Concentration and Distribution of Toxic and Essential Elements in Traditional Rice Varieties of Sri Lanka Grown on an Anuradhapura District Farm

Toxic heavy metals have been the focus of many investigations into chronic kidney disease of unknown aetiology (CKDu) within Sri Lanka. It has been hypothesised that exposure to nephrotoxic arsenic, cadmium and lead could play a role in the development of CKDu, and these metals have previously been found in unsafe concentrations in Sri Lankan rice. Traditional varieties of Sri Lankan rice remain popular due to their perceived health benefits, but their uptake of trace and toxic heavy metals remained unexplored. Here, we report a one-time, cross-sectional dataset on the concentrations of essential and toxic elements present in eleven samples of polished and unpolished traditional rice varieties, all regularly grown and sold in the Anuradhapura district, a CKDu hotspot. All rice was sourced from the same farm, with the exception of one store bought sample grown on another, unidentified farm. Cadmium concentrations varied significantly between varieties, and potentially unsafe concentrations of cadmium were detected in the store-bought sample (Suwadel, 113±13 μg kg-1). Elemental imaging of the grains revealed lead to be stored mainly in the rice bran, which is removed during polishing, while cadmium was distributed in the edible portion of the grain. Essential elements were generally higher in the traditional rice varieties than those reported for non-traditional varieties and are a potential source of trace elements for nutrient-deficient communities. The concentration of selenium, an element that plays a protective role in the kidneys, was too low to provide the minimum recommended intake. The methods developed in this study could be applied to a more comprehensive study of elemental uptake of rice under controlled growing conditions.

Characterization and childhood exposure assessment of toxic heavy metals in household dust under true living conditions from 10 China cities

Health hazards caused by metal exposure in household dust are concerning environmental health problems. Exposure to toxic metals in household dust imposes unclear but solid health risks, especially for children. In this multicenter cross-sectional study, a total of 250 household dust samples were collected from ten stratified cities in China (Panjin, Shijiazhuang, Qingdao, Lanzhou, Luoyang, Ningbo, Xi'an, Wuxi, Mianyang, Shenzhen) between April 2018 and March 2019. Questionnaire was conducted to gather information on individuals' living environment and health status in real-life situations. Multivariate logistic regression and principal component analysis were conducted to identify risk factors and determine the sources of metals in household dust. The median concentration of five metals in household dust from 10 cities ranged from 0.03 to 73.18 μg/g. Among the five heavy metals, only chromium in household dust of Mianyang was observed significantly both higher in the cold season and from the downwind households. Mercury, cadmium, and chromium were higher in the third-tier cities, with levels of 0.08, 0.30 and 97.28 μg/g, respectively. There were two sources with a contribution rate of 38.3 % and 25.8 %, respectively. Potential risk factors for increased metal concentration include long residence time, close to the motorway, decoration within five years, and purchase of new furniture within one year. Under both moderate and high exposure scenarios, chromium showed the highest level of exposure with 6.77 × 10-4 and 2.28 × 10-3 mg·kg-1·d-1, and arsenic imposed the highest lifetime carcinogenic risk at 1.67 × 10-4 and 3.17 × 10-4, respectively. The finding highlighted the priority to minimize childhood exposure of arsenic from household dust.

Hemispheric-scale heavy metal pollution from South American and Australian mining and metallurgy during the Common Era

Records from polar and alpine ice reflect past changes in background and industrial toxic heavy metal emissions. While Northern Hemisphere records have been used to evaluate environmental effects and linkages to historical events such as foreign conquests, plagues, economic downturns, and technological developments during the past three millennia, little is known about the magnitude and environmental effects of such emissions in the Southern Hemisphere or their historical linkages, especially prior to late 19th century industrialization. Here we used detailed measurements of the toxic heavy metals lead, cadmium, and thallium, as well as non-toxic bismuth, cerium, and sulfur in an array of five East Antarctic ice cores to investigate hemispheric-scale pollution during the Common Era. While thallium showed no anthropogenic increases, the other three metals increased by orders of magnitude in recent centuries after accounting for crustal and volcanic components. These first detailed records indicate that East Antarctic lead pollution started in the 13th century coincident with Late Intermediate Period metallurgy in the Andes and was pervasive during the Spanish Colonial period in parallel with large-scale exploitation of Andean silver and other ore deposits. Lead isotopic variations suggest that 19th-century increases in lead, cadmium, and bismuth resulted from Australian lead and Bolivian tin mining emissions, with 20th century pollution largely the result of the latter. As in the Northern Hemisphere, variations in heavy metal pollution coincided with plagues, cultural and technological developments, as well as global economic and political events including the Great Depression and the World Wars. Estimated atmospheric heavy metal emissions from Spanish Colonial-era mining and smelting during the late 16th and early 17th century were comparable to estimated European emissions during the 1st-century apex of the Roman Empire, with atmospheric model simulations suggesting hemispheric-scale toxic heavy metal pollution during the past five centuries as a result.

