Residual levels and health risk assessment of rare earth elements in Chinese resident diet: A market-based investigation

Towards a European sustainable beneficiation of rare earth elements bearing minerals: a review

This review explores the multifaceted aspects of sustainable extraction of rare earth elements (REEs) bearing minerals within Europe, stressing the exploitation of local deposits, that together with the integration of cleaner and greener approaches (including circular economy approaches) might help to reduce dependency on imports and contribute to a greener economy. The mineralogical characteristics and distribution of REEs in European deposits are examined, alongside current and emerging beneficiation techniques aimed at enhancing extraction efficiency and sustainability. Key challenges, such as the mineral extraction complexities (technological and economic limitations), radiochemical and environmental impacts, as well as social acceptance, are critically assessed. Innovative and new approaches that aim to be applied to mainly primary sources (mineral deposits) but also secondary sources (secondary raw materials) are presented and suggested for a sustainable mineral extraction. Finally, Europe's over-dependence on foreign countries and prospects for the mineral extraction of REEs are discussed, outlining a strategic roadmap for achieving sustainable and economically viable extraction practices in Europe. This comprehensive and holistic analysis stresses the importance of an integrated approach that combines developing unexploited mineral resources within Europe, boosting recycling initiatives, technological innovation, implementing environmental standards and community engagement to foster a sustainable REE supply chain within Europe.

Levels of Rare Earth Elements in Food and Human Dietary Exposure: A Review

Rare earth elements (REEs) are a group consisting of the following 17 metals: Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Pm, Sc, Sm, Tb, Tm, Y and Yb. In the current century, the number of applications of REEs has significantly increased. They are being used as components in high technology devices of great importance industrial/economic. However, information on the risk of human exposure to REEs, as well as the potential toxic effects of these elements is still limited. In general terms, dietary intake is the main route of exposure to metals for non-occupationally exposed individuals, which should be also expected for REEs. The current paper aimed at reviewing the studies -conducted over the world- that focused on determining the levels of REEs in foods, as well as the dietary intake of these elements. Most studies do not suggest potential health risk for consumers of freshwater and marine species of higher consumption, or derived from the intake of a number of vegetables, fruits, mushrooms, as well as other various foodstuffs (honey, tea, rice, etc.). The current estimated daily intake (EDI) of REEs does not seem to be of concern. However, considering the expected wide use of these elements in the next years, it seems to be clearly recommendable to assess periodically the potential health risk of the dietary exposure to REEs. This is already being done with well-known toxic elements such as As, Cd, Pb and Hg, among other potentially toxic metals.

State-of-the-art Investigation on the Role of Indium, Terbium, Yttrium, and Lanthanum in Recurrent Pregnancy Loss

We aimed to explore the role of Indium (In), Terbium (Tb), Yttrium (Y), and Lanthanum (La) in the serum of women with recurrent pregnancy loss (RPL) and compare them to controls. Additionally, the study aimed to examine the relationship between REE levels and oxidative DNA damage, to identify potential risk factors contributing to RPL. This case-control study included 30 RPL cases and 30 controls with uncomplicated pregnancy. Inductively Coupled Plasma Mass Spectrometer was used to evaluate levels of In, Tb, Y, and La in the serum samples in both groups. The relationship between REE levels, Total Antioxidant Capacity (TAC), and DNA damage was studied by correlation analysis. There was a significant increase in levels of In, Tb, Y, and La in the serum of the RPL group in contrast to the control group (P < 0.001). Furthermore, a negative correlation was observed between increased Y, Tb, La, and TAC in RPL cases (significant at P < 0.05), indicative of weakened antioxidant defenses. Moreover, increased levels of Y, Tb, and La exhibited a positive correlation with the DNA damage marker, statistically significant at P < 0.05. These findings highlight the potential role of oxidative stress-induced DNA damage and metal intoxication in the development of RPL, underscoring the importance of further research to clarify underlying mechanisms and develop preventive strategies.

