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Electronic cigarettes (e-cigarettes) have become popular, in part because they are perceived as a safer alternative to tobacco cigarettes. An increasing number of studies, however, have found toxic metals/metalloids in e-cigarette emissions. We summarized the evidence on metal/metalloid levels in e-cigarette liquid (e-liquid), aerosols, and biosamples of e-cigarette users across e-cigarette device systems to evaluate metal/metalloid exposure levels for e-cigarette users and the potential implications on health outcomes. We searched PubMed/TOXLINE, Embase®, and Web of Science for studies on metals/metalloids in e-liquid, e-cigarette aerosols, and biosamples of e-cigarette users. For metal/metalloid levels in e-liquid and aerosol samples, we collected the mean and standard deviation (SD) if these values were reported, derived mean and SD by using automated software to infer them if data were reported in a figure, or calculated the overall mean (mean ± SD) if data were reported only for separate groups. Metal/metalloid levels in e-liquids and aerosols were converted and reported in micrograms per kilogram and nanograms per puff, respectively, for easy comparison. We identified 24 studies on metals/metalloids in e-liquid, e-cigarette aerosols, and human biosamples of e-cigarette users. Metal/metalloid levels, including aluminum, antimony, arsenic, cadmium, cobalt, chromium, copper, iron, lead, manganese, nickel, selenium, tin, and zinc, were present in e-cigarette samples in the studies reviewed. Twelve studies reported metal/metalloid levels in e-liquids (bottles, cartridges, open wick, and tank), 12 studies reported metal/metalloid levels in e-cigarette aerosols (from cig-a-like and tank devices), and 4 studies reported metal/metalloid levels in human biosamples (urine, saliva, serum, and blood) of e-cigarette users. Metal/metalloid levels showed substantial heterogeneity depending on sample type, source of e-liquid, and device type. Metal/metalloid levels in e-liquid from cartridges or tank/open wicks were higher than those from bottles, possibly due to coil contact. Most metal/metalloid levels found in biosamples of e-cigarette users were similar or higher than levels found in biosamples of conventional cigarette users, and even higher than those found in biosamples of cigar users. E-cigarettes are a potential source of exposure to metals/metalloids. Differences in collection methods and puffing regimes likely contribute to the variability in metal/metalloid levels across studies, making comparison across studies difficult. Standardized protocols for the quantification of metal/metalloid levels from e-cigarette samples are needed. https://doi.org/10.1289/EHP5686.

Polyamines (PAs) are found in all living organisms and serve many vital physiological processes. In plants, PAs are ubiquitous in plant growth, physiology, reproduction, and yield. In the last decades, PAs have been studied widely for exploring their function in conferring abiotic stresses (salt, drought, and metal/metalloid toxicity) tolerance. The role of PAs in enhancing antioxidant defense mechanism and subsequent oxidative stress tolerance in plants is well-evident. However, the enzymatic regulation in PAs biosynthesis and metabolism is still under research and widely variable under various stresses and plant types. Recently, exogenous use of PAs, such as putrescine, spermidine, and spermine, was found to play a vital role in enhancing stress tolerance traits in plants. Polyamines also interact with other molecules like phytohormones, nitric oxides, trace elements, and other signaling molecules to providing coordinating actions towards stress tolerance. Due to the rapid industrialization metal/metalloid(s) contamination in the soil and subsequent uptake and toxicity in plants causes the most significant yield loss in cultivated plants, which also hamper food security. Finding the ways in enhancing tolerance and remediation mechanism is one of the critical tasks for plant biologists. In this review, we will focus the recent update on the roles of PAs in conferring metal/metalloid(s) tolerance in plants.

