Chromium in drinking water: sources, metabolism, and cancer risks

Intrauterine chromium exposure and cognitive developmental delay: The modifying effect of genetic predisposition

There is limited evidence on the effects of intrauterine chromium (Cr) exposure on children's cognitive developmental delay (CDD). Further, little is known about the genetic factors in modifying the association between intrauterine Cr exposure and CDD. The present study involved 2361 mother-child pairs, in which maternal plasma Cr concentrations were assessed, a polygenic risk score for the child was constructed, and the child's cognitive development was evaluated using the Bayley Scales of Infant Development. The risks of CDD conferred by intrauterine Cr exposure in children with different genetic backgrounds were evaluated by logistic regression. The additive interaction between intrauterine Cr exposure and genetic factors was evaluated by calculating the relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP), and synergy index (SI). According to present study, higher intrauterine Cr exposure was significantly associated with increased CDD risk [each unit increase in ln-transformed maternal plasma Cr concentration (ln-Cr): adjusted OR (95 % CI), 1.18 (1.04-1.35); highest vs lowest quartile: adjusted OR (95 % CI), 1.57 (1.10-2.23)]. The dose-response relationship of intrauterine Cr exposure and CDD for children with high genetic risk was more prominent [each unit increased ln-Cr: adjusted OR (95 % CI), 1.36 (1.09-1.70)]. Joint effects between intrauterine Cr exposure and genetic factors were found. Specifically, for high genetic risk carriers, the association between intrauterine Cr exposure and CDD was more evident [highest vs lowest quartile: adjusted OR (95 % CI), 2.33 (1.43-3.80)]. For those children with high intrauterine Cr exposure and high genetic risk, the adjusted AP was 0.39 (95 % CI, 0.07-0.72). Conclusively, intrauterine Cr exposure was a high-risk factor for CDD in children, particularly for those with high genetic risk. Intrauterine Cr exposure and one's adverse genetic background jointly contribute to an increased risk of CDD in children.

Molecular and toxicological mechanisms behind the effects of chromium (VI) on the male reproductive system of Mytilus galloprovincialis: First evidence for poly-ADP-ribosylation of protamine-like II

Studies on the molecular mechanisms of heavy metal toxicity in invertebrate reproduction are limited. Given that PARP-catalysed ADP-ribosylation is also involved in counteracting heavy metal toxicity and maintaining genomic integrity, and that PARylation is implicated in chromatin remodelling but its role in sperm chromatin remains to be elucidated, we investigated the effects of chromium(VI) at 1, 10 and 100 nM on the reproductive health of Mytilus galloprovincialis. The damage to the gonads was assessed by morphological analyses and the damage indices PARP and ɣH2A.X were measured. Changes in the binding of protamine-like (PL) to DNA and the possibility of poly(ADP-ribosyl)ation of PL proteins were also investigated. Gonadal chromium accumulation and morphological damage were found, especially when the mussels were exposed to the highest dose of chromium(VI). In addition, the maximum expression of gonadal ɣH2A.X and PARP were obtained at 100 and 10 nM Cr(VI), respectively. Interestingly, for the first time in all exposed conditions, poly(ADP)-ribosylation was detected on PL-II, which, together with PL-III and PL-IV, are the major nuclear basic proteins of Mytilus galloprovincialis sperm chromatin. Since PL-II is involved in the final high level of sperm chromatin compaction, this post-translational modification altered the binding of the PL protein to DNA, favouring the action of micrococcal nuclease on sperm chromatin. This study provides new insights into the effects of chromium(VI) on Mytilus galloprovincialis reproductive system and proposes a molecular mechanism hypothesis describing the toxic effects of this metal on PL-DNA binding, sperm chromatin and gonads.

Evaluation of contaminated groundwater for excessive heavy metal presence and its further assessment of the potential risk to public health

Water plays a significant role in human life. However, the contamination of groundwater by heavy metals (HMs) has profound implications for public health. Industrialization, urbanization, and agricultural activities are turning out to be major causes for the increasing concentration of HMs in rapidly industrializing areas like Rohtak district, Haryana, India. The current study aimed at evaluating and predicting the health hazards associated with the radical rise of HMs in the groundwater of Rohtak district. For this purpose, 45 seasonal-based groundwater samples were collected from five blocks in Rohtak district, namely Kalanaur, Meham, Lakhan Majra, Rohtak City, and Sampla, both during pre- and post-monsoon seasons. Besides physicochemical analysis, these groundwater samples were analyzed for the contamination of HMs. The findings revealed that groundwater samples were relatively more contaminated during the post-monsoon period rather than pre-monsoon. The water quality index (WQI), devised to classify water quality into specific classes, depicted the Kalanaur region as "very poor." Another index named the HM pollution index (HPI) denoted the levels of HMs and categorized Kalanaur as most deteriorated, followed by Meham, Lakhan Majra, Sampla, and Rohtak City. Additionally, principal component analysis (PCA) was employed that showed a significant variation in the distribution pattern of HMs, with the major load being attributed to PC1 and PC2 for both seasons. Pearson's correlation analysis indicated a significant association of pH (R2 = 0.917) with HMs (specifically for Cd and Cr). In terms of health risk assessment, carcinogenic human health risk due to Pb and Cr was found to be higher in children than adults. Non-carcinogenic risk, indicative of harmful human health effects, apart from cancer, was calculated in terms of hazard quotient (HQ) and hazard index (HI). Results of the same, designated "children" as a vulnerable category compared with "adults," especially in the Kalanaur, Sampla, and Rohtak City blocks of the study area. The results thus reiterated that Kalanaur is the most contaminated block among the five blocks chosen and should be given urgent attention. The study holds importance as it provides a framework regarding the methodology that should be adapted for the evaluation, management, and protection of groundwater at a regional level, which could further be replicated by environmentalists and hydrogeologists across the world. PRACTITIONER POINTS: Water logging is one of the most common problems in Kalanaur block of Rohtak district, responsible for causing groundwater pollution. Cadmium and lead pollution was prevalent in Rohtak due to electroplating industries, paint industry, automobile sector, and industrial discharge. Bioremediation is one of the suitable techniques that can be used for the treatment of groundwater that involves the use of microorganisms. Efficient use of groundwater resources is necessary for sustainable development.

Assessment of the health risks associated with heavy metal contamination in the groundwaters of the Leh district, Ladakh

There has been a significant rise in cancer-related mortality in the Ladakh region during the past 10 years. The most common type of case is gastrointestinal cancer, which has been linked in theory by medical research to lifestyle factors, high altitude conditions, and the prevalence of Helicobacter pylori bacteria brought on by poor hygiene. Nevertheless, the precise cause of the rise in cancer cases is still unknown. Concurrently, there has been a significant change in Ladakh's water use practices due to development, improved basic utilities, and related vocational shifts. The local population has become increasingly reliant on groundwater since it provides a year-round, continuous water supply for home and agricultural uses. In this study, we assessed heavy metal contamination in groundwaters and associated human health risks. The results indicate that 46-96% of the groundwater samples have heavy metal pollution with a health hazard index > 1, which means using these groundwaters for drinking, food preparation, and agriculture is likely to result in carcinogenic and non-carcinogenic health hazards. The main heavy metal contaminants found in the groundwater of the Leh district include Cr, As, Hg, and U. According to the health risk assessment, 46-76% of the groundwater samples contain unsafe levels of Cr and As. Prolonged exposure to these levels is likely to cause gastrointestinal cancer in the local population. Acute to chronic exposure to U and Hg concentrations present in some groundwater samples is likely to result in various non-carcinogenic health risks.

Geospatial analysis of toxic metal contamination in groundwater and associated health risks in the lower Himalayan industrial region

Once known for its clean and natural environment, the lower Himalayan region is now no exception to human-induced disturbances. Rapid industrial growth in Baddi-Barotiwala (BB) industrial region has led to degradation of groundwater resources in the area. Groundwater samples were collected from 37 locations to study the groundwater chemistry, geospatial variation of 15 toxic metals in groundwater, source apportionment, metals of concern and associated health risks in the region. The results showed rock dominated hydrogeology with decreasing order of anion and cation abundance as HCO3- > Cl- > SO42- > NO3- > Br- > F- and Ca+ > Na+ > Mg2+ > K+ > Li+ respectively. Concentrations of Iron (BDL-3.6 mg/l), Nickel (BDL-0.023 mg/l), Barium (0.22-0.89 mg/l), Lead (0.0001-0.085 mg/l) and Zinc (0.006-21.4 mg/l) were found above the permissible limits at few locations. Principal component analysis (PCA) and coefficient of variance (CV) showed both geogenic and anthropogenic origin of metals in groundwater of the BB industrial region. A consistent concentration of Uranium was detected at all the sampling locations with an average value of 0.0039 mg/l and poor spatial variation indicating its natural presence. Overall, non-carcinogenic (N-CR) risk in the study area via oral pathway was high for adults and children (Hazard Index > 1) with geogenic Uranium as the major contributor (Hazard Quotient > 1) followed by Zinc, Lead and Cobalt. Carcinogenic (CR) risk in the region was high for adults having mean value above the threshold (1E-04) with Nickel and Chromium as the metals of major concern. Spatial variation of health risks was overlayed on village boundaries of the region to identify the potential industrial sources of the metals of major concern. The results highlight the need for immediate remediation of groundwater resources in order to achieve a harmonious coexistence between industrialization and human well-being.

