Adverse hematological effects of hexavalent chromium: an overview

Prenatal metal exposures and kidney function in adolescence in Project Viva

BACKGROUND

The developing kidney is vulnerable to prenatal environmental factors such as metal exposure, potentially altering the risk of later-life kidney dysfunction. This study examines the relationship between prenatal metal exposures, individually and as mixtures, and adolescent kidney function in Project Viva, a prospective longitudinal birth cohort in Massachusetts, USA.

METHODS

We used data on metals measured in blood during pregnancy including 15 in the first trimester and four in the second trimester. We calculated estimated glomerular filtration rate (eGFR) in adolescents (mean: 17.7 years) using cystatin C- (eGFRcys) and creatinine-based (eGFRcreat) equations for children. We used linear regression for single metal analyses, and Bayesian kernel machine regression and quantile-based g-computation for mixture analyses, adjusting for relevant covariates. To account for multiple comparisons in the single metal analyses, we applied the Holm-Bonferroni procedure to control the false discovery rate.

RESULTS

This study included 371 participants with first trimester metals and adolescent eGFR, and 256 with second trimester metals. Each doubling in first trimester cadmium concentration was associated with lower adolescent eGFRcys (β:-1.51; 95% CI:-2.83, -0.18). Each doubling in first trimester chromium (β:-1.45; 95% CI:-2.71, -0.19), nickel (β:-1.91; 95% CI:-3.65, -0.16), and vanadium (β:-1.69; 95% CI:-3.21, -0.17) was associated with lower adolescent eGFRcreat. After adjusting for multiple comparisons, p-values for associations between adolescent eGFR and chromium, nickel, vanadium and cadmium did not meet the criteria for significance. Metal mixture analyses did not identify statistically significant associations with adolescent eGFR.

CONCLUSIONS

These findings have important implications for future studies investigating the potential mechanisms through which prenatal metal exposures affect long-term kidney health in children.

Chromium Affects Mitochondrial Function, Leading to Apoptosis and Autophagy in Turtle Primary Hepatocytes

Hexavalent chromium (Cr(VI)), a pervasive industrial contaminant, is highly toxic to both humans and animals. However, its effects on turtles are largely unexplored. Our study aimed to investigate the toxic effects of Cr(VI) on the Reeves' turtles (Mauremys reevesii) primary hepatocytes. We exposed hepatocytes to two concentrations (25 μM and 50 μM) of Cr(VI) for 24 h. The results showed that compared to controls, Cr(VI)-treated cells showed elevated antioxidant enzyme activity (catalase (CAT) and superoxide dismutase (SOD)) and increased reactive oxygen species (ROS) levels. Adenosine triphosphatae (ATP) levels decreased, indicating mitochondrial dysfunction. Additionally, we found significant changes in mitochondrial dynamics related genes, with downregulation of mitofusin 2 (Mfn2) and silent information regulator 1 (SIRT1) and a decrease in sirtuin 3 (SIRT3) and tumor protein 53 (p53) mRNA levels. Annexin V-FITC fluorescence staining-positive cells increased with higher Cr(VI) concentrations, marked by elevated bcl-2-associated X protein (Bax) and cysteinyl aspartate specific proteinase (Caspase3) mRNA levels and reduced B-cell lymphoma-2 (Bcl2) expression. Autophagy-related genes were also affected, with increased microtubule-associated protein 1 light chain 3 (LC3-I), microtubule-associated protein light chain 3II (LC3-II), unc-51-like autophagy-activating kinase 1 (ULK1), and sequestosome 1 (p62/SQSTM1) mRNA levels and decreased mammalian target of rapamycin (mTOR) and Beclin1 expression. Taken together, Cr(VI) promotes cell apoptosis and autophagy in turtle hepatocytes by inducing oxidative stress and disrupting mitochondrial function. These findings highlight the serious health risks posed by Cr(VI) pollution and emphasize the need for protecting wild turtle populations.

Abnormal erythrocyte-related parameters in children with Pb, Cr, Cu and Zn exposure

The link between exposure to a particular heavy metal or metalloid and the development of anemia is well established. However, the association between combined exposure to multiple heavy metal(loid)s and anemia in children is still lacking in evidence. In this study, a total of 266 children aged 3 to 7 were recruited from Guiyu, China. Inductively coupled plasma mass spectrometry (ICP-MS) was used to measure blood heavy metal(loid) concentrations. Blood cell count, hemoglobin (HGB), mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), hematocrit (HCT), and red blood cell distribution width (RDW) were measured by an automated hematology analyzer. Erythrocyte-related parameters were negatively correlated with the Cu and Cu/Zn ratios and positively correlated with Cr, Ni, Zn, and Se by Spearman correlation analysis. Only blood Cu level was negatively correlated with HGB [β = -2.74, (95% Cl: -4.49, -0.995)], MCH [β = -0.505, (95% Cl: -0.785, -0.226)], MCV [β = -1.024, (95% Cl: -1.767, -0.281)], and MCHC [β = -2.137, (95% Cl: -3.54, -0.734)] by multiple linear regression analysis. The Bayesian Kernel Machine Regression (BKMR) model analysis indicated a negative correlation between the combined exposure to Cu, Zn, Pb, and Cr and MCH and MCV. The single-factor analysis showed a considerable statistical difference only with Cu on MCV, MCH, and HGB. Furthermore, the interaction analysis highlighted the interdependent effects of Cu and Zn, Pb and Zn, and Cr and Zn on MCH and MCV levels. Additionally, the oxidation and/or antioxidation reactions may play a significant role in the development of metal(loid)-induced anemia risk. It is crucial to investigate the effects of co-exposure to multiple heavy metal(loid) elements on anemia, especially the interrelationships and mechanisms among them.

Development of a continuous electrochemical reactor incorporated with waste-derived activated carbon electrode for the effective removal of hexavalent chromium from industrial effluent

Being a recognized carcinogen, hexavalent chromium is hazardous to both human and environmental health. Thus, it is imperative to regulate and oversee their levels in a variety of industries, including textiles, dyes, pigments, and metal finishing. This study strives to reduce Cr(VI) in wastewater by using capacitive deionization in conjunction with an activated carbon-based electrode and a continuous electrochemical reactor (CER). Activated carbon derived from rubberwood sawdust demonstrated excellent properties, including a high surface area of 1157 m2 g-1. The electrical conductivity and mechanical stability of the electrode were enhanced by the incorporation of synthesized expanded graphite (EG) into the AC. Key parameters were optimized via systematic batch electroreduction experiments with an optimal response surface design. The efficacy of the fabricated CER was proved when it successfully reduced Cr(VI) in a 5 mg L-1 solution within 15 min under optimized conditions, in contrast to the considerably longer durations anticipated by conventional methods. Validation of these findings was done by treating industrial wastewater of 30 mg L-1 in the CER. The electroreduction of Cr(VI) followed the Langmuir isotherm with a maximum capacity of 13.491 mg g-1 and pseudo-second-order kinetics. These results indicate that the combined use of the modified AC electrode and CER holds potential as a sustainable and economical approach to effectively eliminate Cr(VI) from wastewater.

Always positive covalent organic nanosheet enabling pH-independent adsorption and removal of Cr(Ⅵ)

Rapid and highly effective removal of hexavalent chromium (Cr(Ⅵ)) is extremely vital to water resources restoration and environmental protection. To overcome the pH limitation faced by most ionic absorbents, an always positive covalent organic nanosheet (CON) material was prepared and its Cr(VI) adsorption and removal capability was investigated in detail. As-prepared EB-TFB CON (TFB = 1,3,5-benzaldehyde, EB = ethidium bromide) shows strong electropositivity in the tested pH range of 1 ∼ 10, display a pH-independent Cr(VI) removal ability, and work well for Cr(VI) pollution treatment with good anti-interference capability and reusability in a wide pH range covering almost all Cr(VI)-contaminated real water samples, thus eliminating the requirement for pH adjustment. Moreover, the nanosheet structure, which is obtained by a facile ultrasonic-assisted self-exfoliation, endows EB-TFB CON with fully exposed active sites and shortened mass transfer channels, and the Cr(VI) adsorption equilibrium can be reached within 15 min with a high adsorption capacity of 280.57 mg·g-1. The proposed Cr(VI) removal mechanism, which is attributed to the synergetic contributions of electrostatic adsorption, ion exchange and chemical reduction, is demonstrated by experiments and theoretical calculations. This work not only provides a general Cr(VI) absorbent without pH limitation, but also presents a paradigm to prepare ionic CONs with relatively constant surface charges.