Gold mining is a major source of metal and metalloid emissions into the environment. Studies were carried out in Krugersdorp, South Africa, to evaluate the ecological and human health risks associated with exposure to metals and metalloids in mine tailings contaminated soils. Concentrations of arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni), and zinc (Zn) in soil samples from the area varied with the highest contamination factors (expressed as ratio of metal or metalloid concentration in the tailings contaminated soil to that of the control site) observed for As (3.5x102), Co (2.8x102) and Ni (1.1x102). Potential ecological risk index values for metals and metalloids determined from soil metal and metalloid concentrations and their respective risk factors were correspondingly highest for As (3.5x103) and Co (1.4x103), whereas Mn (0.6) presented the lowest ecological risk. Human health risk was assessed using Hazard Quotient (HQ), Chronic Hazard Index (CHI) and carcinogenic risk levels, where values of HQ > 1, CHI > 1 and carcinogenic risk values > 1×10-4 represent elevated risks. Values for HQ indicated high exposure-related risk for As (53.7), Cr (14.8), Ni (2.2), Zn (2.64) and Mn (1.67). Children were more at risk from heavy metal and metalloid exposure than adults. Cancer-related risks associated with metal and metalloid exposure among children were also higher than in adults with cancer risk values of 3×10-2 and 4×10-2 for As and Ni respectively among children, and 5×10-3 and 4×10-3 for As and Ni respectively among adults. There is significant potential ecological and human health risk associated with metal and metalloid exposure from contaminated soils around gold mine tailings dumps. This could be a potential contributing factor to a setback in the health of residents in informal settlements dominating this mining area as the immune systems of some of these residents are already compromised by high HIV prevalence.

Concern about metals and metalloids, especially heavy metals in seaweeds has risen due to potential health risk. This study investigated the distribution of 10 metals and metalloids in 295 dried seaweeds (brown and red) and estimated the possible health risk via hazard index (HI). Elements in seaweeds can be sequenced in descending order by mean values: Al > Mn > As > Cu > Cr > Ni > Cd > Se > Pb > Hg. The levels of Cd, Cu, Mn and Ni in red seaweeds were significantly higher than those in brown seaweeds ( P  < 0.01). Correlation analysis showed contents of Ni-Cr ( r  = 0.59, P  < 0.01) in seaweeds had moderate positive correlations. Seaweeds from different geographical origins had diverse element distribution. Risk assessment showed that HI at mean level was less than the threshold of 1. It indicates that for the general people there is low health risk to these elements by the intake of seaweeds. Furthermore, in terms of the confirmative toxicity of some metals, such as Cd, Pb and Hg, surveillance of metals in seaweeds should be performed continuously.

Phytochelatins (PCs) are small cysteine-rich peptides capable of binding metal(loid)s via SH-groups. Although the biosynthesis of PCs can be induced in vivo by various metal(loid)s, PCs are mainly involved in the detoxification of cadmium and arsenic (III), as well as mercury, zinc, lead, and copper ions, which have high affinities for S-containing ligands. The present review provides a comprehensive account of the recent data on PC biosynthesis, structure, and role in metal(loid) transport and sequestration in the vacuoles of plant cells. A comparative analysis of PC accumulation in hyperaccumulator plants, which accumulate metal(loid)s in their shoots, and in the excluders, which accumulate metal(loid)s in their roots, investigates the question of whether the endogenous PC concentration determines a plant’s tolerance to metal(loid)s. Summarizing the available data, it can be concluded that PCs are not involved in metal(loid) hyperaccumulation machinery, though they play a key role in metal(loid) homeostasis. Unraveling the physiological role of metal(loid)-binding ligands is a fundamental problem of modern molecular biology, plant physiology, ionomics, and toxicology, and is important for the development of technologies used in phytoremediation, biofortification, and phytomining.

Topological quantum phases in two-dimensional materials have been a fascinating research topic since the discovery of graphene. Particularly, the topological quantum phases could appear in two-dimensional magnetic systems. However, identifying concrete materials that host topological quantum phases is still a challenge, especially the magnetic ones. In this work, we propose a novel hybrid Weyl semimetal in two dimensions, the monolayer AgCrS₂. We show that this material has a stable ferromagnetic ground state with an in-plane magnetic moment. Particularly, it hosts a hybrid of two Weyl nodes close to the Fermi level: one is a double Weyl point, and the other one is type-II linear Weyl point. The features of their band structure could be inferred from the effective models for them. When the spin-orbital coupling is included, the double Weyl point is gapped. In comparison, the type-II linear Weyl nodes on high-symmetry path can be tuned by controlling the orientation of the magnetization direction. To be specific, the magnetization could change locations of type-II linear Weyl nodes and control its stability. Therefore, our results offer a platform to study novel hybrid of Weyl nodes in two-dimensional ferromagnetic system.