Urolithin A attenuates hexavalent chromium-induced small intestinal injury by modulating PP2A/Hippo/YAP1 pathway

Hexavalent chromium (Cr(VI)) exposure has been linked with gastrointestinal toxicity, whereas the molecular pathways and key targets remain elusive. Computational toxicology analysis predicted the correlation between protein phosphatase 2A (PP2A) and genes regarding Cr(VI)-induced intestinal injury. Here, we generated a mouse model with intestinal epithelium-specific knock-out of Ppp2r1a (encoding PP2A Aα subunit) to investigate the mechanisms underlying Cr(VI)-induced small intestinal toxicity. Heterozygous mice (HE) and matched wild-type (WT) littermates were administrated with Cr(VI) at 0, 5, 20, 80 mg/L for 28 successive days. Cr(VI) treatment led to crypt hyperplasia, epithelial cell apoptosis, and intestinal barrier dysfunction, accompanied by the decline of goblet cell counts and Occludin expression in WT mice. Notably, these effects were aggravated in HE mice, indicating that PP2A Aα deficiency conferred mice with susceptibility to Cr(VI)-induced intestinal injury. Integrated data analysis and biological experiments revealed Cr(VI) exposure could decrease YAP1 phosphorylation at Ser127 but increase protein expression and activity, together with elevated TAZ protein driving epithelial crypt cells proliferation following damage, suggesting the involvement of Hippo/YAP1 signaling pathway in Cr(VI)-induced intestinal toxicity. Nevertheless, the enhanced phosphorylation of YAP1 in HE mice resulted in proliferation/repair defects in intestinal epithelium, thereby exacerbating Cr(VI)-induced gut barrier dysfunction. Notably, by molecular docking and further studies, we identified Urolithin A, a microbial metabolite, attenuated Cr(VI)-induced disruption of intestinal barrier function, partly by modulating YAP1 expression and activity. Our findings reveal the novel molecular pathways participated in Cr(VI)-caused small intestinal injury and urolithin A could potentially protect against environmental hazards-induced intestinal diseases.

Is chromium(III) pharmacologically relevant? An update focused on studies with diabetic rodent models

A decade ago, the author assessed the status of chromium as the trivalent ion as an essential element and as a therapeutic agent based on rodent studies for this journal. The current review was undertaken to update considerations regarding the status of chromium, focusing on studies of Cr supplementation of diabetic rodent models over the last decade. Cr can no longer be considered an essential trace element for humans. Observed effects of Cr on rodent models of insulin resistance and diabetes are best interpreted in terms of a pharmacological role for Cr. The review of studies on the effects of Cr on rat models of diabetes is updated, and the results continue to suggest Cr increases insulin sensitivity in peripheral tissues of the rodent models. The lack of effects in human studies may stem from humans receiving a comparably smaller dose than the rodent models. However, given the different responses to Cr in the rodent models, humans could potentially have different responses to Cr. Recent studies primary utilizing rodents suggest two potential complementary but also contradictory modes of action for Cr(III) at a molecular level.

Chronic low-dose chromium VI exposure induces oxidative stress and apoptosis with altered expressions of DNA repair genes and promoter hypermethylation in the liver of Swiss albino mice

The present investigation dealt with harmful effects of hexavalent chromium (Cr [VI]) on liver of Swiss albino mice. This variant exhibited cytotoxicity, mutagenicity, and carcinogenicity. Our study focused on elucidating the hepatotoxic effects of chronic low-dose exposure to Cr (VI) (2, 5, and 10 ppm) administered via drinking water for 4 and 8 months. The observed elevation in SGPT, ALP, and SGOT and increased oxidative stress markers unequivocally confirmed the severe disruption of liver homeostasis at these low treatment doses. Noteworthy alterations in histoarchitecture, body weight, and water intake provided further evidences of the harmful effects of Cr (VI). Production of reactive oxygen species (ROS) during metabolism led to DNA damages. Immunohistochemistry and qRT-PCR analyses revealed that chronic low-dose exposure of Cr (VI) induced apoptosis in liver tissue. Our study exhibited alterations in the expression pattern of DNA repair genes (Rad51, Mutyh, Mlh1, and Ogg1), coupled with promoter hypermethylation of Mutyh and Rad51, leading to transcriptional inhibition. Our findings underscored the potential of low-dose Cr (VI) exposure on hepatotoxicity by the intricate interplay between apoptosis induction and epigenetic alterations of DNA repair genes.

Aerogels of Polypyrrole/Tannic Acid with Nanofibrillated Cellulose for the Removal of Hexavalent Chromium Ions

The preparation of conducting polymer aerogels is an effective strategy to produce innovative materials with enhanced physicochemical properties. Herein, polypyrrole (PPy) aerogels were oxidatively prepared in the presence of tannic acid (TA) with different concentrations (2.5, 5, and 10% mole ratio to pyrrole monomer) under freezing conditions. Nanofibrillated cellulose (NFC) was added during the PPy/TA synthesis to enhance mechanical stability. The effect of TA concentration on the aerogels' morphology, conductivity, thermal stability, and adsorption capacity was investigated. The conductivity of 9.6 ± 1.7 S cm-1 was achieved for PPy/TA prepared with 2.5% TA, which decreased to 0.07 ± 0.01 S cm-1 when 10% TA was used. PPy/TA aerogels have shown high efficacy in removing Cr(VI) ions from aqueous solutions. Adsorption experiments revealed that all the aerogels follow pseudo-second-order kinetics. PPy/TA prepared with NFC has a maximum adsorption capacity of 549.5 mg g-1.

Colorimetric Sensor for Cr(VI) Ion Detection in Tap Water Using a Combination of AuNPs and AgNPs

Colorimetric sensors are a promising technique for the simple screening of water, food, and environmental samples contaminated with interferents, allowing for color changes to be observed with the naked eye or a spectrophotometer. In this study, a colorimetric sensor for the selective detection of hexavalent chromium ion (Cr(VI)) contamination in water was developed. A combination of sodium borohydride-coated gold and citrate-capped silver nanoparticles (Na-AuNPs/cit-AgNPs) was employed as a colorimetric probe. Upon the addition of Cr(VI)-contaminated tap water in the colorimetric probe solution, the color sequentially transitioned from its initial orange to dark reddish-purple, dark purplish-red, dark blue-violet, and gray. This colorimetric strategy relies on AgNP dissolution and AuNP aggregation in the presence of the Cr(VI) ions. The dissolution of AgNPs is evidenced by the reduction of the characteristic peak of AgNPs at 400 nm, while the aggregation of AuNPs leads to a red shift in the absorption band at 514 nm, accompanied by broad absorption in the 500-700 nm range. The limits of detections were found to be 22.9 and 50 ppb using a spectrometer and by visual observation, respectively. The synthesized AuNPs and AgNPs are very stable in the presence of media containing complicated ions. We further demonstrated the practical applicability of the developed system for detecting Cr(VI) in real samples, including natural water and artificial urine, highlighting its potential for addressing Cr(VI) contamination in practical scenarios.

Amino-modified upcycled biochar achieves selective chromium removal in complex aqueous matrices

Chromium pollution of groundwater sources is a growing global issue, which correlates with various anthropogenic activities. Remediation of both the Cr(VI) and Cr(III), via adsorption technologies, has been championed in recent years due to ease of use, minimal energy requirements, and the potential to serve as a highly sustainable remediation technology. In the present study, a biochar sorbent sourced from pineapple skins, allowed for the upcycling of agricultural waste into water purification technology. The biochar material was chemically modified, through a green amination method, to produce an efficient and selective adsorbent for the removal of both Cr(VI) and Cr(III) from complex aqueous matrices. From FTIR analysis it was evident that the chemical modification introduced new C-N and N-H bonds observed in the modified biochar along with a depletion of N-O and C-H bonds found in the pristine biochar. The amino modified biochar was found to spontaneously adsorb both forms of chromium at room temperature, with binding capacities of 46.5 mg/g of Cr(VI) and 27.1 mg/g of Cr(III). Interference studies, conducted in complex matrices, showed no change in adsorption capacity for Cr(VI) in matrices containing up to 3,000× the concentration of interfering ions. Finally, Cr(III) removal was synergized to 100% adsorption at interfering ions concentrations up to 330× of the analyte, which were suppressed at higher interference concentrations. Considering such performance, the amino modified biochar achieved selective removal for both forms of chromium, showing great potential for utilization in complex chromium pollution sources.

