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Graphical abstract, Nanotechnology has received much attention because of its distinctive properties and many applications in various fields. Nanotechnology is a new approach to increase agricultural production with premium quality, environmental safety, biological support, and financial stability. Ecofriendly technology is becoming progressively important in modern agricultural applications as alternatives to traditional fertilizers and pesticides. Nanotechnology offers an alternative solution to overcome the disadvantages of conventional agriculture. Therefore, recent developments in using nanoparticles (NPs) in agriculture should be studied. This review presented a novel overview about the biosynthesis of NPs, using NPs as nano-fertilizers and nano-pesticides, the applications of NPs in agriculture, and their role in enhancing the function of biofactors. We also, show recent studies on NPs-plant interactions, the fate and safety of nanomaterials in plants, and NPs' function in alleviating the adverse effects of abiotic stress and heavy metal toxicity. Nano-fertilizers are essential to reduce the use of inorganic fertilizers and reduce their antagonistic effects on the environment. Nano-fertilizers are more reactive, can penetrate the epidermis allowing for gradual release, and targeted distribution, and thus reducing nutrients surplus, enhancing nutrient use efficiency. We also, concluded that NPs are crucial in alleviating abiotic stress and heavy metal toxicity. However, some studies reported the toxic effects of NPs on higher plants by induction of oxidative stress signals via depositing NPs on the cell surface and in organelles. The knowledge in our review article is critical in defining limitations and future perspectives of using nano-fertilizers as an alternative to conventional fertilizers.

Humans and animals are frequently exposed to heavy metals in the environment, which are highly toxic to the physiological milieu and organs of the body. We investigated the ameliorative potentials of ethanol leaf extract of Ruspolia hypocrateriformis against redox imbalance due to exposure of rats to heavy metals. The in vitro study explored the antioxidant potentials of the ethanol leaf extract using 1,1-diphenyl-2-picryl hydrazyl, nitric oxide and ferric reducing antioxidant potential assays respectively. HPLC was used to quantify the amount of flavonoids and phenolic acids in the extract. For in vivo study, 30 rats were randomly divided into 5 groups. Group A received normal saline. Group B received combined solution of Lead Nitrate and Mercury Chloride (11.25 mg/kg and 0.4 mg/kg) per Bwt/day. Group C, D and E were administered with the leaf extract at doses of 200, 400 and 600 mg/kg body weight respectively for 28 consecutive days. Biomarkers of hepatic dysfunctions and oxidative stress were investigated in the study rats. The HPLC study revealed high amount of gallic and ferulic acids (17.86 ± 2.68), which are the major phenolic compounds found in the extract. The extract further exhibited high antioxidant potentials in inhibiting the scavenging activity of free radicals produced in vitro. Interestingly, 600 mg/kg dosage of the leaf extract successfully ameliorated the distorted redox imbalance and oxidative damage in the liver of the rats caused by exposure to the heavy metals. Leaf extract of Ruspolia hypocrateriformis demonstrated strong antioxidant potentials, which could be exploited in pharmaceutical preparations.

Graphical abstract, Highlights • Nigeria locally made painkiller drugs contained As, Cd, Cr, Pb, Ni and Hg. • Cancer and non-cancer risk values were below1 × 10−6 – 1 × 10−4 and one (1) US EPA standard value. • True metal intake resulting from consumption of painkiller drugs were calculated. • There exist a toxicological relationship between painkiller drugs and its heavy metal content. • Painkiller drugs and its heavy metal content can act synergistically., In the informal sector of Nigeria’s economy, jobs are done manually as against automation resulting in body stress and pain, hence the need for painkiller drugs. Thirty different locally manufactured painkiller drugs, with analgesic, antipyretic and anti-inflammatory effects, were randomly sampled from pharmaceutical shops within Awka in October 2016. The drugs were pulverised, sieved and ashed before digestion using conc aqua regia HCl : HNO3 (3:1), carcinogenic heavy metals (arsenic, cadmium, chromium, mercury, nicked and lead) were assayed using Varian AA240 atomic absorption spectrophotometer (AAS). Risk assessment was carried out using US EPA model. The highest levels of arsenic (0.350 mg/kg) were found in samples with code 01, 03 and 020, cadmium (0.107 mg/kg and 0.144 mg/kg) were in samples code 013 and 028, and samples 03 and 011 had chromium levels as 6.637 mg/kg and 5.298 mg/kg. Highest value of mercury (0.470 mg/kg) was in sample code 01. All the painkiller drugs have nickel in the range of 0.046−0.448 mg/kg while highest values of lead were in sample code 05, 025 and 029 as 2.47 mg/kg, 1.11 mg/kg and 1.16 mg/kg. Non-cancer risk ranged as As (Nd -1.60 × 10−3), Cd (Nd–1.97 × 10−4), Cr (Nd-6.06 × 10−6), Hg (Nd–2.15 × 10−4), Ni (9.93 × 10-6–3.34 × 10−5) and Pb (Nd-4.36 × 10−4) while the cancer risk were As (Nd-1.63 × 10−7), Cd (Nd–4.45 × 10−9), Cr (Nd–1.56 × 10−7), Hg (Nd -1.53 × 10−9), Ni (1.50 × 10−10 –1.46 × 10−9) and Pb (Nd-8.82 × 10−9). The total cancer risk (TCR) and total non-cancer risk (TNCR) for all the heavy metals were in the range of 7.21 × 10−13–1.25 × 10−10 and 1.51 × 10−7–5.56 × 10−5 respectively. The TCR was below 1 × 10−6 -1 × 10−4 range while TNCR for heavy metals was below 1; the values established by US EPA. In conclusion, continuous consumption of locally Nigerian made painkiller drugs may expose the subjects to heavy metal toxicity.

