Environmental Science › Health, Toxicology and Mutagenesis

Chromium effects and bioremediation

Works Count: 31694

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This cluster of papers focuses on the bioremediation of chromium-contaminated environments using microbial processes, as well as the health impacts and mechanisms of chromium toxicity, genotoxicity, and carcinogenicity. It explores the interactions of chromium with microorganisms, plants, and human health, addressing the detoxification, resistance, and reduction of chromium in various environmental matrices.

Keywords

Chromium; Bioremediation; Microbes; Heavy Metals; Genotoxicity; Carcinogenicity; Environmental Health; Bacteria; Hexavalent Chromium; Soil Remediation

Minerals in Animal and Human Nutrition

2003-01-01

Lee Russell McDowell

Chromium toxicity in plants

2005-04-04

Arun K. Shanker , Carlos Cervantes , Herminia Loza‐Tavera +1 more

Chromium (VI) biosorption and bioaccumulation by chromate resistant bacteria

2002-07-01

Thiruneelakantan Srinath , Tuhina Verma , Pramod W. Ramteke +1 more

Surface reactions of chromium in soils and waters

1995-06-01

Scott Fendorf

Trace element risk assessment: essentiality vs. toxicity

2003-09-22

Susan Goldhaber

Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and Chromium

2007-10-30

Konstantin Salnikow , Anatoly Zhitkovich

Chronic exposure to nickel(II), chromium(VI), or inorganic arsenic (iAs) has long been known to increase cancer incidence among affected individuals. Recent epidemiological studies have found that carcinogenic risks associated with … Chronic exposure to nickel(II), chromium(VI), or inorganic arsenic (iAs) has long been known to increase cancer incidence among affected individuals. Recent epidemiological studies have found that carcinogenic risks associated with chromate and iAs exposures were substantially higher than previously thought, which led to major revisions of the federal standards regulating ambient and drinking water levels. Genotoxic effects of Cr(VI) and iAs are strongly influenced by their intracellular metabolism, which creates several reactive intermediates and byproducts. Toxic metals are capable of potent and surprisingly selective activation of stress-signaling pathways, which are known to contribute to the development of human cancers. Depending on the metal, ascorbate (vitamin C) has been found to act either as a strong enhancer or suppressor of toxic responses in human cells. In addition to genetic damage via both oxidative and nonoxidative (DNA adducts) mechanisms, metals can also cause significant changes in DNA methylation and histone modifications, leading to epigenetic silencing or reactivation of gene expression. In vitro genotoxicity experiments and recent animal carcinogenicity studies provided strong support for the idea that metals can act as cocarcinogens in combination with nonmetal carcinogens. Cocarcinogenic and comutagenic effects of metals are likely to stem from their ability to interfere with DNA repair processes. Overall, metal carcinogenesis appears to require the formation of specific metal complexes, chromosomal damage, and activation of signal transduction pathways promoting survival and expansion of genetically/epigenetically altered cells.

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Potential hazards of hexavalent chromate in our drinking water

2003-04-01

Max Costa

A Critical Assessment of Chromium in the Environment

1999-01-01

David Eugene Kimbrough , Yoram Cohen , Arthur M. Winer +2 more

Abstract This article reviews the emissions, environmental fate and transport, analytical chemistry, uptake and metabolism, toxicology, and human epidemiology of chromium. Chromium is unique among regulated toxic elements in the … Abstract This article reviews the emissions, environmental fate and transport, analytical chemistry, uptake and metabolism, toxicology, and human epidemiology of chromium. Chromium is unique among regulated toxic elements in the environment in that different species of chromium, specifically chromium (III) and chromium (VI), are regulated in different ways, in contrast to other toxic elements where the oxidation state is not distinguished. In both industrial and environmental situations chromium (III) and chromium (VI) can inter-convert, with reduction of chromium (VI) to chromium (III) generally being favored in most environmental situations. Chromium released into the air, water, and soil can be transported among the various environmental media through various intermedia transport processes. Once in the environment, chromium can be taken up by human and other ecological receptors. Chromium (III) is generally absorbed through cell membranes albeit to a significantly lesser degree than chromium (VI). Because most of the biosphere is reducing for chromium (VI) and chromium (III) is relatively immobile, there is little bioconcentration or biomagnification of chromium (VI). Chromium appears to be a nutrient for at least some plants and animals, including humans, although chromium (VI) species have been reported to be toxic to bacteria, plants, and animals. Human toxicity includes lung cancer, liver, kidney and gastric damage, and epidermal irritation and sensiti-zation. However, it is noted that medical, toxicological, and epidemiological evidence suggests that not all compounds containing chromium (VI) species (e.g., chromate salts) are carcinogenic. Keywords: chromium (III)chromium (VI)intermedia transport and transformationsexposuretoxicology.

Chromium occurrence in the environment and methods of its speciation

2000-03-01

J. Kotaś , Zofia Stasicka

The toxicology of chromium with respect to its chemical speciation: A review

1993-05-01

Sidney Katz , Harry Salem

Abstract The properties of trivalent and hexavalent chromium are reviewed with respect to acute and chronic oral toxicity, dermal toxicity, systemic toxicity, toxicokinetics, cytotoxicity, genotoxicity and carcinogenicity. The hexavalent chromium … Abstract The properties of trivalent and hexavalent chromium are reviewed with respect to acute and chronic oral toxicity, dermal toxicity, systemic toxicity, toxicokinetics, cytotoxicity, genotoxicity and carcinogenicity. The hexavalent chromium compounds appear to be 10–100 times more toxic than the trivalent chromium compounds when both are administered by the oral route. Dermal irritancy and allergy are more frequently caused by contact with soluble hexavalent chromium compounds. The cytotoxicity of soluble and insoluble hexavalent chromium compounds to fibroblasts is 100‐1000 times greater than that demonstrated by trivalent chromium compounds. In short‐term tests, the hexavalent chromium compounds demonstrated genotoxic effects four times more frequently than did the trivalent chromium compounds. Carcinogenicity appears to be associated with the inhalation of the less soluble/insoluble hexavalent chromium compounds. The toxicology of chromium does not reside with the elemental form. It varies greatly among a wide variety of very different chromium compounds. Oxidation state and solubility are particularly important factors in considering the toxicity of chromium with respect to its chemical speciation.

Chromium(III) and the glucose tolerance factor

1959-11-01

Klaus Schwarz , Walter Mertz

Mechanism of hexavalent chromium detoxification by microorganisms and bioremediation application potential: A review

2006-12-23

K.H. Cheung , Ji‐Dong Gu

The degradation of dyestuffs: Part II Behaviour of dyestuffs in aerobic biodegradation tests

1986-01-01

Udo Pagga , D. Brown

A review of chemical, electrochemical and biological methods for aqueous Cr(VI) reduction

2012-04-30

Carlos Barrera-Díaz , Violeta Lugo-Lugo , Bryan Bilyeu

Chemical and microbial remediation of hexavalent chromium from contaminated soil and mining/metallurgical solid waste: A review

2013-01-28

B. Dhal , Hrudayanath Thatoi , Nigamananda Das +1 more

The Essential Trace Elements

1981-09-18

Walter Mertz

Essential trace elements are required by man in amounts ranging from 50 micrograms to 18 milligrams per day. Acting as catalytic or structural components of larger molecules, they have specific … Essential trace elements are required by man in amounts ranging from 50 micrograms to 18 milligrams per day. Acting as catalytic or structural components of larger molecules, they have specific functions and are indispensable for life. Research during the past quarter of a century has identified as essential six trace elements whose functions were previously unknown. In addition to the long-known deficiencies of iron and iodine, signs of deficiency for chromium, copper, zinc, and selenium have been identified in free-living populations. Four trace elements were proved to be essential for two or more animal species during the past decade alone. Marginal or severe trace element imbalances can be considered risk factors for several diseases of public health importance, but proof of cause and effect relationships will depend on a more complete understanding of basic mechanisms of action and on better analytical procedures and functional tests to determine marginal trace element status in man.