Insights into the effects of chronic combined chromium-nickel exposure on colon damage in mice through transcriptomic analysis and in vitro gastrointestinal digestion assay

Heavy metals interact with each other in a coexisting manner to produce complex combined toxicity to organisms. At present, the toxic effects of chronic co-exposure to heavy metals hexavalent chromium [Cr(VI)] and divalent nickel [Ni(II)] on organisms are seldom studied and the related mechanisms are poorly understood. In this study, we explored the mechanism of the colon injury in mice caused by chronic exposure to Cr or/and Ni. The results showed that, compared with the control group, Cr or/and Ni chronic exposure affected the body weight of mice, and led to infiltration of inflammatory cells in the colon, decreased the number of goblet cells, fusion of intracellular mucus particles and damaged cell structure of intestinal epithelial. In the Cr or/and Ni exposure group, the activity of nitric oxide synthase (iNOS) increased, the expression levels of MUC2 were significantly down-regulated, and those of ZO-1 and Occludin were significantly up-regulated. Interestingly, factorial analysis revealed an interaction between Cr and Ni, which was manifested as antagonistic effects on iNOS activity, ZO-1 and MUC2 mRNA expression levels. Transcriptome sequencing further revealed that the expression of genes-related to inflammation, intestinal mucus and tight junctions changed obviously. Moreover, the relative contents of Cr(VI) and Ni(II) in the Cr, Ni and Cr+Ni groups all changed with in-vitro gastrointestinal （IVG）digestion, especially in the Cr+Ni group. Our results indicated that the chronic exposure to Cr or/and Ni can lead to damage to the mice colon, and the relative content changes of Cr(VI) and Ni(II) might be the main reason for the antagonistic effect of Cr+Ni exposure on the colon damage.

Exploring the Efficiency of Algerian Kaolinite Clay in the Adsorption of Cr(III) from Aqueous Solutions: Experimental and Computational Insights

The current study comprehensively investigates the adsorption behavior of chromium (Cr(III)) in wastewater using Algerian kaolinite clay. The structural and textural properties of the kaolinite clay are extensively characterized through a range of analytical methods, including XRD, FTIR, SEM-EDS, XPS, laser granulometry, N2 adsorption isotherm, and TGA-DTA. The point of zero charge and zeta potential are also assessed. Chromium adsorption reached equilibrium within five minutes, achieving a maximum removal rate of 99% at pH 5. Adsorption equilibrium is modeled using the Langmuir, Freundlich, Temkin, Elovich, and Dubinin-Radushkevitch equations, with the Langmuir isotherm accurately describing the adsorption process and yielding a maximum adsorption capacity of 8.422 mg/g for Cr(III). Thermodynamic parameters suggest the spontaneous and endothermic nature of Cr(III) sorption, with an activation energy of 26.665 kJ/mol, indicating the importance of diffusion in the sorption process. Furthermore, advanced DFT computations, including COSMO-RS, molecular orbitals, IGM, RDG, and QTAIM analyses, are conducted to elucidate the nature of adsorption, revealing strong binding interactions between Cr(III) ions and the kaolinite surface. The integration of theoretical and experimental data not only enhances the understanding of Cr(III) removal using kaolinite but also demonstrates the effectiveness of this clay adsorbent for wastewater treatment. Furthermore, this study highlights the synergistic application of empirical research and computational modeling in elucidating complex adsorption processes.

Emerging contaminants in water environments: progress, evolution, and prospects

This article employs bibliometric tools like VOSviewer, Bibliometrix, and CiteSpace for a comprehensive visual analysis of 1,612 documents on Emerging Contaminants in Waters from the Web of Science database. The objective is to elucidate the historical development, research hotspots, and trends in international studies of this field, offering valuable insights and guidance for future research directions. The analysis reveals a consistent increase in publications from 2003 to 2023, with the United States, China, and Spain being the most prolific contributors. A detailed examination of keyword co-occurrence and cluster analysis shows a predominant focus on themes such as pollutant detection, risk assessment, and biogeochemical cycling. Furthermore, the study underscores the significance of forming interdisciplinary networks among authors and institutions, highlighting its critical role in enhancing the quality and innovation of scientific research. The findings of this study not only chart the progression and focal points of research in this domain but also underscore the pivotal role of international collaboration, serving as an indispensable reference for shaping future research trajectories and fostering global cooperation.

Metalloestrogens exposure and risk of gestational diabetes mellitus: Evidence emerging from the systematic review and meta-analysis

BACKGROUND

Metalloestrogens are metals and metalloid elements with estrogenic activity found everywhere. Their impact on human health is becoming more apparent as human activities increase.

OBJECTIVE

Our aim is to conduct a comprehensive systematic review and meta-analysis of observational studies exploring the correlation between metalloestrogens (specifically As, Sb, Cr, Cd, Cu, Se, Hg) and Gestational Diabetes Mellitus (GDM).

METHODS

PubMed, Web of Science, and Embase were searched to examine the link between metalloestrogens (As, Sb, Cr, Cd, Cu, Se, and Hg) and GDM until December 2023. Risk estimates were derived using random effects models. Subgroup analyses were conducted based on study countries, exposure sample, exposure assessment method, and detection methods. Sensitivity analyses and adjustments for publication bias were carried out to assess the strength of the findings.

RESULTS

Out of the 389 articles identified initially, 350 met our criteria and 33 were included in the meta-analysis, involving 141,175 subjects (9450 cases, 131,725 controls). Arsenic, antimony, and copper exposure exhibited a potential increase in GDM risk to some extent (As: OR = 1.28, 95 % CI [1.08, 1.52]; Sb: OR = 1.73, 95 % CI [1.13, 2.65]; Cu: OR = 1.29, 95 % CI [1.02, 1.63]), although there is a high degree of heterogeneity (As: Q = 52.93, p < 0.05, I2 = 64.1 %; Sb: Q = 31.40, p < 0.05, I2 = 80.9 %; Cu: Q = 21.14, p < 0.05, I2 = 71.6 %). Conversely, selenium, cadmium, chromium, and mercury exposure did not exhibit any association with the risk of GDM in our study.

DISCUSSION

Our research indicates that the existence of harmful metalloestrogens in the surroundings has a notable effect on the likelihood of GDM. Hence, we stress the significance of environmental elements in the development of GDM and the pressing need for relevant policies and measures.

Polypyrrole Coating via Lemieux-von Rudloff Oxidation on Magnetite Nanoparticles for Highly Efficient Removal of Chromium(VI) from Wastewater

An alternative way for the coating of polypyrrole (PPy) polymer on hydrophobic magnetite (Fe3O4) nanoparticles is reported here to capture toxic chromium ions, Cr (VI), present in water. Iron oxide magnetic nanoparticles (Fe3O4) were synthesized by the conventional coprecipitation technique using FeCl3·6H2O and FeSO4·7H2O iron precursors and subsequently modified with oleic acid (OA). Then OA-Fe3O4 hydrophobic nanoparticles were oxidized using the Lemieux-von Rudloff reaction to transfer OA into hydrophilic azelaic acid (AA) (HOOC(CH2)7COOH-modified magnetic nanoparticles (AA-Fe3O4). Finally, a PPy polymer coating was formed by a seeded polymerization of pyrrole, using AA-Fe3O4 as seeds. The average size of PPy/Fe3O4 nanocomposites is 12.33 nm and is almost spherical in shape. The surface composition is confirmed by FTIR and thermogravimetry analyses. An X-ray diffraction study confirmed the formation of highly crystalline Fe3O4 nanoparticles, and the crystallinity was retained after the surface modification. The adsorption study suggested that the Cr(VI) ion adsorption is highly pH-dependent and the maximum amount of adsorption is obtained at pH 2.0. The adsorption results revealed that the Langmuir model provided the best fit for the isotherm, with a maximum adsorption capacity reaching approximately 173.22 mg g-1 at 323 K. Spontaneous and endothermic adsorption processes were confirmed by evaluating the thermodynamic parameters obtained in this investigation. The kinetics study showed that the interaction between Cr(VI) ions and magnetic nanocomposites was directed by a pseudo-second-order rate process indicating chemisorption. The prepared PPy/Fe3O4 nanocomposites would be promising adsorbents to purify water by eliminating Cr(VI) metal ions from wastewater.

Design of Modified Polymer Membranes Using Machine Learning

Surface modification is an attractive strategy to adjust the properties of polymer membranes. Unfortunately, predictive structure-processing-property relationships between the modification strategies and membrane performance are often unknown. One possibility to tackle this challenge is the application of data-driven methods such as machine learning. In this study, we applied machine learning methods to data sets containing the performance parameters of modified membranes. The resulting machine learning models were used to predict performance parameters, such as the pure water permeability and the zeta potential of membranes modified with new substances. The predictions had low prediction errors, which allowed us to generalize them to similar membrane modifications and processing conditions. Additionally, machine learning methods were able to identify the impact of substance properties and process parameters on the resulting membrane properties. Our results demonstrate that small data sets, as they are common in materials science, can be used as training data for predictive machine learning models. Therefore, machine learning shows great potential as a tool to expedite the development of high-performance membranes while reducing the time and costs associated with the development process at the same time.