Seaweeds are known to be rich source of micronutrients and bioactive compounds. The main objective of this study was to find the toxicological evaluation and heavy metal accumulation of five under-exploited edible seaweeds in animal model followed by dosage determination for regular consumption as a food by humans and food application. Some under-exploited seaweeds like Acanthophora spicifera, Gracilaria edulis, Padina gymnospora, Ulva fasciata and Enteromorphoa flexuosa were selected forthis study. The ED50 study was conducted in Wistar strain rats for 90 days with single dose administration of seaweed extract of 2000 mg/kg/BW. At the end of 90th day rats were euthanized, serum of the rats examined for biochemical, haematological, liver enzymes, and vital organs were dissected out for heavy metal analysis and urine samples collected intermediary to analyse electrolyte minerals. Result showed that no-observed adverse effect level (NOEL) on five seaweeds, did not cause any death and no significant variation in biochemical and haematological parameters, the values were found within standard values. Locomotor activity suggests normal action, organ necropsy showed no histopathology lesions, regular cell alignment in the tissue cross section. Heavy metals like arsenic, lead were found in trace amount and no mercury accumulation found in kidney, liver and brain of rats. Therefore, these five seaweeds were safe for human consumption and also for food product developement. Keywords: Seaweed, Sub-chronic toxicity, Acanthophora spicifera, Gracilaria edulis, Padina gymnospora, Ulva fasciata, Enteromorphoa flexuosa

Epidemiological methods are crucial to extract as much valid information as possible from human metal exposures. Thus, modern epidemiological approaches have elucidated human health effects that were not apparent in the past. At the same time, metal toxicology has served as a useful arena for testing and further refining methods for study design and data analysis. In contrast to most organic compounds, metals are not broken down, and many of them are retained in the body for long periods, thereby facilitating exposure assessment. In conjunction with the use of inexpensive metal analytical methods, exposures can be characterized from the analysis of blood, urine, and other biological samples. The availability of multiple approaches for exposure assessment allows a calculation of the total imprecision, thus paving the way for adjustment for measurement error. Likewise, due to their propensity to cause chronic or delayed toxicity, epidemiological studies of metal toxicity have focused on a wide variety of organ systems, subtle effects as well as mortality, and differences in susceptibility. Toxic metals often serve as paradigms of environmental and occupational toxicity. For these reasons, this chapter highlights the fields within epidemiology that are most relevant to toxic metals and discusses where these substances serve to illustrate important epidemiological concepts. Chapter sections include subjects such as epidemiological terms, study design, study population, exposure assessment, assessment of effects, data analysis, and assessment of benchmark dose, and inference.

Stress shifts plant growth in nearly all species evident by developmental problems, such as decreased yield of dry matter and leaf area. However, few plants remain least affected or may nearly be remain unaffected. Primarily stress includes metal toxicity, a key source of abiotic stress influencing the health of plants. In general, metal toxification has been one of the major challenges in developmental processes. To combat this, remarkable number of plants have been recognized that have produced noteworthy effects in detoxification. In the current scenario, remediation focused on plants shows a growing potential against organic/inorganic polluted soils which is technically termed as “Phytoremediation.” Phytoremediation requires multiple methods for eliminating toxins from soil, in general through altered expression of genes and enzymes in plants. Few studies have also reported the application of plant-associated microbiota for decontamination polluted soils, sediments, and underground water and thus are currently being expanded as an ecologically sound and budget-friendly technology. Various latest advancements in recognizing plant cell/molecular processes of uptake/tolerance have also been well studied. New innovative molecular technologies have improved the perspective further into metabolic pathways involved in stress tolerance/prevention mechanisms in frequent cultivated crops and hyperaccumulator plants. The purpose of this chapter is to concentrate on the underlying molecular basis associated in detoxification and tolerance to contaminants by plants. In addition, the focus in this chapter is on the ability of “omics” and genetic modification strategies to effectively remediate a contaminated environment has also been described

