EnvironmentalChemistryandEcotoxicologyofHazardous …downloads.hindawi.com/journals/jchem/2019/6730305.pdftence, bioaccumulation, and toxicity (Figure 2). Toxic substances which are

Review ArticleEnvironmental Chemistry and Ecotoxicology of HazardousHeavy Metals Environmental Persistence Toxicityand Bioaccumulation

Hazrat Ali 1 Ezzat Khan 2 and Ikram Ilahi3

1Environmental Chemistry Ecotoxicology and Ecology Laboratory Department of Zoology University of MalakandChakdara 18800 Dir Lower Khyber Pakhtunkhwa Pakistan2Department of Chemistry University of Malakand Chakdara 18800 Dir Lower Khyber Pakhtunkhwa Pakistan3Environmental Toxicology and Entomology Laboratory Department of Zoology University of Malakand Chakdara 18800Dir Lower Khyber Pakhtunkhwa Pakistan

Correspondence should be addressed to Hazrat Ali hazrataliuomedupk and Ezzat Khan ekhanuomedupk

Received 25 November 2018 Revised 5 February 2019 Accepted 19 February 2019 Published 5 March 2019

Academic Editor Yuangen Yang

Copyright copy 2019 Hazrat Ali et al is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Heavy metals are well-known environmental pollutants due to their toxicity persistence in the environment and bioaccumulativenature eir natural sources include weathering of metal-bearing rocks and volcanic eruptions while anthropogenic sourcesinclude mining and various industrial and agricultural activities Mining and industrial processing for extraction of mineralresources and their subsequent applications for industrial agricultural and economic development has led to an increase in themobilization of these elements in the environment and disturbance of their biogeochemical cycles Contamination of aquatic andterrestrial ecosystems with toxic heavy metals is an environmental problem of public health concern Being persistent pollutantsheavy metals accumulate in the environment and consequently contaminate the food chains Accumulation of potentially toxicheavy metals in biota causes a potential health threat to their consumers including humans is article comprehensively reviewsthe different aspects of heavy metals as hazardous materials with special focus on their environmental persistence toxicity forliving organisms and bioaccumulative potentiale bioaccumulation of these elements and its implications for human health arediscussed with a special coverage on fish rice and tobacco e article will serve as a valuable educational resource for bothundergraduate and graduate students and for researchers in environmental sciences Environmentally relevant most hazardousheavy metals and metalloids include Cr Ni Cu Zn Cd Pb Hg and As e trophic transfer of these elements in aquatic andterrestrial food chainswebs has important implications for wildlife and human health It is very important to assess and monitorthe concentrations of potentially toxic heavy metals and metalloids in different environmental segments and in the resident biotaA comprehensive study of the environmental chemistry and ecotoxicology of hazardous heavy metals and metalloids shows thatsteps should be taken to minimize the impact of these elements on human health and the environment

1 Introduction

Environmental pollution is one of the major challenges in themodern human society [1] Environmental contaminationand pollution by heavy metals is a threat to the environmentand is of serious concern [2 3] Rapid industrialization andurbanization have caused contamination of the environmentby heavy metals and their rates of mobilization and transportin the environment have greatly accelerated since 1940s [4 5]

eir natural sources in the environment include weatheringof metal-containing rocks and volcanic eruptions whileprincipal anthropogenic sources include industrial emissionsmining smelting and agricultural activities like application ofpesticides and phosphate fertilizers Combustion of fossil fuelsalso contributes to the release of heavy metals such as cad-mium (Cd) to the environment [6] Heavy metals are per-sistent in the environment contaminate the food chains andcause different health problems due to their toxicity Chronic

HindawiJournal of ChemistryVolume 2019 Article ID 6730305 14 pageshttpsdoiorg10115520196730305

exposure to heavymetals in the environment is a real threat toliving organisms [7]

Metal concentrations above threshold levels affect themicrobiological balance of soils and can reduce their fertility[8] Bioaccumulation of toxic heavy metals in biota of theriverine ecosystems may have adverse effects on animals andhumans [9] Higher levels of heavy metals in biota can havenegative effects on the ecological health of aquatic animalspecies and may contribute to declines in their populations[10] Heavymetals are strong neurotoxins in fish specieseinteraction of heavy metals with chemical stimuli in fish mayinterrupt the communication of fish with their environment[11] Heavy metals have been found associated with fishdeformities in both natural populations and in the labora-tory Generally such deformities have negative effects on fishpopulations because deformities affect their survival growthrates welfare and external image ese deformities in fishcan serve as excellent biomarkers of environmental heavymetal pollution [12] Hartl [13] remarks that ldquometals ofnatural or anthropogenic origin are ubiquitous in theaquatic environment and therefore understanding theirbehavior and interaction with aquatic organisms particu-larly fishes a major source of protein for human con-sumption is of a great socioeconomic importancerdquo

is article comprehensively reviews the different as-pects of heavy metals as hazardous materials with a specialfocus on their environmental persistence toxicity for livingorganisms and bioaccumulative potential e bio-accumulation of these elements and its implications forhuman health are discussed with a special coverage on fishrice and tobacco e article will serve as a valuable edu-cational resource for both undergraduate and graduatestudents and for researchers in environmental sciences

2 Metals and Their Essentiality for Life

Chemically metals are defined as ldquoelements which conductelectricity have a metallic luster are malleable and ductileform cations and have basic oxidesrdquo [14] Terms usually usedin relation to metals in biological and environmental studiesare metal metalloid semimetal light metal heavy metalessential metal beneficial metal toxic metal abundantmetal available metal trace metal and micronutrient [15]Metals have very diverse applications and play an importantrole in the industry-dominated human society Some metalshave critically important physiological and biochemicalfunctions in biological systems and either their deficiency orexcess can lead to disturbance of metabolism and thereforeto various diseases Some metals and metalloids are essentialfor (biological) life ey play important physiological andbiochemical roles in the body as they may be part of bio-molecules such as enzymes which catalyze biochemicalreactions in the body

21 Heavy Metals (HMs) According to Csuros and Csuros[16] a heavymetal is defined as ldquoametal with a density greaterthan 5 gcm3 (ie specific gravity greater than 5)rdquo Accordingto Duffus [15] ldquothe term ldquoheavy metalsrdquo is often used as a

group name for metals and semimetals (metalloids) that havebeen associated with contamination and potential toxicity orecotoxicityrdquo Very recently we have proposed a broaderdefinition for the term and heavy metals have been defined asldquonaturally occurring metals having atomic number greaterthan 20 and an elemental density greater than 5 gmiddotcmminus3rdquo [17]

22 Essential andNonessential HMs Regarding their roles inbiological systems heavy metals are classified as essential andnonessential Essential heavy metals are important for livingorganisms and may be required in the body in quite lowconcentrations Nonessential heavy metals have no knownbiological role in living organisms Examples of essentialheavy metals are Mn Fe Cu and Zn while the heavy metalsCd Pb and Hg are toxic and are regarded as biologicallynonessential [18ndash21] e heavy metals Mn Fe Co Ni CuZn and Mo are micronutrients or trace elements for plantsey are essential for growth and stress resistance as well asfor biosynthesis and function of different biomolecules suchas carbohydrates chlorophyll nucleic acids growth chem-icals and secondary metabolites [22] Either deficiency orexcess of an essential heavy metal leads to diseases or ab-normal conditions However the lists of essential heavymetals may be different for different groups of organisms suchas plants animals and microorganisms It means a heavymetal may be essential for a given group of organisms butnonessential for another onee interactions of heavymetalswith different organism groups are much complex [23]

23 Environmentally Relevant Most Hazardous HMs andMetalloids Heavy metals are among the most investigatedenvironmental pollutants Almost any heavy metal andmetalloid may be potentially toxic to biota depending uponthe dose and duration of exposure Many elements areclassified into the category of heavy metals but some arerelevant in the environmental context List of the envi-ronmentally relevant most toxic heavy metals andmetalloidscontains Cr Ni Cu Zn Cd Pb Hg and As [24] Heavymetal pollutants most common in the environment are CrMn Ni Cu Zn Cd and Pb [25] In 2009 China hassuggested four metals ie Cr Cd Pb Hg and the metalloidAs as the highest priority pollutants for control in the ldquo12th5-year plan for comprehensive prevention and control ofheavy metal pollutionrdquo [26] Some other heavy metals arealso hazardous to living organisms depending upon doseand duration of exposure For example Mansouri et al [27]have found Ag as more toxic than Hg to a freshwater fish

24 Sources of Heavy Metals in the Environment Sources ofheavy metals in the environment can be both naturalgeogeniclithogenic and anthropogenic e natural orgeological sources of heavy metals in the environment in-clude weathering of metal-bearing rocks and volcaniceruptions e global trends of industrialization and ur-banization on Earth have led to an increase in the an-thropogenic share of heavy metals in the environment [28]e anthropogenic sources of heavy metals in the

2 Journal of Chemistry

environment include mining and industrial and agriculturalactivities ese metals (heavy metals) are released duringmining and extraction of different elements from their re-spective ores Heavy metals released to the atmosphereduring mining smelting and other industrial processesreturn to the land through dry and wet deposition Dischargeof wastewaters such as industrial effluents and domesticsewage add heavy metals to the environment Application ofchemical fertilizers and combustion of fossil fuels alsocontribute to the anthropogenic input of heavy metals in theenvironment Regarding contents of heavy metals in com-mercial chemical fertilizers phosphate fertilizers are par-ticularly important