Comprehensive assessment of carbon-, biomaterial- and inorganic-based adsorbents for the removal of the most hazardous heavy metal ions from wastewater

Owing to the high cost of recycling waste, underdeveloped countries discharge industrial, agricultural, and anthropogenic effluents without pretreatment. As a result, pollutant-loaded waste enters water bodies. Among the diverse toxic contaminants, heavy metal ions are the most detrimental because of their chronic toxicity, non-degradability, prevalence, and bioaccumulation. The growing shortage of water resources demands the removal of heavy metal ions from wastewater. Three SDGs of the sustainability agenda of the United Nations appeal for clean water to protect life beneath water and on land depending on the water sources. Therefore, efficient environmentally friendly approaches for wastewater treatment are urgently required. In this regard, several methods have been developed for the removal of heavy metal ions from wastewater, including adsorption as the most widely used method owing to its eco-friendly, cost-effective, and sustainable nature. The present review discusses the progress in the preparation and application of various adsorbents based on carbon, micro-organisms, agricultural waste and inorganic materials for the extraction of toxic metal ions such as Pb2+, Cr6+, As3+, As5+, Hg2+ and Cd2+. Herein, we provide information on the role of the homogeneity and heterogeneity of adsorbents, kinetics of the adsorption of an adsorbate on the surface of an adsorbent, insights into adsorption reaction pathways, the mechanism of the sorption process, and the uptake of solutes from solution. The present review will be useful for researchers working on environmental protection and clean environment.

Element contamination of the Orange-Vaal River basin, South Africa: a One Health approach

Numerous low-income groups and rural communities depend on fish as an inexpensive protein source worldwide, especially in developing countries. These communities are constantly exposed to various pollutants when they frequently consume polluted fish. The largest river basin in South Africa is the Orange-Vaal River basin, and several anthropogenic impacts, especially gold mining activities and industrial and urban effluents, affect this basin. The Department of Environment, Forestry and Fisheries in South Africa has approved the much-anticipated National Freshwater (Inland) Wild Capture Fisheries Policy in 2021. The aims of this study were (1) to analyze element concentrations in the widely distributed Clarias gariepinus from six sites from the Orange-Vaal River basin and (2) to determine the carcinogenic and non-carcinogenic human health risks associated with fish consumption. The bioaccumulation of eight potentially toxic elements (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) was assessed in C. gariepinus from sites with different anthropogenic sources. The human health risks were determined to assess the potential risks posed by consuming contaminated C. gariepinus from these sites. Carcinogenic health risks were associated with fish consumption, where it ranged between 21 and 75 out of 10,000 people having the probability to develop cancer from As exposure. The cancer risk between the sites ranged between 1 and 7 out of 10,000 people to developing cancer from Cr exposure. A high probability of adverse non-carcinogenic health risks is expected if the hazard quotient (HQ) is higher than one. The HQ in C. gariepinus from the six sites ranged between 1.5 and 5.6 for As, while for Hg, it was between 1.8 and 5.1. These results highlight the need for monitoring programs of toxic pollutants in major river systems and impoundments in South Africa, especially with the new fisheries policy, as there are possible human health risks associated with the consumption of contaminated fish.

Human Health Effects of Oral Exposure to Chromium: A Systematic Review of the Epidemiological Evidence

The toxicity and carcinogenicity of hexavalent chromium via the inhalation route is well established. However, a scientific debate has arisen about the potential effects of oral exposure to chromium on human health. Epidemiological studies evaluating the connection between ingested chromium and adverse health effects on the general population are limited. In recent years, a wealth of biomonitoring studies has emerged evaluating the associations between chromium levels in body fluids and tissues and health outcomes. This systematic review brings together epidemiological and biomonitoring evidence published over the past decade on the health effects of the general population related to oral exposure to chromium. In total, 65 studies were reviewed. There appears to be an inverse association between prenatal chromium exposure and normal fetal development. In adults, parameters of oxidative stress and biochemical alterations increase in response to chromium exposure, while effects on normal renal function are conflicting. Risks of urothelial carcinomas cannot be overlooked. However, findings regarding internal chromium concentrations and abnormalities in various tissues and systems are, in most cases, controversial. Environmental monitoring together with large cohort studies and biomonitoring with multiple biomarkers could fill the scientific gap.

Combined effects of biochar and biodegradable mulch film on chromium bioavailability and the agronomic characteristics of tobacco

Biochar (BC) and biodegradable mulch film (BMF) are both commonly used means of production in agriculture. In recent years, most studies have focused on the effects of BC or BMF on soil heavy metal pollution, while they have neglected the combined effects. In this study, a pot experiment was conducted to examine the impacts of BMF, BC, and combined BMF and BC (CMB) on the mobility of chromium (Cr) and the agronomic characteristics of flue-cured tobacco. Compared with the control, BMF, BC, and CMB significantly reduced the concentrations of diethylenetriamine pentaacetic acid (DTPA) extractable Cr in soils by 29.07-29.75%, 45.35-48.54%, and 34.21-37.92%, respectively. In comparison to the application of BMF and BC alone, co-application reduced the availability of Cr in soil via increasing the adsorption of soil Cr and soil enzyme activity, which resulted in the decrease of Cr content and bioconcentration factor and in plants. Moreover, the combined application increased the plant height, stem diameter, leaf area, total root area, root tip number, and root activity of tobacco, which leaded to increase in leaf and root biomass by 11.40-67.01% and 23.91-50.74%, respectively. Therefore, the application of CMB can reduce the heavy metal residues in tobacco leaves and improve tobacco yield and quality.

Design and application of metal organic frameworks for heavy metals adsorption in water: a review

The growing apprehension surrounding heavy metal pollution in both environmental and industrial contexts has spurred extensive research into adsorption materials aimed at efficient remediation. Among these materials, Metal-Organic Frameworks (MOFs) have risen as versatile and promising contenders due to their adjustable properties, expansive surface areas, and sustainable characteristics, compared to traditional options like activated carbon and zeolites. This exhaustive review delves into the synthesis techniques, structural diversity, and adsorption capabilities of MOFs for the effective removal of heavy metals. The article explores the evolution of MOF design and fabrication methods, highlighting pivotal parameters influencing their adsorption performance, such as pore size, surface area, and the presence of functional groups. In this perspective review, a thorough analysis of various MOFs is presented, emphasizing the crucial role of ligands and metal nodes in adapting MOF properties for heavy metal removal. Moreover, the review delves into recent advancements in MOF-based composites and hybrid materials, shedding light on their heightened adsorption capacities, recyclability, and potential for regeneration. Challenges for optimization, regeneration efficiency and minimizing costs for large-scale applications are discussed.

Humic acid-nanoceria composite as a sustainable adsorbent for simultaneous removal of uranium(VI), chromium(VI), and fluoride ions from aqueous solutions

In this article, the multifunctional behavior of novel, efficient, and cost-effective humic acid-coated nanoceria (HA@CeO2 NPs) was utilized for the sorptive removal of U(VI), Cr(VI), and F- ions at different conditions. The production cost of HA@CeO2 was $19.28/kg and was well characterized by DLS, FESEM, HRTEM, FTIR, XRD, XPS, and TGA. Batch adsorption study for U(VI) (at pH ~ 8), Cr(VI) (at pH ~ 1), and F- (at pH ~ 2) revealed that the maximum percentage of sorption was > 80% for all the cases. From the contact time experiment, it was concluded that pseudo-second-order kinetics followed, and hence, the process should be a chemisorption. The adsorption study revealed that U(VI) and Cr(VI) followed the Freundlich isotherm, whereas F- followed the Langmuir isotherm. Maximum adsorption capacity for F- was 96 mg g-1. Experiments in real water suggest that adsorption is decreased in Kaljani River water (~ 12% for Cr(VI) and ~ 11% for F-) and Kochbihar Lake water (25.04% for Cr(VI) and 20.5% for F-) because of competing ion effect. Mechanism was well established by the kinetic study as well as XPS analysis. Because of high adsorption efficiency, HA@CeO2 NPs can be used for the removal of other harmful water contaminants to make healthy aquatic life as well as purified drinking water.