Sources and toxicity of hexavalent chromium

2011-05-19

Rumpa Saha , Rumki Nandi , Bidyut Saha

Chromium exists in oxidation states ranging from −IV to +VI, inclusively. The compounds exhibit a wide range of geometries including square planar, tetrahedral, octahedral, and various distorted geometries. Ore refining, … Chromium exists in oxidation states ranging from −IV to +VI, inclusively. The compounds exhibit a wide range of geometries including square planar, tetrahedral, octahedral, and various distorted geometries. Ore refining, chemical and refractory processing, cement-producing plants, automobile brake lining, catalytic converters for automobiles, leather tanneries, and chrome pigments contribute to the atmospheric burden of chromium. Hexavalent chromium is known to have 100-fold more toxicity than trivalent chromium, for both acute and chronic exposures because of its high water solubility and mobility, as well as easy reduction. The respiratory tract is the major target organ for hexavalent chromium following the inhalation exposure in humans. Chronic inhalation exposure to hexavalent chromium results in effects on the respiratory tract, with perforations and ulcerations of the septum, bronchitis, decreased pulmonary function, pneumonia, and nasal itching and soreness as reported. Chronic human exposure to high levels of hexavalent chromium by inhalation or oral exposure may produce effects on the liver, kidney, gastrointestinal, and immune systems, and possibly the blood. Dermal exposure to hexavalent chromium may cause contact dermatitis, sensitivity, and ulceration of the skin.

Mechanisms of chromium toxicity, carcinogenicity and allergenicity: Review of the literature from 1985 to 2000

2001-09-01

A.D. Dayan , Alan J. Paine

Laboratory and clinical reports about the pathogenesis of the carcinogenicity and allergenicity of chromium compounds published between 1985 and 2000 have been reviewed as a basis for consideration of the … Laboratory and clinical reports about the pathogenesis of the carcinogenicity and allergenicity of chromium compounds published between 1985 and 2000 have been reviewed as a basis for consideration of the pathogenetic mechanisms involved. There is good evidence from the clinic and the laboratory that Cr[VI] is the ion responsible for most of the toxic actions, although much of the under lying molecular damage may be due to its intracellular reduction to the even more highly reactive and short-lived chemical species Cr[III] and Cr[V]. Exposure to Cr[VI] can result in various point mutations in DNA and to chromosomal damage, as well as to oxidative changes in proteins and to adduct formation. The relative importance of these effects of chromium ions and of the free oxidising radicals they may generate in the body in causing tumours and allergic sensitisation remain to be demonstrated. Biochemical studies of the DNA-damaging effects and of the pathogenesis of the allergic reactions to chromium ions have not kept up with advances in understanding of the molecular basis of the effects of other carcinogens and allergens.

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Cytotoxicity and oxidative mechanisms of different forms of chromium

2002-10-09

Debasis Bagchi

Oxidative Mechanisms in the Toxicity of Chromium and Cadmium Ions

2001-01-01

S.J. Stohs , Debasis Bagchi , Ezdihar A. Hassoun +1 more

Chromium and cadmium are widely used industrial chemicals. The toxicities associated with both metal ions are well known. However, less information is available concerning the mechanisms of toxicity. The results … Chromium and cadmium are widely used industrial chemicals. The toxicities associated with both metal ions are well known. However, less information is available concerning the mechanisms of toxicity. The results of in vitro and in vivo studies demonstrate that both cations induce an oxidative stress that results in oxidative deterioration of biological macromolecules. However, different mechanisms are involved in the production of oxidative stress by chromium and cadmium. Chromium undergoes redox cycling, while cadmium depletes glutathione and protein-bound sulfhydryl groups, resulting in enhanced production of reactive oxygen species such as superoxide ion, hydroxyl radicals, and hydrogen peroxide. These reactive oxygen species result in increased lipid peroxidation, enhanced excretion of urinary lipid metabolites, modulation of intracellular oxidized states, DNA damage, membrane damage, altered gene expression, and apoptosis. Enhanced production of nuclear factor-кВ and activation of protein kinase С occur. Furthermore, the p53 tumor suppressor gene is involved in the cascade of events associated with the toxicities of these cations. In summary, the results clearly indicate that although different mechanisms lead to the production of reactive oxygen species by chromium and cadmium, similar subsequent mechanisms and types of oxidative tissue damage are involved in the overall toxicities.

Aqueous geochemistry of chromium: A review

1991-07-01

Françoise C. Richard , Alain C.M. Bourg

Environmental chemistry of chromium

1989-10-01

P. Raics , L. E. Eary , John M. Zachara

Chromium in Drinking Water: Sources, Metabolism, and Cancer Risks

2011-07-18

Anatoly Zhitkovich

Drinking water supplies in many geographic areas contain chromium in the +3 and +6 oxidation states. Public health concerns are centered on the presence of hexavalent Cr that is classified … Drinking water supplies in many geographic areas contain chromium in the +3 and +6 oxidation states. Public health concerns are centered on the presence of hexavalent Cr that is classified as a known human carcinogen via inhalation. Cr(VI) has high environmental mobility and can originate from anthropogenic and natural sources. Acidic environments with high organic content promote the reduction of Cr(VI) to nontoxic Cr(III). The opposite process of Cr(VI) formation from Cr(III) also occurs, particularly in the presence of common minerals containing Mn(IV) oxides. Limited epidemiological evidence for Cr(VI) ingestion is suggestive of elevated risks for stomach cancers. Exposure of animals to Cr(VI) in drinking water induced tumors in the alimentary tract, with linear and supralinear responses in the mouse small intestine. Chromate, the predominant form of Cr(VI) at neutral pH, is taken up by all cells through sulfate channels and is activated nonenzymatically by ubiquitously present ascorbate and small thiols. The most abundant form of DNA damage induced by Cr(VI) is Cr-DNA adducts, which cause mutations and chromosomal breaks. Emerging evidence points to two-way interactions between DNA damage and epigenetic changes that collectively determine the spectrum of genomic rearrangements and profiles of gene expression in tumors. Extensive formation of DNA adducts, clear positivity in genotoxicity assays with high predictive values for carcinogenicity, the shape of tumor-dose responses in mice, and a biological signature of mutagenic carcinogens (multispecies, multisite, and trans-sex tumorigenic potency) strongly support the importance of the DNA-reactive mutagenic mechanisms in carcinogenic effects of Cr(VI). Bioavailability results and kinetic considerations suggest that 10-20% of ingested low-dose Cr(VI) escapes human gastric inactivation. The directly mutagenic mode of action and the incompleteness of gastric detoxification argue against a threshold in low-dose extrapolation of cancer risk for ingested Cr(VI).

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Interactions of chromium with microorganisms and plants

2001-05-01

Carlos Cervantes , Jesús Campos-Garcı́a , Silvia Devars +4 more

Chromium is a highly toxic non-essential metal for microorganisms and plants. Due to its widespread industrial use, chromium (Cr) has become a serious pollutant in diverse environmental settings. The hexavalent … Chromium is a highly toxic non-essential metal for microorganisms and plants. Due to its widespread industrial use, chromium (Cr) has become a serious pollutant in diverse environmental settings. The hexavalent form of the metal, Cr(VI), is considered a more toxic species than the relatively innocuous and less mobile Cr(III) form. The presence of Cr in the environment has selected microbial and plant variants able to tolerate high levels of Cr compounds. The diverse Cr-resistance mechanisms displayed by microorganisms, and probably by plants, include biosorption, diminished accumulation, precipitation, reduction of Cr(VI) to Cr(III), and chromate efflux. Some of these systems have been proposed as potential biotechnological tools for the bioremediation of Cr pollution. In this review we summarize the interactions of bacteria, algae, fungi and plants with Cr and its compounds.