Production of extracellular superoxide radical in microorganisms and its environmental implications: A review

Extracellular superoxide radical (O2•-) is ubiquitous in microbial environments and has significant implications for pollutant transformation. Microbial extracellular O2•- can be produced through multiple pathways, including electron leakage from the respiratory electron transport chain (ETC), NADPH oxidation by the transmembrane NADPH oxidase (NOX), and extracellular reactions. Extracellular O2•- significantly influences the geochemical processes of various substances, including toxic metals and refractory organic pollutants. On one hand, extracellular O2•- can react with variable-valence metals and detoxify certain highly toxic metals, such as As(III), Cr(VI), and Hg(II). On the other hand, extracellular O2•- can directly or indirectly (via Bio-Fenton) degrade many organic pollutants, including a variety of emerging contaminants. In this work, we summarize the production mechanisms of microbial extracellular O2•-, review its roles in the transformation of environmental pollutants, and discuss the potential applications, limiting factors, and future research directions in this field.

Exploring the potential of sulphur forms in Northeastern Indian coals: Implications in environmental remediation and heavy metal sensing

The Sampar Coalfield in Northeastern India is a source of plentiful coal reserves, which are burnt for energy production and industrial applications, resulting in the release of pollutants such as sulphur , arsenic, and lead, which are hazardous to the environment and public health. In this work, samples from the Sampar coalfield have been analyzed to understand the origin, distribution, and various forms of sulphur and their ability to detect toxic heavy metals. The total sulphur concentration ranged from 4.31% to 6%, with organic sulphur being the predominant form at 69.21%, followed by pyritic sulphur at 16.49% and sulphate sulphur at 14.28%. With high sulphur content, this coal indicates a marine influence in the peat-forming swamps. The samples have also been examined for petrographic and elemental analysis, which have revealed the presence of vitrinite, liptinite, inertinite, carbon, hydrogen, nitrogen, oxygen, and mineral matter. In addition, the same coal sample has also been used for electrochemical sensing-based detection of toxic heavy metals like arsenic and lead, and the findings indicate an improved efficacy. These results are expected to have significant implications in the development of effective bio-based remediation strategies in the region to mitigate the harmful effects of coal-related pollution.

Pollution Characteristics, Source Identification, and Health Risk of Heavy Metals in the Soil-Vegetable System in Two Districts of Bangladesh

The consequences of climate change, food security, and self-sufficiency goals are driving excessive human activity onto vegetable farms in Bangladesh, and harmful heavy metal exposure is spreading. So, the study assessed the toxic metals (Pb, Cd, and Cr) exposure, characteristics, and human health risk regarding the soil-vegetable system of two distinct locations in Bangladesh using atomic absorption spectrometry. The average concentration of metals in soil and fertilizer/pesticide samples followed the same order (Cr > Pb > Cd), but for vegetable samples, the order was Pb > Cr > Cd, with some extra Pb compared to the World Health Organization (WHO) allowable limit (0.3 mg/kg). Low levels of pollution with negligible ecological concerns were predicted for both locations by the soil quality indexing. But industrial influence boosted the Pb content in location B, and common sources (fertilizer/pesticide) for both locations might be responsible for a moderate level of Cd. The toxic metals transferred to vegetables followed the trend of Cd > Pb > Cr. However, the human health risks arising from harmful metals exposure at both locations were ineffective (< 1) in evaluating noncarcinogenic risk patterns through the target hazard quotient (THQ), total THQ, and hazard index (HI). Again, considering probable carcinogenic risk patterns, vegetable consumption with studied exposure levels of toxic metals followed within the acceptable range (between 1.0E-04 and 1.0E-06). Overall, location B is slightly more vulnerable than location A by considering metal exposure, pollution distribution, and risk evaluation in the study area (significant at p < 0.05). So, systematic monitoring and protective measures are required to ensure food safety and sustainable vegetable production.

Risk assessment of combined exposure to lead, cadmium, and total mercury among the elderly in Shanghai, China

Lead (Pb), cadmium (Cd) and total mercury (THg) are toxic heavy metals (THMs) that are widely present in the environment and can cause substantial health problems. However, previous risk assessment studies have rarely focused on the elderly population and have usually targeted a single heavy metal, which might underestimate the long-term accumulative and synergistic effects of THMs in humans. Based on the food frequency questionnaire and inductively coupled plasma mass spectrometry, this study assessed external and internal exposures to Pb, Cd and THg in 1747 elderly people in Shanghai. Probabilistic risk assessment with the relative potential factor (RPF) model was used to assess the neurotoxicity and nephrotoxicity risks of combined THMs exposures. The mean external exposures of Pb, Cd and THg in Shanghai elderly were 46.8, 27.2 and 4.9 μg/day, respectively. Plant-based foods are the main source of Pb and THg exposure, while Cd is mainly from animal-based foods. The mean concentrations of Pb, Cd and THg were 23.3, 1.1 and 2.3 μg/L in the whole blood, and 6.2, 1.0 and 2.0 μg/L in the morning urine, respectively. Combined exposure to THMs leading to 10.0 % and 7.1 % of Shanghai elderly at risk of neurotoxicity and nephrotoxicity. The results of this study have important implications for understanding the profiles of Pb, Cd and THg exposure in the elderly living in Shanghai and provide data support for risk assessment and control of nephrotoxicity and neurotoxicity from combined THMs exposure in the elderly.