The comprehensive review about elements accumulation in industrial hemp (Cannabis sativa L.)

Cannabis sativa L., commonly known as industrial hemp, is a versatile plant with applications ranging from medicinal to agricultural and industrial uses. Despite its benefits, there is a notable gap in regulatory toxicology, in understanding the extent of element accumulation in hemp, which is critical due to its ability to absorb various elements from the soil, including heavy metals (Pb, Cd, Hg, and As), uptakes potential toxic elements (e.g., Sb, Sn, Sr, Bi, Tl), problematic elements (Ni, Cr, Co), and essential elements (Zn, Cu, Fe, Mn). The paper aims to enrich current understandings by offering a comprehensive analysis of elements absorption in industrial hemp. This study emphasizes the potential health risks linked with hemp consumption including regulatory toxicology aspects: limits, Permitted Daily Exposures (PDE), recommendations in different countries and from different agencies/bodies (like the WHO and the EU) based on route of administration, jurisdiction and actual literature review. This review contributes significantly to the knowledge base on hemp safety, serving as a valuable resource for researchers, regulatory bodies, and industry stakeholders.

Trace metal biomonitoring in the farming of tambaqui (Colossoma macropomum), an Amazonian neotropical fish

In Brazil, studies evaluating the concentration of trace metals in fish farms are scarce. Therefore, studies investigating the presence and levels of these metals in aquatic biota, particularly in fish tissues, are crucial for developing appropriate strategies to mitigate the impact of possible toxic metals. Herein, we investigated the levels of trace metals (Cr, Mn, Co, Ni, Cu, Zn, Al, Ag, Cd, Pb, Fe, Na, Mg, Ca, K, and Ba) in water, feed, and sediment, as well as the bioconcentration and bioaccumulation factors in tambaqui muscles (Colossoma macropomum). For this purpose, eight commercial fish farms, which are also engaged in other agricultural activities, were selected. Fe, Zn, Mg, and Cr concentration in tambaqui muscles exceeded the limits set by the Brazilian regulations for daily consumption by adults. Mn, Zn, Al, Pb, Fe, Na, Cu, Co, Ag, Cd, and Ba levels were substantially higher in the liver tissue of tambaquis than those in the muscle tissue. The most prevalent metals found in the feed were Ca, K, Na, Mg, and Fe. However, the levels of Cr and Cd in the sediment, as well as Pb, Mn, Cu, and Fe in the water, exceeded the maximum limits allowed by the Brazilian legislation. The highest bioconcentration factors were observed for the metals, Na, Zn, and K, with concentrations up to 4.74, 12.61, and 72.08 times, respectively, higher in tambaqui muscle compared to those in water. The bioaccumulation factors for Ca, Zn, Mg, Na, and K were 2.90, 6.96, 21.21, 212.33, and 492.02 times, respectively, higher in the muscle tissue than those in the sediment values in fishponds across all fish farms. Therefore, our findings suggest that tambaquis have a remarkable ability to bioaccumulate trace metals, particularly the essential ones, and can be categorized as a bioindicator species for environmental quality. Furthermore, we observed that, although water exhibits the highest prevalence and diversity of elements above the values recommended by the Brazilian legislation, sediment is the primary source of trace metal contamination for tambaquis.

Assessment of heavy metal distribution and bioaccumulation in soil and plants near coal mining areas: implications for environmental pollution and health risks

Monitoring heavy metals (HMs) across source distance and depth distribution near coal mining sites is essential for preventing environmental pollution and health risks. This study investigated the distribution of selected HMs, cadmium (Cd2+), chromium (Cr2+), copper (Cu2+), manganese (Mn2+), nickel (Ni2+), lead (Pb2+), and zinc (Zn2+), in soil samples collected from ten sites (S-1-S-10) at two different depths (0-15 and 15-30 cm) and distances of 50, 100, and 200 m from a mining source. Additionally, three plant species, Prosopis spp., Justicia spp., and wheat, were collected to assess HM bioavailability and leaf accumulation. Coal mine activities' impact on soil properties and their HM associations were also explored. Results reveal HM concentrations except for Cr2+ exceeding World Health Organization (WHO) limits. In surface soil, Cd2+ (58%), Cu2+ (93%), Mn2+ (68%), Ni2+ (80%), Pb2+ (35%), and Zn2+ (88%) surpassed permissible limits. Subsurface soil also exhibited elevated Cd2+ (53%), Cu2+ (83%), Mn2+ (60%), Ni2+ (80%), Pb2+ (35%), and Zn2+ (77%). Plant species displayed varying HM levels, exceeding permissible limits, with average concentrations of 1.4, 1.34, 1.42, 4.1, 2.74, 2.0, and 1.98 mg kg-1 for Cd2+, Pb2+, Cr2+, Cu2+, Mn2+, Ni2+, and Zn2+, respectively. Bioaccumulation factors were highest in wheat, Prosopis spp., and Justicia spp. Source distance and depth distribution significantly influenced soil pH, electrical conductivity (EC), and soil organic carbon (SOC). Soil pH and EC increased with an increase in soil depth, while SOC decreased. Pearson correlation analysis revealed varying relationships between soil properties and HMs, showing a considerably negative correlation. Concentrations of HMs decreased with increasing depth and distance from mining activities, validated by regression analysis. Findings suggest crops from these soils may pose health risks for consumption.

Serum metallomics reveals insights into the associations of elements with the progression of preleukemic diseases toward acute leukemia

Acute leukemia (AL) is a critical neoplasm of white blood cells with two main subtypes: acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). This study is focused on understanding the association of the preleukemic disease aplastic anemia (APA) with ALL and AML at metallomic level, using healthy subjects as a control. In this study, a validated and efficient inductively coupled plasma-mass spectrometry/MS-based workflow was employed to profile a total of 13 metallomic features. The study encompassed 41 patients with AML, 62 patients with ALL, 46 patients with APA, and 55 age-matched healthy controls. The metallomic features consisted of eight essential elements (Ca, Co, Cu, Fe, Mg, Mn, Se, and Zn) and five non-essential/toxic elements (Ag, Cd, Cr, Ni, and Pb). Six out of the 13 elements were found to be substantially different (P < .05) using absolute concentrations between serum samples of AL (ALL and AML) and preleukemia (APA) patients in comparison with healthy subjects. Elements including magnesium, calcium, iron, copper, and zinc were upregulated and only one element (chromium) was downregulated in serum samples of disease when compared with healthy subjects. Through the utilization of both univariate tests and multivariate classification modeling, it was determined that chromium exhibited a progressive behavior among the studied elements. Specifically, chromium displayed a sequential upregulation from healthy individuals to preleukemic disease (APA), and ultimately in patients diagnosed with ALL. Overall, metallomic-based biomarkers may have the utility to predict the association of APA with ALL.

Alshamari AKA, Alshammari EM, Ahmed A. O, Sherwani S, Ali Khan MW. Bioremediation potential of Pseudomonas fluorescens strain isolated from the Ha'il region of Saudi Arabia

Increased amounts of toxicants may cause sever health issues in humans as well as in aquatic life. Scientists are developing new technologies to combat these problems. Biological methods of detoxification are always beneficial for the environment. Pseudomonas fluorescens is known for its detoxification capacity. In this study Pseudomonas fluorescens stains were isolated from different locations of the Ha'il region, Saudia Arabia. The microbial strain AM-1 displayed resistance to heavy metals (Cr6+, Ni2+, Cd2+, Pb2+) and pesticides (BHC, 2,4-D, Mancozeb) at pollutant levels typical of highly contaminated areas. Additionally, AM-1 exhibited substantial detoxification potential, reducing toxicity by 40.67% for heavy metals and 47.4% for pesticides at 3x concentrations. These findings suggest that the AM-1 strain supports environmental remediation and pollution mitigation. Atomic absorption spectrometry (AAS) results exhibited bioremediation efficiency for metals Cr6+, Ni2+, and Pb2+ using immobilized cells of P. fluorescens AM-1 isolate, estimated to be 60.57%, 68.4%, and 53.93% respectively. These findings show that AM-1 strain has a potential role in bioremediation of water pollutants and may have future implications in wastewater treatment.