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Elevated Intakes of Supplemental Chromium Improve Glucose and Insulin Variables in Individuals With Type 2 Diabetes

1997-11-01

Richard A. Anderson , Nanzheng Cheng , Noella A. Bryden +4 more

Chromium is an essential nutrient involved in normal carbohydrate and lipid metabolism. The chromium requirement is postulated to increase with increased glucose intolerance and diabetes. The objective of this study … Chromium is an essential nutrient involved in normal carbohydrate and lipid metabolism. The chromium requirement is postulated to increase with increased glucose intolerance and diabetes. The objective of this study was to test the hypothesis that the elevated intake of supplemental chromium is involved in the control of type 2 diabetes. Individuals being treated for type 2 diabetes (180 men and women) were divided randomly into three groups and supplemented with: 1) placebo, 2) 1.92 μmol (100 μg) Cr as chromium picolinate two times per day, or 3) 9.6 μmol (500 μg) Cr two times per day. Subjects continued to take their normal medications and were instructed not to change their normal eating and living habits. HbA1c values improved significantly after 2 months in the group receiving 19.2 pmol (1,000 pg) Cr per day and was lower in both chromium groups after 4 months (placebo, 8.5 ± 0.2%; 3.85 pmol Cr, 7.5 ± 0.2%; 19.2 pmol Cr, 6.6 ± 0.1%). Fasting glucose was lower in the 19.2-μmol group after 2 and 4 months (4-month values: placebo, 8.8 ± 0.3 mmol/1; 19.2 μmol Cr, 7.1 ± 0.2 mmol/1). Two-hour glucose values were also significantly lower for the subjects consuming 19.2 μmol supplemental Cr after both 2 and 4 months (4-month values: placebo, 12.3 ± 0.4 mmol/1; 19.2 μmol Cr, 10.5 ± 0.2 mmol/1). Fasting and 2-h insulin values decreased significantly in both groups receiving supplemental chromium after 2 and 4 months. Plasma total cholesterol also decreased after 4 months in the subjects receiving 19.2 μmol/day Cr. These data demonstrate that supplemental chromium had significant beneficial effects on HbA1c, glucose, insulin, and cholesterol variables in subjects with type 2 diabetes. The beneficial effects of chromium in individuals with diabetes were observed at levels higher than the upper limit of the Estimated Safe and Adequate Daily Dietary Intake.

Biosorption of chromium and nickel by heavy metal resistant fungal and bacterial isolates

2006-12-14

Shankar Congeevaram , Sridevi Dhanarani , Joonhong Park +2 more

Efflux-mediated heavy metal resistance in prokaryotes

2003-05-13

Dietrich H. Nies

What makes a heavy metal resistant bacterium heavy metal resistant? The mechanisms of action, physiological functions, and distribution of metal-exporting proteins are outlined, namely: CBA efflux pumps driven by proteins … What makes a heavy metal resistant bacterium heavy metal resistant? The mechanisms of action, physiological functions, and distribution of metal-exporting proteins are outlined, namely: CBA efflux pumps driven by proteins of the resistance-nodulation-cell division superfamily, P-type ATPases, cation diffusion facilitator and chromate proteins, NreB- and CnrT-like resistance factors. The complement of efflux systems of 63 sequenced prokaryotes was compared with that of the heavy metal resistant bacterium Ralstonia metallidurans. This comparison shows that heavy metal resistance is the result of multiple layers of resistance systems with overlapping substrate specificities, but unique functions. Some of these systems are widespread and serve in the basic defense of the cell against superfluous heavy metals, but some are highly specialized and occur only in a few bacteria. Possession of the latter systems makes a bacterium heavy metal resistant.

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Toxicity and Carcinogenicity of Chromium Compounds in Humans

2006-01-01

Max Costa , Catherine B. Klein

Chromium is a human carcinogen primarily by inhalation exposure in occupational settings. Although lung cancer has been established as a consequence of hexavalent chromium exposure in smokers and nonsmokers, some … Chromium is a human carcinogen primarily by inhalation exposure in occupational settings. Although lung cancer has been established as a consequence of hexavalent chromium exposure in smokers and nonsmokers, some cancers of other tissues of the gastrointestinal and central nervous systems have also been noted. Except for a few reports from China, little is known about the health risks of environmental exposures to chromium. Likewise, there has been a lack of epidemiological studies of human exposure to hexavalent Cr by drinking water or ingestion, and it has been suggested that humans can perhaps tolerate hexavalent Cr at higher levels than the current drinking water standard of 50 ppb. This review highlights the most recent data on the induction of skin tumors in mice by chronic drinking-water exposure to hexavalent chromium in combination with solar ultraviolet light. This experimental system represents an important new animal model for chromate-induced cancers by ingestion of drinking water, and it suggests by extrapolation that chromate can likely be considered a human carcinogen by ingestion as well. The potential use of this animal model for future risk assessment is discussed.

Toxicity and Carcinogenicity of Cr(VI) in Animal Models and Humans

1997-01-01

Max Costa

The toxicity and carcinogenicity of hexavalent chromium (Cr) in animal and human models are reviewed. The focus of this review is not on the well-established fact that hexavalent Cr compounds … The toxicity and carcinogenicity of hexavalent chromium (Cr) in animal and human models are reviewed. The focus of this review is not on the well-established fact that hexavalent Cr compounds of low and high water solubility can induce respiratory cancers, but rather this review addresses other types of cancers induced by exposure to hexavalent Cr compounds. Additionally, non-cancer endpoints are also discussed with documentation of human and animal studies showing non-cancer health effects of hexavalent Cr exposure on the respiratory system, GI system, immune system, liver, and kidney. There is an emerging understanding that because hexavalent chromate is isostructural with phosphate and sulfate, it is readily taken up by the G.I. tract and penetrates to many tissues and organs throughout the body. This is supported by animal studies and experiments using human volunteers. From the epidemiological studies, there is suggestive evidence that hexavalent Cr causes increased risk of bone, prostate, lymphomas, Hodgkins, leukemia, stomach, genital, renal, and bladder cancer, reflecting the ability of hexavalent chromate to penetrate all tissues in the body. A high accumulation of Cr(III) in all tissues and organs is a strong indication of the wide toxic potential of exposure to soluble hexavalent Cr in the drinking water and in the ambient environment.

Chromium deficiency, glucose intolerance, and neuropathy reversed by chromium supplementation, in a patient receiving long-term total parenteral nutrition

1977-04-01

K.N. Jeejeebhoy , Richard C. Chu , Errol B. Marliss +2 more

Bioremedial potential of microbial mechanisms of metal mobilization and immobilization