In general phosphate fertilizers are produced fromphosphate rock (PR) by acidulation In the acidulation ofsingle superphosphate (SSP) sulfuric acid is used while inacidulation of triple superphosphate (TSP) phosphoric acidis used [29] e final product contains all of the heavymetals present as constituents in the phosphate rock [30]Commercial inorganic fertilizers particularly phosphatefertilizers can potentially contribute to the global transportof heavymetals [31] Heavymetals added to agricultural soilsthrough inorganic fertilizers may leach into groundwaterand contaminate it [29] Phosphate fertilizers are particu-larly rich in toxic heavy metals e two main pathways fortransfer of toxic heavy metals from phosphate fertilizers tothe human body are shown below [29]

(i) Phosphate rock⟶ fertilizer⟶ soil⟶ plant⟶food⟶ human body

(ii) Phosphate rock⟶ fertilizer⟶water⟶ humanbody

Combustion of fossil fuels in industries homes andtransportation is an anthropogenic source of heavy metalsVehicle traffic is among the major anthropogenic sources ofheavy metals such as Cr Zn Cd and Pb [32] Higherconcentrations of environmentally important heavy metalshave been reported in soils and plants along roads in urbanand metropolitan areas Regarding anthropogenic sourcesof heavy metals emissions from coal combustion and othercombustion processes are very important [5] During coalcombustion Cd Pb and As are partially volatile while Hgis fully volatile In China combustion of coal is one of themajor sources of atmospheric emissions of hazardous traceelements [33] Table 1 lists some environmentally impor-tant data for eight key hazardous trace elements (HTEs) ofprime environmental concern in Chinese coals

e anthropogenic sources of Cr include electroplatingindustries leather tanneries textile industries and steelindustries [34] Globally about 50000 tyear of Cr may beemitted from coal combustion wood burning and refuseincineration [5] Fertilizers also usually contain significantcontents of Cr [35] Globally about 60000 tyear of Ni maybe generated from coal combustion its greater portionremains in the ash [5] e natural sources of Cd in theenvironment are volcanic action and weathering of rockswhereas an anthropogenic source is nonferrous metalmining especially processing of Pb-Zn ores [36] Globally

about 7000 tyear of Cd may be emitted from coal com-bustion and sewage sludge incineration is also a source ofCd [5] Anthropogenic increases in Cd concentrations arealso caused by excessive application of chemical fertilizers[37] P-containing fertilizers contain Cd as a contaminant atconcentrations ranging from trace quantities to 300 ppm ondry weight basis and hence may be a main source of input ofthis metal to agricultural systems [38] Pb is released to theenvironment from different sources including acid batteriesold plumbing systems and lead shots used for hunting ofgame birds Combustion of leaded gasoline is also a source ofPb in the environment Although use of the tetraethyl lead asan antiknock agent in gasoline has been banned it is stillused in some developing regions of the world

3 ContaminationofNaturalWatersSedimentsand Soils by Heavy Metals

Toxic trace metals pose an important threat to bothaquatic and terrestrial ecosystems [39] After release fromboth natural and anthropogenic sources heavy metalscontaminate natural water bodies sediments and soilsHeavy metals released into the atmosphere in volcaniceruptions and in different industrial emissions also ulti-mately return to the land and cause contamination ofwaters and soils Since heavy metals are persistent in theenvironment they either accumulate in biota or leachdown into ground waters Contamination of biota andgroundwater with potentially toxic heavy metals hasimportant implications for human health It is importantto assess the degree of heavy metal pollution in riverineecosystems by investigating the concentrations of theseelements and their distribution [40] Figure 1 shows aconceptual schematic of contamination of an aquatic(riverine) ecosystem with heavy metals Different physi-cochemical and climatic factors affect the overall dy-namics and biogeochemical cycling of heavy metals in theenvironment

31 Water It is said that water is the ldquolife-blood of thebiosphererdquo Since water is a universal solvent it dissolvesdifferent organic and inorganic chemicals and environmentalpollutants Aquatic ecosystems both freshwater and marineare vulnerable to pollution Contamination of water resourcesby heavy metals is a critical environmental issue which ad-versely affects plants animals and human health [41] Heavymetals are extremely toxic to aquatic organisms even at verylow concentrations [42] ese elements can cause significanthistopathological alterations in tissues of aquatic organismssuch as fish [43] Aquatic ecosystems are contaminated byheavy metals from different sources One source of heavymetals in the aquatic ecosystems is effluents from miningoperations [44] Other sources of water contamination withheavy metals include different industrial effluents domesticsewage and agricultural run-off e release of industrialeffluents without treatment into the aquatic bodies is a majorsource of pollution of surface and groundwater water [45]Pollution of water bodies with heavy metals is a worldwide

Journal of Chemistry 3

problem because of the environmental persistence bio-accumulation and biomagnification in food chains andtoxicity of these elements [46]

32 Sediments Contamination of sediments with heavymetalsis an environmentally important issue with consequences foraquatic organisms and human health Sediments act as themainpool of metals in the aquatic environment eir quality canindicate the status of water pollution [47] Sediments serve asboth sink and source of heavy metals releasing them into thewater column [48] Continuing deposition of heavy metals insediments can also lead to contamination of groundwaterwith these pollutants [49] e adsorption desorption and

subsequent concentrations of heavy metals in sediments areaffected by many physicochemical factors such as temperaturehydrodynamic conditions redox state content of organicmatter and microbes salinity and particle size [50] Distribu-tion of heavy metals in sediments is affected by chemicalcomposition of the sediments grain size and content of totalorganicmatter (TOM) [51] An important determinant ofmetalbioavailability in sediments is pH A lowering in pH increasesthe competition between metal ions and H+ for binding sites insediments and may result in dissolution of metal complexesthereby releasing free metal ions into the water column [52]Higher concentrations of toxic heavy metals in riverine sedi-ments may pose ecological risk to benthos (bottom-dwellingorganisms) [53]

Figure 1 Schematic showing contamination of a river with heavy metals

Table 1 Some environmentally important data for key hazardous trace elements (HTEs) of prime environmental concern in Chinese coals[33]

Element Simulated mean conc (ppm) Emissions from coal use in China in 2007 (t)Cr 3037 82178Ni 1744 23084Cd 061 2454Pb 2304 125470Hg 020 3059As 578 22055Se 366 23530Sb 201 5467


33 Soils Heavy metals and metalloids are released intosoils from the parent material (lithogenic source) anddierent anthropogenic sources [54] Factors aecting thepresence and distribution of heavy metals in soils includecomposition of parent rock degree of weathering andphysical chemical and biological characteristics of soil andclimatic conditions [55] Signicant enrichment of heavymetals has been reported in soils receiving more input offertilizers and Cu fungicide compared to virgin soils andsoils receiving low inputs [56] In urban areas soils may becontaminated with heavy metals from heavy vehiculartrac on roads Soil samples in urban areas have elevatedconcentrations of Pb out of which 45ndash85 is bioaccessible[57] e bioavailability of heavy metals in soils is veryimportant for their fate in the environment and for theiruptake in plants Dierent heavy metals have dierentbioavailabilities in soils and this bioavailability is de-pendent on metal speciation and on dierent physico-chemical properties of soils

4 Heavy Metals as Hazardous Materials

Heavy metals are considered as hazardous chemicals in theenvironment Nonessential heavy metals are toxic to plantsanimals and humans at very low concentrations Even theessential heavy metals also cause adverse health eects athigh concentrations [58] Procedures developed for hazardidentication of chemical contaminants in the aquatic en-vironments consider three characteristic features persis-tence bioaccumulation and toxicity (Figure 2) Toxicsubstances which are both persistent and bioaccumulativeare more hazardous [59]

Toxicity refers to the property of a chemical to aectsurvival growth and reproduction of an organism Certainheavy metals have been reported to be carcinogenic mu-tagenic andor teratogenic to dierent species depending ondose and duration of exposure Heavy metals aect bothwildlife and human health Some species are more sensitiveto heavy metals than others e mechanisms by whichheavy metals aect dierent organs tissues and systems indierent organisms are very complex and so far some ofthem are not fully explored Exposure of the bivalve Ano-donta anatina to Cd has been found to aect carbonicanhydrase (CA) in its tissues an enzyme playing a role inosmoregulation and Ca metabolism [60] Cd has beenconsidered as one of the factors likely responsible for thedecline in populations of freshwater mussels due to its hightoxicity bioaccumulation potential and transfer throughfood chains [61]

5 Trophic Transfer of Heavy Metals

Since heavy metals are persistent in the environment theyaccumulate in living organisms and are transferred from onetrophic level to another in the food chains e extent ofaccumulation of heavy metals in biota depends on their rateof accumulation and their rate of elimination from the bodyus dierent heavy metals have dierent half lives indierent species