Discrimination of brewing technologies and assessment of health risks based on rare earth elements: Evidence of fingerprint in Chinese famous vinegars

Considering the essential influence of vinegar brewing processes on human health, this study determined the content and fractionation of rare earth elements (REEs) in 40 Chinese vinegar products to assess food safety and probe the application of REEs in tracing brewing processes. The total REEs contents in different products exhibited great variations (1.66 μg/kg to 124.54 μg/kg), which should be attributed to the difference in brewing techniques. Vinegars produced by solid brewing fermentation normally contain higher REEs contents than those produced by liquid brewing fermentation. The REEs contents in vinegars from inland areas were higher than those from coastal areas. The health risk assessment indicated that REEs contents were below the daily intake standards; however, considerable attention should be paid on the risk to children. This study contributes foundational data for understanding REEs behavior in vinegars, which is crucial for ensuring food safety and identifying the actual vinegar production process.

Transcriptional profiling of exosomes derived from serum of patients with rare earth pneumoconiosis by RNA-sequencing and PI3K/Akt pathway is activated in lung of mice exposed to rare earth Nd2O3

Rare earth is used extensively around the world, and rare earth particles cause a respiratory disease in workers termed rare earth pneumoconiosis(REP) that have attracted considerable attention. However, the mechanisms of REP, characterized by diffuse pulmonary fibrosis, are elusive. REP progression involves various signaling pathway networks comprising numerous cell types and cytokines. Acting as an important medium for communication between cells, exosomes are emerging as a major research topic. However, the role of exosomal lncRNAs, miRNAs and mRNAs in REP remains unclear. In the present study, we conducted high-throughput RNA sequencing to generate long non-coding RNA(lncRNA), microRNA (miRNA) and mRNA profiles from the serum exosomes of nine patients with rare earth pneumoconiosis and nine healthy people. Our results identified a total of 94 lncRNAs, 93miRNAs, and 29 mRNAs were differentially expressed in the serum exosomes of patients with rare earth pneumoconiosis. Subsequently, Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were used to analyze the differentially expressed RNAs. The abundant enriched GO terms of exosomal genes are cytoplasm, protein binding, cytoskeleton, Nuclear cytoplasmic transport, and KEGG pathways of exosomal genes included metabolic and cancer pathway, PI3K/Akt, wnt, mTOR, HIF-1, actin cytoskeleton and cell cycle and so on. RT-qPCR results showed that lnc-KCNMB2-AS1, hsa-miR-186-5p, hsa-miR-100-5p, hsa-miR-381-5p, NCOA4 and PLXDC1 were up-regulated, and lnc-TMEM151A, hsa-miR-758-5p and hsa-miR-6842-5p were significantly down-regulated in exosomes. In addition, our study fuond that the PI3K/Akt pathway was activated, and the expression level of miR-100-5p was increased synchronously in lung tissue of mice exposed to rare earth Nd2O3. In this study, PI3K/Akt pathway is significant helpful in elucidating the mechanism of REP. These findings can provide new insights into the mechanism of REP and develop a novel treatment strategy and biomarker.

Evaluating the bioavailability of rare earth elements in paddy soils and their uptake in rice grains for human health risk

Rare earth elements (REEs) are a critical global focus due to their increasing use, raising concerns about their environmental distribution and human exposure, both vital to food safety and human health. Surface soil (0-30 cm) and corresponding rice grain samples (n = 85) were collected from paddy fields in Taiwan. This study investigated the total REE contents in soil through aqua regia digestion, as well as their labile forms extracted using 0.05 M ethylenediaminetetraacetic acid (EDTA), 0.10 M hydrogen chloride (HCl), and 0.01 M calcium chloride (CaCl2). The REE concentrations in the rice grains (Oryza sativa L.) were also analyzed. The estimated daily intake (EDI) of REEs through rice consumption for males was 1.3 times higher than that for females. Children under 12 years of age, regardless of gender, had the highest EDI of REEs compared to other age groups. High rice consumption and a high proportion of children are potentially at higher risk for elevated REE exposure. The transport of REEs from soil to rice demonstrated their shift of fractionation by the lower ratio of light REEs and heavy REEs in rice grain compared to soil and their upper continental crust (UCC)-normalized patterns. Empirical equations were developed to estimate the concentrations of REEs in rice grains based on soil pH, clay content, organic carbon, cation exchange capacity, dithionite-citrate-bicarbonate extractable iron, and labile REEs. This study provides critical insights into the health risks of REEs, clarifying their human exposure and the bioavailability from paddy soil to rice.