2000-06-01

Geoffrey Michael Gadd

Chromium in Human Nutrition: A Review

1993-04-01

Walter Mertz

Role of Chromium in Human Health and in Diabetes

2004-11-01

William T. Cefalu , Frank B. Hu

Despite widespread use by patients with diabetes and anecdotal reports in the past regarding its efficacy, until recently, data in humans concerning chromium’s effects on insulin action in vivo or … Despite widespread use by patients with diabetes and anecdotal reports in the past regarding its efficacy, until recently, data in humans concerning chromium’s effects on insulin action in vivo or on cellular aspects of insulin action were scarce. Consequently, significant controversy still exists regarding the effect of chromium supplementation on parameters assessing human health. Furthermore, elucidating the cellular and molecular mechanisms by which chromium supplements affect carbohydrate metabolism in vivo is necessary before specific recommendations can be made regarding its routine use in the management of diabetes. This review focuses on providing current information about this trace mineral’s specific mechanisms of action and clinical trials in patients with diabetes. Chromium, one of the most common elements in the earth’s crust and seawater, exists in our environment in several oxidation states, principally as metallic (Cr), trivalent (+3), and hexavalent (+6) chromium. The latter is largely synthesized by the oxidation of the more common and naturally occurring trivalent chromium and is highly toxic. Trivalent chromium, found in most foods and nutrient supplements, is an essential nutrient with very low toxicity. The interest in chromium as a nutritional enhancement to glucose metabolism can be traced back to the 1950s, when it was suggested that brewer’s yeast contained a glucose tolerance factor (GTF) that prevented diabetes in experimental animals (1). This factor was eventually suggested to be a biologically active form of trivalent chromium that could substantially lower plasma glucose levels in diabetic mice (2). Interest regarding chromium administration in patients with diabetes was kindled by the observation in the 1970s that it truly was an essential nutrient required for normal carbohydrate metabolism. A patient receiving total parenteral nutrition (TPN) developed severe signs of diabetes, including weight loss and hyperglycemia that was refractory to increasing insulin dosing (3). Based on previous animal studies …

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Nitroaromatic Compounds, from Synthesis to Biodegradation

2010-05-27

Kou‐San Ju , Rebecca E. Parales

SUMMARY Nitroaromatic compounds are relatively rare in nature and have been introduced into the environment mainly by human activities. This important class of industrial chemicals is widely used in the … SUMMARY Nitroaromatic compounds are relatively rare in nature and have been introduced into the environment mainly by human activities. This important class of industrial chemicals is widely used in the synthesis of many diverse products, including dyes, polymers, pesticides, and explosives. Unfortunately, their extensive use has led to environmental contamination of soil and groundwater. The nitro group, which provides chemical and functional diversity in these molecules, also contributes to the recalcitrance of these compounds to biodegradation. The electron-withdrawing nature of the nitro group, in concert with the stability of the benzene ring, makes nitroaromatic compounds resistant to oxidative degradation. Recalcitrance is further compounded by their acute toxicity, mutagenicity, and easy reduction into carcinogenic aromatic amines. Nitroaromatic compounds are hazardous to human health and are registered on the U.S. Environmental Protection Agency's list of priority pollutants for environmental remediation. Although the majority of these compounds are synthetic in nature, microorganisms in contaminated environments have rapidly adapted to their presence by evolving new biodegradation pathways that take advantage of them as sources of carbon, nitrogen, and energy. This review provides an overview of the synthesis of both man-made and biogenic nitroaromatic compounds, the bacteria that have been identified to grow on and completely mineralize nitroaromatic compounds, and the pathways that are present in these strains. The possible evolutionary origins of the newly evolved pathways are also discussed.

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Improvement in the RFLP procedure for studying the diversity of nifH genes in communities of nitrogen fixers in soil

2001-01-01

Franck Poly , Lucile Jocteur Monrozier , René Bally

Microbial influence on metal mobility and application for bioremediation

2004-09-11

Geoffrey Michael Gadd

Actinobacteria: Current research and perspectives for bioremediation of pesticides and heavy metals

2016-09-27

Analía Álvarez , Juliana M. Saez , José Sebastián Dávila Costa +6 more

A New Strategy for Heavy Metal Polluted Environments: A Review of Microbial Biosorbents

2017-01-19

Ayansina Segun Ayangbenro , Olubukola Oluranti Babalola

Persistent heavy metal pollution poses a major threat to all life forms in the environment due to its toxic effects. These metals are very reactive at low concentrations and can … Persistent heavy metal pollution poses a major threat to all life forms in the environment due to its toxic effects. These metals are very reactive at low concentrations and can accumulate in the food web, causing severe public health concerns. Remediation using conventional physical and chemical methods is uneconomical and generates large volumes of chemical waste. Bioremediation of hazardous metals has received considerable and growing interest over the years. The use of microbial biosorbents is eco-friendly and cost effective; hence, it is an efficient alternative for the remediation of heavy metal contaminated environments. Microbes have various mechanisms of metal sequestration that hold greater metal biosorption capacities. The goal of microbial biosorption is to remove and/or recover metals and metalloids from solutions, using living or dead biomass and their components. This review discusses the sources of toxic heavy metals and describes the groups of microorganisms with biosorbent potential for heavy metal removal.

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Chromium speciation, bioavailability, uptake, toxicity and detoxification in soil-plant system: A review

2017-03-24

Muhammad Shahid , Saliha Shamshad , Marina Rafiq +5 more

Microbial and Plant-Assisted Bioremediation of Heavy Metal Polluted Environments: A Review

2017-12-04

Omena Bernard Ojuederie , Olubukola Oluranti Babalola

Environmental pollution from hazardous waste materials, organic pollutants and heavy metals, has adversely affected the natural ecosystem to the detriment of man. These pollutants arise from anthropogenic sources as well … Environmental pollution from hazardous waste materials, organic pollutants and heavy metals, has adversely affected the natural ecosystem to the detriment of man. These pollutants arise from anthropogenic sources as well as natural disasters such as hurricanes and volcanic eruptions. Toxic metals could accumulate in agricultural soils and get into the food chain, thereby becoming a major threat to food security. Conventional and physical methods are expensive and not effective in areas with low metal toxicity. Bioremediation is therefore an eco-friendly and efficient method of reclaiming environments contaminated with heavy metals by making use of the inherent biological mechanisms of microorganisms and plants to eradicate hazardous contaminants. This review discusses the toxic effects of heavy metal pollution and the mechanisms used by microbes and plants for environmental remediation. It also emphasized the importance of modern biotechnological techniques and approaches in improving the ability of microbial enzymes to effectively degrade heavy metals at a faster rate, highlighting recent advances in microbial bioremediation and phytoremediation for the removal of heavy metals from the environment as well as future prospects and limitations. However, strict adherence to biosafety regulations must be followed in the use of biotechnological methods to ensure safety of the environment.

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Biological approaches to tackle heavy metal pollution: A survey of literature

2018-04-05

Jaya Mary Jacob , Chinnannan Karthik , Rijuta Ganesh Saratale +4 more

Biosorption and biotransformation of hexavalent chromium [Cr(VI)]: A comprehensive review

2018-05-09

Renitta Jobby , Pamela Jha , Anoop Yadav +1 more

Toxicity and Bioremediation of Heavy Metals Contaminated Ecosystem from Tannery Wastewater: A Review

2018-09-27

Bernard E. Igiri , Stanley I.R. Okoduwa , Grace O. Idoko +3 more

The discharge of untreated tannery wastewater containing biotoxic substances of heavy metals in the ecosystem is one of the most important environmental and health challenges in our society. Hence, there … The discharge of untreated tannery wastewater containing biotoxic substances of heavy metals in the ecosystem is one of the most important environmental and health challenges in our society. Hence, there is a growing need for the development of novel, efficient, eco-friendly, and cost-effective approach for the remediation of inorganic metals (Cr, Hg, Cd, and Pb) released into the environment and to safeguard the ecosystem. In this regard, recent advances in microbes-base heavy metal have propelled bioremediation as a prospective alternative to conventional techniques. Heavy metals are nonbiodegradable and could be toxic to microbes. Several microorganisms have evolved to develop detoxification mechanisms to counter the toxic effects of these inorganic metals. This present review offers a critical evaluation of bioremediation capacity of microorganisms, especially in the context of environmental protection. Furthermore, this article discussed the biosorption capacity with respect to the use of bacteria, fungi, biofilm, algae, genetically engineered microbes, and immobilized microbial cell for the removal of heavy metals. The use of biofilm has showed synergetic effects with many fold increase in the removal of heavy metals as sustainable environmental technology in the near future.