Association Between Essential and Non-essential Metals, Body Composition, and Metabolic Syndrome in Adults

Growing evidence indicates that metal exposure is associated with metabolic syndrome (MetS); however, mixed results have been reported. The aim of this study was to clarify associations of exposure to essential and non-essential metals with body composition and risks of obesity and MetS. Anthropometry and blood biochemistry of metabolic parameters were obtained from 150 middle-aged Taiwanese adults. Plasma metals were assessed using inductively coupled plasma mass spectrometry, and body compositions were measured by a bioelectrical impedance analysis (BIA). The essential metals of copper (Cu), manganese (Mn), and chromium (Cr) were positively correlated with the body fat mass but inversely correlated with the skeletal muscle mass (all p < 0.05). An adjusted logistic regression showed that Mn [odds ratio (OR) = 1.624 (95% confidence interval 1.072, 2.462), p = 0.02] and, to a lesser extent, Cu [OR = 1.501 (0.985, 2.292), p = 0.059] predicted abdominal obesity, while plasma Cu [OR = 2.211 (1.146, 4.266), p = 0.02] and zinc (Zn) [OR = 2.228 (1.048, 4.736) p = 0.04] predicted MetS. Significant correlations between dyslipidemia and lithium [OR = 1.716 (1.080, 2.726)], Cu [OR = 2.210 (1.415, 3.454)], Mn [OR = 2.200 (1.320, 3.666)], molybdenum [OR = 1.853 (1.160, 2.958)], and Zn [OR = 1.993 (1.186, 3.349)], and between boron [OR = 2.583 (1.137, 5.868)] and hyperglycemia were observed (all p < 0.05). Exposure to essential metals may affect the body composition and metabolic profiles, exacerbating the risk of MetS.

Bioavailability and health risk of toxic heavy metals (As, Hg, Pb and Cd) in urban soils: A Monte Carlo simulation approach

Toxic heavy metals pollution in urban soil has become a major global issue due to its adverse effects on the environment and human health. In this paper, 26 soil samples were analyzed to assess the speciation, bioavailability and human health risk of Arsenic (As), Mercury (Hg), Lead (Pb) and Cadmium (Cd) in urban soils of a heavy industrial city in NE China by using a Monte Carlo simulation approach. The results showed that As, Hg, Pb and Cd concentrations in the soil all exceed the corresponding background value of study area. Mercury displays the highest value of geo-accumulation index (Igeo), followed by Cd, Pb and As. The pollution load index (PLI) value (>2) indicates a moderate pollution level in the study area. The chemical speciation of HMs mainly exists in residual fraction except Cd. The probabilistic health risk assessment demonstrated that the mean values of Total Carcinogenic Risk (TCR) and Hazard Index (HI) calculated with total concentration are at the unacceptable level, with a higher risk to children than adults. However, the mean values calculated with bioavailable fraction are all within the acceptable level. The mean value of TCR and HI obtained by bioavailable fraction is about 96% and 95% lower than that obtained by total concentration, respectively. Thus, this study suggested that the bioavailable fraction of HMs is a more reliable parameter for health risk assessment, while the total concentration of HMs can overestimate the true risk. The results of this study provide some insight into the speciation, bioavailability and health risks of toxic heavy metals in urban soils in those heavy industrial cities.

Effect of Cadmium on Macro and Micronutrient Uptake and Translocation by Leucaena leucocephala

Environmental contamination with Cadmium (Cd) is of great concern due to its hazardous effects on living organisms.Query In the present research, Leucaena leucocephala plants were exposed to Cd concentrations of 5, 10, and 15 mg/L to determine their potential use in Cd remediation. Different parameters including Cd uptake, macro/micronutrient content, chlorophyl, and catalase production were determined. Results indicated that Cd uptake by L. leucocephala roots did not show a significant difference between treatments. However, a significant increase in Cd content (Tukey´s HSD) was observed in stems as Cd levels in the media augmented. The highest Cd content (830 ± 20 mg/kg) was determined in stems of plants exposed to 15 mg/L Cd, and no Cd was detected in leaves. Data showed that as Cd concentration increased in the media, Ca, Mg, K, Zn, and Mn decreased. Moreover, while the presence of Cd reduced catalase activity in roots, chlorophyll production was not affected.