Heavy metals may enter the body of an organism directlyfrom the abiotic environment ie water sediments and soilor may enter the organism body from its foodprey Forexample heavy metals may enter the sh body directly fromwater or sediments through the sh gillsskin or from thesh foodprey through its alimentary canal e concen-tration of a heavy metal may increase or decrease alongsuccessive trophic levels in a food chain e retention ofheavy metals in the body of an organism depends on manyfactors such as the speciation of the metal concerned and thephysiological mechanisms developed by the organism forthe regulation homeostasis and detoxication of the heavymetal Methylated forms of heavy metals such as Hg areaccumulated in biota to a greater extent and thereforebiomagnied in food chains due to their lipophilicityCertain plants have the ability to thrive on metal-richhabitats and are called metallophytes ese special plantshave developed special mechanisms for coping with higherheavy metal concentrations in soil and are divided into threecategories ie excluders indicators and hyper-accumulators Certain terms are used to describe the trophictransfer of heavy metals (Figure 3) (for details refer [62])

6 Heavy Metal Transfer from Soil to Plant

e soil-to-plant transfer of heavy metals is a very importantstep in the trophic transfer of such metals in food chainsese metals are taken up by plants from polluted soil andsubsequently transferred to herbivorous animals along thefood chain [63] Regarding contamination of the humanfood chain contamination of crops such as cereals andvegetables is a very serious issue Consumption of cerealscontaminated with toxic heavy metals may cause risk tohuman health [64] Heavy metals in higher concentrationranges have been reported in vegetables grown with

Hazard in the aquatic environment

Persistence Bioaccumulation

Figure 2 Hazard of a substance in the aquatic environment is afunction of its persistence bioaccumulation and toxicity (PBT)


wastewaters compared to those grown with groundwaterFurthermore higher concentrations of these metals havebeen found in leafy vegetables compared to those in othertypes of vegetables such as bulbs and tubers [65]

7 Quantification of Trophic Transfer ofHeavy Metals

Certain terms have been used to quantify the degree orextent of accumulation of heavy metals in biota Some ofthese quantitative terms are bioconcentration factor (BCF)bioaccumulation factor (BAF) bioaccumulation coecient(BAC) etc Some of these terms are discussed below

71 Bioconcentration Factor (BCF) BCF is indicative of thedegree of enrichment of a heavy metal in an organismrelative to that in its habitat It is dened as ldquothe ratio of theconcentration of a heavy metal in an organism tissue to itsconcentration in the abiotic medium (water and sedi-ments)rdquo It is calculated by the following equation

BCF Corganism tissue

Cabioticmedium (1)

where Corganism is the metal concentration in the organismtissue and Cabioticmedium is the metal concentration in theabiotic medium

Some authors use the alternative terms transfer factor(TF) metal transfer factor (MTF) accumulation factor (AF)bioaccumulation factor (BAF) and biota-sediments accu-mulation factor (BSAF) and calculate them accordinglyHowever all these indices show the magnitude of accu-mulation of a heavy metal in the organism relative to that inthe environment where it growslives

72 Bioaccumulation Coecient (BAC) BAC is calculatedby the following equation [66]

BAC Cplant

Csoil (2)

where Cplant is the metal concentration in plant and Csoil isthe metal concentration in soil

It is evident that the values of BCF BAF BAC etcdepend on the concentration of the heavy metal in theorganism and in the concerned environmental mediumSince the values of these indices are inversely related to themetal concentration in the environmental medium (watersediments and soil) the values of these indices should beused with caution for assessment of heavy metal contami-nation in biota For example the BCF value for a heavymetalin muscles of a sh dwelling in less contaminated water maybe higher than for the sh dwelling in more contaminatedwater simply because of the lower metal concentration in thehabitat of the former sh It has been reported that bio-concentration factor (BCF) values of seven typical heavymetals in crop grains decreased exponentially with averageconcentrations of the metals in soil [67]

8 Bioaccumulation of Heavy Metals in Biota

Since heavy metals are persistent in the environment theyenter from the environment to the organisms and accu-mulate therein As mentioned earlier the uptake andbioaccumulation of heavy metals in biota depend on severalfactors For example the uptake of heavy metals in plantsdepends on bioavailability of the metal in soil which inturn depends on several factors such as metal speciationpH and organic matter contents in soil Metals which are

3rd trophic level

2nd trophic level

1st trophic level

Preyfood

Abiotic environment+

Preyfood

Abiotic environmentwater and sediments

Bioaccumulation

Dietary accumulation

Bioconcentra

tion

HMs

Sediments

Elimination (depuration)HMs

Cd Pb Hg As

Biod

ilutio

n

Biom

agni

ficat

ion

Trophic transfer

Trophic transfer

HMs

HMs

Figure 3 Schematic summarizing terms and concepts involved in trophodynamics of heavymetals ([62] used with permission of Tailor andFrancis)


more bioavailable in soil may be accumulated in plantsmore easily and thus will have more bioaccumulationpotential An assessment of bioaccumulation of heavymetals in plants may be used for an estimation of bio-availability of the metals in soil Such an assessment mayalso be used for knowing the contamination status of theenvironment It has been reported that plants seem to bemore sensitive to environmental changes than soils [68]Different plant species have been suggested as bioindicatorsof heavy metal pollution in the environment Differentanimal species have also been suggested as bioindicators ofheavy metal pollution For example the date mussel(Lithophaga lithophaga) has been suggested as a validbioindicator of marine pollution [69]

Bioaccumulation of heavy metals in biota is importantfrom environmental ecological and human health point ofview and has important implications for wildlife and humanhealth Contamination of aquatic and terrestrial food chainswith potentially toxic heavy metals poses a threat to thehealth of consumer organisms including humans In aquaticecosystems organisms are simultaneously exposed to dif-ferent metals which may have additive synergistic or an-tagonistic interactions [70] e topic of bioaccumulation ofheavy metals in biota is a very broad topic Here the dis-cussion of the topic will be limited to bioaccumulation ofheavy metals in fish and rice which serve as the majordietary sources of heavy metal exposure for the generalhuman population Additionally bioaccumulation of heavymetals in cigarette tobacco will also be discussed as tobaccosmoke acts as an additional source of heavy metal exposurefor the smoking human population

9 Bioaccumulation of Heavy Metals inFreshwater Fish

Aquatic biota is exposed to heavy metals through differentroutes such as water sediments and food [71] Freshwaterfish are exposed to different toxic heavy metals released tofreshwater bodies from different natural and anthropogenicsources Contamination of fish by heavy metals has becomean important global issue because it presents a threat to fishand poses health risks to fish consumers [72] Assessment ofheavy metal bioaccumulation in fish species of differentaquatic habitats is very important [73] Assessment of heavymetal levels in fish tissues is essential for aquatic ecosystemmanagement and human consumption of fish [74] Fishhave high levels of unsaturated fatty acids and low levels ofcholesterol ey are an important source of proteins [75]Use of an edible fish in human diet is beneficial and thereforerecommended in balanced diet However contamination offish by toxic heavy metals is considered as a risk for humanhealth and has raised concerns about their consumptionespecially in more sensitive groups of human populationsuch as women children and people at risk of diseases fromother causes

e bioaccumulation of heavy metals in freshwater fishdepends on various factors both fish characteristics andexternal environmental factors Factors related to fish in-clude fish age size (weight and length) feeding habits and

body physiology while external environmental factors in-clude concentration and bioavailability of metals in thewater column physicochemical properties of water andother climatic factors e degree of accumulation of heavymetals in different tissues of fish is generally differentdepending on the structure and function of tissues Gen-erally metabolically active tissues such as gills liver andkidneys have higher accumulations of heavy metals thanother tissues such as skin and muscles e comparativelyhigher heavy metal accumulation in metabolically activetissues of fish is generally explained by the inductionoccurrence of metal-binding proteins called metal-lothioneins (MTs) in these tissues upon exposure to heavymetals Fish gills have been found as the target tissue foraccumulation and elimination of heavy metals such as Ni[76] Although fish muscles are the tissue of poor heavymetal accumulation [77] they are important from the viewpoint of consumption by humans Bioaccumulation of tracemetals in muscles of fish is generally species specific [78]Most studies on bioaccumulation of heavy metals in fishhave investigated metal concentrations in fish muscles be-cause this tissue is edible and is the most relevant regardinghuman health

Bioaccumulation of toxic heavy metals in freshwater fishhas important environmental ecological and social con-sequences it has implications for humans and other fishconsuming carnivorous wildlife [79ndash83] Waterborne heavymetals are incorporated in fish and enter the human bodythrough the food chain and therefore have impact on humanhealth [84] Furthermore toxic heavy metals also affect fishhealth and well-being It has been reported that pollution ofriver with heavy metals-containing wastewater inducedstress in the freshwater fish Channa punctatus making itweak and more vulnerable to diseases [85] Heavy metalpollution is regarded as one of the possible causes forpopulation declines of freshwater fish and other aquaticspecies in freshwater ecosystems It has been reported thatincreased contamination in River Indus Pakistan hascaused decline in the number and diversity of freshwater fishand other aquatic species in this river [86]