Metallic anions including antimonate (SbV), arsenate (AsV), chromate (CrVI), molybdate (MoVI), selenate (SeVI), tungstate (WV) and vanadate (VV) are important pollutants in the terrestrial environment due to their impacts on human and ecological health. It is essential that appropriate assays are used for derivation of toxicity models and guidance values, and to assess potential impacts on a site-specific basis. Root elongation is a simple and quick method for assessment of metal toxicity, yet there has been little to no validation. This study outlines results demonstrating low sensitivity of metallic anions in the often used 4-d root elongation test relative to 28-day nutrient culture assays. Therefore, root elongation assays may not be suitable for AsV, CrVI, MoVI, SbV, SeVI, and WV toxicity studies based on estimated toxicity parameters given the sensitivity of longer test assays. Only vanadate showed equivalent toxicity in the 4 d and 28 d assays. These results have significant implications for development of toxicity models and derivation of safe soil guidance values involving metallic anions.

Metals being released into the environment are posing an increasing risk to both environments and public health. Developing improved approaches to remove these metals from the environment is urgent. A current publication discovered that metal bioremediation was significantly improved by nanoparticles (NPs), and the remediation duration was shortened. However, there is no relevant method for the preparation and evaluation of this novel idea. Hence, we developed this method for bacteria in-situ-EPS (Extracellular Polymeric Substances) cultivation, bacteria sub-cellular fractionation, and metal determinations in cultivating solution, EPS and different fractions of bacteria to evaluate metal removal by the combination of NPs and bacteria, including (1) the enhancement of metal bioremediation by NPs, (2) the influence of NPs on bacteria growth and metal toxicity alleviation, (3) the ability of EPS to adsorb metals and the influence of NPs on the EPS metal adsorption, (4) the contribution of bacteria to metal removal in different part, the effects of NPs on metal distribution patterns in bacteria, and the role of NPs in this process.•The design and experimental procedure for the evaluation of metal removal by combing bacteria and NPs.•In-situ EPS cultivation and separation in the study of bioremediation for metals., Graphical abstract Image, graphical abstract

Silicon (Si) is the second richest element in the soil and surface of earth crust with a variety of positive roles in soils and plants. Different soil factors influence the Si bioavailability in soil-plant system. The Si involves in the mitigation of various biotic (insect pests and pathogenic diseases) and abiotic stresses (salt, drought, heat, and heavy metals etc.) in plants by improving plant tolerance mechanism at various levels. However, Si-mediated restrictions in heavy metals uptake and translocation from soil to plants and within plants require deep understandings. Recently, Si-based improvements in plant defense system, cell damage repair, cell homeostasis, and regulation of metabolism under heavy metal stress are getting more attention. However, limited knowledge is available on the molecular mechanisms by which Si can reduce the toxicity of heavy metals, their uptake and transfer from soil to plant roots. Thus, this review is focused the following facets in greater detail to provide better understandings about the role of Si at molecular level; (i) how Si improves tolerance in plants to variable environmental conditions, (ii) how biological factors affect Si pools in the soil (iii) how soil properties impact the release and capability of Si to decrease the bioavailability of heavy metals in soil and their accumulation in plant roots; (iv) how Si influences the plant root system with respect to heavy metals uptake or sequestration, root Fe/Mn plaque, root cell wall and compartment; (v) how Si makes complexes with heavy metals and restricts their translocation/transfer in root cell and influences the plant hormonal regulation; (vi) the competition of uptake between Si and heavy metals such as arsenic, aluminum, and cadmium due to similar membrane transporters, and (vii) how Si-mediated regulation of gene expression involves in the uptake, transportation and accumulation of heavy metals by plants and their possible detoxification mechanisms. Furthermore, future research work with respect to mitigation of heavy metal toxicity in plants is also discussed.