Thermodynamic valorisation of lignocellulosic biomass green sorbents for toxic pollutants removal

Various toxic heavy metals have become hazardous to human health as well as the environment. This research has been focused on a biosorption/bioremoval process of chromium (III), copper (II) and lead (II) ions from an aqueous solution by utilizing lignocellulosic biomass of Citrus limon peel (CLP) powder. CLP powder biomass was selected based on dietary fibre components having greater potential to remove target heavy metal ions in order to purify wastewater by following the eco-friendly biosorption method. At optimum conditions, the observed maximum removal efficiency of 97.47, 87.13 and 95.71% for Cr, Cu and Pb ions, respectively, was observed. An investigation has been made as a work of pH, CLP amount and temperature. The presented bio-removal processes by prepared CLP biosorbent manifested as a temperature-independent. Langmuir isotherm model was found an excellent fit of the isotherm data for tested systems with the calculated biosorption capacities of 111.11 (Cr), 76.92 (Cu) and 100 (Pb) mg/g. The positive ΔH values for selected target heavy metal ions, except lead ions, confirmed that the reaction was spontaneous and endothermic. A cooperative mechanism of second-order and intraparticle diffusion models during the adsorption processes of all three target ions was established with a higher coefficient of determination and more closely anticipated take-up (adsorption capacity). Furthermore, the interaction of -OH and -COOH functional groups of CLP that have a major role in the removal of Cr, Cu and Pb ions from single-ion aqueous solution and/or a surface biosorption was confirmed based on the results presented by SEM-EDS and FTIR analysis. Analysis from XRD revealed peak corresponding to amorphous cellulose type I as observed by FT-IR analysis.

Simple and rapid quantification of chromium, arsenic, and selenium in bituminous coal samples using a desktop energy dispersive X-ray fluorescence analyzer

In this study, the simple and rapid quantification of Cr, As, and Se in bituminous coal was achieved by energy dispersive X-ray fluorescence (EDXRF) spectrometry using pressed and powdered samples. The accuracy of the EDXRF method was improved by spectral processing optimization so the net intensity of the analytical X-ray line reflected the actual value. The EDXRF method provides results that are comparable to those obtained using traditional chemical analysis methods with two types of samples and it reduces the analysis time by 66% for pellet samples and 90% for powder samples.

A novel dispersive magnetic solid phase microextraction using ionic liquid-coated amino silanized magnetic graphene oxide nanocomposite for high efficient separation/preconcentration of toxic ions from shellfish samples

A novel dispersive magnetic solid phase microextraction (d-MSPE) method using ionic liquid-coated amino silanized magnetic graphene oxide (MGO@SiO₂-APTES-IL) as adsorbent has been established for enriching and extracting lead(II), copper(II) and cadmium(II) in shellfish samples. The novel nanocomposite was proved synthesized successfully by various characterization technologies. Parameters that could affect the recoveries of target ions were investigated and optimized focusing on adsorption and desorption using Box-Behnken design of response surface methodology (BBD-RSM). The limits of detection (LODs) for three target heavy metal ions were 2.42, 3.36, 3.75 ng L^-1, respectively. Additionally, the maximum adsorption capacities of the nanocomposite for target ions were 251.23, 138.51, 159.31 mg g^-1 at 298 K, respectively, the nanoadsorbent can be regenerated without significant adsorption capacities loss for four times. These observations revealed that the novel nanocomposite can be used as an excellent adsorbent for separation and preconcentration of the target ions.

Bioremediation of noxious metals from e-waste printed circuit boards by Frankia

The environmental noxious e-waste was collected and physicochemical characterized by Scanning electron microscopy (SEM) along with energy dispersive X-ray spectroscopy (EDX), Atomic absorption spectrometry (AAS), and X-ray diffraction analysis (XRD) exploration to understand the presence of toxic metals like Hg, Cd, Pd, Si, Ru. Therefore, the finding provides vital knowledge about the impact of toxic metals from e-waste printed circuit boards as contaminants in the environment and its impact on humans. The Frankia sp. DDNSF-03 and Frankia casuarinae DDNSF-04 were isolated and identified, further utilized for removal of e-waste toxic metals by one and two steps bioremediation experiments executed with various e-waste concentrations. The two-step bioremediation experiment is efficient in the expression of toxic metals that were removed at a lesser concentration of e-waste. Consequently, the presence of organic acids in the Frankia primary metabolites was confirmed by FT-IR analysis besides decreasing the pH level in the Frankia growth medium. The positive control Frankia and negative control e-waste were maintained throughout the bioremediation experiments. The initial Hg 4.3, Cd 8.3, Pd 4.6 (ppm) in the e-waste and final treated with Frankia sp. DDNSF-03 Hg 0.09, Cd 5.09, Pb 0.49 (ppm), and Frankia casuarinae DDNSF-04 Hg 2.15, Cd 5.6, Pb 2.82 (ppm) concentration of toxic metals was quantified by AAS spectrum analysis. The toxic metals mercury and lead were significantly mineralized by Frankia sp. when compare the Frankia casuarinae. The above finding was confirmed the manifestation of morphological changes by an accumulation of e-waste in Frankia hyphae using SEM analysis and obtain the qualitative of toxic metals parallel peaks in EDX analysis.

Development of predicitve models to distinguish metals from non-metal toxicants, and individual metal from one another

BACKGROUND

Evaluating the toxicity of chemical mixture and their possible mechanism of action is still a challenge for humans and other organisms. Microarray classifier analysis has shown promise in the toxicogenomic area by identifying biomarkers to predict unknown samples. Our study focuses on identifying gene markers with better sensitivity and specificity, building predictive models to distinguish metals from non-metal toxicants, and individual metal from one another, and furthermore helping understand underlying toxic mechanisms.