Appraisal of treated drinking water quality from arsenic removal units in West Bengal, India: Approach on safety, efficiency, sustainability, future health risk and socioeconomics

The present study depicts the true failed scenario of the arsenic (As) removal units (ARU) in West Bengal by evaluating their treated water quality. Annual As removal efficiency of the 12 studied ARUs range between 35.2% and 82.6%. A comprehensive physico-chemical parameters and trace elements analysis find almost 25% and 16.7% of treated drinking water samples with poor water quality index (WQI) and high heavy metal evaluation index (HEI), respectively. The pond-based water treatment plant maintains the production of continuous As-safe water with a range between 60.2% and 66.7% due to its high Fe/As ratio. It's a discontent concluding the treated drinking water of the groundwater based-ARUs were observed with sufficient As mediated cancer risk (3 ×10-3). The non-cancer risk (HQ) of As is safe for the surface water treatment plant (0.38), whereas it is threatening for the groundwater based-ARUs (7.44). However, the drinking water samples are safe in view of HQ from the other trace elements like Hg, Al, Cd, Cr, Pb, F- and NO3-. Small scale ARU could be a feasible mitigation strategy in reducing the As menace in the long run if the plants are maintained correctly. Nevertheless, surface treated water is the most sustainable solution as withdrawal of groundwater for drinking purpose is not a viable practice.

The comprehensive strategy in the human health risk assessment of total chromium impurities in cough syrups with Marshmallow Root (Althaea officinalis) available in Polish pharmacies: regulatory aspects and special emphasis on Cr(VI) mode of action

Chromium, which can currently only be considered pharmacologically active and not an essential element, is a very intriguing elemental impurity in final pharmaceutical products, especially traditional herbal medicinal products. This kind of traditional herbal medicinal product with Marshmallow root (Althaea officinalis L., radix) registered in the EU is widely used among the European population. The aim of this article is to propose a double regulatory strategy in assessing the human health risk of total chromium impurities in cough syrups with Marshmallow Root (Althaea officinalis) available in Polish pharmacies. We applied the strategy based on the requirements of the ICH Q3D (R1) guideline for the assessment of Cr impurities in final traditional herbal medicinal products with Marshmallow Root registered in the EU. Furthermore, we applied the strategy based on the concept of margin of exposure (MoE) considering Cr(VI) genotoxicity mode of action (MOA) and based on BMD10 for Cr(VI) as a point of departure (PoD). The total Cr content was in the range: 1.12-9.61 µg/L (in comparison with the ICH Q3D R1 guidelines: 1100 µg/g). Total Cr levels in a single dose were relatively high compared to raw results, but were not a threat to patients. Comparison of estimated results with oral PDE value for Cr in final drugs suggested by the ICH Q3D R1 guideline (10,700 µg/day) show that all the products analyzed were below this value (the highest result was 278.40 ng/day). Despite conservative assumptions, the MoE values obtained for Cr in daily dose for each Marshmallow Root cough syrup were above 10,000; therefore, exposure to Cr would not cause a health risk for specific population groups (children and adults). It can be summarized that each of the phytopharmaceuticals analysed with Marshmallow root available in Polish pharmacies does not represent a health hazard to patients. We confirm the safety of Cr impurities by applying a double regulatory strategy without the application of an expansive and demanding HPLC-ICP-MS technique for Cr speciation.

Associations between multiple metal exposure and fertility in women: A nested case-control study

Metal pollution can cause a decline in female fertility, however, previous studies have focused more on the effect of a single metal on fertility. In this study, we evaluated the effect of metal mixtures on female fertility based on nested case-control samples. The plasma levels of 22 metal elements from 180 women were determined by an inductively coupled plasma mass spectrometer (ICP-MS). Minimum absolute contraction and selection operator (LASSO) penalty regression selected metals with the greatest influence on clinical outcome. Logistic regression was used to analyze the correlation between single metals and fertility while a Bayesian kernel function regression (BKMR) model was used to analyze the effect of mixed metals. Eight metals (Calcium (Ca), Chromium (Cr), Cobalt (Co), Copper (Cu), Zinc (Zn), Rubidium (Rb), Strontium (Sr) and Zirconium (Zr)) were selected by LASSO regression for subsequent analysis. After adjusting for covariates, the logistic model showed that Cu (Odds Ratio(OR):0.33, 95% CI: 0.13 - 0.84) and Co (OR:0.38, 95% CI: 0.15 -0.94) caused a significant reduction in fertility, and identified the protective effect of Zn (OR: 2.96, 95% CI:1.21 -7.50) on fertility. Trend tests showed that increased Cr, Cu, and Rb levels were associated with reduced fertility. The BKMR model showed that Cr, Co, Cu, and Rb had a nonlinear relationship with fertility decline when controlling for the concentrations of other metals and suggested that Cu and Cr might exert an influence on fertility. Analysis showed a negative correlation between Cu, Cr, Co, Rb, and fertility, and a positive correlation between Zn and fertility. Furthermore, we found evidence for the interaction between Cu and Cr. Our findings require further validation and may identify new mechanisms in the future.

Using neutron activation to assess heavy metal pollution in water and sediment along Savannah River

A comprehensive study was conducted to assess heavy elemental pollution in the Savannah River, which flows through diverse landscapes encompassing agricultural, industrial, and commercial zones in South Carolina and Georgia. The investigation focused on the impacts of various anthropogenic activities on the river, potentially harming human health and aquatic ecosystems. Thirty samples, collected from the beginning of the Savannah River at Lake Hartwell to the Savannah River estuary near the Atlantic Ocean, were analyzed using Instrumental Neutron Activation Analysis. In regions of intense industrial activities, water samples exhibited elevated concentrations of elements such as Al (0.04-1.99 mg/L), Mg (0.4-5.5 mg/L), Ba (0.08-2.8 mg/L), Zn (0.017-0.9 mg/L), Cr (0.005-1.5 mg/L), and Fe (2.8-110.13 mg/L). Similarly, sediment samples near industrial areas also exhibited enhanced concentrations of heavy elements like Cr, Zr, Rb, Co, Zn, Mg, Mn, and Al. The outcome of this study has identified a spatial trend along the Savannah River, revealing major elements responsible for pollution that could disrupt the ecological environment and potentially impact human health.

Study of the Toxicity and Translocation of Chromium (VI) in Vicia faba Plant

In soil, chromium can be found in two main valence forms: hexavalent Cr (VI) and trivalent Cr (III). In terms of toxicity, the most toxic form to plants is Cr (VI). In the present study, we investigated the impact of Cr (VI) (0, 25, 50, 75 and 100 ppm) on growth, physiological parameters and the translocation kinetics of Cr (VI) in the faba bean plant (Vicia faba L.). The results showed that Cr (VI) negatively affects growth parameters (- 15% to - 72%), tolerance index (- 34.05% to - 64.7%), and reduce the total chlorophyll content (until 40%) compared to control plants without Cr (VI). However, the increase of Cr (VI) concentration in the soil, stimulated the synthesis of sugars (max 6,97 mg/g FM), proteins (max 62.89 µg/mg FM) and proline (max 98.57 µg/mg FM) and increased the electrolyte leakage (+ 2.5% to + 9%) compared to control plants. Cr (VI) concentrations in shoots and roots increased significantly for all Cr (VI) doses applied. The translocation factor results showed that the majority of the Cr (VI) absorbed by the plant is stored in the roots, with a very low bioaccumulation factor, which does not exceed 0.4. The findings show that Cr (VI) negatively affects the morpho-physiological parameters of Vicia faba, the bioaccumulation of organic solutes and the low bioaccumulation factor of Cr (VI) can be considered as a strategy of tolerance to Cr(V).

Biochar as Alternative Material for Heavy Metal Adsorption from Groundwaters: Lab-Scale (Column) Experiment Review

The purpose of this manuscript is to present a review of laboratory experiments (including methodology and results) that use biochar, a specific carbon obtained by a pyrolysis process from different feedstocks, as an alternative material for heavy metal adsorption from groundwater. In recent years, many studies have been conducted regarding the application of innovative materials to water decontamination to develop a more sustainable approach to remediation processes. The use of biochar for groundwater remediation has particularly attracted the interest of researchers because it permits the reuse of materials that would be otherwise disposed of, in accordance with circular economy, and reduces the generation of greenhouse gases if compared to the use of virgin materials. A review of the different approaches and results reported in the current literature could be useful because when applying remediation technologies at the field scale, a preliminary phase in which the suitability of the adsorbent is evaluated at the lab scale is often necessary. This paper is therefore organised with a short description of the involved metals and of the biochar production and composition. A comprehensive analysis of the current knowledge related to the use of biochar in groundwater remediation at the laboratory scale to obtain the characteristic parameters of the process that are necessary for the upscaling of the technology at the field scale is also presented. An overview of the results achieved using different experimental conditions, such as the chemical properties and dosage of biochar as well as heavy metal concentrations with their different values of pH, is reported. At the end, numerical studies useful for the interpretation of the experiment results are introduced.