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.

Recent Advances in Polymer-Based Biosensors for Food Safety Detection

The excessive use of pesticides and drugs, coupled with environmental pollution, has resulted in the persistence of contaminants on food. These pollutants tend to accumulate in humans through the food chain, posing a significant threat to human health. Therefore, it is crucial to develop rapid, low-cost, portable, and on-site biosensors for detecting food contaminants. Among various biosensors, polymer-based biosensors have emerged as promising probes for detection of food contaminants in recent years, due to their various functions such as target binding, enrichment, and simple signal reading. This paper aims to discuss the characteristics of five types of food pollutants-heavy metals, pesticide residues, pathogenic bacteria, allergens, and antibiotics-and their adverse effects on human health. Additionally, this paper focuses on the principle of polymer-based biosensors and their latest applications in detecting these five types of food contaminants in actual food samples. Furthermore, this review briefly examines the future prospects and challenges of biosensors for food safety detection. The insights provided in this review will facilitate the development of biosensors for food safety detection.

Biogeochemical behaviour and toxicology of chromium in the soil-water-human nexus: A review

Chromium (Cr) affects human health if it accumulates in organs to elevated concentrations. The toxicity risk of Cr in the ecosphere depends upon the dominant Cr species and their bioavailability in the lithosphere, hydrosphere, and biosphere. However, the soil-water-human nexus that controls the biogeochemical behaviour of Cr and its potential toxicity is not fully understood. This paper synthesizes information on different dimensions of Cr ecotoxicological hazards in the soil and water and their subsequent effects on human health. The various routes of environmental exposure of Cr to humans and other organisms are also discussed. Human exposure to Cr(VI) causes both carcinogenic and non-carcinogenic health effects via complicated reactions that include oxidative stress, chromosomal and DNA damage, and mutagenesis. Chromium (VI) inhalation can cause lung cancer; however, incidences of other types of cancer following Cr(VI) exposure are low but probable. The non-carcinogenic health consequences of Cr(VI) exposure are primarily respiratory and cutaneous. Research on the biogeochemical behaviour of Cr and its toxicological hazards on human and other biological routes is therefore urgently needed to develop a holistic approach to understanding the soil-water-human nexus that controls the toxicological hazards of Cr and its detoxification.

Coenzyme Q10, Biochanin A and Phloretin Attenuate Cr(VI)-Induced Oxidative Stress and DNA Damage by Stimulating Nrf2/HO-1 Pathway in the Experimental Model

Hexavalent chromium [Cr(VI)] has emerged as a prevailing environmental and occupational contaminant over the past few decades. However, the knowledge is sparse regarding Cr(VI)-induced neurological aberrations, and its remediation through natural bioactive compounds has not been fully explored. This study intended to probe the possible invigorative effects of nutraceuticals such as coenzyme Q10 (CoQ10), biochanin A (BCA), and phloretin (PHL) on Cr(VI) intoxicated Swiss albino mice with special emphasis on Nrf2/HO-1/NQO1 gene expressions. Mice received potassium dichromate (75 ppm) through drinking water and were simultaneously co-treated intraperitoneally with CoQ10 (10 mg/kg), BCA, and PHL (50 mg/kg) each for 30-day treatment period. The statistics highlight the elevated levels of lipid peroxidation (LPO) and protein carbonyl content (PCC) with a concomitant reduction in the superoxide dismutase (SOD), glutathione-S-transferase (GST), reduced glutathione (GSH), total thiols (TT), catalase (CAT), and cholinesterase activities in the Cr(VI)-exposed mice. The collateral assessment of DNA fragmentation, DNA breakages, and induced histological alterations was in conformity with the above findings in conjugation with the dysregulation in the Nrf2 and associated downstream HO-1 and NQO1 gene expressions. Co-treatment with the selected natural compounds reversed the above-altered parameters significantly, thereby bringing cellular homeostasis in alleviating the Cr(VI)-induced conciliated impairments. Our study demonstrated that the combination of different bioactive compounds shields the brain better against Cr(VI)-induced neurotoxicity by revoking the oxidative stress-associated manifestations. These compounds may represent a new potential combination therapy due to their ability to modulate the cellular antioxidant responses by upregulating the Nrf2/HO-1/NQO1 signaling pathway against Cr(VI)-exposed population. HIGHLIGHTS: Cr(VI)-associated heavy metal exposure poses a significant threat to the environment, especially to living organisms. Cr(VI) exposure for 30 days resulted in the free radical's generation that caused neurotoxicity in the Swiss albino mice. Natural compounds such as coenzyme Q10, biochanin A, and phloretin counteracted the neurotoxic effect due to Cr(VI) exposure in scavenging of free radicals by enhancing Nrf2/HO-1/NQO1 gene expressions in maintaining the cellular homeostasis.

Oxidative stress and toxicity produced by arsenic and chromium in broiler chicks and application of vitamin E and bentonite as ameliorating agents

The present study investigated the adverse effects of arsenic and chromium in broilers and ascertained the role of vitamin E and bentonite in alleviating their harmful effects. For this purpose, we experimented on 180 one-day-old broiler chickens. The feed was administered to broiler chicks of groups 2, 6, 7, 8, and 9 chromium @ (270 mg.kg−1 BW). Groups 3, 6, 7, 8, and 9 were administered arsenic @ (50 mg.kg−1 BW). Groups 4, 7, and 9 received vitamin E (150 mg.kg−1 BW), and groups 5, 8, and 9 received bentonite (5%), respectively. Group 1 was kept in control. All the broiler chicks treated with chromium and arsenic showed a significant (p &lt; 0.05) decline in erythrocytic parameters on experimental days 21 and 42. Total proteins decreased significantly, while ALT, AST, urea, and creatinine increased significantly (p &lt; 0.05). TAC and CAT decreased significantly (p &lt; 0.05), while TOC and MDA concentrations increased significantly (p &lt; 0.05) in chromium and arsenic-treated groups on experimental days 21 and 42. Pearson correlation analysis revealed a strong positive correlation between TAC and CAT (Pearson correlation value = 0.961; p &lt; 0.001), similarly TOC and MDA positive correlation (Pearson correlation value = 0.920; p &lt; 0.001). However, TAC and CAT showed a negative correlation between TOC and MDA. The intensity of gross and microscopic lesions was more in chromium (270 mg.kg−1) and arsenic (50 mg.kg−1) singly or in combination-treated groups. Thus, broiler chicks treated with chromium plus arsenic exhibited higher gross and microscopic lesion intensity than other treated groups. Fatty degeneration, severe cytoplasmic vacuolar degeneration, and expansion of sinusoidal spaces were the main lesions observed in the liver. Kidneys showed renal epithelial cells necrosis, glomerular shrinkage, and severe cytoplasmic vacuolar degeneration. Co-administration of bentonite along with chromium and arsenic resulted in partial amelioration (group 8) compared to groups 7 and 9, administered arsenic + chromium + vitamin E and arsenic + chromium + vitamin E + bentonite, respectively. It was concluded that arsenic and chromium cause damage not only to haemato-biochemical parameters but also lead to oxidation stress in broilers. Vitamin E and bentonite administration can ameliorate toxicity and oxidative stress produced by arsenic and chromium.