The objective of the current study was to evaluate the biochemical and immunological responses of tilapia, Oreochromis niloticus due to heavy metals pollution. Histomorphological alterations in the liver and kidney suggested tissue damages due to this polluted water exposure. The brain acetylcholinesterase (AChE) as an indicator of neurotoxicity was significantly (P < 0.01) decreased after 10 days exposure of fish to heavy metal contained river water, while plasma glutamate oxalacetate transaminase and plasma glutamate pyruvate transaminase were significantly increased (P < 0.01). Moreover, superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase enzyme activities, as well as reduced glutathione and malondialdehyde levels were significantly increased in heavy metals contained river water treated fish compared to the control. Additionally, glucose level and blood serum Ca2+ concentrations were significantly (P < 0.01) decreased in fish exposed to heavy metal contained river water compared to the control. Hematological indices such as Hemoglobin, RBC, WBC, MCV etc. of polluted river water treated fish were significantly (P < 0.01) different in comparison to that of control fish. The cytokines i.e. IL-1β, IL-6, and TNF-α level were significantly (P < 0.01) increased in the fish exposed to heavy metals contained river water in comparison to that of control fish. The present findings explored the detrimental effects of heavy metal contained river water on fish at biochemical and immunological levels., Acetylcholinesterase; Antioxidant enzyme; Cytokine; Haematological indices; Heavy metals; Histopathological changes.

Heavy metals are widely distributed in the environment due to the natural processes and anthropogenic human activities. Their migration into no contaminated areas contributing towards pollution of the ecosystems e.g. soils, plants, water and air. It is recognized that heavy metals due to their toxicity, long persistence in nature can accumulate in the trophic chain and cause organism dysfunction. Although the popularity of herbal medicine is rapidly increasing all over the world heavy metal toxicity has a great impact and importance on herbal plants and consequently affects the quality of herbal raw materials, herbal extracts, the safety and marketability of drugs. Effective control of heavy metal content in herbal plants using in pharmaceutical and food industries has become indispensable. Therefore, this review describes various important factors such as ecological and environmental pollution, cultivation and harvest of herbal plants and manufacturing processes which effects on the quality of herbal plants and then on Chinese herbal medicines which influence human health. This review also proposes possible management strategies to recover environmental sustainability and medication safety. About 276 published studies (1988-2021) are reviewed in this paper.

Sugars are physiologically important biomolecules acting as the chief carbon source in plants. They are also crucial osmolytes that maintain the cellular osmotic potential and turgor during abiotic stresses like salinity, drought, variations in temperatures, and heavy metal toxicity. These unfavorable suboptimal conditions trigger the production of toxic reactive oxygen species that severely deteriorate the cellular integrity. Legume crops belonging to Leguminoseae or Fabaceae are economically important plants, susceptible to an array of environmental stresses. This chapter critically analyzes the mechanisms of sugar molecules in generating stress tolerance in plants. The most recent reports on sugar-mediated stress management in legume plants are also critically analyzed and illustrated.

This work assessed effects of metal binding on membrane fluidity, liposome size, and lateral organization in biomimetic membranes composed of 1 mol% of selected phosphorylated phosphoinositides in each system. Representative examples of phosphoinositide phosphate, bisphosphate and triphosphate were investigated. These include phosphatidylinositol-(4,5)-bisphosphate, an important signaling lipid constituting a minor component in plasma membranes whereas phosphatidylinositol-(4,5)-bisphosphate clusters support the propagation of secondary messengers in numerous signaling pathways. The high negative charge of phosphoinositides facilitates electrostatic interactions with metals. Lipids are increasingly identified as toxicological targets for divalent metals, which potentially alter lipid packing and domain formation. Exposure to heavy metals, such as lead and cadmium or elevated levels of essential metals, like cobalt, nickel, and manganese, implicated with various toxic effects were investigated. Phosphatidylinositol-(4)-phosphate and phosphatidylinositol-(3,4,5)-triphosphate containing membranes are rigidified by lead, cobalt, and manganese whilst cadmium and nickel enhanced fluidity of membranes containing phosphatidylinositol-(4,5)-bisphosphate. Only cobalt induced liposome aggregation. All metals enhanced lipid clustering in phosphatidylinositol-(3,4,5)-triphosphate systems, cobalt in phosphatidylinositol-(4,5)-bisphosphate systems, while all metals showed limited changes in lateral film organization in phosphatidylinositol-(4)-phosphate matrices. These observed changes are relevant from the biophysical perspective as interference with the spatiotemporal formation of intricate domains composed of important signaling lipids may contribute to metal toxicity.