Association between concentrations of rare earth elements in chorionic villus and risk for unexplained spontaneous abortion

Rare earth elements (REEs) exposure during pregnancy may increase the risk of unexplained spontaneous abortion. However, the association between REEs intrauterine exposure and unexplained spontaneous abortion had yet to be studied. In order to conduct this large case-control study, we thus collected chorionic villus from 641 unexplained spontaneous abortion and 299 control pregnant women and detected the concentrations of 15 REEs by inductively coupled plasma mass spectrometer (ICP-MS). Because the detection rates of 10 REEs were less than 80%, the remaining 5 REEs, which were lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd) and yttrium (Y), underwent to further analysis. The association between 5 REEs and unexplained spontaneous abortion was assessed by using the logistic regression, bayesian kernel regression (BKMR) and weighted quantile sum regression (WQS) models. In the adjusted logistic regression model, Pr, Nd and Y enhanced the incidence of unexplained spontaneous abortion in a dose-dependent way and Ce increased the risk only at high concentration group. The result of BKMR model demonstrated that the risk of unexplained spontaneous abortion increased as the percentile of five mixed REEs increased. Y and Nd were both significantly associated with an increased incidence of unexplained spontaneous abortion, but La was correlated with a decrease in the risk of unexplained spontaneous abortion. Pr was substantially associated with an increase in the risk of unexplained spontaneous abortion when other REEs concentrations were fixed at the 25th and 50th percentiles. According to WQS regression analysis, the WQS index was significantly associated with unexplained spontaneous abortion (OR = 3.75, 95% CI:2.40-5.86). Y had the highest weight, followed by Nd and Pr, which was consistent with the analysis results of our other two models. In short, intrauterine exposure to REEs was associated with an increased risk of unexplained spontaneous abortion, with Y, Nd and Pr perhaps playing an essential role.

Trophic Transfer and Toxic Potency of Rare Earth Elements along a Terrestrial Plant-Herbivore Food Chain

Extensive rare earth element (REE) mining activities have caused REE contamination of ambient agricultural soils, posing threats to associated food webs. Here, a simulated lettuce-snail food chain was conducted to evaluate the trophic transfer characteristics and the consequent effects of REEs on consumers. After 50-day exposure to soil, lettuce roots dose-dependently accumulated 9.4-76 mg kg-1 REEs and translocated 3.7-20 mg kg-1 REEs to shoots. Snails feeding on REE-contaminated shoots accumulated 3.0-6.7 mg kg-1 REEs with trophic transfer factors of 0.20-0.98, indicating trophic dilution in the lettuce-snail system. REE profiles in lettuce and snails indicated light REE (LREE) enrichment only in snails and the varied REE profiles along the food chain. This was corroborated by toxicokinetics. Estimated uptake (Ku) and elimination (Ke) parameters were 0.010-2.9 kgshoot kgsnail-1 day-1 and 0.010-1.8 day-1, respectively, with higher Ku values for LREE and HREE. The relatively high Ke, compared to Ku, indicating a fast REE elimination, supports the trophic dilution. Dietary exposure to REEs dose-dependently affected gut microbiota and metabolites in snails. These effects are mainly related to oxidative damage and energy expenditure, which are further substantiated by targeted analysis. Our study provides essential information about REE bioaccumulation characteristics and its associated risks to terrestrial food chains near REE mining areas.

Associations between maternal urinary rare earth elements during pregnancy and birth weight-for-gestational age: Roles of cord blood vitamin D levels

Prenatal exposure to rare earth elements (REEs) may contribute to adverse birth outcomes in previous studies. Cord blood vitamin D has been suggested to modify or mediate the effects of environmental exposures. However, none has investigated these roles of cord blood vitamin D in the associations of prenatal exposure to REEs with fetal growth. Maternal trimester-specific urinary concentrations of 13 REEs, cord blood total 25-hydroxyvitamin D at delivery, and birth weight (BW)-for-gestational age (GA) were determined in 710 mother-newborn pairs from Wuhan, China. Higher maternal average urinary concentrations of europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), erbium (Er), and ytterbium (Yb) across three trimesters, either individually or jointly, were significantly associated with lower BW-for-GA Z-scores and higher odds of small for gestational age (SGA) [β = -0.092; 95 % confidence interval (CI): -0.149, -0.035 for BW-for-GA Z-scores, and odds ratio = 1.60; 95 % CI: 1.14, 2.24 for SGA involved in each unit increase in weighted quantile sum index of REEs mixture]. When stratified by cord blood vitamin D levels, the associations mentioned above persisted in participants with relatively low vitamin D levels (<13.94 μg/L, the first tertile of distribution), but not among those with relatively high levels (≥13.94 μg/L) (all p-values for interaction < 0.05). The mediation analyses taking account of exposure-mediator interaction showed that the relationships between REEs (as individual and mixture) exposure and lower BW-for-GA were partly mediated through decreasing cord blood vitamin D levels. The proportions mediated by cord blood vitamin D levels were 24.48 % for BW-for-GA Z-scores and 29.05 % for SGA corresponding to the REEs mixture exposure. Conclusively, our study revealed that prenatal exposures to Eu, Gd, Dy, Ho, Er, and Yb were related to fetal growth restriction. Cord blood vitamin D might alleviate toxic effects of these REEs and its reduction might partly mediate REE-induced fetal growth restriction.