10 Bioaccumulation of Heavy Metals in Rice(Oryza sativa)

Rice is a very important human food and is the staple food inAsian countries especially in South Asia and China Con-tamination of rice fields with toxic heavy metals leads tobioaccumulation of these elements in the rice plant etranslocation of heavy metals from roots of the rice plant tostem leaves and rice grains is of human health concern Ricecrop is especially susceptible to heavy metal contaminationbecause it needs water during most of its growth period etrace elements Cd Pb Hg and As are ubiquitous in theenvironment with harmful effects on human health Re-garding their presence in rice as a public health concern Asis on top followed by Cd [87] Human intake of Cd has beenreported to be highest through consumption of rice [88]Contamination of rice with toxic heavy metals is especially ahealth concern in developing countries [89]


Irrigation of agricultural soils with wastewater is awidespread practice in developing countries which resultsin elevated uptake of metals in crops Elevated levels of heavymetals in crops affect food quality and pose health risks tothe consumers [90] Application of phosphate fertilizers richin Cd can also lead to Cd contamination in rice fields [91]For the general population consumption of rice may be apotential exposure source of toxic heavy metals particularlyCd Pb and As [92] Long-term consumption of rice grownon polluted areas may cause potential health hazards to theconsumers [93] Efforts are being made to minimize uptakethrough roots and translocation to grains of toxic heavymetals especially Cd in rice Genetic engineering is used asan approach to achieve this goal and some transgenic ricevarieties have been developed to meet the challenge

11 Bioaccumulation of Heavy Metals inTobacco (Nicotiana tabacum)

Bioaccumulation of toxic heavymetals in cigarette tobacco isa human health concern because tobacco leaves are used formaking cigarettes Tobacco plants naturally accumulaterelatively high concentrations of heavy metals in their leavesand the metal bioaccumulation in tobacco leaves varies withthe geographical origin of the tobacco plants [94] Tobaccocrop is grown with application of commercial inorganicfertilizers especially phosphate fertilizers which containconsiderable concentrations of some toxic heavy metalsDuring growth uptake of heavy metals by tobacco roots isconsiderable and the same are translocated from soil toleaves During cigarette smoking a fraction of heavy metalsis inhaled in the smoke and thus reaches the lungs of thesmoker Tobacco smoke both mainstream and side streamis an important source of environmental metal exposurePassive smoking has an important contribution in the ex-posure of children to Pb [95] Heavy metals inhaled duringtobacco smoking are easily absorbed in the body from thelungs and reach the blood from where they may reach otherparts of the body Higher levels of toxic heavy metals havebeen reported in blood of cigarette smokers compared tothat of nonsmokers

As stated by Dissanayake and Chandrajith [29] theapplication of inorganic fertilizers in agriculture has un-fortunately become a ldquonecessary evilrdquo Since commercialchemical fertilizers are usually not purified enough duringthe manufacturing processes they usually contain heavymetals as impurities [96] Much of the phosphate fertilizersin the world are commercially produced from phosphaterocks that contain the mineral apatite [Ca5(PO4)3OHFCl]Due to their geological and mineralogical nature phos-phate rocks contain different environmentally hazardouselements including Cr Cd Pb Hg As and U Applicationof chemical fertilizers leads to increase in the concentra-tions of these potentially toxic heavy metals in agriculturalsoils [97] A high correlation has been reported betweenconcentrations of metals ie Cr Ni Cd and Pb andcontent of phosphate in fertilizers [98] A study in-vestigating concentrations of Cr Mn Fe Ni Cu Zn SnCd Pb and As in tobacco products in the UK has

concluded that overapplication of phosphatenitrate fer-tilizers is the most likely cause of their transfer to theseproducts [99] However Bozhinova [100] reported a lim-ited impact of application of phosphate fertilizers on ac-cumulation of Ni Cu Cd and Pb in soil and tobaccoplants In summary the addition of toxic heavy metals fromlong-term application of phosphate fertilizers to agricul-tural soils and their subsequent transfer to the human foodchain is a matter of great concern with respect to humanhealth especially in case of low-quality phosphate fertil-izers containing elevated levels of heavy metals

12 Human Exposure to Heavy Metals

Humans are exposed to toxic heavy metals in the envi-ronment through different routes including ingestion in-halation and dermal absorption People are more exposed totoxic metals in developing countries [101] Generally peoplehave no awareness and knowledge about exposure to heavymetals and its consequences for human health especially inthe developing countries [102] People may be exposed toheavy metals in the work place and in the environmentHuman exposure to toxic chemicals in the work place iscalled occupational exposure while exposure to suchchemicals in the general environment is called non-occupational or environmental exposure Workers are ex-posed to heavy metals in mining and industrial operationswhere they may inhale dust and particulate matter-containing metal particles People extracting gold throughthe amalgamation process are exposed to Hg vapors It hasbeen reported that welders with occupational prolongedexposure to welding fumes had significantly higher levels ofthe heavymetals Cr Ni Cd and Pb in blood than the controland showed increased oxidative stress [103] Cigarettesmoking is also a principal source of human exposure to Cd[104] and other toxic heavy metals present in the tobaccoleaves

Ingestion of heavy metals through food and drinkingwater is a major exposure source for the general humanpopulation Industrialization urbanization and the rapideconomic development around the globe have led to in-tensification in industrial and agricultural activities Suchactivities may cause contamination of water air and soilswith toxic heavy metals Growing human foods in heavymetal-contaminated media lead to bioaccumulation of theseelements in the human food chains from where these ele-ments ultimately reach the human body

13 Bioaccumulation and Biomagnification ofHeavy Metals in the Human Food Chains

Humans are omnivorous ey may be exposed to toxicheavy metals through different food items such as fishcereals and vegetables Heavy metal contamination infreshwater bodies such as rivers lakes and streams leads tobioaccumulation of these elements in freshwater fish whilesuch contamination in agricultural lands leads to bio-accumulation of these elements in agricultural cropsContamination of the human food chains with toxic heavy


metals poses a threat to human health Certain examplesfrom the twentieth century have shown that such con-tamination is a serious human health issue Minamatadisease (MD) and itai-itai disease both in Japan werecaused by consumption of Hg-contaminated fish and Cd-contaminated rice respectively Figure 4 depicts thetransfer of heavy metals from contaminated fish tohumans

Although biomagnification of heavy metals is a con-troversial issue in metal ecotoxicology numerous studieshave reported biomagnification of heavy metals in certainfood chains In case of biomagnification of these metals infood chains organisms at higher trophic levels in the foodchains are at greater risk Higher concentrations of tracemetals in organisms of higher trophic levels as a result ofbiomagnification can pose health risk to these organisms orto their human consumers [105] To protect human healthfrom the harmful effects of toxic heavy metals the humanfood chains should be constantly monitored for bio-accumulation and biomagnification of heavy metalsHowever nondestructive sampling techniques and use ofenvironmental biomarkers should be opted to avoid loss ofbiota due to analysis Furthermore in order to avoidcontamination of food chains with heavy metals untreatedmunicipal and industrial wastewaters should not bedrained into natural ecosystems such as rivers and farm-lands [106]

14 Heavy Metal Toxicity

Although some heavy metals called essential heavy metalsplay important roles in biological systems they are generallytoxic to living organisms depending on dose and duration ofexposure It is a well-known fact in toxicology that ldquoexcess ofeverything is badrdquo Nonessential heavy metals (Cd Pb andHg) and metalloids (As etc) may be toxic even at quite lowconcentrations Essential heavy metals are required in tracequantities in the body but become toxic beyond certain limitsor threshold concentrations For some elements the windowof essentiality and toxicity is narrow Heavy metals have beenreported to be carcinogenic mutagenic and teratogeniceycause generation of reactive oxygenic species (ROS) and thusinduce oxidative stress Oxidative stress in organisms leads tothe development of various diseases and abnormal conditionsHeavy metals also act as metabolic poisons Heavy metaltoxicity is primarily due to their reaction with sulfhydryl (SH)enzyme systems and their subsequent inhibition eg thoseenzymes involved in cellular energy production [16] Figure 5shows the reaction of a heavy metal (M) with glutathione(GSH) an important antioxidant in the body Here the metalreplaces H atoms from SH groups on two adjacent gluta-thione molecules e engagement of the two glutathionemolecules in formation of strong bond with the metal de-activates them for further reactions

2 glutathione + metal ion M2+1113872 1113873⟶ M(glutathione)2 + 2H+

(3)

15 Effects of Toxic Heavy Metals onHuman Health

e heavy metals Cd Pb Hg and As deplete the majorantioxidants of cells particularly antioxidants and enzymeshaving the thiol group (mdashSH) Such metals may increase thegeneration of reactive oxygen species (ROS) like hydroxylradical (HO_) superoxide radical (O2_

minus) and hydrogenperoxide (H2O2) Increased generation of ROS can devastatethe inherent antioxidant defenses of cells and lead to acondition called ldquooxidative stressrdquo [108] Heavy metalsincluding Cd Pb and Hg are nephrotoxic especially in therenal cortex [109] e chemical form of the heavy metals isimportant in toxicity Mercury toxicity largely depends onHg speciation [110] Relatively higher concentrations oftoxic heavy metals ie Cr Cd and Pb and relatively lowerconcentrations of the antioxidant element Se have beenfound in patients of cancer and diabetes compared to thosein the normal subjects in Lahore city Pakistan [111]