The gradual increase in environmental contamination by toxic heavy metals is a serious concern for biotic communities, and since plants are immobile and stationary, they are highly exposed to heavy metal toxicity during changing environmental conditions. Thus efforts are being made to recognize plant stress response and tolerance strategies to cope with heavy metal stress. Plants produce low-molecular weight thiols that show high affinity for toxic metals. This chapter highlights the significance of thiol compounds in relation to metal hyperaccumulation and tolerance in plants. The most important biological thiols discussed are glutathione (GSH), cysteine, phytochelatins (PC), and metallothioneins (MT). Further, this chapter overviews the future perspectives related to role of thiol compounds in metal phytoextraction or hyperaccumulation mechanisms in plants.

Abiotic stress is a physiological state that results in the overproduction and accumulation of reactive oxygen species in higher plants in response to their exposure to unfavorable environmental conditions. During the past few years, advancement in characterization techniques and genetic engineering has made a significant impact on our understanding of how plants protect themselves against abiotic stress conditions. Numerous genes involved in plant’s antioxidant pathways have been cloned and characterized. This chapter comprises a detailed understanding of abiotic stress and the various morphophysiological as well as biochemical mitigation strategies employed by a plant to combat abiotic stress condition generated by multiple environmental factors such as light intensity, drought, waterlogging, salinity, wound, low or high temperature, heavy metal toxicity, and oxidative stress. A more in-depth understanding could help in conceptualizing the idea of how plants adopt different approaches to survive in stress-prone conditions and also in the development of stress-resistant varieties of plants with more efficient mechanisms to mitigate the individual as well as combined side effects of abiotic stresses thereby enhancing grain production and yield, leading to higher agricultural productivity.

Hydrogen sulfide (H2S) is a gaseous signal molecule. Initially it was considered to be a toxic gaseous molecule, but recent studies have revealed its various roles in the control of plant growth and developmental. H2S exerts a positive impact on plant growth, development, and on plant tolerance against stress. It efficiently induces production of cellular enzymatic and nonenzymatic antioxidants. Pollution from heavy metals in soil, air, and water is a global problem that is causing a great loss to crop yields and exerts hazardous effects on human health when these metals enter the food chain. The heavy metals are widely used as industrial chemicals and their discharged effluents contaminate soil, water increasing their availability to plants. All stages of plant life are affected by metals. Metal stress activates endogenous H2S production and H2S alleviates metal toxicity in plants. To understand the role of H2S in alleviating metal toxicity it is necessary to review the physiological and molecular mechanisms behind the functions of H2S. In this chapter, we aim to highlight the possible role of H2S as an emerging signaling molecule involved in the regulation of several physiological processes in plants under metal stress.

In natural conditions, plants encounter adverse conditions, including drought, heavy metal accumulation, and pathogen infection. Due to globalization, toxic compounds are routinely released into the environment and have become an added obstacle for improving crop productivity. Plants evade the toxicity of these heavy metals either by hyperaccumulating them in the vacuoles or by extruding them out of the plant cells. Transport proteins that are the major players are ATP-binding cassette (ABC) transporter family, Multidrug and toxic compound extrusion (MATE) protein family, heavy metal-transporting ATPases (HMA-transporters), zinc-iron permeases (ZIP) proteins, and organelle transporters. ABC transporters are a diverse group of proteins, ubiquitously found in all organisms, that mediate cellular trafficking across biological membranes by functioning as ATP-dependent pumps, ion channels, and channel regulators. ABC transporters exist in several isoforms and are actively involved in the detoxification of heavy metals. Similarly, transporters like MATE and aluminum-activated malate transporter (ALMT) family of proteins exude organic compounds, namely citric acid and malic acid, respectively, to the rhizosphere and alleviate the toxicity caused by aluminum through chelation. This chapter will summarize the studies on ABC transporters and other transporter proteins implicated in heavy metal toxicity, their functions, and their mechanisms of action.

Microbes share a long history with heavy metals. The microbial ancestors deduced the use of metals for catalyzing energy generation and the formation of cellular components. As a result, metals were incorporated into various cellular macromolecules and became integral to the functioning of such macromolecules. Microbes utilized some metals relevant to their physiology while developed mechanisms to defend against toxic metals. Anthropogenic activities in the last few decades have released heavy metals into the environment in bioavailable forms. Microbes are known to respond immediately to the environmental changes thereby employing a host of processes like efflux, immobilization, translocation, transformation, biosorption, and bioaccumulation to alleviate metal toxicity. Biological macromolecules in microbes like carbohydrates, proteins, and nucleic acids contribute immensely toward metal bioremediation. This chapter discusses the imperative roles exhibited by microbial macromolecules in the transformation/reduction of metal toxicity in the environment. Extracellular polymeric substances comprising of polysaccharides that represent carbohydrates, various proteins like metallothioneins, metal-binding peptides, metal effluxing PIB ATPases, several enzymes important for alleviating metal-induced oxidative stress or precipitating metals have been highlighted here in the context of metal detoxification or remediation. Metal detection is the first step toward any remediation process. In recent times, there has been a great emphasis on developing functional nucleic acids -based sensors for the detection of heavy metal ions. In this regard, aptamers, DNAzymes, metal ion-specific DNAs, G-quadruplexes, and riboswitches have been detailed in this chapter. Overall, the information augments our understanding of the essential interactions of microbial macromolecules with the metals which are useful for metal remediation applications.