A human health risk assessment of rare earth elements through daily diet consumption from Bayan Obo Mining Area, China

Rare earth elements (REEs) have been broad application in a range of industries, including the electronics industry, advanced materials, and medicine. However, health risks associated with REEs received increasing attention. 31 residents (16 males and 15 females) from Bayan Obo mining in Inner Mongolia, China, were enrolled in this study. In total, 677 food samples, the major human exposure matrices (drinking water and duplicate diets), and bio-samples (urine and blood) of 31 participants were obtained. The concentrations of REEs were measured to characterize their external and internal exposures, and the potential health risk of exposure to REE through the ingestion route was analyzed. The results revealed that the detection rate in blood samples (100%) is higher than in urine (32.86%), and only a few REEs were detected in water samples (8.06%), the urine concentrations were considerably lower than in blood. Exposure to REEs through drinking water was considered negligible compared to food intake. Lanthanum and cerium were the most concentrated REEs in food samples. Health risks were calculated based on a dose-response model, the total hazard quotients (THQ) values for all food groups were within normal levels, and the Monte Carlo simulation results show that the 5th, the 50th, and the 95th percentile values of HI were found as 1.45 × 10-2, 3.52 × 10-2, and 9.13 × 10-2, respectively, neither exceeds the threshold, indicating low health risks associated with food intake exposure for this area. The sensitivity results suggest that underweight people are at higher risk, cerium, lanthanum, and yttrium concentrations, and food intake contributes more to health risks. The use of probability distribution methods can improve the accuracy of the results. The cumulative health risk through food intake is negligible, and further attention should be paid to the health risk induced by other routes of exposure to REEs by the local residents.

Association between light rare earth elements in maternal plasma and the risk of spontaneous preterm birth: a nested case-control study from the Beijing birth cohort study

BACKGROUND

Parental exposure to rare earth elements (REEs) could increase the risk of premature rupture of membranes, a major cause of spontaneous preterm birth (SPB). In addition, different subtypes of SPB, such as spontaneous preterm labor (SPL) and preterm premature rupture of membranes (PPROM), may have different susceptibility to environmental exposure. Therefore, we investigated the potential associations between REE exposure in different trimesters and SPB and its subtypes.

METHODS

A nested case-control study was performed. We included 244 women with SPB as cases and 244 women with full-term delivery as controls. The plasma concentrations of light REEs were measured in the first and third trimesters. Logistic regression was used to analyze the associations between single REE levels and SPB, and Bayesian kernel machine regression (BKMR) was used to analyze the mixed-exposure effect.

RESULTS

Exposure to light REEs was associated with SPB and its subtypes only in the third trimester. Specifically, the intermediate- and highest-tertile concentration groups of La and the highest-tertile concentration group of Sm were associated with an increased risk of SPL, with adjusted odds ratios (AORs) of 2.00 (95% CIs: 1.07-3.75), 1.87 (95% CIs: 1.01-3.44), and 1.82 (95% CIs: 1.00-3.30), respectively. The highest-tertile concentration group of Pr was associated with an increased risk of PPROM, with an AOR of 1.69 (95% CIs: 1.00-2.85). Similar results were also found in BKMR models.

CONCLUSIONS

La and Sm levels in plasma may be associated with the risk of SPL, and Pr levels in plasma may be associated with the risk of PPROM.