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Microorganism remediation strategies towards heavy metals

2018-11-01

Kun Yin , Qiaoning Wang , Min Lv +1 more

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Heavy metal pollution and human biotoxic effects

2007-05-31

Duruibe , Ogwuegbu , Egwurugwu

Some heavy metals have bio-importance as trace elements but, the biotoxic effects of many of them in human biochemistry are of great concern. Hence, there is the need for proper … Some heavy metals have bio-importance as trace elements but, the biotoxic effects of many of them in human biochemistry are of great concern. Hence, there is the need for proper understanding of the conditions, such as the concentrations and oxidation states, which make them harmful, and how biotoxicity occurs. It is also important to know their sources, leaching processes, chemical conversions and their modes of deposition to pollute the environment, which essentially supports lives. Literature sources point to the fact that these metals are released into the environment by both natural and anthropogenic sources, especially mining and industrial activities, and automobile exhausts (for lead). They leach into underground waters, moving along water pathways and eventually depositing in the aquifer, or are washed away by run-off into surface waters thereby resulting in water and subsequently soil pollution. Poisoning and toxicity in animals occur frequently through exchange and co-ordination mechanisms. When ingested, they combine with the body’s biomolecules, like proteins and enzymes to form stable biotoxic compounds, thereby mutilating their structures and hindering them from the bioreactions of their functions. This paper reviews certain heavy metals and their biotoxic effects on man and the mechanisms of their biochemical activities. Keywords: Biochemical, biotoxic, environment, heavy metals, pollution.

The Biological Chemistry of the Elements

2001-08-16

J J R Fraústo da Silva , Richard J. Williams

Abstract Twenty inorganic elements, mostly metal ions, are consistently found in living systems and are essential for living systems to function correctly. The aim of this text is to discuss, … Abstract Twenty inorganic elements, mostly metal ions, are consistently found in living systems and are essential for living systems to function correctly. The aim of this text is to discuss, describe, and explain the functional relevance of those elements: the reasons for their selection; the processes of their uptake, transport and final localization in cells; the regulation of these processes; and the interactive network of their reactions that connects the in vivo inorganic elements to the environment and to the genome. The first seven chapters describe the physical, chemical, and biological principles of the involvement of the elements in cellular activity, stressing how inorganic and organic chemicals react differently together in different compartments. The next twelve chapters describe the uses of the individual essential inoranic elements and a section on the genetic control of each element is included. The final chapter discusses how the interaction of genes, proteins, small molecules, and inorganic elements plays an important role in evolution and the speciation of organisms. The second edition of 'The Biological Chemistry of The Elements' has been thoroughly revised in content and style. The main additions to the first edition concern the discussion of the links to the genome of the uptake and transfer of inorganic elements and the regulation of homeostasis, the functional co-operative activities of the elements, the interaction with the environment, and the evolution of usage. Recent structural and mechanistic knowledge of many biomolecules and organelles are also included. Like the higly praised first edition, this text will be the bible of bioinorganic chemistry.

Chromium in the natural and human environments

1988-01-01

Jerome O. Nriagu , Evert Nieboer

Historical Perspectives (J. Nriagu). Biological Chemistry of Chromium (E. Nieboer & A. Jusys). Production and Uses of Chromium (J. Nriagu). Atmospheric Emissions of Chromium from Natural and Anthropogenic Sources (J. … Historical Perspectives (J. Nriagu). Biological Chemistry of Chromium (E. Nieboer & A. Jusys). Production and Uses of Chromium (J. Nriagu). Atmospheric Emissions of Chromium from Natural and Anthropogenic Sources (J. Pacyna & J. Nriagu). Distribution and Characteristic Features of Chromium in the Atmosphere (J. Nriagu, et al.). Geochemistry of Chromium in the Oceans (L. Mayer). Occurrence and Distribution of Chromium in Natural Waters of India (B. Handa). Chromium Contamination of Groundwater (L. Calder). Chromium Removal from Industrial Wastewaters (S. Beszedits). Mobility and Bioavailability of Chromium in Soils (R. Bartlett & B. James). Chromium Toxicity to Algae and Bacteria (P. Wong & J. Trevors). The Significance of the Interactions of Chromium and Bacteria in Aquatic Habitats (M. Loutit, et al.). Chromium Toxicity: Effects of Microogranisms with Special Reference to the Soil Matrix (R. Coleman). Genetic Approaches in the Study of Chromium Toxicity and Resistance in Yeast and Bacteria (B.--I. Ono). The Toxicity of Chromium to Fish (D. Holdway) Mutagenic and Other Genotoxic Effects of Chromium Compounds (E. Nieboer & S. Shaw). Carcinogenicity of Chromium Compounds (A. Yassi & E. Nieboer). Chromium Hypersensitivity (A. Haines & E. Nieboer). Other Health Effects of Chromium Compounds (E. Nieboer & A. Yassi). Index.

Study of thoron exhalation from soil under different temperature and humidity conditions

2025-06-25

N. Chitra , Kothai Pathasarathy | Research Square (Research Square)

<title>Abstract</title> Radon (222Rn) and thoron (220Rn) exhalation from soil is governed by the soil properties as well as the ambient meteorological parameters. The temperature and humidity cause significant changes in … <title>Abstract</title> Radon (222Rn) and thoron (220Rn) exhalation from soil is governed by the soil properties as well as the ambient meteorological parameters. The temperature and humidity cause significant changes in the radon and thoron flux from the earth’s crust. Exhalation rate measurements can be made rapidly for thoron due to its short half-life leading to speedy attainment of steady state under closed conditions.<bold> </bold>In the present study, thoron exhalation from beach sand rich in 232Th, is studied in the controlled environment of a (0.5 m3 volume) radon chamber. The chamber is equipped with air- heater and moisture generator with automated temperature and humidity controller. Experiments were conducted in the temperature and relative humidity (RH) ranges 35-50°C and 40-60% respectively. For different combinations of temperature and RH, the steady state thoron concentration near the floor was measured and the exhalation rate was estimated by solving the mass balance equation. Common to all levels of RH, the thoron exhalation rate was found to steadily increase with temperature. For a total of 15°C (in steps of 5°C) temperature increase, the average percentage increase in exhalation rate is 34%. . At all temperatures, when the RH increased from 40 to 45%, an increase in the exhalation rate was observed. When the RH is further increased to 50%, the exhalation rate shows a dip. Above RH 50%, there is further drastic decrease in exhalation rate<bold> </bold>and this was explained by formulating a modified mass balance equation accounting for the decreased concentration gradient in the higher layers of air due to the restricted diffusion of thoron.

Review on the robustness of technologies and strategies in removal of hexavalent chromium: a biological perspective

2025-06-24

A. Ebrahim , Parry Dey , Jastin Samuel +1 more | BioMetals

Advancements in Heavy Metal Remediation: A Comprehensive Review of Physical, Chemical and Biological Strategies

2025-06-24

Y. Gwamna , Yu Miao , Abidina Abba +4 more | Asian Journal of Advanced Research and Reports

The objective of the review is to highlight the various ways to remediate heavy metal contamination especially Chemical remediation technologies which are of tremendous interest because they can remove and … The objective of the review is to highlight the various ways to remediate heavy metal contamination especially Chemical remediation technologies which are of tremendous interest because they can remove and decompose contaminants in contaminated areas. Environmental contamination remains one of the most important global issues. Efforts are made to prevent the discharge of toxic substances into the environment. Many technologies for the remediation of soil, surface water, and groundwater have been developed over time. Nanoremediation and Biological methods, including phytoremediation and mycoremediation, are also discussed for their eco-friendly and cost-effective potential. This review focuses on various remediation strategies, including precipitation, flocculation, adsorption/ ion exchange, chemical oxidation, and soil washing among others. Remediation technologies are typically always intergrated, however, they can also be utilised alone. The type of pollutants and site conditions will determine which system is most cost-effective and efficient. Future Research should be directed towards improving existing and developing new environmentally friendly remedial solutions.