Fagonia indica ameliorates chromium-induced nephrotoxicity: Role of antioxidant activity and pro-inflammatory cytokines in in-vivo renoprotection

Chromium (Cr) is an environmental pollutant, has high redox potential, and can exist in various oxidation states, possibly leading to nephrotoxicity. As a potential treatment option, Fagonia indica (F. indica) is an herb remedy traditionally used as a phytomedicine to cure ailments. However, efficient validation of its protective effect and molecular mechanisms has not yet been established. As such, this study aims to investigate the protective effect of F. indica against Cr-induced nephrotoxicity in Swiss mice. Mice were divided into five groups: group I (negative control), group II (F. indica), group III (potassium dichromate [PDC]-treated), group IV (PDC + saline), and group V (PDC + F. indica). Our results demonstrate that group III exhibited decreases in superoxide dismutase (SOD), glutathione s-transferases (GST), glutathione peroxidase (GSH-Px), catalase (CAT), and thioredoxin peroxidase (TPX) levels. Meanwhile, protein carbonyl (PCO) and malondialdehyde (MDA) levels increased in kidney homogenates, increasing the expression of the pro-inflammatory cytokine interleukin-6 (IL-6). This was followed by elevated NF-κB, blood urea nitrogen (BUN), and creatinine serum levels in group III compared with group I. Moreover, histopathological and immunohistochemical examinations demonstrated severe damage to the renal tubular epithelial cells, as well as marked congestion and expressions of caspase-3 and NF-κB. Further, group V showed an improvement in antioxidant activity parameters and reductions in the IL-6, caspase-3, and NF-κB expressions, followed by significant decreases in NF-κB, BUN, and creatinine serum levels. Furthermore, fewer histopathological disturbances were observed compared with untreated group III. Such alterations may be attributed to the antioxidant and anti-inflammatory effects of F. indica. Therefore, our exploration reveals that F. indica is effective in protecting against Cr-induced nephrotoxicity, and it could be applied in the future to human kidney diseases caused by environmental pollutants.

Metabolic pathway of Cr(VI) reduction by bacteria: A review

Heavy metal wastes, particularly hexavalent chromium [Cr(VI)], are generated from anthropogenic activities, and their increasing abundance has been a research concern due to their toxicity, genotoxicity, carcinogenicity and mutagenicity. Exposure to these dangerous pollutants could lead to chronic infections and even mortality in humans and animals. Bioremediation using microorganisms, particularly bacteria, has gained considerable interest because it can remove contaminants naturally and is safe to the surrounding environment. Bacteria, such as Pseudomonas putida and Bacillus subtilis, can reduce the toxic Cr(VI) to the less toxic trivalent chromium Cr(III) through mechanisms including biotransformation, biosorption and bioaccumulation. These mechanisms are mostly linked to chromium reductase and nitroreductase enzymes, which are involved in the Cr(VI) reduction pathway. However, relevant data on the nitroreductase route remain insufficient. Thus, this work proposes an alternative metabolic pathway of nitroreductase, wherein nitrate activates the reaction and indirectly reduces toxic chromium. This nitroreductase pathway occurs concurrently with the chromium reduction pathway.

Ecological effects, remediation, distribution, and sensing techniques of chromium

Chromium is detected in most ecosystems due to the increased anthropogenic activities in addition to that developed from natural pollution. Chromium contamination in the food chain results due to its persistent and non-degradable nature. The release of chromium in the ecosystem accretes and thereafter impacts different life forms, including humans, aquatic and terrestrial organisms. Leaching of chromium into the ground and surface water triggers several health ailments, such as dermatitis, eczematous skin, allergic reactions, mucous and skin membrane ulcerations, allergic asthmatic reactions, bronchial carcinoma and gastroenteritis. Physiological and biological treatments for the removal of chromium have been discussed in depth in the present communication. Adsorption and biological treatment methods are proven to be alternatives to chemical removal techniques in terms of cost-effectiveness and low sludge formation. Chromium sensing is an alternative approach for regular monitoring of chromium in different water bodies. This review intended to explore different classes of sensors for chromium monitoring. However, the spectrochemical methods are more sensitive in chromium ions sensing than electrochemical methods. Future study should focus on miniaturization for portability and on-site measurements without requiring a large instrument provides a good aspect for future research.

The Effects of Chromium and Vanadium on Biomarkers of Carbohydrate and Lipid Metabolism in Workers Exposed to Coal Fly Ash

Chromium (Cr) and vanadium (V) are micronutrients playing a role in carbohydrate and lipid metabolism but can be toxic at high concentrations, especially in specific forms. The study documents the effect of Cr and V concentrations on glucose and lipid metabolism in workers exposed to coal fly ash. We quantified selected metals (Cr, V) in the blood and serum of workers from a thermal power plant in Kosovo and compared them with the reference biological values. We determined fasting serum glucose and lipid profiles using a biochemical analyzer Synchron CX7 (Beckman Coulter). We quantified blood and serum Cr and V by inductively coupled plasma mass spectrometry. We also evaluated the association between carbohydrate and lipid metabolism biomarkers (glucose, cholesterol, and triglycerides) and co-exposure to coal fly ash. Power plant workers had significantly higher blood Cr and V levels (p < 0.0001) and significantly lower serum Cr and V levels (p < 0.0001) than the controls. We also found statistically significant (p < 0.0001) correlations between high blood Cr levels and low glucose/blood Cr ratios as well as between high serum Cr levels and low glucose/serum Cr ratios. Finally, in power plant workers, high blood V levels significantly correlated with low triglycerides/blood V and cholesterol/blood V ratios (p < 0.0001), while high serum V levels correlated with low cholesterol/serum V ratios (p = 0.005). Based on these findings, we concluded that the glucose/Cr, triglycerides/V and cholesterol/V ratios should be considered when evaluating carbohydrate and lipid metabolism disorders in occupationally-exposed workers.

Spatially Resolved Distribution, Sources, Exposure Levels, and Health Risks of Heavy Metals in <63 μm Size-Fractionated Road Dust from Lucknow City, North India

In the present study, a total of 64 road dust samples were collected from five different functional areas (residential, commercial, parks, high-traffic, and industrial) in urban Lucknow to assess the accumulation, distribution, and health risk of heavy metals (HMs) (i.e., Fe, Mn, Zn, Cu, Pb, Cd, As, Cr and Ni). Acid digestion methods were used to analyze HMs, followed by inductively coupled plasma-mass spectrometry (ICPMS). The ascending frequency of HMs was Cd < As < Ni < Cr < Pb < Cu < Zn < Mn < Fe for all different functional areas. Almost all HMs exceed the limits of Indian natural soil background values (INSB) across all functional areas. The pollution assessment results reveal that the urban road dust of Lucknow is highly enriched with Zn and Pb, causing deterioration of dust quality. The spatial distribution of HMs shows that road dust found in the central and southwestern zones of the Lucknow urban area are more contaminated than in other areas. The ecological risk assessment demonstrates that Cd was the highest risk contributor, followed by Pb, Zn and Cu. The result of the health risk assessment i.e., the cumulative hazard index (HI) and the cumulative lifetime cancer risk (LCR), reveal that children (mean HIchildren = 1.26, LCRchildren = 0.000187) are more vulnerable to HM exposure than adults (HIadults = 0.14, LCRadults = 0.0000804). For carcinogenic and non-carcinogenic risk, ingestion appears to be the major pathway of HM exposure in both age groups. It is alarming that all studied four carcinogenic HMs were found in concentrations higher than 1 × 10-6 (the permissible limit for humans). This indicates slight chances of developing cancer for both age groups in all functional areas.

On the Determination of Cr(VI) in Cr(III)-Rich Particulates: From the Failure of Official Methods to the Development of an Alternative Protocol

The goals of this work are the evaluation of the performances of official methods in the challenging determination of Cr(VI) in Cr(III)-rich particulate matter, and the development of a novel and robust analytical protocol for this issue. A liquid chromatography inductively coupled plasma mass spectrometry apparatus (LC-ICP-MS), together with an isotope-enriched spike addition technique, was used to allow the study of Cr(III)/Cr(VI) interconversions during the extraction step. An original separation strategy based on Cr(OH)₃ head-column stacking was developed to tolerate high concentrations of Cr(III) (up to 10 mg/kg, with a Cr(VI) limit of detection of 0.51 µg/kg) without the need of any sample pretreatment. After observing, the official extraction protocols always yield false positive values in the challenging situation of particulate matter of leather industries (where huge amounts of Cr(III) are present), a new extraction strategy was developed. The novel procedure involves a 48-h extraction at room temperature using a pH-8 phosphate buffer, which demonstrated that no Cr(III)/Cr(VI) interconversions occur during this phase. To get rid of any possible interference caused by co-extracted substances, the measurement of the redox potential, together with the addition of a Fe(II)/Fe(III) redox buffer was performed to fix chromium speciation during the overall analytical protocol.