Quantification of rare earth elements in Australian and imported rice samples from different origins using ICP-MS

Rare earth elements (REEs) are also known as lanthanides and are comprised of seventeen elements including lanthanum to lutetium in the periodic table. Despite their increased utilization, little attention is given to them as emerging environmental contaminants and their associated health risks. The concentration of these elements in urban and agronomic soil may trigger bioaccumulation in plants and may enter the food chain. Also, the consumption of fertilizers in agricultural practices on a larger scale is a significant challenge. The REEs enriched fertilizers are a risk factor for contamination in soil and food. However, there is very limited data in the literature regarding the occurrence of these elements in a staple food such as rice. Thus, this study is aimed at quantification of rare earth elements in Australian and imported rice samples from different countries by using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The developed analytical method was validated by using two certified reference materials (CRMs) for precision and accuracy. The method was applied for analysing rice samples (including polished, brown, and parboiled) imported from different countries and sourced locally and consumed by the Australian population. The average concentration of REEs in Australian, Thailand and Vietnamese rice samples were quantified as 0.013-2.974 μg/kg, 0.012-3.113 μg/kg, 0.009-0.919 μg/kg respectively and were lower than other countries. The highest average concentrations of REEs were found in Pakistan (0.299-128.2 μg/kg), India (0.063-20.574 μg/kg), and Sri Lankan (0.022-11.522 μg/kg) rice samples imported to Australia. Scandium and yttrium were found in the range of 107.463-85.961 μg/kg. The pattern of Light rare earth elements (LREE) was more abundant than heavy rare earth elements (HREE). This study did not include field experiments to find the translocation factors of REEs from soil to different parts of plant bodies, thus cannot establish the correlation between fertilizers and REEs concentration in rice grains. However, this study presented the general interpretation of REEs quantification in rice grains from different Countries. The outcome of this study includes filling the subsequent knowledge gaps in analysing REEs in rice. This study indicated the need to establish a monitoring program for this type of staple cereals, aiming at promoting public health.

Hair-biomonitoring assessment of rare-earth-element exposure in residents of the largest rare-earth mining and smelting area of China

The long-term and large-scale mining of rare earth minerals may lead to an accumulation of rare earth elements (REEs) in the environment, posing potential health risks to residents. We collected scalp hair (n = 254) from residents of a smelting area, a mining area, and a reference area to clarify human exposure to REEs. The contents of 15 REEs investigated in human hair samples were notably higher in the mining and smelting areas than in the reference area. Significant differences between some REEs were observed between the mining and smelting areas, for instance, cerium (Ce), dysprosium, and praseodymium. In the study areas, exposure to different sources of REEs may be one of the factors that contributed to the variations of REE correlations and clusters in human hair. Furthermore, in the smelting area, Ce contents in hair decreased with increasing age of children. However, Ce contents in the hair of adults increased with age. In contrast, Ce accumulation continuously increased in the reference area residents' hair with age. Regression results indicated that age and location were more important than sex when considering the influence on REE accumulation in residents' hair. The results of this study may help policymakers to implement guidelines to alleviate residents' exposure to REE in mining and smelting areas.

Neodymium affects the generation of reactive oxygen species via GSK-3β/Nrf2 signaling in the gill of zebrafish

Rare earth element neodymium (Nd) is widely used in industry and agriculture, which may result in the pollution of aquatic environment. In this study, we exposed zebrafish with 10, 50, and 100 μg/L Nd for four weeks. The results showed that Nd could be accumulated in fish gill and Nd accumulation affected the equilibrium of nutrient elements. Nd decreased the antioxidant enzymes' activity and gene expression level, but enhanced the generation of reactive oxygen species (ROS). Moreover, various concentration of Nd treatments inhibited Nrf2 signaling in gill. To examine the critical role of GSK-3β/Nrf2 signaling on ROS generation under Nd stress, we further interfered gsk-3β gene in zebrafish under 100 μg/L Nd exposure. The result showed that gsk-3β gene interference induced Nrf2 signaling as well as the expression and activity of antioxidant enzymes in fish gill. In all, Nd could be accumulated in fish gill, and the signaling of GSK-3β/Nrf2 was involved in regulating ROS generation under Nd treatments.