16 Monitoring and Analysis of Heavy Metals inthe Environment

Monitoring and analysis of heavy metal concentrations inthe environment are necessary for pollution assessment andcontrol [112] e levelsconcentrations of potentially toxicmetals and metalloids should be regularly monitored in thedifferent environmental media such as water sediments andsoils as well as in the resident biota Such environmentalanalysis will provide useful information about distributionprincipal sources and fate of these elements in the envi-ronment and their bioaccumulation in the food chains Suchanalysis is also used to assess the risk posed by these elementsto wildlife and human health

17 Use of Bioindicators and Biomarkers forAssessment of Heavy Metal Pollution

Regarding the use of bioindicators for monitoring and as-sessment of heavy metal pollution Morgan [113] summa-rizes that ldquoa more meaningful assessment of the impact ofmetal pollution may be obtained by measuring metal con-centrations in selected species of the resident biotardquo Dif-ferent plant and animal species have been used as biologicalindicators or bioindicators to assess and monitor heavymetal contamination and pollution in the environmentDifferent environmental biomarkers are also used to assessand monitor pollution pertaining to heavy metals in theenvironment

18 The Nature and Scope of Studies on HeavyMetals in the Environment

Environmental studies on different aspects of heavy metalsand metalloids are interdisciplinary in nature and requirebackground knowledge in environmental chemistry eco-toxicology and ecology Analysis of xenobiotics such as


toxic heavy metals in food chains is an important study areaand has environmental ecological and economic impor-tance It has a scope for public health Such studies involveaquatic chemistry which has a scope for public health asremarked by Johnston [114] ldquoaquatic chemistry is a fun-damental element of public healthrdquo Bioaccumulation dataof toxic heavy metals in dierent biota such as sh and ricecan be used for health risk assessment for the generalhuman population

19 Conclusions and Recommendations

Heavy metals and metalloids are ubiquitous environmentalpollutants in both aquatic and terrestrial ecosystems ehazard of an environmental chemical is a function of its

environmental persistence toxicity and bioaccumulativepotential Toxic environmental chemicals which are per-sistent and bioaccumulative are more hazardous Heavymetals are considered hazardous due to these three char-acteristics persistence bioaccumulation and toxicity(PBT) Environmentally relevant most hazardous heavymetals and metalloids include Cr Ni Cu Zn Cd Pb Hgand As e trophic transfer of these elements in aquaticand terrestrial food chainswebs has important implica-tions for wildlife and human health It is very important toassess and monitor the concentrations of potentially toxicheavy metals and metalloids in dierent environmentalsegments as well as in the resident biota A comprehensivestudy of the environmental chemistry and ecotoxicology ofhazardous heavy metals and metalloids shows that stepsshould be taken to minimize the impact of these elementson human health and the environment e followingrecommendations are made

(i) Background concentrations of heavy metals andmetalloids should be documented in the dierentenvironmental media around the world for lateruse as a reference

(ii) e levels of potentially toxic heavy metals andmetalloids in water sediments soils and the res-ident biota should be assessed and monitoredregularly

(iii) Regular surveys should be conducted to record theper capita daily consumption of freshwater sh andother food items such as rice by the residentpopulation around the world Such data will bevaluable for a more accurate and reliable humanand ecological risk assessment

Transfer of HMs from fish to humans as aresults of bioaccumulation and

biomagnification in the aquatic food chain

Naturalgeological andanthropogenic sources

Heavy metals(HMs)

Freshwater environment

Cr

Pb NiHMs

Cd

HMs

Adsorption DesorptionSediments

Figure 4 Trophic transfer of heavy metals from freshwater sh to humans in the human food chain

C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H

Metal-glutathione complex

Figure 5 Reaction of a metal with glutathione (adapted from[107])


(iv) Efforts should be made to minimize heavy metalcontamination in aquatic and terrestrial ecosystemsto safeguard the biota and the health of theirconsumers

(v) e public should be educated about the harmfuleffects of toxic heavy metals on human health andthe environment

(vi) Wastewaters from industries should be treatedeffectively before their discharge into the naturalwater bodies

(vii) Scientific research on environmental assessment oftoxic chemicals including toxic heavy metals andmetalloids should be encouraged and promotedthrough allocation of appropriate funds for pro-tecting human health and the environment

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

References

[1] H Ali and E Khan ldquoEnvironmental chemistry in the twenty-first centuryrdquo Environmental Chemistry Letters vol 15 no 2pp 329ndash346 2017

[2] H Ali E Khan andM A Sajad ldquoPhytoremediation of heavymetals-Concepts and applicationsrdquo Chemosphere vol 91no 7 pp 869ndash881 2013

[3] M A Hashem M S Nur-A-Tomal N R Mondal andM A Rahman ldquoHair burning and liming in tanneries is asource of pollution by arsenic lead zinc manganese andironrdquo Environmental Chemistry Letters vol 15 no 3pp 501ndash506 2017

[4] F U Khan A U Rahman A Jan and M Riaz ldquoToxic andtrace metals (Pb Cd Zn Cu Mn Ni Co and Cr) in dustdustfallsoilrdquo Journal of the Chemical Society of Pakistanvol 26 no 4 pp 453ndash456 2004

[5] E Merian ldquoIntroduction on environmental chemistry andglobal cycles of chromium nickel cobalt beryllium arseniccadmium and selenium and their derivativesdaggerrdquo Toxicolog-ical amp Environmental Chemistry vol 8 no 1 pp 9ndash38 1984

[6] H Spiegel ldquoTrace element accumulation in selected bio-indicators exposed to emissions along the industrial facilitiesof Danube Lowlandrdquo Turkish Journal of Chemistry vol 26no 6 pp 815ndash823 2002

[7] M Wieczorek-Dabrowska A Tomza-Marciniak B Pilarczykand A Balicka-Ramisz ldquoRoe and red deer as bioindicators ofheavy metals contamination in north-western PolandrdquoChemistry and Ecology vol 29 no 2 pp 100ndash110 2013

[8] M Barbieri ldquoe importance of enrichment factor (EF) andgeoaccumulation index (Igeo) to evaluate the soil contam-inationrdquo Journal of Geology ampGeophysics vol 5 no 1 p 2372016

[9] D S Malik and P K Maurya ldquoHeavy metal concentration inwater sediment and tissues of fish species (Heteropneustisfossilis and Puntius ticto) from Kali River Indiardquo Toxico-logical amp Environmental Chemistry vol 96 no 8pp 1195ndash1206 2014

[10] J Luo Y Ye Z Gao and W Wang ldquoEssential and non-essential elements in the red-crowned craneGrus japo-nensisof Zhalong Wetland northeastern Chinardquo

Toxicological amp Environmental Chemistry vol 96 no 7pp 1096ndash1105 2014

[11] E Baatrup ldquoStructural and functional effects of heavy metalson the nervous system including sense organs of fishrdquoComparative Biochemistry and Physiology Part C Compar-ative Pharmacology vol 100 no 1-2 pp 253ndash257 1991

[12] D G Sfakianakis E Renieri M Kentouri andA M Tsatsakis ldquoEffect of heavy metals on fish larvae de-formities a reviewrdquo Environmental Research vol 137pp 246ndash255 2015

[13] M G J Hartl ldquoBook review homeostasis and toxicology ofnon-essential metals Edited by C M Wood A P Farrell ampC J Brauner 528 pp Published by Elsevier London UK2012 Price pound6699 ISBN 978-0-12-378636-0rdquo Journal ofFish Biology vol 83 pp 1476-1477 2013

[14] P Atkins and L Jones ChemistrymdashMolecules Matter andChange W H Freeman New York NY USA 3rd edition1997

[15] J H Duffus ldquoldquoHeavy metalsrdquo a meaningless term (IUPACTechnical Report)rdquo Pure and Applied Chemistry vol 74no 5 pp 793ndash807 2002

[16] M Csuros and C Csuros Environmental Sampling andAnalysis for Metals Lewis Publishers Boca Raton FL USA2002

[17] H Ali and E Khan ldquoWhat are heavy metals Long-standingcontroversy over the scientific use of the termrsquo heavy metalsrsquo-proposal of a comprehensive definitionrdquo Toxicological ampEnvironmental Chemistry vol 100 no 1 pp 6ndash19 2018

[18] R Ramırez ldquoe gastropodOsilinus atrataas a bioindicatorof Cd Cu Pb and Zn contamination in the coastal waters ofthe Canary Islandsrdquo Chemistry and Ecology vol 29 no 3pp 208ndash220 2013

[19] M Jovic A Onjia and S Stankovic ldquoToxic metal health riskby mussel consumptionrdquo Environmental Chemistry Lettersvol 10 no 1 pp 69ndash77 2012

[20] M Rahim I Ullah A Khan and M R H M Haris ldquoHealthrisk from heavy metals via consumption of food crops in thevicinity of District Shanglardquo Journal of the Chemical Societyof Pakistan vol 38 no 1 pp 177ndash185 2016

[21] M Turkmen A Turkmen Y Tepe Y Tore and A AtesldquoDetermination of metals in fish species from Aegean andMediterranean seasrdquo Food Chemistry vol 113 no 1pp 233ndash237 2009