Evaluation of trace elements in essential thrombocytosis and reactive thrombocytosis

BACKGROUND

Trace elements (TE) are vital for cellular mechanisms at biological, chemical and molecular levels. The effects of TE in diagnosis, progression and treatment of essential thrombocytosis (ET), which is one of the chronic myeloproliferative neoplasms is a rare clonal stem cell disease characterized by increased thrombocyte numbers with impaired function, have not been elucidated in detail yet. The aim of the present study was to investigate the effects of TE alterations in an ET model and the efficacy of TE in ET treatment protocol by means of a vast number of TE.

METHODS

Study groups were categorized as patients with ET diagnosis (ET group, n:30), patients with reactive thrombocytosis secondary to iron deficiency anemia (IDA-RT) (IDA-RT group, n:30) and healthy controls (HC group, n:30). Serum levels of copper (Cu), iron (Fe), cobalt (Co), chromium (Cr), aluminum (Al), silicon (Si), nickel (Ni), zinc (Zn), selenium (Se), manganese (Mn), boron (B) and magnesium (Mg) were analyzed utilizing inductively coupled plasma-optical emission spectrophotometer instrument (ICP-OES). Statistical analysis was evaluated using SPSS 23.0.

RESULTS

ET group had statistically higher serum levels of Co and Mg (p < 0.05), Ni and Mn (p < 0.001), and lower Si (p < 0.05) than IDA-RT group. ET group had statistically higher serum levels of Co and Mn (p < 0.05), and Ni (p < 0.001), and lower Al, Si and Se (p < 0.001) than HC group. Serum levels of Fe, Al and Se (p < 0.001), and Mg (p < 0.01), and Zn (p < 0.05) in IDA-RT group were significantly lower than HC group.

CONCLUSION

This novel study pointed out that alterations of many serum TE by means of both increment or decrement might have close relationship with mechanisms and complications of ET onset and follow-up. We consider that further research of TE would elucidate ethiopathogenesis and prognosis of ET. Thus, analysis of serum trace elements in essential thrombocytosis patients may be an important protocol by means of diagnosis, treatment and follow-up intervals.

Modified and pristine biochars for remediation of chromium contamination in soil and aquatic systems

Chromium (Cr) contamination in soil and water poses high toxicity risks to organisms and threatens food and water security worldwide. Biochar has emerged as a promising material for cleaning up Cr contamination owing to biochar's strong capacity to immobilize Cr. This paper synthesizes information on biochar modification for the efficient remediation of Cr contamination in soil and water, and critically reviews mechanisms of Cr adsorption on pristine and modified biochars. Biochar modification methods include physical activation via ball milling or ultraviolet irradiation, chemical activation via magnetization, alkali/acid treatment, nano-fabrication or loading of reductive agents, and biological activation via integrating biochars with microorganisms and their metabolites. Modified biochars often have multi-fold enhancement in Cr adsorption/reduction capacity than pristine biochars. Iron (Fe)-supported magnetic biochars have the most promising Cr removal abilities with high reusability of the biochars. Pre-pyrolysis modification with Fe could load Fe₃O₄ micro-/nanoparticles on biochars, and increase the surface area and electrostatic attraction between chromate anions and biochar surfaces, and reduce Cr(VI) to Cr(III). Post-pyrolysis modification could enrich oxygen-containing functional groups such as CO and -OH on biochar surfaces and promote Cr reduction and adsorption. Future research directions for Cr mitigation using advanced biochar products are discussed in this review.

HBM4EU Chromates Study-Genotoxicity and Oxidative Stress Biomarkers in Workers Exposed to Hexavalent Chromium

A study was conducted within the European Human Biomonitoring Initiative (HBM4EU) to characterize occupational exposure to Cr(VI). Herein we present the results of biomarkers of genotoxicity and oxidative stress, including micronucleus analysis in lymphocytes and reticulocytes, the comet assay in whole blood, and malondialdehyde and 8-oxo-2′-deoxyguanosine in urine. Workers from several Cr(VI)-related industrial activities and controls from industrial (within company) and non-industrial (outwith company) environments were included. The significantly increased genotoxicity (p = 0.03 for MN in lymphocytes and reticulocytes; p < 0.001 for comet assay data) and oxidative stress levels (p = 0.007 and p < 0.001 for MDA and 8-OHdG levels in pre-shift urine samples, respectively) that were detected in the exposed workers over the outwith company controls suggest that Cr(VI) exposure might still represent a health risk, particularly, for chrome painters and electrolytic bath platers, despite the low Cr exposure. The within-company controls displayed DNA and chromosomal damage levels that were comparable to those of the exposed group, highlighting the relevance of considering all industry workers as potentially exposed. The use of effect biomarkers proved their capacity to detect the early biological effects from low Cr(VI) exposure, and to contribute to identifying subgroups that are at higher risk. Overall, this study reinforces the need for further re-evaluation of the occupational exposure limit and better application of protection measures. However, it also raised some additional questions and unexplained inconsistencies that need follow-up studies to be clarified.

Photo–Redox Properties of –SO3H Functionalized Metal-Free g-C3N4 and Its Application in the Photooxidation of Sunset Yellow FCF and Photoreduction of Cr (VI)

In this work, we synthesized a metal-free sulfonic functionalized graphitic carbon nitride using sulfuric acid through the wet impregnation technique. The functionalization of sulfonic groups (–SO3H) on g-C3N4 will promote a high surface charge density and charge separation owing to its high electronegativity. The g-C3N4–SO3H shows excellent optical/electronic and surface properties towards enhanced photo–redox reactions. The sulfonic groups also facilitate the availability of more separated charge carriers for photocatalytic oxidation and reduction reactions. The as-synthesized material has been characterized by different spectroscopic tools to confirm the presence of functionalized –SO3H groups and optoelectronic possessions. The photocatalytic responses of g-C3N4–SO3H result in 99.56% photoreduction of Cr (VI) and 99.61% photooxidation of Sunset Yellow FCF within 16 min and 20 min, respectively, of visible light irradiation. The g-C3N4–SO3H catalyst exhibits a high apparent rate constant (Kapp) towards the degradation of Cr (VI), and SSY, i.e., 0.783 min−1 and 0.706 min−1, respectively. The intense optical–electrochemical properties and potentially involved active species have been analyzed through transient photocurrent, electrochemical impedance, and scavenging studies. Consequently, the photocatalytic performances are studied under different reaction parameters, and the plausible photocatalytic mechanism is discussed based on the results.

Biocompatible Carbon Dot Decorated α-FeOOH Nanohybrid for an Effective Fluorometric Sensing of Cr (VI) in Wastewater and Living Cells

This article reports the fluorometric detection of toxic hexavalent chromium Cr (VI)) in wastewater and Cr (VI) contaminated living cells using in-situ grown carbon quantum dots into the goethite (α-FeOOH) nano-matrix. The synthesized nano-hybrid shows enormous potential in determining the chromium contamination levels in various types of water samples. This selective fluorometric probe is enormously sensitive (LOD 81 nM) toward hexavalent chromium, which makes it a dedicated chromium sensor. Moreover, the sensing mechanism has been assessed using Stern-Volmer's equation and fluorescence lifetime experiments showing the simultaneous occurrence of photoinduced electron transfer and the inner filter effect. This chromium sensor has also been employed to assess the contamination level in real-life industrial wastewater. The performance of this probe in a real-life wastewater sample is quite commendable. Further, this biocompatible fluorometric probe has been used to demonstrate the in-vitro sensing of Cr (VI) in HeLa cells. The rapid detection mechanism of hexavalent chromium in living cells has been validated using theoretical docking simulations. Henceforth, this fluorometric sensor material could open new avenues not only in wastewater monitoring but also in biomedical applications.