Cytotoxicity and hemolysis of rare earth ions and nanoscale/bulk oxides (La, Gd, and Yb): Interaction with lipid membranes and protein corona formation

The widespread application of rare earth elements (REEs) has raised concerns about their potential release into the environment and subsequent ingestion by humans. Therefore, it is essential to evaluate the cytotoxicity of REEs. Here, we investigated the interactions between three typical REEs (La, Gd, and Yb) ions as well as their nanometer/μm-sized oxides and red blood cells (RBCs), a plausible contact target for nanoparticles when they enter the bloodstream. Hemolysis of REEs at 50-2000 μmol L^-1 was examined to simulate their cytotoxicity under medical or occupational exposure. We found that the hemolysis due to the exposure of REEs was highly dependent on their concentration, and the cytotoxicity followed the order of La³⁺ > Gd³⁺ > Yb³⁺. The cytotoxicity of REE ions (REIs) is higher than REE oxides (REOs), while nanometer-sized REO caused more hemolysis than that μm-sized REO. The production of reactive oxygen species (ROS), ROS quenching experiment, as well as the detection of lipid peroxidation, confirmed that REEs causes cell membrane rupture by ROS-related chemical oxidation. In addition, we found that the formation of a protein corona on REEs increased the steric repulsion between REEs and cell membranes, hence mitigating the cytotoxicity of REEs. The theoretical simulation indicated the favorable interaction of REEs with phospholipids and proteins. Therefore, our findings provide a mechanistic explanation for the cytotoxicity of REEs to RBCs once they have entered the blood circulation system of organisms.

Research progress on the content and distribution of rare earth elements in rivers and lakes in China

This study reviewed the content and distribution of rare earth elements (REE) in rivers and lakes in China based on the online literature. The sequence distribution of REE presented the decreasing trends in the order: of Ce > La > Nd > Pr > Sm > Gb > Dy>Er > Yb > Eu > Lu > Ho > Tb > Tm in rivers water. Pearl River and the Jiulong River constitute a significant sediments REE reservoir with an average value mean of 229.6 mg/kg and 266.86 mg/kg, respectively; both have higher concentrations than the global river average (174.8 mg/kg) and higher than the local soil background (Chinese soil background). The Liaohe River is one of China's most polluted rivers, with REE distribution ranging from 106.61 to 174.71 g/L (average 144.59 g/L in water). The total concentrations of dissolved REE in rivers near REE mining areas in China are higher than in other rivers. Increasing anthropogenic inputs to natural systems may permanently alter the natural signatures of REE. The distribution characteristics of REE in Chinese lakes (sediments) varied greatly, and the mean enrichment factor (EF) was sorted as follows: Ce > La > Nd > Pr > Sm > Gd > Dy>Er > Yb > Eu > Ho > Tb > Tm > Lu, where Ce was the most abundant followed by La, Nd, and Pr, and these four elements account for 85.39 % of the total concentration of REE. The REE in the sediments obtained from Poyang Lake and Dongting Lake had an average concentration respectively of 254.0 μg/g and 197.95 μg/g; both are considerably higher than the average upper continental crust (146.4 μg/g) and higher than in other lakes in China and around the world. The distribution and accumulation of LREE in most lake sediments result from the joint action of human activities and natural processes. It concluded that mining tailings were the primary cause of REE pollution in sediments, and industrial and agricultural activities are mainly responsible for water contamination.

Fate and Trophic Transfer of Rare Earth Elements in a Tropical Estuarine Food Web

We sampled abiotic and food web components in an impacted estuarine system to assess the transfer and fate of rare earth elements (REE). REE (based on dry weight) were measured in sediments, suspended particulate matter (SPM), and organisms from different trophic levels. The highest ∑REE concentrations were measured in sediments (180 ± 4.24 mg kg^-1) and SPM (163 ± 12.6 mg kg^-1). Phytoplankton (45.7 ± 5.31 mg kg^-1), periphyton (51.6 ± 1.81 mg kg^-1), and zooplankton (68.5 ± 1.27 mg kg^-1) are the major sources of exposure and transfer of REE to the food web. REE concentrations were several orders of magnitude lower in bivalves, crustaceans, and fish (6.01 ± 0.11, 1.22 ± 0.18, and 0.059 ± 0.003 mg kg^-1, respectively) than in plankton. The ∑REE declined as a function of the trophic position, as determined by functional feeding groups and δ¹⁵N, indicating that REE were subject to trophic dilution. Our study suggests that the consumption of seafood is unlikely to be an important source of REE for humans. However, given the numerous sources of dietary introduction of REE, they should be monitored for a possible harmful cumulative effect. This study provides new key information on REE's baseline concentrations and trophic transfers and patterns.