[22] K-J Appenroth ldquoWhat are ldquoheavy metalsrdquo in Plant Sci-encesrdquo Acta Physiologiae Plantarum vol 32 no 4pp 615ndash619 2010

[23] O Chalkiadaki M Dassenakis and N Lydakis-SimantirisldquoBioconcentration of Cd and Ni in various tissues of twomarine bivalves living in different habitats and exposed toheavily polluted seawaterrdquo Chemistry and Ecology vol 30no 8 pp 726ndash742 2014

[24] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011

[25] T Khan S Muhammad B Khan and H Khan ldquoIn-vestigating the levels of selected heavymetals in surface waterof shah alam river (a tributary of River Kabul KhyberPakhtunkhwa)rdquo Journal of Himalayan Earth Sciencesvol 44 no 2 pp 71ndash79 2011

[26] Z Fu W Guo Z Dang et al ldquoRefocusing on nonprioritytoxic metals in the aquatic environment in Chinardquo Envi-ronmental Science amp Technology vol 51 no 6 pp 3117-31182017


[27] B Mansouri R Baramaki and M Ebrahimpour ldquoAcutetoxicity bioassay of mercury and silver on Capoeta fusca(black fish)rdquo Toxicology and Industrial Health vol 28 no 5pp 393ndash398 2012

[28] P C Nagajyoti K D Lee and T V M Sreekanth ldquoHeavymetals occurrence and toxicity for plants a reviewrdquo Envi-ronmental Chemistry Letters vol 8 no 3 pp 199ndash216 2010

[29] C B Dissanayake and R Chandrajith ldquoPhosphate mineralfertilizers trace metals and human healthrdquo Journal of theNational Science Foundation of Sri Lanka vol 37 no 3pp 153ndash165 2009

[30] J J Mortvedt ldquoHeavy metal contaminants in inorganic andorganic fertilizersrdquo Fertilizer Research vol 43 no 1ndash3pp 55ndash61 1996

[31] L G de Lopez Carnelo S R de Miguez and L MarbanldquoHeavy metals input with phosphate fertilizers used inArgentinardquo Science of the Total Environment vol 204 no 3pp 245ndash250 1997

[32] M Ferretti E Cenni F Bussotti and P Batistoni ldquoVehicle-induced lead and cadmium contamination of roadside soiland plants in Italyrdquo Chemistry and Ecology vol 11 no 4pp 213ndash228 1995

[33] H Z Tian L Lu J M Hao et al ldquoA review of key hazardoustrace elements in Chinese coals abundance occurrencebehavior during coal combustion and their environmentalimpactsrdquo Energy amp Fuels vol 27 no 2 pp 601ndash614 2013

[34] P R Palaniappan and S Karthikeyan ldquoBioaccumulation anddepuration of chromium in the selected organs and wholebody tissues of freshwater fish Cirrhinus mrigala individuallyand in binary solutions with nickelrdquo Journal of Environ-mental Sciences vol 21 no 2 pp 229ndash236 2009

[35] O Kruger F Fiedler C Adam C Vogel and R SenzldquoDetermination of chromium (VI) in primary and secondaryfertilizer and their respective precursorsrdquo Chemospherevol 182 pp 48ndash53 2017

[36] M Hutton ldquoSources of cadmium in the environmentrdquoEcotoxicology and Environmental Safety vol 7 no 1pp 9ndash24 1983

[37] D Wang Z Dang H Feng and R Wang ldquoDistribution ofanthropogenic cadmium and arsenic in arable land soils ofHainan Chinardquo Toxicological amp Environmental Chemistryvol 97 no 3-4 pp 402ndash408 2015

[38] C A Grant and S C Sheppard ldquoFertilizer impacts oncadmium availability in agricultural soils and cropsrdquoHumanand Ecological Risk Assessment An International Journalvol 14 no 2 pp 210ndash228 2008

[39] V I Slaveykova and G Cheloni ldquoPreface special issue onenvironmental toxicology of trace metalsrdquo Environmentsvol 5 no 12 p 138 2018

[40] M S Islam R Proshad and S Ahmed ldquoEcological risk ofheavy metals in sediment of an urban river in BangladeshrdquoHuman and Ecological Risk Assessment An InternationalJournal vol 24 no 3 pp 699ndash720 2018

[41] S Rezania S M Taib M F Md Din F A Dahalan andH Kamyab ldquoComprehensive review on phytotechnologyheavy metals removal by diverse aquatic plants species fromwastewaterrdquo Journal of Hazardous Materials vol 318pp 587ndash599 2016

[42] M Akif A R Khan K Sok et al ldquoTextile effluents and theircontribution towards aquatic pollution in the Kabul River(Pakistan)rdquo Journal of the Chemical Society of Pakistanvol 24 no 2 pp 106ndash111 2002

[43] M K Ahmed E Parvin M M Islam M S Akter S Khanand M H Al-Mamun ldquoLead- and cadmium-induced

histopathological changes in gill kidney and liver tissue offreshwater climbing perch Anabas testudineus (Bloch1792)rdquo Chemistry and Ecology vol 30 no 6 pp 532ndash5402014

[44] P Zhuang Z-a Li M B McBride B Zou and G WangldquoHealth risk assessment for consumption of fish originatingfrom ponds near Dabaoshan mine South Chinardquo Envi-ronmental Science and Pollution Research vol 20 no 8pp 5844ndash5854 2013

[45] M S Afzal A Ashraf and M Nabeel ldquoCharacterization ofindustrial effluents and groundwater of Hattar industrialestate Haripurrdquo Advances in Agriculture and EnvironmentalScience Open Access (AAEOA) vol 1 no 2 pp 70ndash77 2018

[46] G Rajaei B Mansouri H Jahantigh and A H HamidianldquoMetal concentrations in the water of Chah nimeh reservoirsin Zabol Iranrdquo Bulletin of Environmental Contaminationand Toxicology vol 89 no 3 pp 495ndash500 2012

[47] A Zahra M Z Hashmi R N Malik and Z AhmedldquoEnrichment and geo-accumulation of heavy metals and riskassessment of sediments of the Kurang Nallah-Feedingtributary of the Rawal Lake Reservoir Pakistanrdquo Scienceof the Total Environment vol 470-471 pp 925ndash933 2014

[48] L L Fernandes and G N Nayak ldquoHeavy metals contami-nation in mudflat and mangrove sediments (Mumbai In-dia)rdquo Chemistry and Ecology vol 28 no 5 pp 435ndash4552012

[49] T Sanyal A Kaviraj and S Saha ldquoDeposition of chromiumin aquatic ecosystem from effluents of handloom textileindustries in Ranaghat-Fulia region of West Bengal IndiardquoJournal of Advanced Research vol 6 no 6 pp 995ndash10022015

[50] S Zhao X Shi C Li H Zhang and Y Wu ldquoSeasonalvariation of heavy metals in sediment of Lake UlansuhaiChinardquo Chemistry and Ecology vol 30 no 1 pp 1ndash14 2014

[51] N Ali Azadi B Mansouri L Spada M H SinkakarimiY Hamesadeghi and A Mansouri ldquoContamination of lead(Pb) in the coastal sediments of north and south of Iran areview studyrdquo Chemistry and Ecology vol 34 no 9pp 884ndash900 2018

[52] M Nowrouzi B Mansouri S Nabizadeh andA Pourkhabbaz ldquoAnalysis of heavy metals concentration inwater and sediment in the Hara biosphere reserve southernIranrdquo Toxicology and Industrial Health vol 30 no 1pp 64ndash72 2014

[53] S C Decena M Arguilles and L Robel ldquoAssessing heavymetal contamination in surface sediments in an urban riverin the Philippinesrdquo Polish Journal of Environmental Studiesvol 27 no 5 pp 1983ndash1995 2018

[54] B J Alloway ldquoSources of heavy metals and metalloids insoilsrdquo in Heavy Metals in Soils Trace Metals and Metalloidsin Soils and their Bioavailability pp 11ndash50 Springer Dor-drecht Netherlands 2013

[55] K K I U Arunakumara B C Walpola and M-H YoonldquoCurrent status of heavy metal contamination in Asiarsquos ricelandsrdquo Reviews in Environmental Science and BioTechnol-ogy vol 12 no 4 pp 355ndash377 2013

[56] E Semu and B R Singh ldquoAccumulation of heavy metals insoils and plants after long-term use of fertilizers and fun-gicides in Tanzaniardquo Fertilizer Research vol 44 no 3pp 241ndash248 1996

[57] A K Mackay M P Taylor N C MunksgaardK A Hudson-Edwards and L Burn-Nunes ldquoIdentificationof environmental lead sources and pathways in a mining and


smelting town mount Isa Australiardquo Environmental Pol-lution vol 180 pp 304ndash311 2013

[58] S Mahboob H F Alkkahem Al-Balwai F Al-MisnedK A Al-Ghanim and Z Ahmad ldquoA study on the accu-mulation of nine heavy metals in some important fish speciesfrom a natural reservoir in Riyadh Saudi Arabiardquo Toxico-logical amp Environmental Chemistry vol 96 no 5 pp 783ndash798 2014

[59] D K DeForest K V Brix and W J Adams ldquoAssessingmetal bioaccumulation in aquatic environments the inverserelationship between bioaccumulation factors trophictransfer factors and exposure concentrationrdquo Aquatic Tox-icology vol 84 no 2 pp 236ndash246 2007