Recent progress in chromium removal from wastewater using covalent organic frameworks - A review

Covalent organic frameworks (COFs) offer a pivotal solution to urgently address heavy metal removal from wastewater due to their exceptional attributes such as high adsorption capacity, tunable porosity, controllable energy band structures, superior photocatalytic performance, and high stability-reusability. Despite these advantages, COFs encounter certain challenges, including inefficient utilization of visible light, rapid recombination of photogenerated carriers, and limited access to active sites due to close stacking. To enhance the photocatalytic and adsorptive performance of COF-based catalysts, various modification strategies have been reported, with a particular focus on molecular design, structural regulation, and heterostructure engineering. This review comprehensively explores recent advancements in COF-based photocatalytic and adsorptive materials for chromium removal from wastewater, addressing kinetics, mechanisms, and key influencing factors. Additionally, it sheds light on the influence of chemical composition and functional groups of COFs on the efficiency of hexavalent chromium [Cr (VI)] removal.

Forming a chromium-based interstrand DNA crosslink: Implications for carcinogenicity

The reduction of the carcinogen chromate has been proposed to lead to three Cr(III)-containing DNA lesions: binary adducts (Cr(III) and DNA), interstrand crosslinks, and ternary adducts (Cr(III) linking DNA to a small molecule or protein). Although the structures of binary adducts have recently been elucidated, the structures of interstrand crosslinks and ternary adducts are not known. Analysis of Cr(III) binding to an oligonucleotide duplex containing a 5'-CG site allows elucidation of the structure of an oxide- or hydroxide-bridged binuclear Cr(III) assembly bridging the two strands of DNA. One Cr(III) is directly coordinated by the N-7 atom of a guanine residue, and the complex straddles the helix to form a hydrogen bond between another guanine residue and a Cr(III)-bound aquo ligand. No involvement of the phosphate backbone was observed. The properties and stability of this Cr-O(H)-Cr-bridged complex differ significantly from those reported for Cr-induced interstrand crosslinks, suggesting that interstrand crosslinks resulting from chromate reduction may be organic in nature.

Simultaneous binding characterization of different chromium speciation to serum albumin

The binding process between three species of chromium and serum albumin (SA) was investigated, as well as the interaction between K2Cr2O7 and bovine serum albumin (BSA) under coexistence of different chromium forms. CrCl3, K2Cr2O7 and Crpic bound to SA spontaneously through Van der Waals force, and their binding constants were 103-104 M-1 at 298 K, respectively. K2Cr2O7 and Crpic both had strong binding affinity for BSA, and significantly affected the secondary structure of BSA and the microenvironment surrounding amino acid residues. Chromium exhibited a greater fluorescence quenching constant towards HSA than toward BSA, and K2Cr2O7 induced greater conformational changes in human serum albumin (HSA) than in BSA. A weak binding of CrCl3 to BSA had no significant effect on the binding affinity of K2Cr2O7 to BSA. K2Cr2O7 and BSA have a greater binding affinity when coexisting with Crpic, and K2Cr2O7 induces a greater conformational change in BSA.

Impacts of climate change on the fate of contaminants through extreme weather events

The direct impacts of climate change involve a multitude of phenomena, including rising sea levels, intensified severe weather events such as droughts and flooding, increased temperatures leading to wildfires, and unpredictable fluctuations in rainfall. This comprehensive review intends to examine firstly the probable consequences of climate change on extreme weather events such as drought, flood and wildfire. This review subsequently examines the release and transformation of contaminants in terrestrial, aquatic, and atmospheric environments in response to extreme weather events driven by climate change. While drought and flood influence the dynamics of inorganic and organic contaminants in terrestrial and aquatic environments, thereby influencing their mobility and transport, wildfire results in the release and spread of organic contaminants in the atmosphere. There is a nascent awareness of climate change's influence of climate change-induced extreme weather events on the dynamics of environmental contaminants in the scientific community and decision-making processes. The remediation industry, in particular, lags behind in adopting adaptive measures for managing contaminated environments affected by climate change-induced extreme weather events. However, recognizing the need for assessment measures represents a pivotal first step towards fostering more adaptive practices in the management of contaminated environments. We highlight the urgency of collaboration between environmental chemists and climate change experts, emphasizing the importance of jointly assessing the fate of contaminants and rigorous action to augment risk assessment and remediation strategies to safeguard the health of our environment.

Safeguarding drinking water: A brief insight on characteristics, treatments and risk assessment of contamination

Water pollution stands as a critical worldwide concern, bearing extensive repercussions that extend to human health and the natural ecosystem. The sources of water pollution can be diverse, arising from natural processes and human activities and the pollutants may range from chemical and biological agents to physical and radiological contaminants. The contamination of water disrupts the natural functioning of the system, leading to both immediate and prolonged health problems. Various technologies and procedures, ranging from conventional to advanced, have been developed to eliminate water impurities, with the choice depending on the type and level of contamination. Assessing risks is a crucial element in guaranteeing the safety of drinking water. Till now, research is continuing the removal of contaminates for the sake of supplying safe drinking water. The study examined physical, inorganic, organic, biological and radiological contaminants in drinking water. It looked at where these contaminants come from, their characteristics, the impact they have and successful methods used in real-world situations to clean the contaminated water. Risk assessment methodologies associated with the use of unsafe drinking water as future directives are also taken into consideration in the present study for the benefit of public concern. The manuscript introduces a comprehensive study on water pollution, focusing on assessing and mitigating risks associated with physical, inorganic, organic, biological and radiological contaminants in drinking water, with a novel emphasis on future directives and sustainable solutions for public safety.

Optimized Polymeric Membranes for Water Treatment: Fabrication, Morphology, and Performance

Conventional polymers, endowed with specific functionalities, are extensively utilized for filtering and extracting a diverse set of chemicals, notably metals, from solutions. The main structure of a polymer is an integral part for designing an efficient separating system. However, its chemical functionality further contributes to the selectivity, fabrication process, and resulting product morphology. One example would be a membrane that can be employed to selectively remove a targeted metal ion or chemical from a solution, leaving behind the useful components of the solution. Such membranes or products are highly sought after for purifying polluted water contaminated with toxic and heavy metals. An efficient water-purifying membrane must fulfill several requirements, including a specific morphology attained by the material with a specific chemical functionality and facile fabrication for integration into a purifying module Therefore, the selection of an appropriate polymer and its functionalization become crucial and determining steps. This review highlights the attempts made in functionalizing various polymers (including natural ones) or copolymers with chemical groups decisive for membranes to act as water purifiers. Among these recently developed membrane systems, some of the materials incorporating other macromolecules, e.g., MOFs, COFs, and graphene, have displayed their competence for water treatment. Furthermore, it also summarizes the self-assembly and resulting morphology of the membrane materials as critical for driving the purification mechanism. This comprehensive overview aims to provide readers with a concise and conclusive understanding of these materials for water purification, as well as elucidating further perspectives and challenges.

Effects of hexavalent chromium on mitochondria and their implications in carcinogenesis

Hexavalent chromium (Cr(VI)) is a well-known occupational and environmental human carcinogen. The cellular effect of Cr(VI) is complex and often nonspecific due to its ability to modulate multiple cellular targets. The toxicity of Cr(VI) is strongly linked to the generation of reactive oxygen species (ROS) during its reduction process. ROS can cause oxidation of cellular macromolecules, such as proteins, lipids, and DNA, thereby altering their functions. A major genotoxic effect of Cr(VI) that contributes to carcinogenesis is the formation of DNA adducts, which can lead to DNA damage. Modulations of cellular signaling pathways and epigenetics may also contribute to the carcinogenic effects of Cr(VI). Cr(VI) has a major impact on many aspects of mitochondrial biology, including oxidative phosphorylation, mitophagy, and mitochondrial biogenesis. These effects have the potential to alter the trajectory of Cr(VI)-induced carcinogenic process. This perspective article summarizes current understandings of the effect of Cr(VI) on mitochondria and discusses the future directions of research in this area, particularly with regard to carcinogenesis.

Evidence for the accumulation of toxic metal(loid)s in agricultural soils impacted from long-term application of phosphate fertilizer

Phosphate fertilizers may contain elevated concentrations of toxic metals and metalloids and therefore, their excessive application can result in the accumulation of both phosphorus (P) and metal(loid)s in agricultural soils. This study aims to investigate the occurrence, distribution, and potential plant-availability of metal(loid)s originating from phosphate fertilizer in a long-term experimental field at the Tidewater Research Station in North Carolina, where topsoil (10-20 cm deep) and subsoil (up to 150 cm deep) samples were collected from five plots with consistent and individually different application rates of P-fertilizer since 1966. We conducted systematic analyses of P and metal(loid)s in bulk soils, in the plant available fraction, and in four sequentially extracted soil fractions (exchangeable, reducible, oxidizable, and residual). The results show that P content in topsoils were directly associated with the rate of P-fertilizer application (ρ = 1, p < 0.05). Furthermore, P concentrations were highly correlated with concentrations of Cd, U, Cr, V, and As in the bulk topsoil (ρ > 0.58, p < 0.05), as well as the potential plant-available fraction (ρ > 0.67, p < 0.01), indicating the accumulation of the fertilizer-derived toxic metal(loid)s in the topsoil. Significant correlations (p < 0.001) of metal(loid)s concentrations between the bulk soil and the potential plant-available fraction raises the possibility that P-fertilizer application could increase the accumulation of toxic metal(loid)s in plants, which could increase human exposure. Results from sequential leaching experiments revealed that large portions of the trace elements, in particular Cd, occur in the soluble (exchangeable and reducing) fractions of topsoil with higher P-fertilizer input, whereas the levels of redox-sensitive elements (As, V, U, Cr) were higher in the reducible and oxidizable fractions of the soils. Overall, the data presented in this study demonstrate the effect of long-term P-fertilizer application on the occurrence and accumulation of a wide range of toxic metal(loid)s in agricultural topsoil.