Dietary Exposure Assessment of Rare Earth Elements in the Chinese Population

Rare earth elements (REEs) are widely found in foods. A high intake of REEs may have associations with adverse effects on human health. This study aimed to investigate the concentrations of REEs in foods in China and to assess the risk of dietary REEs exposure in the Chinese population. The mean concentrations of the total REEs in 27,457 food samples from 11 food categories ranged from 0.04 to 1.41 mg/kg. The daily mean dietary exposure of the total REEs was 1.62 μg/kg BW in the general Chinese population and ranged from 1.61 to 2.80 μg/kg BW in different sex-age groups. The high consumer exposure (95th percentile, P95) was 4.83 μg/kg BW, 9.38% of the temporary ADI (tADI) of REEs (51.5 μg/kg BW). None of the P95 exposure exceeded the tADI in all of the sub-groups. Lanthanum, cerium, and yttrium accounted for approximately 63% of the total exposure of the 16 REEs. The hazard index of 16 REEs was far below 1. Therefore, the health risk of dietary REEs exposure in the general Chinese population was low. No cumulative risk was found for the 16 REEs in China. The results indicate there was no need to stipulate the limits of REEs in foods.

Occupational exposure to rare earth elements: Assessment of external and internal exposure

Our study investigated occupational exposure to rare earth elements (REEs) in a major REE processing plant from North China by assessing both external exposure and internal exposure in the workers. An exposure group, including 50 workers in the processing plant, and a control group, including 50 workers from a liquor factory located 150 km away from the exposure group, were recruited in the study. Portable air sampler was employed to accurately measure individual exposure to the external environment, and the data demonstrating significantly higher contamination in the REE processing plant compared with the control group (i.e., 87.5 versus 0.49 μg/m³ of ΣREEs). Blood concentrations were also significantly higher in the exposure group (3.47 versus 2.24 μg/L of ΣREEs). However, the compositional profiles of REEs resembled between the exposure and control group in blood or air particles, indicating the influence of mining/processing activities on the surrounding regions. External exposure in the occupational environment appeared to significantly influence internal REE exposure in the REE processing workers. Some other sociodemographic and occupational factors, including the residence time and the type of work, could also influence occupational exposure to selected REEs. Our data clearly demonstrated the highly elevated REE contamination in both working environment and human bodies compared with the control subjects, raising the critical need for better assessing the health risks from occupational REE exposure and efficient management for occupational hazards.

U-Shaped Relationship of Rare Earth Element Lanthanum and Oral Cancer Risk: A Propensity Score-Based Study in the Southeast of China

As an important rare earth element (REE) extensively applied to industry, agriculture, and medicine, lanthanum (La) has attracted a host of health concerns. This study aimed to explore the relationship between La exposure and the risk of developing oral cancer through a case-control study with a large sample size. Serum La levels of 430 oral cancer patients and 1,118 healthy controls were detected by inductively coupled plasma mass spectrometry (ICP-MS). The association of La level with the risk of oral cancer was assessed in two ways: (1) as a continuous scale based on restricted cubic splines (RCS); (2) as a priori defined centile categories using multivariate logistic regression model, based on propensity score matching (PSM) and inverse probability of treatment weighting (IPTW). The RCS revealed a non-linear U-shaped relationship between serum La and oral cancer risk. Serum La deficiency or excess was associated with an increased risk of oral cancer. When the La level was analyzed as a categorical variable, a similar U-shaped association was observed. Of note, compared to those with La concentrations of 0.243-0.341 μg/L (reference quantiles, 41st-60th), the risk was increased in those with the lower or higher quantiles (0.132-0.242 μg/L vs. 0.243-0.341 μg/L: OR = 1.80, 95%CI: 1.07-3.02; 0.342-0.497 μg/L vs. 0.243-0.341 μg/L: OR = 2.30, 95%CI: 1.38-3.84). The results were generally consistent with the PSM and IPTW analyses. This preliminary study provides strong evidence that there was a U-shaped relationship between serum La levels and oral cancer risk. Much additional work is warranted to confirm our findings.