[60] H T T Ngo S Gerstmann and H Frank ldquoSubchroniceffects of environment-like cadmium levels on the bivalveAnodonta anatina (Linnaeus 1758) III Effects on carbonicanhydrase activity in relation to calcium metabolismrdquoToxicological amp Environmental Chemistry vol 93 no 9pp 1815ndash1825 2011

[61] H T T Ngo Effects of cadmium on calcium homeostasis andphysiological conditions of the freshwater mussel Anodontaanatina PhD thesis Faculty of Biology Chemistry andGeosciences University of Bayreuth Bayreuth Germany2008

[62] H Ali and E Khan ldquoTrophic transfer bioaccumulation andbiomagnification of non-essential hazardous heavy metalsand metalloids in food chainswebs concepts and implica-tions for wildlife and human healthrdquo Human and EcologicalRisk Assessment An International Journal 2018 in Press

[63] D V Nica M Bura I Gergen M Harmanescu andD-M Bordean ldquoBioaccumulative and conchological as-sessment of heavy metal transfer in a soil-plant-snail foodchainrdquo Chemistry Central Journal vol 6 no 1 p 55 2012

[64] O E Orisakwe J K Nduka C N Amadi D O Dike andO Bede ldquoHeavy metals health risk assessment for populationvia consumption of food crops and fruits in Owerri SouthEastern Nigeriardquo Chemistry Central Journal vol 6 no 1p 77 2012

[65] A Mahmood and R N Malik ldquoHuman health risk assess-ment of heavy metals via consumption of contaminatedvegetables collected from different irrigation sources inLahore PakistanrdquoArabian Journal of Chemistry vol 7 no 1pp 91ndash99 2014

[66] S-x Liang N Gao Z-c Li S-g Shen and J Li ldquoIn-vestigation of correlativity between heavy metals concen-tration in indigenous plants and combined pollution soilsrdquoChemistry and Ecology vol 32 no 9 pp 872ndash883 2016

[67] S Wang W Wu F Liu R Liao and Y Hu ldquoAccumulationof heavy metals in soil-crop systems a review for wheat andcornrdquo Environmental Science and Pollution Research vol 24no 18 pp 15209ndash15225 2017

[68] I V Shtangeeva ldquoBehaviour of chemical elements in plantsand soilsrdquo Chemistry and Ecology vol 11 no 2 pp 85ndash951995

[69] O Miedico A Ferrara M Tarallo C Pompa D Biscegliaand A E Chiaravalle ldquoHazardous and essential trace ele-ments profile in the different soft tissues of Lithophagalithophaga (Linnaeus 1758) from Southern Adriatic Sea(Italy)rdquo Toxicological amp Environmental Chemistry vol 98no 8 pp 877ndash885 2016

[70] N DIrIlgen ldquoAccumulation of heavy metals in freshwaterorganisms assessment of toxic interactionsrdquo Turkish Journalof Chemistry vol 25 no 2 pp 173ndash179 2001

[71] D H Youssef and F T Tayel ldquoMetal accumulation bythreeTilapiaspp from some Egyptian inland watersrdquoChemistry and Ecology vol 20 no 1 pp 61ndash71 2004

[72] M S Rahman A H Molla N Saha and A Rahman ldquoStudyon heavy metals levels and its risk assessment in some ediblefishes from Bangshi River Savar Dhaka Bangladeshrdquo FoodChemistry vol 134 no 4 pp 1847ndash1854 2012

[73] A M Yousafzai F Ullah F Bari et al ldquoBioaccumulation ofsome heavy metals analysis and comparison of Cyprinuscarpio and Labeo rohita from Sardaryab Khyber Pak-htunkhwardquo BioMed Research International vol 2017 ArticleID 5801432 5 pages 2017

[74] M Ariyaee N A Azadi F Majnoni and B MansourildquoComparison of metal concentrations in the organs of twofish species from the Zabol Chahnimeh Reservoirs IranrdquoBulletin of Environmental Contamination and Toxicologyvol 94 no 6 pp 715ndash721 2015

[75] M Malakootian M S Mortazavi and A Ahmadi ldquoHeavymetals bioaccumulation in fish of southern Iran and riskassessment of fish consumptionrdquo Environmental HealthEngineering and Management vol 3 no 2 pp 61ndash68 2016

[76] B Mansouri M Ebrahimpour and H Babaei ldquoBio-accumulation and elimination of nickel in the organs of blackfish (Capoeta fusca)rdquo Toxicology and Industrial Healthvol 28 no 4 pp 361ndash368 2012

[77] A Khaled ldquoTrace metals in fish of economic interest fromthe west of Alexandria Egyptrdquo Chemistry and Ecologyvol 25 no 4 pp 229ndash246 2009

[78] B Kumar K Senthil Kumar M Priya D Mukhopadhyayand R Shah ldquoDistribution partitioning bioaccumulation oftrace elements in water sediment and fish from sewage fedfish ponds in eastern Kolkata Indiardquo Toxicological amp En-vironmental Chemistry vol 92 no 2 pp 243ndash260 2010

[79] H AliW Ali K Ullah et al ldquoBioaccumulation of Cu and Znin Schizothorax plagiostomus and Mastacembelus armatusfrom river swat river panjkora and river barandu inmalakand division Pakistanrdquo Pakistan Journal of Zoologyvol 49 no 5 pp 1555ndash1561 2017

[80] H Ali and E Khan ldquoAssessment of potentially toxic heavymetals and health risk in water sediments and different fishspecies of River Kabul PakistanrdquoHuman and Ecological RiskAssessment An International Journal vol 24 no 8pp 2101ndash2118 2018

[81] H Ali and E Khan ldquoBioaccumulation of non-essentialhazardous heavy metals and metalloids in freshwater fishRisk to human healthrdquo Environmental Chemistry Lettersvol 16 no 3 pp 903ndash917 2018

[82] H Ali W Ali K Ullah F Akbar and H Khan ldquoAssessmentof Cu and Zn in water sediments and in the carnivorous fishChanna gachua from river swat and River Barandu Mala-kand Division Pakistanrdquo Iranian Journal of Science andTechnology Transactions A Science pp 1ndash11 In press

[83] H Ali and E Khan ldquoBioaccumulation of Cr Ni Cd and Pbin the economically important freshwater fish Schizothoraxplagiostomus from three rivers of Malakand DivisionPakistan risk assessment for human healthrdquo Bulletin ofEnvironmental Contamination and Toxicology vol 102no 1 pp 77ndash83 2019

[84] A C Dwivedi A Tiwari and P Mayank ldquoSeasonal de-termination of heavymetals in muscle gill and liver tissues ofNile tilapia Oreochromis niloticus (Linnaeus 1758) from thetributary of the Ganga River Indiardquo Zoology and Ecologyvol 25 no 2 pp 166ndash171 2015


[85] M Javed and N Usmani ldquoStress response of biomolecules(carbohydrate protein and lipid profiles) in fish Channapunctatus inhabiting river polluted by ermal Power Planteffluentrdquo Saudi Journal of Biological Sciences vol 22 no 2pp 237ndash242 2015

[86] K A Al-Ghanim S Mahboob S Seemab et al ldquoMonitoringof trace metals in tissues of Wallago attu (lanchi) from theIndus River as an indicator of environmental pollutionrdquoSaudi Journal of Biological Sciences vol 23 no 1 pp 72ndash782016

[87] S Beebout ldquoRice health and toxic metalsrdquo in Rice Today2013

[88] L-M Cai Z-C Xu J-Y Qi Z-Z Feng and T-S XiangldquoAssessment of exposure to heavy metals and health risksamong residents near Tonglushan mine in Hubei ChinardquoChemosphere vol 127 pp 127ndash135 2015

[89] J Besante J Niforatos and A Mousavi ldquoCadmium in ricedisease and social considerationsrdquo Environmental Forensicsvol 12 no 2 pp 121ndash123 2011

[90] G Murtaza W Javed A Hussain A Wahid B MurtazaandG Owens ldquoMetal uptake via phosphate fertilizer and citysewage in cereal and legume crops in Pakistanrdquo Environ-mental Science and Pollution Research vol 22 no 12pp 9136ndash9147 2015

[91] A Sebastian and M N V Prasad ldquoCadmium minimizationin rice A reviewrdquo Agronomy for Sustainable Developmentvol 34 no 1 pp 155ndash173 2014

[92] K N Jallad ldquoHeavy metal exposure from ingesting rice andits related potential hazardous health risks to humansrdquoEnvironmental Science and Pollution Research vol 22 no 20pp 15449ndash15458 2015

[93] S Ke X-Y Cheng N Zhang et al ldquoCadmium contami-nation of rice from various polluted areas of China and itspotential risks to human healthrdquo Environmental Monitoringand Assessment vol 187 no 7 p 408 2015

[94] G Regassa and B S Chandravanshi ldquoLevels of heavy metalsin the raw and processed Ethiopian tobacco leavesrdquoSpringerPlus vol 5 no 1 p 232 2016