Metal pollution nowadays has become one of the most serious environmental challenges. Unfortunately, heavy metals are not biodegradable. Plants evolve different strategies to cope with metal toxicity or to maintain the level of essential metals within the physiological range. Phytoremediation is a special strategy used to clean up toxic metals from the environment components by using specially selected or genetically engineered plants and their associated microbes. There are several strategies explored to remediate soils contaminated with heavy metal including phytoextraction, phytostabilization, phytovolatilization, and rhizofiltration. Redox potential is one of various crucial factors regulating phytoremediation strategy. Redox process reduces heavy metal ions to a lower oxidation state to become less bioactive. In addition, the importance of the redox systems comes from the fact that redox potential at cellular or whole plant level can be used as an indicator of soil health during remediation processes. This chapter therefore presents an overview on the redox defense mechanisms that overcoming oxidative damage in heavy metal stressed plants, thus enhancing phytoremediation capacity. It also discusses the molecular mechanisms involved in metal tolerance and the biotechnological approaches to improve phytoremediation efficiency. We believe that the knowledge gathered here could participate in the biotechnological improvement of phytoremediation efficiency and hence reduces metal toxicity to a marginal level.

Metal tolerance is an important aspect for optimal production of edible plants for horticulture, cereals, spices, and medicinal and aromatic plants. Extravagant use of chemicals, fertilizers, and pesticides in agriculture along with contamination of irrigation water has made the soil and water resources unusable or highly contaminated with heavy metals. This chapter provides information in a nutshell on status and sources of metal contamination, role of metals in physiological and biological success of plants, and mechanistic part of metal toxicity (how metals inhibit different physiological processes in different plants) and further explains different mechanism prevailing to metal tolerance among different plant groups. Later a little information on molecular aspects of plants tolerance has also been highlighted. At current scenario, this information will be highly important to understand the specific role and significance of some metals in plant physiological processes and different mechanisms of removal of toxic metals as exclusion, avoidance, and tolerance for selecting or engineering specific metal toxicity-tolerant edible plant.

Silver nanoparticles (AgNPs) and their hybrids have gained major attention in the field of wastewater remediation strategies. Hybrids of AgNPs with materials like cellulose, activated carbons, chitosan, alginate, graphene oxides, titanium dioxides, silicon dioxide, etc. have been used extensively in wastewater treatment. Dyes such as rhodamine, Congo red, and methyl orange are common contaminants of water. Heavy metal toxicity is another serious concern for water contamination. Additionally, the presence of harmful bacteria and their toxins pose a significant threat to the aquatic ecosystem and human health. AgNPs have desirable antibacterial properties and enhanced adsorption capacities that make them valuable alternatives in removing contaminants from wastewater bodies. Despite the advantages of AgNPs in water remediation, reckless use of these materials could result in the augmentation of major environmental pollution. Hence, careful exploitation of the unique properties of AgNPs is necessary for the effective use of these nanoparticles in wastewater management.

Abiotic stresses are challenging problem in agriculture crop production and can occur from a limit of an essential resource, due to change in environmental condition and excess amounts of toxic substances. The common adverse environmental conditions, namely, salinity, drought, heavy metal toxicity, heat, cold, and oxidative stress, affect production and productivity of crop worldwide. Beneficial microbes are cost efficient and climate friendly that can be used to control abiotic stresses and to improve plant health for better yield. However, most of the work with beneficial microbes is checked only in controlled condition. So, there is need to use these microbes under field condition for the management of abiotic stresses. Microorganisms increase tolerance in plant against abiotic stresses and are very effective tool in agriculture. Fungi that are responsible for plant growth promotion can alleviate impact of abiotic stresses effectively. Two types of soil fungi such as arbuscular mycorrhizal fungi and Trichoderma spp. can be considered effective natural plants stimulants. Generally, most of the experiment and investigations showed that these fungi are safe and also effective for use as natural remedies devoted to agriculture production. Fungi used as natural stress management are favorable with recent tendency of environmental conservation and crop and food production. Here, in this chapter, we described the agronomical, physiological, biochemical, and molecular interventions that provide tolerance to salinity, drought, temperature, and nutrient deficiency stresses in mycostimulant plants.