RESULTS

Based on an independent dataset test, using only 15 gene markers, we were able to distinguish metals from non-metal toxicants with 100% accuracy. Of these, 6 and 9 genes were commonly down- and up-regulated respectively by most of the metals. 8 out of 15 genes belong to membrane protein coding genes. Function well annotated genes in the list include ADORA2B, ARNT, S100G, and DIO3. Also, a 10-gene marker list was identified that can discriminate an individual metal from one another with 100% accuracy. We could find a specific gene marker for each metal in the 10-gene marker list. Function well annotated genes in this list include GSTM2, HSD11B, AREG, and C8B.

CONCLUSIONS

Our findings suggest that using a microarray classifier analysis, not only can we create diagnostic classifiers for predicting an exact metal contaminant from a large scale of contaminant pool with high prediction accuracy, but we can also identify valuable biomarkers to help understand the common and underlying toxic mechanisms induced by metals.

Risk assessment via oral and dermal pathways from heavy metal polluted water of Kolleru lake - A Ramsar wetland in Andhra Pradesh, India

The Kolleru Lake, India is a famous wetland of international significance. Analyses of certain potentially toxic heavy metal ions in water indicate that this freshwater lake is characterized by highly heterogeneous distribution of chromium (Cr; 4.5‒80 μg/L), copper, iron (Cu, Fe; below detection limit), manganese (Mn; 1‒313 μg/L) and zinc (Zn; below detection limit). Non-carcinogenic health risk assessment indices like hazard quotients (HQ) and hazard indices (HI) are estimated following the guidelines recommended by the US Environmental Protection Agency (USEPA). These indices are found to be within the acceptable limit (&lt;1), indicating negligible potential health risk via ingestion and dermal routes. However, when the average values of these indices pertaining to the Kolleru lake are normalized with similar estimates from clean and uncontaminated global surface water, both high and low ratios are obtained. While Cr (12.5), Cu (2.3) and Mn (3.7) exhibit high ratios, those of Fe (0.09) and Zn (0.99) show respectively low and comparable values. The significance of such heterogeneous distribution of hazard indices and their ratios are discussed. Further, average carcinogenic risk levels of the adults and children due to Cr ingestion are estimated to be 0.00154 and 0.0022, respectively. Both values are higher than the permissible levels recommended by the USEPA. As a remediation measure, it is recommended that monitoring the levels of heavy metal in water and other items like fish in the lake or rice and vegetables grown in the area is needed to be carried out at regular intervals. This study therefore offers requisite perception to the local government and health officials to evolve their plan of action so that effective management and mitigation of water quality of the Kolleru lake can be administered.

Biological and anthropogenic predictors of metal concentration in the Eurasian otter, a sentinel of freshwater ecosystems

Toxic metals have been linked to a range of adverse health effects in freshwater organisms. However, for higher vertebrates, there is little understanding of the large-scale drivers of exposure. We quantified toxic metal/semi-metal concentrations in a sentinel freshwater top predator, the Eurasian otter (Lutra lutra), across England and Wales, and determined how this varied with key natural and anthropogenic factors. We related liver concentrations in 278 otters that died between 2006 and 2017 to habitat biogeochemistry, proximity to point source contamination and to biological characteristics (length, sex, condition). Evidence for any positive association with putative anthropogenic sources (mining, human population, known discharges) was weak or lacking in nearly all cases, with the exception of a positive association between lead and human population density. Despite concerns that burgeoning use of nanosilver in consumer products might increase silver concentrations in waste waters, there was no increase over time. Spatial variation in soil/sediment pH, precipitation, and soil calcium oxide are indicated as significant predictors of metal concentrations in otters (higher cadmium and silver in areas with lower pH and higher rainfall, and higher chromium and lead in areas of lower calcium oxide). Liver chromium and nickel concentrations declined significantly over time (Cr 0.030 ± 1.2 to 0.015 ± 1.3 μg/g dry weight, Ni 0.0038 ± 1.2 to 0.00068 ± 1.5 μg/g, between 2006-2009 and 2014-2017), but other metals showed no temporal change. Biotic associations were important, with age related accumulation indicated for mercury and cadmium (as well as interactions with body condition). Our results suggest that larger-scale geochemical and hydrological processes are important in determining metal exposure in otters, and we provide an indication of risk factors that may be of relevance for freshwater vertebrates in other countries with well-developed water pollution management.