Fabrication of Copper(II)-Coated Magnetic Core-Shell Nanoparticles Fe3O4@SiO2: An Effective and Recoverable Catalyst for Reduction/Degradation of Environmental Pollutants

In this work, we report the synthesis of a magnetically recoverable catalyst through immobilizing copper (II) over the Fe3O4@SiO2 nanoparticles (NPs) surface [Fe3O4@SiO2-L–Cu(II)] (L = pyridine-4-carbaldehyde thiosemicarbazide). Accordingly, synthesized catalysts were determined and characterized by energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FESEM), and thermogravimetric-differential thermal analysis (TG-DTA) procedures. The [Fe3O4@SiO2-L–Cu(II)] was used for the reduction of Cr(VI), 4-nitrophenol (4-NP) and organic dyes such as Congo Red (CR) and methylene blue (MB) in aqueous media. Catalytic performance studies showed that the [Fe3O4@SiO2–L–Cu(II)] has excellent activity toward reduction reactions under mild conditions. Remarkable attributes of this method are high efficiency, removal of a homogeneous catalyst, easy recovery from the reaction mixture, and uncomplicated route. The amount of activity in this catalytic system was almost constant after several stages of recovery and reuse. The results show that the catalyst was easily separated and retained 83% of its efficiency after five cycles without considerable loss of activity and stability.

Influence of Urban Informal Settlements on Trace Element Accumulation in Road Dust and Their Possible Health Implications in Ekurhuleni Metropolitan Municipality, South Africa

The study was aimed at assessing the influence of urban informal settlement on trace element accumulation in road dust from the Ekurhuleni Metropolitan Municipality, South Africa, and their possible health implications. The concentration of major and trace elements was determined using the wavelength dispersive XRF method. The major elements in descending order were SiO₂ (72.76%), Al₂O₃ (6.90%), Fe₂O₃ (3.88%), CaO (2.71%), K₂O (1.56%), Na₂O (0.99%), MgO (0.94%), MnO (0.57%), TiO₂ (0.40%), and P₂O₅ (0.16%), with SiO₂ and P₂O₅ at above-average shale values. The average mean concentrations of 17 trace elements in decreasing order were Cr (637.4), Ba (625.6), Zn (231.8), Zr (190.2), Sr (120.2), V (69), Rb (66), Cu (61), Ni (49), Pb (30.8), Co (17.4), Y (14.4), Nb (8.6), As (7.2), Sc (5.8), Th (4.58), and U (2.9) mg/kg. Trace elements such as Cr, Cu, Zn, Zr, Ba, and Pb surpassed their average shale values, and only Cr surpassed the South African soil screening values. The assessment of pollution through the geo-accumulation index (Igeo) revealed that road dust was moderately to heavily contaminated by Cr, whereas all other trace elements were categorized as being uncontaminated to moderately contaminated. The contamination factor (CF) exhibited road dust to be very highly contaminated by Cr, moderately contaminated by Zn, Pb, Cu, Zr, and Ba, and lowly contaminated by Co, U, Nb, Ni, As, Y, V, Rb, Sc, Sr, and Th. The pollution load index (PLI) also affirmed that the road dust in this study was very highly polluted by trace elements. Moreover, the results of the enrichment factor (EF) categorized Cr as having a significant degree of enrichment. Zn was elucidated as being minimally enriched, whereas all other trace elements were of natural origin. The results of the non-carcinogenic risk assessment revealed a possibility of non-carcinogenic risks to both children and adults. For the carcinogenic risk, the total CR values in children and adults were above the acceptable limit, signifying a likelihood of carcinogenic risk to the local inhabitants. From the findings of this study, it can be concluded that the levels of trace elements in the road dust of this informal settlement had the possibility to contribute to both non-carcinogenic and carcinogenic risks, and that children were at a higher risk than the adult population.

The price of persistence: Assessing the drivers and health implications of metal levels in indicator carnivores inhabiting an agriculturally fragmented landscape

Patterns and practices of agricultural expansion threaten the persistence of global biodiversity. Wildlife species surviving large-scale land use changes can be exposed to a suite of contaminants that may deleteriously impact their health. There is a paucity of data concerning the ecotoxicological impacts associated with the global palm oil (Elaeis guineensis) industry. We sampled wild Malay civets (Viverra tangalunga) across a patchwork landscape degraded by oil palm agriculture in Sabah, Malaysian Borneo. Using a non-lethal methodology, we quantified the levels of 13 essential and non-essential metals within the hair of this adaptable small carnivore. We robustly assessed the biological and environmental drivers of intrapopulation variation in measured levels. Metal concentrations were associated with civet age, weight, proximity to a tributary, and access to oxbow lakes. In a targeted case study, the hair metal profiles of 16 GPS-collared male civets with differing space use patterns were contrasted. Civets that entered oil palm plantations expressed elevated aluminium, cadmium, and lead, and lower mercury hair concentrations compared to civets that remained exclusively within the forest. Finally, we paired hair metal concentrations with 34 blood-based health markers to evaluate the possible sub-lethal physiological effects associated with varied hair metal levels. Our multi-facetted approach establishes these adaptable carnivores as indicator species within an extensively altered ecosystem, and provides critical and timely evidence for future studies.

Recycled mesoporous magnetic composites with high surface area derived from plastic and de-oiled sludge wastes: An empirical comparison on their competitive performance for toxic Cr (VI) removal

The current study focused on the comparative removal of hexavalent chromium using two magnetically modified hybrid adsorbent composites. Their precursor chars were prepared from bio sludge and plastic waste derivatives. The coating of magnetite on the chars' surface was evident from the SEM micrographs. Infusion of magnetite nanoparticles in the native chars aided in the reduction of the composite particles' sizes, thus, forming high surface area composites. Screening of uptake capacities among various blends of char and magnetite were surveyed. Composites of both kinds with a 1:5 ratio of char: iron salts composition answered well. The pH_ZPC and zeta potential values of the composites indicated the neutral charge on the composites' surface. This suggested the need for a highly acidic environment for efficient Cr(VI) removal. Optimum economic conditions for Cr(VI) removal were obtained from the batch studies (solution pH - 1.5; contact time - (a) MPC [magnetic plastic char] - 60 min (b) MBC [magnetic biochar] - 40 min; temperature - 25 °C). The maximum monolayer adsorption capacity of MPC and MBC were found to be 84.67 mg/g and 53.83 mg/g respectively. Isotherm, kinetic and thermodynamic studies revealed the adsorption systems' inclination towards physisorption. From the characterization and modeling results, electrostatic force of attraction and pore filling was anticipated to be the mechanism of adsorption for both MPC and MBC. Thus, in the relative removal studies, MBC was found to compete better than MPC due to its enhanced porosity and surface area.

A Comparative Study of Aluminium and Titanium Warm Sprayed Coatings on AZ91E Magnesium Alloy

Aluminium (Al) and titanium (Ti) coatings were applied on AZ91E magnesium alloy using a low-pressure warm spray (WS) method. The deposition was completed using three different nitrogen flow rates (NFR) for both coatings. NFR effects on coating microstructure and other physical properties were systematically studied. Microstructural characterization was performed using scanning electron microscopy (SEM), and the porosity was estimated using two methods-image analysis and X-ray microtomography. The coating adhesion strength, wear resistance, and hardness were examined. The protective properties of the coatings were verified via a salt spray test. Decreasing NFR during coating deposition produced more dense and compact coatings. However, these conditions increased the oxidation of the powder. Al coatings showed lower hardness and wear resistance than Ti coatings, although they are more suitable for corrosion protection due to their low porosity and high compactness.

Interlaboratory Comparison Investigations (ICIs) for human biomonitoring of chromium as part of the quality assurance programme under HBM4EU

BACKGROUND

The pan-European human biomonitoring initiative HBM4EU targets the harmonization of human biomonitoring (HBM) procedures and data for both environmental and occupational exposure, including chromium. The determination of chromium in urine (U-Cr), plasma (P-Cr) and whole blood (WB-Cr) is a common HBM application in employees occupationally exposed to chromium (VI) compounds.

METHODS

European laboratories which have registered as candidate laboratories for chromium analysis within HBM4EU were invited to participate in a quality assurance/qualitycontrol (QA/QC) programme comprising interlaboratory comparison investigations (ICI) for the parameters U-Cr, P-Cr and WB-Cr. Participating laboratories received two samples of different concentrations in each of four rounds and were asked to analyse the samples using their standard analytical procedure. The data were evaluated by the Z-score approach and were reported to the participants after each round.