Transporters are crucial proteins that facilitate the uptake, mobility, and exclusion of ions and molecules within organisms. Phosphate, nitrate, and polyamines are important metabolites that have varied and well-reported roles as nutrients and also under abiotic stresses like temperature, light, oxidative stress, heavy metal toxicity, etc. This chapter concisely focuses on the involvement and reported roles of the phosphate, nitrate, and polyamine transporters under such stress conditions. We observed that the phosphate transporters regulate the ionome during heat and light stress. Among the three types of transporters, those mobilizing nitrate and polyamines were found to be associated with the stress phytohormone, abscisic acid. Thus, in this chapter, we have overviewed the physiological responses mediated by these transporters in reported plant species and also discussed their roles in generating systemic tolerance against different abiotic stresses.

For a better and accurate risk assessment of metal toxicity, the concentration of the bioaccessible fraction (BAF) is more relevant than the total metal concentration. This review describes different extraction methods with different leaching agents for various chemical forms of elements such as As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in ambient particulate matter (APM). Several leaching agents simulating the human body fluids have been developed to determine the bioaccessible metal fractions in APM. This study aims to enhance the knowledge of the bioaccessible concentrations and its impact on human health, documented for different locations worldwide. Furthermore, this study disclosed that confined observations have been found concerning the application and evolution of standard methods for the estimation of biologically relevant elements in ambient particulate matter. This review also revealed that human body simulated fluids like lung and gastric fluids, on comparing to water, provide more realistic values of bioaccessible fractions of potentially toxic elements (PTEs) in assessing human health risks. This study is mainly supported by SERB, India project proposal (EMR/2015/000928) and partially supported by DST FIST, India program (SR/FST/CSI-259/2014 (c)) and UGC-SAP-DRS-II, India program (F-540/7/DRS-II/2016 (SAP-I)). One of the authors, Archi Mishra (AM) is grateful to Pt. Ravishankar Shukla University for providing laboratory facilities. Carla Candeias is grateful for the support to FCT for financial support to Research Unit GeoBioTec (UID/GEO/04035/2019+UIDB/04035/2020).

Metal tolerance in marine diatoms vary between morphotypes, strains, and species due to their long-term adaptations to stochastic environments. The mechanisms underlying this highly variable trait remain a matter of interest in ecotoxicology. In this study, we used several cutting-edge techniques, including a non-invasive micro-test technique, atomic force microscopy, and X-ray photoelectron spectroscopy to examine cadmium (Cd) accumulation and tolerance in the three morphotypes of Phaeodactylum tricornutum. Subcellular Cd distribution, metal transporter expression, and glutathione and phytochelatin activity were also analyzed to characterize the morphology-dependent Cd homeostasis and detoxification. We found that the oval morphotype accumulated more Cd, but was also more Cd tolerant than the other morphotypes. The greater surface binding of Cd to the oval morphotype is attributable to its smaller spherical form, rougher cell surface, and lower surface potential. Moreover, the oval morphotype was less permeable to Cd ions and contained higher phytochelatin and glutathione levels, which explained its higher metal tolerance. Our study offers new explanations for diatom's adaptations to changing environments that may contribute to its evolutionary success.

Metallothionein (MT) is a cysteine (Cys)-rich protein that acts as a crucial antioxidant and chelator of heavy metals in plants. Increase in the endogenous MT content has been verified and observed in multiple abiotic stress responses, especially those associated with heavy metal toxicity. The Cys-rich motif of MT makes the protein nucleophilic in nature as a result of which it can efficiently attach to positively charged inorganic heavy metal elements. This leads to cellular detoxification and efficient chelation of the heavy metals. This chapter aims to present a concise and focused discussion on the most recently reported roles of MT in mediating the responses and mitigating the toxic effects of the inorganic xenobiotics. In this chapter, we have mainly focused on the heavy metal toxicity in plants and have highlighted the most recent developments of MT-mediated phytoremediation of polluted soil and water resources.

Owing to rapid growth in urbanization, removal of environmental contaminants is the biggest challenge in the present scenario. Heavy metals are naturally occurring elements in the environment, but their negligent and indiscriminate discharge in the environment through anthropogenic and industrial activities has altered the ecosystem balance severely. The issue of heavy metal pollution thus seems to be a serious menace because of their persistent and recalcitrant nature. The conventional treatment technologies are effective to some extent, but the associated disparate drawbacks make the remediation process complex. Thus the development of nanomaterials has shown to possess distinct properties favoring their use in efficient remediation and more significantly in the ouster of heavy metals from the environment. This chapter presents varied nanomaterials such as metallic nanoparticles, nanowires, nanotubes, nanofibers, etc., with their advantages and mechanisms involved in the easy detection and removal of heavy metals and organic pollutants from the environment.