Reductive Removal of Hexavalent Chromium from Aqueous Solutions by Silver-Doped Biochar Derived from Azadirachta indica Stem

2025-06-20

B. Thangagiri | Water Air & Soil Pollution

Waste Valorization Technologies in Tannery Sludge, Chromite, and Magnesite Mining

2025-06-20

Εvgenios Kokkinos , E.N. Peleka , Evangelos Tzamos +1 more | Recycling

Waste valorization involves reusing and recycling waste materials to create useful products such as materials, chemicals, fuels, or energy. The primary goal is the transition to a circular economy model … Waste valorization involves reusing and recycling waste materials to create useful products such as materials, chemicals, fuels, or energy. The primary goal is the transition to a circular economy model while minimizing the impacts of hazardous waste. Adopting such policies appears to be a one-way path due to the continuous increase in the consumption of raw materials. According to recent projections, by 2050, 180 billion tonnes of materials will be consumed annually. Since natural resources cannot meet these requirements, new sources must be explored. Waste can serve as an alternative source and cover at least part of the needs that arise. In this work, good practices regarding waste valorization are presented. The case studies examined include the waste/by-products of ultrabasic rocks resulting in chromite and magnesite mining, as well as the tannery sludge produced after the corresponding wastewater treatment.

Chromium in Biological Samples in Association with Cancer Risk by Site: A Systematic Literature Review

2025-06-20

Maddalena Carretti , Andrea Graziani , Giovanna Berti +4 more | Current Epidemiology Reports

Bioremediation of Cr(VI) using novel thermophilic bacteria Brevibacillus borstelensis SSAU-3 T: optimization, mechanism and phytotoxicity study

2025-06-20

Manshi Agrawal , Abhijeet Sharma , Akanksha Singh +1 more | Biodegradation

Chlorella-actinomycetes symbiotic system for heavy metal wastewater remediation: Influence of initial heavy metal concentration and remediation time

2025-06-19

Ying Chen , Jinfeng Wang , Chenglong Wang +3 more | Journal of Water Process Engineering

Chromium(III) Binding to Purified Fulvic and Humic Acids and Their Solid-Solution Partitioning and Speciation in Soil

2025-06-19

Frank van Raffe , Rob N.J. Comans , J.E. Groenenberg | ACS Earth and Space Chemistry

Microbial-induced Flower-like Phosphate Assembly via Endogenous Phosphorus for Heavy Metal Immobilization

2025-06-19

Hui Xu , Yan Zhang , Mingyan Wang +5 more | Journal of environmental chemical engineering

Reducing Cd Uptake by Wheat Through Rhizosphere Soil N-C Cycling and Bacterial Community Modulation by Urease-Producing Bacteria and Organo-Fe Hydroxide Coprecipitates

2025-06-17

Junqing Zhang , Shixiong Tang , Hao Wei +5 more | Microorganisms

The bioavailability of heavy metals is profoundly influenced by their interactions with active soil components (microorganisms, organic matter, and iron minerals). However, the effects of urease-producing bacteria combined with organo-Fe … The bioavailability of heavy metals is profoundly influenced by their interactions with active soil components (microorganisms, organic matter, and iron minerals). However, the effects of urease-producing bacteria combined with organo-Fe hydroxide coprecipitates (OFCs) on Cd accumulation in wheat, as well as the mechanisms underlying these effects, remain unclear. In this study, pot experiments integrated with high-throughput sequencing were employed to investigate the impacts of the urease-producing bacterial strain TJ6, ferrihydrite (Fh), and OFCs on Cd enrichment in wheat grains, alongside the underlying soil-microbial mechanisms. The results demonstrate that the strain TJ6-Fh/OFC consortium significantly (p < 0.05) reduced (50.1-66.7%) the bioavailable Cd content in rhizosphere soil while increasing residual Cd fractions, thereby decreasing (77.4%) Cd accumulation in grains. The combined amendments elevated rhizosphere pH (7.35), iron oxide content, and electrical conductivity while reducing (14.5-21.1%) dissolved organic carbon levels. These changes enhanced soil-colloid-mediated Cd immobilization and reduced Cd mobility. Notably, the NH4+ content and NH4+/NO3- ratio were significantly (p < 0.05) increased, attributed to the ureolytic activity of TJ6, which concurrently alkalinized the soil and inhibited Cd uptake via competitive ion channel interactions. Furthermore, the relative abundance of functional bacterial taxa (Proteobacteria, Gemmatimonadota, Enterobacter, Rhodanobacter, Massilia, Nocardioides, and Arthrobacter) was markedly increased in the rhizosphere soil. These microbes exhibited enhanced abilities to produce extracellular polymeric substances, induce phosphate precipitation, facilitate biosorption, and promote nutrient (C/N) cycling, synergizing with the amendments to immobilize Cd. This study for the first time analyzed the effect and soil science mechanism of urease-producing bacteria combined with OFCs in blocking wheat's absorption of Cd. Moreover, this study provides foundational insights and a practical framework for the remediation of Cd-contaminated wheat fields through microbial-organic-mineral collaborative strategies.

Utilisation of industrial sludge-derived ferrous sulfate for hexavalent chromium mitigation in cement

2025-06-16

Bilguun Mend , Young-Jun Lee , Do-young Kwon +2 more | Advances in Cement Research

Hexavalent chromium in Portland cement poses significant health risks and contributes to environmental pollution. Traditional reduction methods rely on costly, resource-intensive reducing agents derived from primary raw materials. This study … Hexavalent chromium in Portland cement poses significant health risks and contributes to environmental pollution. Traditional reduction methods rely on costly, resource-intensive reducing agents derived from primary raw materials. This study presents a sustainable approach by synthesising ferrous sulfate from industrial iron-rich sludges and waste sulfuric acid to mitigate hexavalent chromium levels in Portland cement. Three types of iron-rich sludges, sourced from municipal wastewater treatment and steel manufacturing, were analysed using X-ray diffraction to identify their iron-bearing phases. Key parameters, including sludge grinding intensity, stirring rate, reaction time and temperature, were systematically optimised to enhance ferrous sulfate yields. Under optimal conditions, approximately 17 g of pure ferrous sulfate were produced from 10 g of sludge and 50 ml of 20% waste sulfuric acid, achieving a recycling efficiency of around 90%. Incorporating the synthesised ferrous sulfate into ordinary Portland cement reduced hexavalent chromium concentrations below 2 ppm, complying with Environmental Protection Agency, USA standards. This method demonstrates the feasibility of repurposing industrial waste to enhance cement’s environmental performance, offering a promising valorisation pathway for iron-rich sludges and waste acids. The approach is cost-effective and environmentally friendly, aligning with circular economic principles and promoting green innovations in industrial waste management.

Bacteria Under Metal Stress—Molecular Mechanisms of Metal Tolerance

2025-06-14

Ewa Oleńska , Wanda Małek , Izabela Święcicka +3 more | International Journal of Molecular Sciences

Metals are natural components of the lithosphere, whose amounts and bioavailability are increasing in many areas due to their continuous release from both natural sources and intensive human activities. Some … Metals are natural components of the lithosphere, whose amounts and bioavailability are increasing in many areas due to their continuous release from both natural sources and intensive human activities. Some metals are essential or beneficial for living organisms, while others are non-essential and potentially toxic. When present at higher concentrations, even essential and beneficial metal ions can become harmful to all forms of life. Bacteria, unicellular organisms that have been exposed to metals since the earliest stages of life on Earth, have evolved metabolic pathways involving essential metals as well as diverse strategies to cope with metal toxicity. In the domain Bacteria, two main strategies have been identified: (i) metal exclusion, which includes cell wall sequestration and immobilization of metals in extracellular exopolysaccharides, siderophores, and other soluble microbial products, as well as (ii) metal tolerance, involving intracellular sequestration of metals (e.g., by metallothioneins, or low molecular weight thiols) as well as enzymatic conversion of metals to less toxic forms and/or its active efflux. Microorganisms possessing such adaptive traits are considered valuable agents for potential application in medicine, environmental sciences, and bioengineering (e.g., bioremediation and/or biomining).