RESULTS

The majority of the 29 participating laboratories obtained satisfactory results, although low limits of quantification were required to quantify chromium concentrations in some of the ICI materials. The robust relative standard deviation of the participants' results (study RSD_R) obtained from all ICI runs ranged from 6 to 16 % for U-Cr, 7-18 % for P-Cr and 4-47 % for WB-Cr. The application of both inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (EAAS) appeared appropriate for the determination of chromium in urine, plasma and whole blood with regard to occupational exposure levels.

CONCLUSION

This QA/QC programme succeeded in establishing a network of laboratories with high analytical comparability and accuracy for the analysis of chromium across Europe.

Towards a toxic-free environment: perspectives for chemical risk assessment approaches

Regulatory frameworks to control chemical exposure in general living and occupational environments have changed exposure scenarios towards a widely spread contamination at relatively low doses in developed countries. In such evolving context, some critical aspects should be considered to update risk assessment and management strategies. Risk assessment in low-dose chemical exposure scenarios should take advantage of: toxicological investigations on emerging substances of interest, like those recognised as endocrine disruptors or increasingly employed nanoscale materials; human biological monitoring studies aimed to identify innovative biomarkers for known chemical exposure; "omic" technologies useful to identify hazards of chemicals and their modes of action. For updated risk assessment models, suitable toxicological studies, analyses of dose-responses at low-concentrations, environmental and biological monitoring of exposure, together with exposome studies, and the proper definition of susceptible populations may all provide helpful contributions. These may guide defining preventive measures to control the exposure and develop safe and sustainable chemicals by design. Occupational medicine can offer know-how and instruments to understand and manage such evolution towards a toxic-free environment to protect the safety and health of the workforce and, in turn, that of the general population.

Process enhancing strategies for the reduction of Cr(VI) to Cr(III) via photocatalytic pathway

This discourse aimed at providing insight into the strategies that can be adopted to boost the process of photoreduction of Cr(VI) to Cr(III). Cr(VI) is amongst the highly detestable pollutants; thus, its removal or reduction to an innocuous and more tolerable Cr(III) has been the focus. The high promise of photocatalysis hinged on the sustainability, low cost, simplicity, and zero sludge generation. Consequently, the present dissertation provided a comprehensive review of the process enhancement procedures that have been reported for the photoreduction of Cr(VI) to Cr(III). Premised on the findings from experimental studies on Cr(VI) reductions, the factors that enhanced the process were identified, dilated, and interrogated. While the salient reaction conditions for the process optimization include the degree of ionization of reacting medium, available photogenerated electrons, reactor ambience, type of semiconductors, surface area of semiconductor, hole scavengers, quantum efficiency, and competing reactions, the relevant process variables are photocatalyst dosage, initial Cr(VI) concentration, interfering ion, and organic load. In addition, the practicability of photoreduction of Cr(VI) to Cr(III) was explored according to the potential for photocatalyst recovery, reactivation, and reuse reaction conditions and the process variables.

Exposure to heavy metals and red blood cell parameters in children: A systematic review of observational studies

BACKGROUND

Mechanistic studies show that heavy metals interfere with the hematopoietic system by inhibiting key enzymes, which could lead to anemia. However, the link between children's exposure and red blood cell (RBC) parameters has been inconsistent. We aimed to summarize evidence on human studies exploring the association between exposure to lead, mercury, cadmium, arsenic, and chromium VI and RBC parameters in children.

METHODS

Following the PRISMA guidelines, we searched PubMed, Scopus, and Web of Science databases for studies published between January 2010 and April 2022. Eligible papers included human observational studies that directly assessed exposure (internal dose) to the heavy metals under study and RBC parameters in participants aged ≤ 18 years. We excluded studies using hospital-based samples. Study quality was assessed using the National Institutes of Health's Quality Assessment Tools for Cohort and Cross-Sectional Studies. We synthesized the evidence using vote counting based on the direction of the relationship.

RESULTS

Out of 6,652 retrieved papers, we included a total of 38 (33 assessing lead, four mercury, two cadmium, and two arsenic; chromium VI was not assessed in any included paper). More than half of the studies were conducted in Asia. We found evidence of a positive relationship between lead concentration and hemoglobin (proportion of studies reporting negative relationships = 0.750; 95% Confidence Interval (CI) 0.583, 0.874) and mean corpuscular hemoglobin (0.875; 95% CI 0.546, 0.986), and a positive relationship with red cell distribution width (0.000; 95%CI 0.000, 0.379). When considering only good-quality studies (24% of the Pb studies), only the relationship with hemoglobin levels remained (0.875; 95% CI: 0.546, 0.986).

CONCLUSION

We found evidence of a negative relationship between lead concentration and hemoglobin and mean corpuscular hemoglobin and of a positive relationship with red cell distribution width in children. We also identified a need to conduct more studies in European countries. Future studies should use standardized practices and make efforts to increase study quality, namely by conducting comprehensive longitudinal studies. Our findings support the need to take further actions to limit heavy metal exposure during childhood.

Direct and Indirect Reduction of Cr(VI) by Fermentative Fe(III)-Reducing Cellulomonas sp. Strain Cellu-2a

Hexavalent chromium (Cr(VI)) is recognized to be carcinogenic and toxic and registered as a contaminant in many drinking water regulations. It occurs naturally and is also produced by industrial processes. The reduction of Cr(VI) to Cr(III) has been a central topic for chromium remediation since Cr(III) is less toxic and less mobile. In this study, fermentative Fe(III)-reducing bacterial strains (Cellu-2a, Cellu-5a, and Cellu-5b) were isolated from a groundwater sample and were phylogenetically related to species of Cellulomonas by 16S rRNA gene analysis. One selected strain, Cellu-2a showed its capacity of reduction of both soluble iron (ferric citrate) and solid iron (hydrous ferric oxide, HFO), as well as aqueous Cr(VI). The strain Cellu-2a was able to reduce 15 μM Cr(VI) directly with glucose or sucrose as a sole carbon source under the anaerobic condition and indirectly with one of the substrates and HFO in the same incubations. The heterogeneous reduction of Cr(VI) by the surface-associated reduced iron from HFO by Cellu-2a likely assisted the Cr(VI) reduction. Fermentative features such as large-scale cell growth may impose advantages on the application of bacterial Cr(VI) reduction over anaerobic respiratory reduction.

Case Report: Two Cases of Salivary Duct Carcinoma in Workers With a History of Chromate Exposure

Background: Salivary duct carcinoma (SDC), one subtype of the 22 different salivary gland cancers, is a rare malignancy. Risk factors for the development of salivary gland cancer and SDC are largely unknown, although pollution has been described as one of the risk factors. In other cancers, especially in lung cancer, the carcinogenicity of chromium VI [Cr(VI)] is well-known. Here we report on two SDC patients who were occupationally exposed to Cr(VI) and discuss a potential relation between their Cr(VI) exposure and the occurrence of SDC. Case Presentation: The work history of two SDC patients was analyzed for chemical exposures. Both patients had a history of Cr(VI) exposure, with maintenance of military equipment considered as the source for this exposure. Inhalation of Cr(VI) containing particles from the removal of old paint by mechanical abrasion was identified as a probable source of exposure for both patients, and one of these patients also applied new paint. Both patients reported not to have used any respiratory protection which may have resulted in substantial inhalation of Cr(VI)-containing chromates. Furthermore, in one patient inhalation of fumes from soldering may have resulted in relevant co-exposure. Conclusion: A causal relation between Cr(VI) exposure and SDC, a rare cancer, cannot be demonstrated on an individual basis but detection in a population-based study is also unlikely because of the extremely low prevalence. Nevertheless, the work history is considered a relevant risk factor in the onset of SDC as occupational exposures to Cr(VI) occurred in poorly ventilated working environment and without using appropriate respiratory protective equipment.