Biochar-bacteria-plant partnerships: Eco-solutions for tackling heavy metal pollution

Over the past 30 years, the ever-rising demands of the modern and growing population have led to the rapid development of agricultural and industrial sectors worldwide. However, this expansion has exposed the environment to various pollutants including heavy metal (HM)s. Almost all HMs are serious toxicants and can pose serious health risks to living organisms in addition to their bioaccumulative and non-biodegradable nature. Different techniques have been developed to restore the ecological functions of the HM-contaminated soil (HMCS). However, the major downfalls of the commonly used remediation technologies are the generation of secondary wastes, high operating costs, and high energy consumption. Phytoremediation is a prominent approach that is more innocuous than the existing remediation approaches. Some microbes-plant interactions enhance the bioremediation process, with heavy metal resistant-plant growth promoting bacteria (HMRPGPB) being widely used to assist phytoremediation of HMs. However, the most common of all major microbial assisted-phytoremediation disturbances is that the HM-contaminated soil is generally deficient in nutrients and cannot sustain the rapid growth of the applied HMRPGPB. In this case, biochar has recently been approved as a potential carrier of microbial agents. The biochar-HMRPGPB-plant association could provide a promising green approach to remediate HM-polluted sites. Therefore, this review addresses the mechanisms through which biochar and HMRPGPB can enhance phytoremediation. This knowledge of biochar-HMRPGPB-plant interactions is significant with respect to sustainable management of the HM-polluted environment in terms of both ecology and economy, and it offers the possibility of further development of new green technologies.

Bioremediation of toxic heavy metals (THMs) contaminated sites: concepts, applications and challenges

Heavy metal contamination is a global issue, where the prevalent contaminants are arsenic (As), cadmium (Cd), chromium (Cr)(VI), mercury (Hg), and lead (Pb). More often, they are collectively known as "most problematic heavy metals" and "toxic heavy metals" (THMs). Their treatment through a variety of biological processes is one of the prime interests in remediation studies, where heavy metal-microbe interaction approaches receive high interest for their cost effective and ecofriendly solutions. In this review, we provide an up to date information on different microbial processes (bioremediation) for the removal of THMs. For the same, emphasis is put on oxidation-reduction, biomineralization, bioprecipitation, bioleaching, biosurfactant technology, biovolatilization, biosorption, bioaccumulation, and microbe-assisted phytoremediation with their selective advantages and disadvantages. Further, the literature briefly discusses about the various setups of cleaning processes of THMs in environment under ex situ and in situ applications. Lately, the study sheds light on the manipulation of microorganisms through genetic engineering and nanotechnology for their advanced treatment approaches.

Tropical climate effect on the toxic heavy metal pollutant course of road-deposited sediments

In modern society, the intense vehicle traffic and the lack of effective mitigating strategies may adversely impact freshwater systems. Road-deposited sediments (RDS) accumulate a variety of toxic substances which are transported into nature during hydrologic events, mainly affecting water bodies through stormwater runoff. The aim of this study was to evaluate the RDS metal enrichment ratio between the end of wet season and the middle of the dry season for Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in samples from Natal, Brazil. Twenty RDS, drainage system and river sediment samples were collected in the wet and dry seasons using a stainless-steel pan, brush and spatula. In the laboratory, the samples were submitted to acid digestion and heavy metal concentrations were measured by atomic absorption spectrometry (AAS). A consistent RDS enrichment by heavy metals in dry season samples was followed by an increase in the finest particle size fraction (D < 63 μm). Maximum concentrations were 5, ND, 108, 23810, 83, ND, 77 and 150 mg kg^-1 for Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn, respectively. The RDS enrichment ratio was Cr(1.3 × ), Cu(2.6 × ), Fe(3.3 × ), Mn(1.5 × ), Pb(1.5 × ) and Zn(2.1 × ). The Geo-accumulation Index values showed that RDS were moderately polluted for Cu and slighted polluted for Zn and Pb. Principal Component Analysis (PCA) showed that the accumulation of toxic heavy metals decreased according to water flow.

Environmental perspectives of interfacially active and magnetically recoverable composite materials - A review

Aquatic ecosystem contaminated with toxic pollutants and heavy metals due to the rapid growth of industrialization has become a top-priority global concern exhibiting highly adverse effects on human health and the environment. Many treatment techniques have been envisioned for the removal of these toxic contaminants from the aqueous environment. Among these techniques, magnetic separation has attracted burgeoning research attention owing to its simplicity, eco-friendly nature, large surface area, electron mobility, and excellent performance for removing water contaminants. In particular, interfacial active nanoparticles and nanocomposites with unique structures and magnetic properties are considered as ideal provides candidates in material science for next-generation water treatment. This review gives an insight into current research activities associated with the synthesis strategies and applications of interfacially active and magnetically responsive nanomaterials and nanocomposites for sustainable purification processes. In the first half, various synthesis routes for magnetic iron oxide nanoparticles development and the corresponding formation mechanism are summarized. In the second half, we reviewed the magnetic and wettability properties of interfacially active and magnetically responsive nanocomposites and their environmental applications including oil-water separation, removal of hazardous dye-based pollutants and potentially toxic heavy metals. Finally, the review is wrapped up with major concluding remarks and future perspectives of these magnetic nanoscale composite materials for sustainable wastewater remediation.