Effects of Exposure to Chromium During Pregnancy on Fetal Growth and a Possible Sex-Dependent Response: Results of Cross-sectional Study

2025-06-14

Yuanyuan Fang , Qingmei Shen , Kai Yang +7 more | Biological Trace Element Research

Extraction and Quantification of Hexavalent Chromium in Eyeshadow Toy Cosmetics Using Ultrasonic Nebulization Mass Spectrometry and Anion Exchange Chromatography: Strategies to Prevent Chromium Species Interconversion

2025-06-09

Clara Sette | Journal of Drugs Addiction & Therapeutics

Hexavalent chromium is a potent carcinogen occasionally detected in cosmetics as a trace impurity originating from raw materials or manufacturing processes. Its presence in children’s toy eyeshadows poses serious health … Hexavalent chromium is a potent carcinogen occasionally detected in cosmetics as a trace impurity originating from raw materials or manufacturing processes. Its presence in children’s toy eyeshadows poses serious health concerns due to potential dermal or mucosal absorption. Accurate Cr (VI) quantification is hampered by interconversion with Cr (III), especially during extraction and chromatographic analysis. This study presents a robust and sensitive analytical method for selective Cr (VI) determination in complex cosmetic matrices using ion chromatography coupled with inductively coupled plasma mass spectrometry, enhanced by ultrasonic nebulization. An optimized extraction protocol was developed employing a weakly alkaline buffer containing 2 mM tetrabutylammonium hydroxide to stabilize Cr (VI) and prevent reduction. The final method achieved a limit of detection of 0.3 µg/L and limit of quantification of 0.9 µg/L. Recovery experiments demonstrated that more than 99% of Cr (VI) could be efficiently extracted after two mild extraction cycles, whereas Cr (III) exhibited poor recoverability, even when subjected to harsh extraction conditions. Consequently, Cr (III) was quantified by subtracting Cr (VI) from total chromium, determined after microwave-assisted digestion. Method validation using in-house prepared reference materials confirmed satisfactory trueness (11-15%) and precision (CV ≤ 7.9%). Application to seven commercial toy eyeshadows revealed Cr (VI) levels below the regulatory limit (1.0 mg/kg), although total chromium concentrations indicated the prevalent presence of Cr (III). This methodology provides a reliable and regulatory-compliant approach for Cr (VI) speciation in cosmetic products, supporting consumer safety, particularly in paediatric populations.

Mechanism of Mn (II) oxidation by Bacillus altitudinis BYD19 under ofloxacin exposure: Insights from transcriptome and metabolomics

2025-06-02

Jie Yu , Jin Xu , Hongjie Wang | Journal of environmental chemical engineering

Chromium‐Tanned Leather and Microbial Consortia: Identification of Taxa With Biodegradation Potential and Chromium Tolerance

2025-06-01

Manuela Bonilla‐Espadas , Irene Lifante‐Martínez , Mónica Camacho +4 more | Environmental Microbiology Reports

ABSTRACT Chromium‐tanned leather waste poses significant environmental challenges due to its resistance to degradation and heavy metal content. This study investigates the potential of naturally selected microbial consortia to initiate … ABSTRACT Chromium‐tanned leather waste poses significant environmental challenges due to its resistance to degradation and heavy metal content. This study investigates the potential of naturally selected microbial consortia to initiate the degradation of chromium‐tanned leather and identifies key bacterial genera capable of tolerating chromium and producing enzymes relevant to collagen breakdown. A novel multidisciplinary approach combining gravimetric assays, metagenomic sequencing, and scanning electron microscopy (SEM) was applied to characterise both microbial composition and degradation dynamics. Dominant genera such as Bacillus , Microbacterium , and Acinetobacter were associated with collagen degradation and metal tolerance, with Bacillus ‐rich communities showing the most pronounced mass loss (up to 3%). SEM analysis revealed the formation of robust biofilms and extensive matrix disruption, indicating enzymatic activity and structural breakdown of the leather. The formation of exopolysaccharide‐rich biofilms was found to be critical for microbial adhesion and biodegradation efficacy. These findings provide initial insights into microbial mechanisms involved in the degradation of chromium‐tanned leather and suggest potential applications for microbial consortia in future sustainable leather waste management strategies.

Oxidative damage, genetic and epigenetic alterations in hexavalent chromium exposed workers - A cross-sectional study within the SafeChrom project

2025-06-01

Zheshun Jiang , Agneta Annika Runkel , Christian Lindh +7 more | Environmental Research

Integrating surface phosphate modification and lattice nitrogen doping for synergistic removal of Cr(VI)

2025-06-01

Yifei Yin , Wenjun Zhou , Mingyu Zhang | Chemical Engineering Journal

Post-depositional effects on chromium in black shales and implications for paleo-redox reconstructions based on chromium isotopes

2025-06-01

Ziyao Fang , Zhang Hen , Xi Yu +4 more | Chemical Geology

Cr(VI)-bioremediation mechanism of a novel strain Bacillus sp. Cr02 with simultaneous aerobic/anaerobic reduction for Cr(VI) from soil to groundwater

2025-06-01

Liping Liu , Rui Liu , Fang Wang +5 more | Journal of Hazardous Materials

Sodium alginate/chitosan/graphene oxide gel beads immobilized Pseudomonas YH-1 enhanced the removal of pyrene-chromium co-contamination: Performance, transcriptomics insights, and mechanisms

2025-06-01

Yuhua Su , Peng Xiao , Liwen Yu +5 more | Journal of environmental chemical engineering

Cadmium detoxification by Stenotrophomonas sp. via cell wall exfoliation and regeneration mediated by mtgA

2025-06-01

Jianming Xu , Tong Wang , Jiawen Zhang +6 more | Pedosphere

Biotransformation of Hexavalent Chromium from Wastewater Using Bacillus firmus

2025-06-01

Pragatisheel , Abhishek Kumar , Leela Manohar Aeshala +1 more | Journal of Water Chemistry and Technology

Study on the bioremediation of methylene blue by Haematococcus pluvialis through synchrotron-FTIR imaging and spectroscopy

2025-06-01

Jinghua Liu , Wenzhe Li , Xuanyi Ren +7 more | Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy

A commentary on “What is it like to be a tetrachromat?” by Michael Newall

2025-05-31

Jordi Galiano-Landeira | Philosophy and the Mind Sciences

Analytical examinations of subjective experience are hampered by the first-person limitation described by Nagel (1974) in “What is it like to be a bat?”. This comment compares two examinations on … Analytical examinations of subjective experience are hampered by the first-person limitation described by Nagel (1974) in “What is it like to be a bat?”. This comment compares two examinations on the nature of subjective experience: Michael Newall’s (2025) analysis of tetrachromatic colour perception and Jordi Galiano-Landeira and Núria Peñuelas’ (2025) exploration of AI phenomenological consciousness within panpsychism. Newall examined whether tetrachromats perceive entirely novel colours or finer gradations of known ones, using analogies with dichromats and empirical evidence. Newall argued for the possibility of novel colour experiences. Galiano-Landeira and Peñuelas proposed that the analog/non-analog distinction is user-dependent, implying that AI could be phenomenologically conscious despite digital information processing. Although both works stemmed from completely different starting points, they emphasize the continuity of experience besides the perceptual resolution, questioning anthropocentric and chauvinistic biases in phenomenal consciousness studies. The structuralist perspective on colour quality spaces is also discussed to further delve into tetrachromatic perception, suggesting that tetrachromats might experience both finer gradations and novel colours.