Magnetic Weyl semimetalsWeyl semimetals (WSMs)—materials that host exotic quasiparticles called Weyl fermions—must break either spatial inversion or time-reversal symmetry. A number of WSMs that break inversion symmetry have been identified, but showing unambiguously that a material is a time-reversal-breaking WSM is tricky. Three groups now provide spectroscopic evidence for this latter state in magnetic materials (see the Perspective by da Silva Neto). Belopolski et al. probed the material Co2MnGa using angle-resolved photoemission spectroscopy, revealing exotic drumhead surface states. Using the same technique, Liu et al. studied the material Co3Sn2S2, which was complemented by the scanning tunneling spectroscopy measurements of Morali et al. These magnetic WSM states provide an ideal setting for exotic transport effects.Science, this issue p. 1278, p. 1282, p. 1286; see also p. 1248Bulk–surface correspondence in Weyl semimetals ensures the formation of topological “Fermi arc” surface bands whose existence is guaranteed by bulk Weyl nodes. By investigating three distinct surface terminations of the ferromagnetic semimetal Co3Sn2S2, we verify spectroscopically its classification as a time-reversal symmetry-broken Weyl semimetal. We show that the distinct surface potentials imposed by three different terminations modify the Fermi-arc contour and Weyl node connectivity. On the tin (Sn) surface, we identify intra–Brillouin zone Weyl node connectivity of Fermi arcs, whereas on cobalt (Co) termination, the connectivity is across adjacent Brillouin zones. On the sulfur (S) surface, Fermi arcs overlap with nontopological bulk and surface states. We thus resolve both topologically protected and nonprotected electronic properties of a Weyl semimetal.

Heavy metals and metalloids (HMMs) pose a serious threat to both environmental and human health. The unique characteristics and environmental toxicity of HMMs make their removal from the environment a major challenge. Constructed wetlands (CWs) are increasingly being used as an eco-friendly system for the removal of HMMs from aqueous environments. In this review, bibliometric analysis was performed using the Scopus database using VOSviewer software to assess the developing use of CWs in recent years. Heavy metal and metalloid (HMM) removal pathways were reviewed (such as precipitation, co-precipitation, adsorption and ion exchange, plant action and microbial action) along with the impact of key factors (pH, chemical oxygen demand, dissolved oxygen, HMM concentration, and temperature). This review aimed to establish the connections between published results, to help effectively optimize the use of CWs for the removal of HMMs and identify the most critical factors for their effective removal. Important aspects that require further research include assessing the synergistic toxicity between different pollutants and combining the use of CWs with other technologies to optimize pollutant remediation efficiency.Graphic abstract

Ranchi is the administrative capital of Jharkhand and is located in the southern part of the Chhotanagpur Plateau. It is rich in forest and mineral resources and hence is suitable for the establishment of many large- and small-scale industries. The estimated population of Ranchi for the year 2023 is 3.54 million. These demographic characteristics make the capital more vulnerable to environmental degradation. Also, previous water quality research focused on river, water, and oceans separately; however, little or no work has been carried out on the comparison of metal or metalloid analysis in rivers, waterfalls, and lakes. Hence, the present study aims to assess the pollution status of mineral-rich and industrial hub city, Ranchi, through analysis of metals or metalloids in abiotic (water and sediment) and biotic (fish and human) components. The water, sediment, and fish ( Labeo rohita and Catla catla ) samples were collected from Subarnarekha river, Jumar river, Dassam fall, Getalsud dam, Hundru fall, Jonha fall, Kanke dam, and Sita fall. Samples were collected following standard methods and analyzed in inductively coupled plasma mass spectrometry (ICP-MS). Among three aquatic systems (rivers, dams, and falls), dams were highly polluted with metals or metalloids, which may be due to effluent discharge from different industries. Additionally, the high population in the city also contributed to metals or metalloids pollution. The reason may be the direct sewage disposal and agricultural and surface runoff in the water systems. It was observed that most of the aquatic systems in Ranchi were severely polluted with metals or metalloids. The fish also accumulated these metals or metalloids in their body and can be life-threatening to the human population consuming them. The THQ (above 1) and HI (2.95) values for As showed that children are more vulnerable to health risk through consumption of contaminated fish. Hence, proper planning and management are needed to overcome the metals or metalloids pollution in Ranchi.