Seasonal environmental parameters influence biochemical responses of the fiddler crab Minuca rapax to contamination in situ

The mudflat fiddler crab Minuca rapax, typical of mangroves and intertidal zones in the Western Atlantic Ocean, responds to fluctuations in environmental parameters by biochemical and physiological adjustments. Such biochemical effects are commonly employed in environmental studies as biomarkers of estuarine contamination. This study evaluates biochemical responses in the gills and hepatopancreas of M. rapax in situ from localities exhibiting different types and levels of contamination, against a backdrop of fluctuations in environmental parameters like salinity and temperature common to estuarine regions. The biochemical biomarkers metallothionein (MT)-like protein titers and glutathione S-transferase (GST), glutathione peroxidase (GPx) and acetylcholinesterase (AChE) activities were used to evaluate responses to environmental contamination and seasonal changes in environmental parameters. Crabs were collected during two seasons, the austral winter and summer, at three sites along the coast of the state of São Paulo, Brazil that present decreasing degrees of environmental contamination: Ilha Diana, Santos (ID) > Rio Itapanhaú, Bertioga (RI) > Picinguaba, Ubatuba (P), a pristine control site. Our findings show that MT were induced in crabs from the contaminated sites (ID and RI) mainly during winter, revealing the activation of detoxification mechanisms; however MT were also induced in P crabs during the summer rainy season. GPX, GST and AChE activities were altered in P crabs during summer and in ID and RI crabs in winter. While enzyme activities in summer crabs may reflect seasonal changes in precipitation and salinity, in winter these altered activities appear to reflect contamination, although an effect of environmental parameters cannot be excluded. These findings reveal a strong seasonal influence on biochemical biomarker responses in Minuca rapax, a relevant factor to consider when interpreting the impact of environmental contamination in estuaries.

Human health risk assessment of potentially toxic heavy metals in the atmospheric dust of city of Hamedan, west of Iran

The atmospheric dust is an important route of human exposure to kinds of pollutants particularly toxic heavy metals. The current study was carried out to assess the ecological and health risk assessment of Co, Cr, and Mn in the atmospheric dust of city of Hamedan, Iran. In so doing, a total of 54 samples of atmospheric dust were collected from the three regions of the study area in 2014. After acid digestion of samples in the laboratory, the Co, Cr, and Mn contents were determined using inductively coupled plasma-optical emission spectrometer (ICP-OES). The results showed that the average contents (mg kg^-1) of Co, Cr, and Mn in the analyzed samples were 0.23, 0.89, and 8.10, respectively. The results of human health risk assessment showed that ingestion of dust particles is the main exposure route to heavy metals in the dust for the local residents. Also, the upper limit of the 95% confidence interval of hazard indices for non-carcinogenic risks of all analyzed metals in the atmospheric dust was within the safe level (= 1) for both children and adults. The carcinogenic risk levels of Co and Cr were all lower than the acceptable range for local citizens. Based on the results, it can be suggested that special attention be paid to toxic heavy metals that long-term exposure to which via atmospheric dust can have adverse effects on the city resident health.

Systematic review and meta-analysis links autism and toxic metals and highlights the impact of country development status: Higher blood and erythrocyte levels for mercury and lead, and higher hair antimony, cadmium, lead, and mercury

BACKGROUND

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder that affects cognitive and higher cognitive functions. Increasing prevalence of ASD and high rates of related comorbidities has caused serious health loss and placed an onerous burden on the supporting families, caregivers, and health care services. Heavy metals are among environmental factors that may contribute to ASD. However, due to inconsistencies across studies, it is still hard to explain the association between ASD and toxic metals. Therefore the objective of this study was to investigate the difference in heavy metal measures between patients with ASD and control subjects.

METHODS

We included observational studies that measured levels of toxic metals (antimony, arsenic, cadmium, lead, manganese, mercury, nickel, silver, and thallium) in different specimens (whole blood, plasma, serum, red cells, hair and urine) for patients with ASD and for controls. The main electronic medical database (PubMed and Scopus) were searched from inception through October 2016.

RESULTS

52 studies were eligible to be included in the present systematic review, of which 48 studies were included in the meta-analyses. The hair concentrations of antimony (standardized mean difference (SMD)=0.24; 95% confidence interval (CI): 0.03 to 0.45) and lead (SMD=0.60; 95% confidence interval (CI): 0.17 to 1.03) in ASD patients were significantly higher than those of control subjects. ASD patients had higher erythrocyte levels of lead (SMD=1.55, CI: 0.2 to 2.89) and mercury (SMD=1.56, CI: 0.42 to 2.70). There were significantly higher blood lead levels in ASD patients (SMD=0.43, CI: 0.02 to 0.85). Sensitivity analyses showed that ASD patients in developed but not in developing countries have lower hair concentrations of cadmium (SMD=-0.29, CI: -0.46 to -0.12). Also, such analyses indicated that ASD patients in developing but not in developed lands have higher hair concentrations of lead (SMD=1.58, CI: 0.80 to 2.36) and mercury (SMD=0.77, CI: 0.31 to 1.23). These findings were confirmed by meta-regression analyses indicating that development status of countries significantly influences the overall effect size of mean difference for hair arsenic, cadmium, lead, and mercury between patients with ASD and controls.