Sll1725, an ABC transporter in Synechocystis sp. PCC 6803 for the detoxification of cadmium ion stress

2025-05-30

Gang Ruan , C. Liu , Gaofei Song +7 more | Ecotoxicology and Environmental Safety

The Global Biogeochemical Cycle of Chromium at the Earth's Surface

2025-05-29

David J. Janssen , Kohen W. Bauer , Sylvie Bruggmann +1 more | Global Biogeochemical Cycles

Abstract The biogeochemistry of Cr and its cycling in Earth's surface environments is reviewed. A synthesis and critical evaluation of the major processes controlling Cr mobility and isotope composition (δ … Abstract The biogeochemistry of Cr and its cycling in Earth's surface environments is reviewed. A synthesis and critical evaluation of the major processes controlling Cr mobility and isotope composition (δ 53 Cr) is presented, taking a source to sink view beginning with Cr mobilization from Earth's crust. Transport and cycling in inland waters and input to the oceans are discussed. Anthropogenic mobilization of Cr results in contributions to the atmosphere and inland waters that are of similar orders of magnitude as natural processes. The principal sources of Cr to the oceans are rivers and diffusive fluxes from marine sediments. Internal cycling of Cr in the ocean is largely controlled by reductive removal onto particles, particularly in O 2 ‐depleted waters, and redistribution through ocean circulation. Chromium removal from the oceans occurs primarily in organic carbon‐rich, O 2 ‐poor shelf sediments. Despite theoretically poor mobility of Cr(III), reductive removal in anoxic waters is non‐quantitative. As a result, isotope fractionation drives δ 53 Cr offsets in removed Cr as well as residual dissolved Cr(III), which accumulates in anoxic water, compared to the corresponding source. The implications for δ 53 Cr‐based reconstructions are discussed, along with an outlook for future proxy applications based on the processes controlling Cr incorporation into sediments. The roles of different source and sink processes are quantified in an updated mass balance for the global ocean. Finally, priority topics for future research are suggested, which at present are the primary uncertainties of the modern Cr biogeochemical cycle and aspects of the Cr isotope mass balance.

Cloning and expression of chromate reductase from Bacillus paramycoides S48 for chromium remediation

2025-05-29

Kalsoom Kalsoom , Salah Ud Din , Esma Ceylan +6 more | Scientific Reports

This study explores the production and characterization of chromium reductase from Bacillus paramycoides S48, focusing on its ability to effectively reduce toxic hexavalent chromium to less harmful chromium. The strain … This study explores the production and characterization of chromium reductase from Bacillus paramycoides S48, focusing on its ability to effectively reduce toxic hexavalent chromium to less harmful chromium. The strain exhibited 65% reduction in Cr(VI) within 96 h at 30 °C. Clear morphological and functional group shifts on strain S48 cell surface treated with metal were noted using analytical tools i.e. SEM-EDX and FT-IR. The physico-chemical conditions such as temperature, pH and nutritional factors were optimized for better chromate reductase yield using Placket-Burman and Central Composite design software. The purified chromate reductase, obtained through size exclusion column chromatography, demonstrated a specific activity of 1416.5 U/mg, and 6.6-fold increase in purity, with a molecular mass of approximately 35 kDa. The enzyme exhibited stability at temperature 30-40 °C and pH 5.0-8.0. Furthermore, the purified chromium reductase achieved, 80% reduction of toxic Cr(VI) at temperature 35 °C after 96 h. The BparChR gene was successfully cloned into the pET-28a vector, expressed in E. coli BL21, and purified through Ni-Affinity ion exchange chromatography. The recombinant BparChR protein displayed a specific activity of 1680 U/mg, and a purification fold of 5.73 times. The BparChR exhibited a remarkable 90% reduction in chromium after 96 h, surpassing the efficacy of whole-cell and native chromium reductase. This study concludes that B. paramycoides S48, holds promise for the cost-effective and environmentally friendly detoxification of chromium in contaminated industrial effluents.

CHROMIUM PICOLINATE PREVENTS OXIDATIVE DAMAGE TO CARDIOMYOCYTES UNDER CONDITIONS OF METABOLIC SYNDROME MODELING

2025-05-29

O.Y. Akimov , A.O. Mykytenko , A.V. Mischenko +1 more | Актуальні проблеми сучасної медицини Вісник Української медичної стоматологічної академії

Introduction. Metabolic syndrome is a systemic pathology commonly associated with eating disorders that lead to excess calorie consumption. In addition to the development of obesity, metabolic syndrome is often associated … Introduction. Metabolic syndrome is a systemic pathology commonly associated with eating disorders that lead to excess calorie consumption. In addition to the development of obesity, metabolic syndrome is often associated with the development of myocardial damage. One of the universal mechanisms of cell damage is oxidative stress. The search for proper medication that will prevent oxidative damage to the myocardium and influence the pathogenetic links in the development of metabolic syndrome is a relevant area of research. Chromium picolinate is a promising agent for preventing myocardial damage in metabolic syndrome, as it may enhance lipolysis in adipocytes. Objectives. The aim of this work is to determine the effect of chromium picolinate on the production of superoxide anion radical, the activity of antioxidant enzymes, and the content of malondialdehyde in the heart of rats under conditions of experimental metabolic syndrome. Materials and methods. The study was performed on 24 Wistar rats weighing 200–260 g. The animals were assigned to four groups (n = 6 per group): control group; metabolic syndrome model group, in which metabolic syndrome(MS) was induced by administering a 20% fructose solution as the sole source of drinking water to the standard vivarium diet for 60 days; chromium picolinate group, which received chromium picolinate orally at a dose of 80 μg/kg daily for 60 days; combined group, receiving both chromium picolinate and the MS-inducing fructose regimen. Cardiac oxidative stress parameters were assessed in 10% heart homogenates. The following indicators were measured: basal and induced production of the superoxide anion radical, activity of superoxide dismutase (SOD) and catalase (CAT), and malondialdehyde (MDA) content. Results. Administration of chromium picolinate to animals modeled with metabolic syndrome reduces basal superoxide anion radical production in the heart of rats by 52.33% compared to the metabolic syndrome group. Under these conditions, NADPH-induced superoxide anion radical production and NADHinduced superoxide anion radical production are reduced by 20.13% and 20.69%, respectively, compared with the metabolic syndrome group. The activity of superoxide dismutase and catalase in the heart of rats under these conditions increases by 78.88% and 137.93%, respectively, compared to the metabolic syndrome group. The content of malondialdehyde in the heart of rats under the conditions decreases by 25.59% compared to the metabolic syndrome group. The content of OMP under these conditions does not change statistically significantly. The use of chromium picolinate effectively reduces the production of reactive oxygen species, enhances antioxidant defense, and reduces the intensity of lipid peroxidation in the heart of rats with metabolic syndrome. This work is a part of the initiative research project No. 0124U000092 “Highand low-intensity phenotypes of systemic inflammatory response: molecular mechanisms and new medical technologies for their prevention and correction”.

Neuroprotective Potential of Chromium-D-Phenylalanine: Insights from Molecular Docking, Dynamics and Rotenone-Induced Parkinsonism in Rats

2025-05-29

K N Anitha , Mohammed Mutahir , Shivsharan B. Dhadde +2 more | Biological Trace Element Research