Cr-Detector: A simple chemosensing system for onsite Cr (VI) detection in water

Due to the increase in urbanization and industrialization, the load of toxicants in the environment is alarming. The most common toxicants, including heavy metals and metalloids such as hexavalent Chromium, have severe pathophysiological impacts on humans and other aquatic biotas. Therefore, developing a portable rapid detection device for such toxicants in the aquatic environment is necessary. This work portrays the development of a field-portable image analysis device coupled with 3,3',5,5'-tetramethylbenzidine (TMB) as a sensing probe for chromium (VI) detection in the aquatic ecosystem. Sensor parameters, such as reagent concentration, reaction time, etc., were optimized for the sensor development and validation using a commercial UV-Vis spectrophotometer. The chemoreceptor integrated with a uniform illumination imaging system (UIIS) revealed the system's applicability toward Cr(VI) detection. The calibration curve using the R-value of image parameters allows Cr(VI) detection in the linear range of 25 to 600 ppb, which covers the prescribed permissible limit by various regulatory authorities. Furthermore, the adjusted R2 = 0.992 of the linear fit and correlation coefficients of 0.99018 against the spectrophotometric method signifies the suitability of the developed system. This TMB-coupled field-portable sensing system is the first-ever reported image analysis-based technology for detecting a wide range of Cr(VI) in aquatic ecosystems to our knowledge.

Biostimulation effect of different amendments on Cr(VI) recovering microbial community

The present study used Cr(VI)-polluted microcosms amended with lactate or yeast extract, and nonamended microcosms as control, to investigate how a native bacterial community varied in response to the treatment and during the pollutant removal. Results suggested that providing electron donors resulted in a proliferation of a few bacterial species, with the consequent decrease in observed species richness and evenness, and was a driving force for the bacterial compositional shift. Lactate promoted, in the first instance, the enrichment of fermentative bacteria belonging to Chromobacteriaceae, including Paludibacterium, and Micrococcaceae as observed after 4 days. When the rate of Cr(VI) removal was maximum in microcosms amended with lactate, the most represented taxa were Pseudarcicella and Azospirillum. Using yeast extract as a carbon source and electron donor led instead to the significant enrichment of Shewanella, followed by Vogesella and Acinetobacter on the 4th day, corresponding to 90% of Cr(VI) removed from the system. After the complete Cr(VI) removal, achieved in 7 days in the presence of yeast extract, α-diversity was notably increased. The amendment-specific turnover of the enriched bacterial taxa resulted in a different kinetic of pollutant removal. In particular, yeast extract promoted the quickest Cr(VI) reduction, while lactate supported a slower, but also considerable, pollutant removal from water. Since it is reasonable to assume that a macroscopic effect, such as the observed Cr(VI) removal, involved the overrepresented taxa, deepening the knowledge of the native bacterial community and its changes were used to hypothesize the possible microbial pathways involved.

Optimizing electronic states of Pd/WO3 nanofibers for enhanced catalytic reduction of hexavalent chromium with formic acid

Through theoretical calculations, we show that integrating Pd with WO3 nanomaterials can trigger the interfacial electron transfer from Pd to WO3, thus upshifting the d-band center (εd) of Pd to optimize toxic hexavalent chromium (Cr(VI)) reduction. The elevated εd can derive stronger chemisorption capability toward crucial formic acid molecules, notably lowering the thermodynamic energy barrier and speeding up the kinetics process. In order to realize this concept, we synthesized unique Pd/WO3 nanofibers by loading Pd nanoparticles onto electrospun WO3 nanofibers through an in situ photodeposition technique. Extensive structural, morphological, and X-ray photoelectron spectrometer (XPS) characterizations confirm the successful formation of the above nanofibers. As anticipated, the as-designed Pd/WO3 nanofibers exhibit enhanced catalytic performance in the Cr(VI) reduction with a high turnover frequency (TOF) value of 62.12 min-1, surpassing a series of reported Pd-based catalysts. Such nanofibrous WO3-induced electronic modification of Pd with a high specific area leads to catalytic enhancement, providing a novel model for catalyst design.

Inhibition of Hexavalent Chromium Release from Drinking Water Distribution Systems: Effects of Water Chemistry-Based Corrosion Control Strategies

In drinking water distribution systems, the oxidation of zerovalent chromium, Cr(0), in iron corrosion scales by chlorine residual disinfectant is the dominant reaction to form carcinogenic hexavalent chromium, Cr(VI). This study investigates inhibitive corrosion control strategies through adjustments of chemical water parameters (i.e., pH, silicate, phosphate, calcium, and alkalinity) on Cr(VI) formation through oxidation of Cr(0)(s) by free chlorine under drinking water conditions. The results show that an increase in pH, silicate, alkalinity, and calcium suppressed Cr(VI) formation that was mainly attributed to in situ surface precipitation of new Cr(III) solids on the surface of Cr(0)(s), including Cr(OH)3(s), Cr2(SiO3)3(s), CrPO4(s), Cr2(CO3)3(s), and Cr10Ca(CO3)16(s). The Cr(III) surface precipitates were much less reactive with chlorine than Cr(0)(s) and suppressed the Cr redox reactivity. The concentration of surface Cr(III) solids was inversely correlated with the rate constant of Cr(VI) formation. Adding phosphate either promoted or inhibited the Cr(VI) formation, depending on the phosphate concentration. This study provides fundamental insight into the Cr(VI) formation mechanisms via Cr(0) oxidation by chlorine and the importance of surface precipitation of Cr(III) solids with different corrosion control strategies and suggests that increasing the pH/alkalinity and addition of phosphate or silicate can be effective control strategies to minimize Cr(VI) formation.

Moringa oleifera seed based green synthesis of copper nanoparticles: Characterization, environmental remediation and antimicrobial activity

Textile dyes and heavy metals like hexavalent chromium [Cr(VI)] are considered major water pollutants. In addition, microbial contamination also seriously threatens potable water availability. The present study used Moringa oleifera seed aqueous extract to synthesize copper nanoparticles (MOS-CuNPs). MOS-CuNPs were characterized by various spectroscopy and microscopic techniques. MOS-CuNPs were shown to be effectual at removal of Cr(VI). The initial concentration of Cr(VI), contact time, pH, and temperature all impacted the removal of Cr(VI) by different concentrations of MOS-CuNPs. At low concentrations of MOS-CuNPs (0.3 mg/ml) pseudo-first order and high concentrations of MOS-CuNPs (0.4 and 0.5 mg/ml), pseudo-second order kinetics were obeyed. Thermodynamic analysis revealed that Cr(VI) was removed spontaneously, and the reaction was exothermic. In adsorption isotherm, equilibrium data followed Langmuir equation for Cr(VI) adsorption by MOS-CuNPs and maximum uptake capacity calculated was 38.6 mg/g. MOS-CuNPs efficiently removed cationic (rhodamine B, malachite green and methylene blue and) and anionic (congo red, titan yellow and methyl orange) dyes within 10 min of contact time. Further MOS-CuNPs showed antimicrobial activity against human pathogenic bacteria and fungi. Altogether, MOS-CuNPs could be used for environmental (water treatment) and biological applications.

Sources, distribution, associated health risks and remedial technologies for inorganic contamination in groundwater: A review in specific context of the state of Haryana, India

Haryana is one of the leading states in India in the agricultural and industrial production. With the expansion of these sectors, a continuous increase in water demand is leading to water crises arising from overexploitation and quality deterioration of the available water. Contamination of aquifer resources is a significant concern, because majority of population depends on the groundwater for various agricultural, industrial, and domestic needs. This review article provides an overview of groundwater contamination, associated health risks with different contaminants with regions severely affected by poor water quality, and delves in identifying the sources, by observing and recognising the types of industries dominant in the state with types of effluents discharge. It further suggests the possible mitigation measures such as advanced remedial technologies and proper management practices from the consequent contamination sources. It has been observed during the perusal of various studies and data that the degree of contamination was considerably higher in districts with heavy agro-industrial activities. The groundwater resources in three highly industrialized districts were found to be gravely contaminated with toxic heavy metals. Alongwith heavy metals, the salinity, hardness, nitrate, and fluoride are also posing significant problems in the aquifer resources of Haryana state. The article also discusses various technologies for remediation of different pollutants from groundwater so it can be made potable after treatment.

