cu, Mn and Zn were highest in oysters, but Fe, Cr, Ni, Se, Co and Mo levels were highest in mussels. Fish had the lowest concentrations for all trace elements, which were at least one order of magnitude lower than in bivalves. The rare earth elements cerium and lanthanum were found at higher levels in mussels than in oysters, but undetectable in fish. The maximum values set by European regulations for Hg, Cd and Pb were never exceeded in the examined samples. However, comparing the estimated human daily intakes (EHDIs) with the suggested tolerable copper and zinc intakes suggested a potential risk for frequent consumers of oysters. Similarly, people who consume high quantities of mussels could be exposed to concentrations of Al that exceed the proposed TWI (tolerable weekly intake).

Both occupational and environmental exposure to asbestos-mineral fibres can be associated with lung diseases. The pathogenic effects are related to the dimension, biopersistence and chemical composition of the fibres. In addition to the major mineral elements, mineral fibres contain trace elements and their content may play a role in fibre toxicity. To shed light on the role of trace elements in asbestos carcinogenesis, knowledge on their concentration in asbestos-mineral fibres is mandatory. It is possible that trace elements play a synergetic factor in the pathogenesis of diseases caused by the inhalation of mineral fibres. In this paper, the concentration levels of trace elements from three chrysotile samples, four amphibole asbestos samples (UICC amosite, UICC anthophyllite, UICC crocidolite and tremolite) and fibrous erionite from Jersey, Nevada (USA) were determined using inductively coupled plasma mass spectrometry (ICP-MS). For all samples, the following trace elements were measured: Li, Be, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, As, Rb, Sr, Y, Sb, Cs, Ba, La, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U. Their distribution in the various mineral species is thoroughly discussed.The obtained results indicate that the amount of trace metals such as Mn, Cr, Co, Ni, Cu and Zn is higher in anthophyllite and chrysotile samples, whereas the amount of rare earth elements (REE) is higher in erionite and tremolite samples. The results of this work can be useful to the pathologists and biochemists who use asbestos minerals and fibrous erionite in-vitro studies as positive cyto- and geno-toxic standard references.

The influence of pH (6.0–9.0), natural organic matter (NOM) (0–10 mg C/L) and ionic strength (IS) (1.7–40 mM) on 14 nm CeO₂ NP aggregation and ecotoxicity towards the alga Pseudokirchneriella subcapitata was assessed following a central composite design. Mean NP aggregate sizes ranged between 200 and 10000 nm. Increasing pH and IS enhanced aggregation, while increasing NOM decreased mean aggregate sizes. The 48 h-EᵣC20s ranged between 4.7 and 395.8 mg CeO₂/L. An equation for predicting the 48 h-EᵣC20 (48 h-EᵣC20 = −1626.4 × (pH) + 109.45 × (pH)² + 116.49 × ([NOM]) − 14.317 × (pH) × ([NOM]) + 6007.2) was developed. In a validation study with natural waters the predicted 48 h-EᵣC20 was a factor 1.08–2.57 lower compared to the experimental values.

Rare earth elements (REEs) concentrated in soils have attracted increasing attention about their impact on soil health as emerging contaminants. However, the sources of REEs enriched in soils are diverse and need to be further investigated. Here, surface soil samples were collected from southern Jiangxi Province, China. REEs contents and soil physicochemical properties were determined, and cerium (Ce) and europium (Eu) anomalies were calculated. Moreover, we established a model to further identify the main sources of REEs accumulation in the studied soils. Results show that the abundance of soil REEs reveals larger spatial variation, suggesting spatially heterogeneous distribution of REEs. The median content of light REEs in soils (154.5 mg kg⁻¹) of the study area was higher than that of heavy REEs and yttrium (35.8 mg kg⁻¹). In addition, most of the soil samples present negative Ce anomalies and all the soil samples present negative Eu anomalies implying the combined effect of weathering and potential exogenous inputs on soil REEs. Positive matrix factorization modeling reveals that soil REEs content is primarily influenced by soil parent materials. Potential anthropogenic sources include mining-related leachate, traffic exhaust, and industrial dust. These results demonstrate that the identification of sources of soil REEs is an important starting point for targeted REEs sources management and regulation of excessive and potentially harmful REEs levels in the soil.

The objective of this study was to evaluate the biological and nutritional characteristics of Spodoptera frugiperda (Lepidoptera: Noctuidae), an arthropod pest widely distributed in agricultural regions, after exposure to nano-CeO₂ via an artificial diet and to investigate the presence of cerium in the body of this insect through X-ray fluorescence mapping. Nano-CeO₂, micro-CeO₂, and Ce(NO₃)₃ were incorporated into the diet (0.1, 1, 10, and 100 mg of Ce L⁻¹). Cerium was detected in caterpillars fed with diets containing nano-CeO₂ (1, 10 and 100 mg of Ce L⁻¹), micro-CeO₂ and Ce(NO₃)₃, and in feces of caterpillars from the first generation fed diets with nano-CeO₂ at 100 mg of Ce L⁻¹ as well. The results indicate that nano-CeO₂ caused negative effects on S. frugiperda. After it was consumed by the caterpillars, the nano-CeO₂ reduced up to 4.8% of the pupal weight and 60% of egg viability. Unlike what occurred with micro-CeO₂ and Ce(NO₃)₃, nano-CeO₂ negatively affected nutritional parameters of this insect, as consumption rate two times higher, increase of up to 80.8% of relative metabolic rate, reduction of up to 42.3% efficiency of conversion of ingested and 47.2% of digested food, and increase of up to 1.7% of metabolic cost and 8.7% of apparent digestibility. Cerium caused 6.8–16.9% pupal weight reduction in second generation specimens, even without the caterpillars having contact with the cerium via artificial diet. The results show the importance of new ecotoxicological studies with nano-CeO₂ for S. frugiperda in semi-field and field conditions to confirm the toxicity.