High levels of heavy metals can lead to multiple toxic effects in plants. They have capability to influence plant growth and development by direct inhibition of molecular, biochemical, and physiological processes or through the production of reactive oxygen species (ROS), which can inhibit most cellular processes at various levels of metabolism. Plants counteract the heavy metal oxidative stress by inducing plant scavenging system including overexpressing of numerous signaling and antioxidative proteins and nonenzymatic antioxidants. Different efficiencies of ROS scavenging system during various environmental stress including heavy metals can result in developing plants that can overcome oxidative stress. The capability of plant species to accumulate and tolerate heavy metals has a great importance for plant selection useful for phytoremediation. This article details the toxicity of heavy metals, the sites of production, and the role of ROS as oxidative damage inducers and the link between heavy metals, oxidative stress, and antioxidative system activity in different plant species. The type of phytoremediation methods and mechanisms of plant tolerance for heavy metal toxicity are also presented.

This study concerns an assessment of essential and toxic metals (Zn, Cu, As, Cr and Cd) in some popular farm fishes which are largely consumed by the populations of the Southern region in Bangladesh. Three different species of fish (T. nilotica, P. pangasius and L. rohita) were collected from four representative farms located in the Fatickchari, Hathazari, Patiya and Raozan Upazila of Chittagong district. Flame Atomic Absorption Spectrometer (FAAS) and Graphite Furnace Atomic Absorption Spectrometer (GFAAS) were used to measure the metal concentrations. The order of concentration of metals in flesh was Zn ​> ​Cu ​> ​Cr ​> ​As ​> ​Cd with values of 16.205 ​± ​0.303 > 0.874 ​± ​0.037 > 0.590 ​± ​0.05 >0.042 ​± ​0.003 > 0.004 ​± ​0.00 (mg/kg dw) in T. nilotica, 20.324 ​± ​0.697 > 1.035 ​± ​0.050> 0.577 ​± ​0.074> 0.045 ​± ​0.005 > 0.006 ​± ​0.000 (mg/kg dw) in P. pangasius and 22.270 ​± ​0.745 > 0.953 ​± ​0.525 > 0.623 ​± ​0.060 > 0.035 ​± ​0.002 > 0.004 ​± ​0.000 (mg/kg dw) in L. rohita. Measured data lie within the permissible limits recommended by WHO/FAO. Potential metal toxicity to human health following the consumption of the studied fishes was estimated via a number of hazard parameters: Daily intake of metal (DIM), Target hazard quotient (THQ), Hazard index (HI) and Target risk (TR), all of the data show values within the recommended level given by regulatory bodies. Estimated TR for potential carcinogenic metals As, Cr and Cd were found in the range (10−6 - 10−5), which lies within the US-EPA risk range of 10−6 - 10−4. Note that, fish consumption forms a minor part of the total diet while the US-EPA risk range is for the dietary intake from all foods. Therefore the estimated risk may not be totally neglected. Moreover, considering the non-biodegradability of toxic metals and their potential uptake in fish tissues, reduction in metal supplementation in fish feed should be introduced and periodic monitoring of fish may help to mitigate non-essential metal toxicity to consumers.

The preparation practices, handling and raw materials for street food vending could be sources of toxic metals in street food vending business which is yet to be explored in-depth as microbial contamination. The concentrations and dietary risk of the toxic metals Al, Fe, and Pb were assessed in fufu and fried-rice, two commonly consumed street-vended foods in Ghana. The mean concentrations for Pb found to be between 3.30 and 11.25 mg kg−1 in the cooked foods, far exceeded the maximum tolerable daily intake of 0.3 mg kg−1 body weight per day for consumers. Al and Fe concentrations were between 3.04 and 18.49 mg kg−1 and 1.44 and 7.82 mg kg−1, respectively. Hazard index was less than 1 at the 5th percentile level of consumption, but greater than 1 at the 50th and 95th percentile level of consumption; indicating risk of metal toxicity with increasing probability as the level of consumption and HI increase. The patronage of street vended foods is unlikely to reduce. Hence vendors must be educated on safe preparation and handling processes such as the use of stainless steel utensils will likely reduce the levels of the toxic metals to acceptable levels. Keywords: Food contamination, Metal toxicity, Toxicology, Human health risk