Contaminant Metals and Cardiovascular Health

A growing body of research has begun to link exposure to environmental contaminants, such as heavy metals, with a variety of negative health outcomes. In this paper, we sought to review the current research describing the impact of certain common contaminant metals on cardiovascular (CV) health. We reviewed ten metals: lead, barium, nickel, chromium, cadmium, arsenic, mercury, selenium, zinc, and copper. After a literature review, we briefly summarized the routes of environmental exposure, pathophysiological mechanisms, CV health impacts, and exposure prevention and/or mitigation strategies for each metal. The resulting article discloses a broad spectrum of pathological significance, from relatively benign substances with little to no described effects on CV health, such as chromium and selenium, to substances with a wide-ranging and relatively severe spectrum of CV pathologies, such as arsenic, cadmium, and lead. It is our hope that this article will provide clinicians with a practical overview of the impact of these common environmental contaminants on CV health as well as highlight areas that require further investigation to better understand how these metals impact the incidence and progression of CV diseases.

Magnetic Polypyrrole-Gelatin-Barium Ferrite Cryogel as an Adsorbent for Chromium (VI) Removal

Polypyrrole-gelatin aerogels, containing magnetic barium ferrite (BaFe) particles, (PPy-G-BaFe) were synthesized by oxidative cryopolymerization and used as adsorbents for the removal of Cr(VI) from aqueous media. The removal was performed at pH 4, which was shown to be the optimal value, due to HCrO4- being the dominant species in these conditions and its more favorable adsorption and reduction compared to CrO42-, present at pH > 4. It was found that the presence of magnetic BaFe particles had no effect on the adsorption performance of PPy aerogels in terms of capacity and kinetics, which was attributed to its relatively low content in the composite. After the adsorption, the presence of chromium in the composites was confirmed by EDX and its electrostatic interaction with the adsorbent was pointed at by vibrational spectroscopy, corresponding to the accepted adsorption mechanism. The adsorption kinetics followed the pseudo-second-order model pointing at chemisorption being the rate-limiting step. The adsorption isotherm data was best fitting with the Temkin model. The maximum adsorption capacity, calculated using the Langmuir model, was 255.8 mg g-1 (the maximum experimental value was 161.6 mg g-1). Additionally, the possibility of Cr(VI) adsorption in the presence of Cl-, Br-, NO3- and SO42- as interfering ions was shown.

Examining the Potential Formation of Ternary DNA Complexes with Chromium‑Cysteine, Chromium-Ascorbate, and Chromium-Glutathione and Implications for Their Carcinogenicity

The mutagenic and carcinogenic properties of chromium(VI) complexes have been ascribed to the formation of ternary Cr(III)-small molecule-DNA complexes. As part of these laboratories' efforts to establish the structure and properties of discrete binary and ternary adducts of Cr(III) and DNA at a molecular level, the properties of Cr(III)-cysteine-DNA, Cr(III)-ascorbate-DNA, and Cr(III)-glutathione-DNA complexes formed from Cr(III) were examined. These studies determined the composition of previously described "pre-reacted" chromium cysteinate and chromium glutathione. Neither of these complexes nor "chromium ascorbate" form ternary complexes with DNA as previously proposed. In fact, these Cr(III) compounds do not measurably bind to DNA and cannot be responsible for the mutagenic and carcinogenic properties ascribed to ternary Cr(III)-cysteine-DNA and Cr(III)-ascorbate-DNA adducts. The results of biological studies where "ternary adducts" of Cr(III), cysteine, glutathione, or ascorbate and DNA were made from "pre-reacted" chromium cysteinate or chromium glutathione or from "chromium ascorbate" must, therefore, be interpreted with caution.

Effect of hexavalent chromium on growth performance and metabolism in broiler chicken

Hexavalent chromium Cr (VI) is one of the most hazardous heavy metals in the environment and is toxic to living organisms causing tissue damage, disruption of the intestinal microbiota and cancer. However, there is little information on the relationship between the Cr (VI) and broiler chickens. The current study was performed to investigate the effect of Cr (VI) on growth performance, serum biochemical analysis, histopathological observations, and metabolomics analysis in broilers. Results show that Cr (VI) exposure significantly decreased the body weight (p < 0.01) and caused liver damages in broilers. With the extension of Cr (VI) action time, the liver appeared obvious pathological changes, including hepatic cord disorder, incomplete hepatocyte additionally, decreased serum biochemical indices of calcium (Ca), phosphorus (P), total protein (TP), phosphatase (ALP), and globin (GLB) significantly (p < 0.01). Moreover, metabolomics analysis indicated that 29 differential metabolites were identified, such as phytosphingosine, L-Serine, 12, 13-DHOME, Alpha-dimorphecolic acid, L-Methionine, L-Phenylalanine, 3-Dehydroshikimate, L-Tyrosine, and N-Acetyl-L-phenylalanine were significantly decreased under the action of Cr (VI) (p < 0.05). These 29 differential metabolites are mainly involved in 35 metabolic pathways, such as aminoacyl-tRNA biosynthesis, phenylalanine metabolism, sphingolipid, and linoleic metabolism. The study revealed that exposure to Cr (VI) resulted in a decrease in growth performance and metabolism, with the hazards and toxicity in broiler chicken. The findings provided new insight and a comprehensive understanding of the relationship between Cr (VI) and broiler chickens.

A review on chromium health hazards and molecular mechanism of chromium bioremediation

Living beings have been devastated by environmental pollution, which has reached its peak. The disastrous pollution of the environment is in large part due to industrial wastes containing toxic pollutants. The widespread use of chromium (Cr (III)/Cr (VI)) in industries, especially tanneries, makes it one of the most dangerous environmental pollutants. Chromium pollution is widespread due to ineffective treatment methods. Bioremediation of chromium (Cr) using bacteria is very thoughtful due to its eco-friendly and cost-effective outcome. In order to counter chromium toxicity, bacteria have numerous mechanisms, such as the ability to absorb, reduce, efflux, or accumulate the metal. In this review article, we focused on chromium toxicity on human and environmental health as well as its bioremediation mechanism.

The overlooked role of Cr(VI) in micropollutant degradation under solar light irradiation

Hexavalent chromium (Cr(VI)) is ubiquitous in natural environments, whereas its role in the transformation of coexisting contaminants may have been overlooked. In this work, it was reported for the first time that the irradiation of Cr(VI) by solar light (solar light/Cr(VI) system) could effectively degrade various micropollutants with different structures. The removal efficiency of selected micropollutants was increased by 13.3-64.8% by the solar light/Cr(VI) system compared to that by direct solar photolysis. Meanwhile, the oxidation rates were enhanced by 2.2-21.5 folds, while they were negligible by Cr(VI) oxidation alone. Experiments by specific scavengers, probe compounds, fluorescence absorbance, and electron spin resonance analysis demonstrated that hydroxyl radical (•OH) was the major reactive species in the solar light/Cr(VI) system. Further experiments showed that the generation of •OH was closely related to the intermediate Cr(V) generated from Cr(VI) reduction, and Cr(V) could be re-oxidized back to Cr(VI). Increasing solution pH negatively affected model micropollutant (carbamazepine (CBZ)) degradation by the solar light/Cr(VI) system, mainly due to the decreased quantum yield of •OH at higher pH. Coexisting sulfate ions showed negligible effect on CBZ degradation in the solar light/Cr(VI) system, while the presence of bicarbonate, chloride, and humic acid inhibited CBZ degradation to varying degrees, owing to their diverse scavenging effects on •OH. Furthermore, moderate CBZ degradation was also achieved by natural solar light photolysis of Cr(VI). This study demonstrated the pivotal role of Cr(VI) in the transformation of micropollutants under solar irradiation, which advances the understanding of the fate of micropollutants in natural environments.

Tin Oxide Nanoparticles via Solar Vapor Deposition for Hexavalent Chromium Remediation

Tin oxide nanoparticles optimized to capture low concentrations of hexavalent chromium from water were developed through a facile, scalable, and low-cost one-step solar vapor deposition methodology. Considering the preservation of high electron donation capacity as the key to support the reduction of mobile Cr(VI) into insoluble forms, the growth of SnO nanoparticles was favored by the co-evaporation of SnO2 with Fe powders at various mass ratios. Characterization techniques indicated that the percentage and the stability of SnO is proportional to the Fe content in the target with a requirement of at least 50% wt to inhibit the formation of a passive SnO2 surface layer. The produced particles were evaluated regarding their efficiency to capture Cr(VI) under conditions similar to water treatment for drinking purposes (pH 7). It was revealed that passivation-free SnO nanoparticles deliver significant improvement in the adsorption capacity corresponding to the residual concentration of 25 μg/L, reaching a value of 1.74 mg/g for the sample prepared with 50% wt Fe in the target. The increase of water acidity was found responsible for the activation of more reduction sites on the particle surface, as reflected through the elevation of efficiency by more than 20% at pH 6.