CONCLUSION

The findings help highlighting the role of toxic metals as environmental factors in the etiology of ASD, especially in developing lands. While there are environmental factors other than toxic metals that greatly contribute to the etiology of ASD in developed lands. It would be, thus, expected that classification of ASD includes etiological entities of ASD on the basis of implication of industrial pollutants (developed vs. developing ASD).

Characteristics, sources and health risk assessment of toxic heavy metals in PM2.5 at a megacity of southwest China

Twenty trace elements in fine particulate matters (i.e., PM2.5) at urban Chengdu, a southwest megacity of China, were determined to study the characteristics, sources and human health risk of particulate toxic heavy metals. This work mainly focused on eight toxic heavy metal elements (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn). The average concentration of PM2.5 was 165.1 ± 84.7 µg m(-3) during the study period, significantly exceeding the National Ambient Air Quality Standard (35 µg m(-3) in annual average). The particulate heavy metal pollution was very serious in which Cd and As concentrations in PM2.5 significantly surpassed the WHO standard. The enrichment factor values of heavy metals were typically higher than 10, suggesting that they were mainly influenced by anthropogenic sources. More specifically, the Cr, Mn and Ni were slightly enriched, Cu was highly enriched, while As, Cd, Pb and Zn were severely enriched. The results of correlation analysis showed that Cd may come from metallurgy and mechanical manufacturing emissions, and the other metals were predominately influenced by traffic emissions and coal combustion. The results of health risk assessment indicated that As, Mn and Cd would pose a significant non-carcinogenic health risk to both children and adults, while Cr would cause carcinogenic risk. Other toxic heavy metals were within a safe level.

Toxic metal interactions affect the bioaccumulation and dietary intake of macro- and micro-nutrients

The present study was conducted to evaluate the effects of heavy metals (cadmium (Cd), lead (Pb) and Cd-Pb mix) on bioaccumulation of different nutrients. Three plant species including potato, tomato and lettuce were grown in pots containing soil contaminated with Cd, Pb and Cd-Pb mix at four different levels. The edible portions of each plant were analysed for Cd, Pb and different macro- and micro-nutrients including protein, vitamin C, nitrogen (N), phosphorous (P), potassium (K), iron (Fe), manganese (Mn), calcium (Ca) and magnesium (Mg). Results indicated significant variations in selected elemental concentrations in all the three plants grown in different treatments. The projected daily dietary intake values of selected metals were significant (P < 0.001) for Fe, Mn, Ca and Mg but not significant for protein, vitamin C, N and P. The elemental contribution to Recommended Dietary Allowance (RDA) was significant for Mn. Similarly, Fe and Mg also showed substantial contribution to RDA, while Ca, N, P, K, protein and vitamin C showed the minimal contribution for different age groups. This study suggests that vegetables cultivated on Cd and Pb contaminated soil may significantly affect their quality, and the consumption of such vegetables may result in substantial negative effects on nutritional composition of the consumer body. Long term and continuous use of contaminated vegetables may result in malnutrition.

Protein sequences insight into heavy metal tolerance in Cronobacter sakazakii BAA-894 encoded by plasmid pESA3

The recently annotated genome of the bacterium Cronobacter sakazakii BAA-894 suggests that the organism has the ability to bind heavy metals. This study demonstrates heavy metal tolerance in C. sakazakii, in which proteins with the heavy metal interaction were recognized by computational and experimental study. As the result, approximately one-fourth of proteins encoded on the plasmid pESA3 are proposed to have potential interaction with heavy metals. Interaction between heavy metals and predicted proteins was further corroborated using protein crystal structures from protein data bank database and comparison of metal-binding ligands. In addition, a phylogenetic study was undertaken for the toxic heavy metals, arsenic, cadmium, lead and mercury, which generated relatedness clustering for lead, cadmium and arsenic. Laboratory studies confirmed the organism's tolerance to tellurite, copper and silver. These experimental and computational study data extend our understanding of the genes encoding for proteins of this important neonatal pathogen and provide further insights into the genotypes associated with features that can contribute to its persistence in the environment. The information will be of value for future environmental protection from heavy toxic metals.

Determination of toxic heavy metals and speciation of arsenic in seaweeds from South Korea

This study aimed at determining the levels of toxic heavy metals including As, Pb, Cd, Al, Hg and As species, such as, As-III, As-V, MMA, DMA, AsB, and AsC in various edible species of seaweeds from South Korea. ICP-MS was used for determination of As, Pb and Cd, ICP-OES was used for Al, DMA was used for Hg, and LC-ICP-MS was used for As speciation. The analytical methods were validated by linearity, detection limits, precision, accuracy and recovery experiments, obtaining satisfactory results in all cases. From the results toxic heavy metals were found in the decreasing order of: Al>As>Pb-Cd>Hg. Generally concentrations of all analysed heavy metals and both organic and inorganic species of As were very low compared to PTWIs specified by JECFA and EC. Their contribution to the overall intake by the subject seafoods was found very low and thus would not pose any threat to consumers.