Chromium contamination in groundwater and Sobol sensitivity model based human health risk evaluation from leather tanning industrial region of South India

The present investigation was conducted to find the possible chromium contamination in groundwater and the related health risks in a leather industrial region of south India using Sobol sensitivity modeling. Thirty-five groundwater samples were sampled from the field sites and were analyzed for pH, TDS (Total Dissolved Solids), EC (Electrical Conductivity), F^- (Fluoride), NO₃^- (Nitrate) and Cr (Chromium). The concentration of nitrate varied from 3 to 81 mg/L with a mean of 48.6 mg/L. About 57% (n = 20) of the wells surpassed the drinkable limit (45 mg/L) for NO₃^- as per World Health Organization (WHO). The fluoride ion ranged from 0.1 to 2.7 mg/L with a mean of 1.5 mg/L. Around 51% (n = 18) of the samples crossed the recommended limit of WHO for F^- (1.5 mg/L). The chromium varied from 0.01 to 0.19 mg/L in groundwater with a mean of 0.1 mg/L. About 66% (n = 23) of the samples overshoot the permissible limit of WHO standards (0.05 mg/L) for Cr. The spatial distribution map of chromium in the groundwater showed that 271.76 km² area is under risk. Based on total hazard index (THI), 66%, 46%, and 43% of the groundwater samples surpassed the allowable limit (THI > 1) for children, women and men, correspondingly. Children pose severe health risks than women and men in this region. Using Sobol sensitivity indices, three different categories of risk effects were assessed: first order effect (FOE), total effect (TE) and second order effect (SOE). In the oral sensitivity model, concentration of Cr (C_w) in water and ingestion rate (IR) had the dominant role, whereas in the dermal model, skin surface area (SA) and contact fraction by skin (F) had vital role in addition to the concentration (C_w). Further, the outcome of this study insists the responsibilities of industrial, municipal and agricultural sectors to keep the environment pollution free and to ensure the supply of potable water to the people.

Systematic review of biomonitoring data on occupational exposure to hexavalent chromium

Occupational exposure to hexavalent chromium (Cr(VI)) can cause serious adverse health effects such as lung cancer and irritation of the skin and airways. Although assessment of chromium (Cr) in urine is not specific for Cr(VI) exposure, the total amount of Cr in urine is the most used marker of exposure for biomonitoring of Cr(VI). The purpose of this systematic review was fourfold: (1) to assess current and recent biomonitoring levels in subjects occupationally exposed to Cr(VI), with a focus on urinary Cr levels at the end of a working week, (2) to identify variables influencing these biomonitoring levels, (3) to identify how urinary Cr levels correlate with other Cr(VI) exposure markers and (4) to identify gaps in the current research. To address these purposes, unpublished and published biomonitoring data were consulted: (i) unpublished biomonitoring data comprised urinary Cr levels (n = 3799) of workers from different industries in Belgium collected during 1998-2018, in combination with expert scores indicating jobs with Cr exposure and (ii) published biomonitoring data was extracted by conducting a systematic literature review. A linear mixed effect model was applied on the unpublished biomonitoring data, showing a decreasing time trend of 30% in urinary Cr levels. Considering the observed decreasing time trend, only articles published between January 1, 2010 and September 30, 2020 were included in the systematic literature search to assess current and recent biomonitoring levels. Twenty-five studies focusing on human biomonitoring of exposure to Cr(VI) in occupational settings were included. Overall, the results showed a decreasing time trend in urinary Cr levels and the need for more specific Cr(VI) biomarkers. Furthermore, this review indicated the importance of improved working conditions, efficient use of personal protective equipment, better exposure control and increased risk awareness to reduce Cr levels in biological matrices. Further investigation of the contribution of the different exposure routes is needed, so that better guidance on the use of control measures can be provided. In addition, this review support the call for more harmonization of human biomonitoring.

Investigation of the biological activity, mechanical properties and wound healing application of a novel scaffold based on lignin-agarose hydrogel and silk fibroin embedded zinc chromite nanoparticles

Given the important aspects of wound healing approaches, in this work, an innovative biocompatible nanobiocomposite scaffold was designed and prepared based on cross-linked lignin-agarose hydrogel, extracted silk fibroin solution, and zinc chromite (ZnCr2O4) nanoparticles. Considering the cell viability technique, red blood cell hemolysis in addition to anti-biofilm assays, it was determined that after three days, the toxicity of the cross-linked lignin-agarose/SF/ZnCr2O4 nanobiocomposite was less than 13%. Moreover, the small hemolytic effect (1.67%) and high level of prevention in forming a P. aeruginosa biofilm with low OD value (0.18) showed signs of considerable hemocompatibility and antibacterial activity. Besides, according to an in vivo assay study, the wounds of mice treated with the cross-linked lignin-agarose/SF/ZnCr2O4 nanobiocomposite scaffold were almost completely healed in five days. Aside from these biological tests, the structural features were evaluated by FT-IR, EDX, FE-SEM, and TG analyses, as well as swelling ratio, rheological, and compressive mechanical study tests. Additionally, it was concluded that adding silk fibroin and ZnCr2O4 nanoparticles could enhance the mechanical tensile properties of cross-linked lignin-agarose hydrogel, and also an elastic network was characterized for this designed nanobiocomposite.

Hexavalent chromium: Regulation and health effects

Despite the knowledge about heavy metals toxicity on humans, its use is widely spread mainly for industrial processes. Chromium is an element that belongs to this group and although it is present in our daily diet, it can also be harmful for humans, causing skin allergies and increasing the risk of lung cancer, among other health effects reported. In this review, we highlight its nutritional role, its toxicokinetic and toxicodynamic in humans, its regulation in the industry and the biomonitoring proposal of this element in blood and urine samples with the aim to control the level of exposure of the workers in military industry and also of the general population.

Assessing hexavalent chromium tissue-specific accumulation patterns and induced physiological responses to probe chromium toxicity in Coturnix japonica quail

Hexavalent chromium (Cr(VI)) is an environmental pollutant with vast mutagenic and carcinogenic potential. Various past and recent studies confirm the deleterious effects of Cr(VI) in different models, from invertebrates to mammalians. However, there is a lack of studies that comprehensively assess and correlate Cr(VI) accumulation patterns and the resulting physiological responses. Here we used an attractive toxicological model, male Japanese quail (Coturnix japonica), as an alternative probing system to evaluate Cr(VI) accumulation in the vital organs, including the brain, heart, kidneys, liver, and testes after 20 days of exposure to 1.2 μg/mL and 2.4 μg/mL potassium dichromate-K₂Cr₂O₇ ingested in the form of drinking water. The observed effects were correlated with the shift in immune system readiness, hematological indices, serum biochemistry and enzyme activity. Regardless of the exposure dose, the Cr(VI) distribution and accumulation pattern in terms of relative Cr(VI) concentration in tissues was: testes > kidneys > liver > heart > brain. Moreover, Cr(VI) triggered the development of microcytic and hypochromic anemia and reduced the immune system's readiness to cope with challenges. Besides, serum biochemistry presented significant shifts, including reduction of serum electrolytes and proteins and an increase in creatine kinase (CK) and lactate dehydrogenase (LDH) activity. Our study provides novel toxicological data that can be translated to higher animal models to help in the extrapolation of Cr(VI) toxicity in humans.

Microbial Mechanisms for Remediation of Hexavalent Chromium and their Large-Scale Applications; Current Research and Future Directions

The increase of anthropogenic activities has led to the pollution of the environment by heavy metals, including chromium (Cr). There are two common oxidative states of Cr that can be found in industrial effluents the trivalent chromium Cr(III) and the hexavalent chromium Cr(VI). While the hexavalent chromium Cr(VI) is highly toxic and can trigger serious human health issues, its reduced form, the trivalent chromium Cr(III), is less toxic and insoluble. Leather tanning is an important industry in many developing countries and serves as a major source of Cr(VI) contamination. Globally, tannery factories generate approximately 40 million m3 of Cr-containing wastewater annually. While the physico-chemical treatments of tannery wastewater are not safe, produce toxic chemicals and require large amounts of chemical inputs, bioremediation using chromium-resistant bacteria (CRB) is safer, efficient and does not produce toxic intermediates. Chromium-resistant bacteria (CRB) utilise three mechanisms for Cr(VI) removal: biotransformation, biosorption and bioaccumulation. This review will evaluate the three Cr(VI) detoxification mechanisms used by bacteria, their limitations and assess their applications for large-scale remediation of Cr(VI). This can be helpful for understanding the nature of Cr(VI) remediation mechanisms used by bacteria, therefore, bridging the gap between laboratory findings and industrial application of microorganisms for Cr(VI) removal.