[95] L del Piano M Abet C Sorrentino et al ldquoUptake anddistribution of lead in tobacco (Nicotiana tabacum L)rdquoJournal of Applied Botany and Food Quality vol 82 no 1pp 21ndash25 2008

[96] E Gimeno-Garcıa V Andreu and R Boluda ldquoHeavy metalsincidence in the application of inorganic fertilizers andpesticides to rice farming soilsrdquo Environmental Pollutionvol 92 no 1 pp 19ndash25 1996

[97] Z Atafar A Mesdaghinia J Nouri et al ldquoEffect of fertilizerapplication on soil heavy metal concentrationrdquo Environ-mental Monitoring and Assessment vol 160 no 1ndash4pp 83ndash89 2010

[98] C F Ukpabi E Akubugwo K N Agbafor N A LebeN J Nwaulari and E D Nneka ldquoAppraisal of heavy metalcontents in commercial inorganic fertilizers blended andmarketed in Nigeriardquo American Journal of Chemistry vol 2no 4 pp 228ndash233 2012

[99] W E Stephens A Calder and J Newton ldquoSource and healthimplications of high toxic metal concentrations in illicittobacco productsrdquo Environmental Science amp Technologyvol 39 no 2 pp 479ndash488 2005

[100] R Bozhinova ldquoHeavy metal concentrations in soil and to-bacco plants following long-term phosphorus fertilizationrdquoBulgarian Journal of Agricultural Science vol 22 no 1pp 16ndash20 2016

[101] S A M A S Eqani R Khalid N Bostan et al ldquoHuman lead(Pb) exposure via dust from different land use settings ofPakistan a case study from two urban mountainous citiesrdquoChemosphere vol 155 pp 259ndash265 2016

[102] R Afrin M Y Mia M A Ahsan and A Akbor ldquoCon-centration of heavy metals in available fish species (bainMastacembelus armatus taki Channa punctatus and beleGlossogobius giuris) in the Turag river Bangladeshrdquo PakistanJournal of Scientific and Industrial Research Series B Bi-ological Sciences vol 58 no 2 pp 104ndash110 2015

[103] Q Mahmood J Wang A Pervez S S MeryemMWaseemand Z Ullah ldquoHealth risk assessment and oxidative stress inworkers exposed to welding fumesrdquo Toxicological amp Envi-ronmental Chemistry vol 97 no 5 pp 634ndash639 2015

[104] L Jarup ldquoHazards of heavy metal contaminationrdquo BritishMedical Bulletin vol 68 no 1 pp 167ndash182 2003

[105] M Barwick and W Maher ldquoBiotransference and bio-magnification of selenium copper cadmium zinc arsenicand lead in a temperate seagrass ecosystem from LakeMacquarie Estuary NSW AustraliardquoMarine EnvironmentalResearch vol 56 no 4 pp 471ndash502 2003

[106] K S Balkhair andM A Ashraf ldquoMicrobial contamination ofvegetable crop and soil profile in arid regions under con-trolled application of domestic wastewaterrdquo Saudi Journal ofBiological Sciences vol 23 no 1 pp S83ndashS92 2016

[107] M D Joesten D O Johnston J T Netterville andJ L Wood World of Chemistry BrooksCole Pacific GroveCA USA 1st edition 1990

[108] N Ercal H Gurer-Orhan and N Aykin-Burns ldquoToxicmetals and oxidative stress Part I mechanisms involved inmetal-induced oxidative damagerdquo Current Topics in Me-dicinal Chemistry vol 1 no 6 pp 529ndash539 2001

[109] AWilk E Kalisinska D I Kosik-Bogacka et al ldquoCadmiumlead and mercury concentrations in pathologically alteredhuman kidneysrdquo Environmental Geochemistry and Healthvol 39 no 4 pp 889ndash899 2017

[110] M Ebrahimpour M Mosavisefat and R Mohabbati ldquoAcutetoxicity bioassay of mercuric chloride an alien fish from ariverrdquo Toxicological amp Environmental Chemistry vol 92no 1 pp 169ndash173 2010

[111] M Salman R Rehman T Mahmud et al ldquoAssessment ofconcentration of lead cadmium chromium and selenium inblood serum of cancer and diabetic patients of PakistanrdquoJournal of the Chemical Society of Pakistan vol 33 no 6pp 869ndash873 2011

[112] A Elzwayie H A Afan M F Allawi and A El-ShafieldquoHeavy metal monitoring analysis and prediction in lakesand rivers state of the artrdquo Environmental Science andPollution Research vol 24 no 13 pp 12104ndash12117 2017

[113] A J Morgan ldquoCalcium-lead interactions involving earth-worms an hypothesisrdquo Chemistry and Ecology vol 2 no 3pp 251ndash261 1986

[114] R Johnston ldquoAquatic chemistry and the human environ-mentrdquo Chemistry and Ecology vol 2 no 2 pp 125ndash1691986


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exposure to heavymetals in the environment is a real threat toliving organisms [7]

Metal concentrations above threshold levels affect themicrobiological balance of soils and can reduce their fertility[8] Bioaccumulation of toxic heavy metals in biota of theriverine ecosystems may have adverse effects on animals andhumans [9] Higher levels of heavy metals in biota can havenegative effects on the ecological health of aquatic animalspecies and may contribute to declines in their populations[10] Heavymetals are strong neurotoxins in fish specieseinteraction of heavy metals with chemical stimuli in fish mayinterrupt the communication of fish with their environment[11] Heavy metals have been found associated with fishdeformities in both natural populations and in the labora-tory Generally such deformities have negative effects on fishpopulations because deformities affect their survival growthrates welfare and external image ese deformities in fishcan serve as excellent biomarkers of environmental heavymetal pollution [12] Hartl [13] remarks that ldquometals ofnatural or anthropogenic origin are ubiquitous in theaquatic environment and therefore understanding theirbehavior and interaction with aquatic organisms particu-larly fishes a major source of protein for human con-sumption is of a great socioeconomic importancerdquo

is article comprehensively reviews the different as-pects of heavy metals as hazardous materials with a specialfocus on their environmental persistence toxicity for livingorganisms and bioaccumulative potential e bio-accumulation of these elements and its implications forhuman health are discussed with a special coverage on fishrice and tobacco e article will serve as a valuable edu-cational resource for both undergraduate and graduatestudents and for researchers in environmental sciences

2 Metals and Their Essentiality for Life

Chemically metals are defined as ldquoelements which conductelectricity have a metallic luster are malleable and ductileform cations and have basic oxidesrdquo [14] Terms usually usedin relation to metals in biological and environmental studiesare metal metalloid semimetal light metal heavy metalessential metal beneficial metal toxic metal abundantmetal available metal trace metal and micronutrient [15]Metals have very diverse applications and play an importantrole in the industry-dominated human society Some metalshave critically important physiological and biochemicalfunctions in biological systems and either their deficiency orexcess can lead to disturbance of metabolism and thereforeto various diseases Some metals and metalloids are essentialfor (biological) life ey play important physiological andbiochemical roles in the body as they may be part of bio-molecules such as enzymes which catalyze biochemicalreactions in the body

21 Heavy Metals (HMs) According to Csuros and Csuros[16] a heavymetal is defined as ldquoametal with a density greaterthan 5 gcm3 (ie specific gravity greater than 5)rdquo Accordingto Duffus [15] ldquothe term ldquoheavy metalsrdquo is often used as a

group name for metals and semimetals (metalloids) that havebeen associated with contamination and potential toxicity orecotoxicityrdquo Very recently we have proposed a broaderdefinition for the term and heavy metals have been defined asldquonaturally occurring metals having atomic number greaterthan 20 and an elemental density greater than 5 gmiddotcmminus3rdquo [17]

22 Essential andNonessential HMs Regarding their roles inbiological systems heavy metals are classified as essential andnonessential Essential heavy metals are important for livingorganisms and may be required in the body in quite lowconcentrations Nonessential heavy metals have no knownbiological role in living organisms Examples of essentialheavy metals are Mn Fe Cu and Zn while the heavy metalsCd Pb and Hg are toxic and are regarded as biologicallynonessential [18ndash21] e heavy metals Mn Fe Co Ni CuZn and Mo are micronutrients or trace elements for plantsey are essential for growth and stress resistance as well asfor biosynthesis and function of different biomolecules suchas carbohydrates chlorophyll nucleic acids growth chem-icals and secondary metabolites [22] Either deficiency orexcess of an essential heavy metal leads to diseases or ab-normal conditions However the lists of essential heavymetals may be different for different groups of organisms suchas plants animals and microorganisms It means a heavymetal may be essential for a given group of organisms butnonessential for another onee interactions of heavymetalswith different organism groups are much complex [23]

23 Environmentally Relevant Most Hazardous HMs andMetalloids Heavy metals are among the most investigatedenvironmental pollutants Almost any heavy metal andmetalloid may be potentially toxic to biota depending uponthe dose and duration of exposure Many elements areclassified into the category of heavy metals but some arerelevant in the environmental context List of the envi-ronmentally relevant most toxic heavy metals andmetalloidscontains Cr Ni Cu Zn Cd Pb Hg and As [24] Heavymetal pollutants most common in the environment are CrMn Ni Cu Zn Cd and Pb [25] In 2009 China hassuggested four metals ie Cr Cd Pb Hg and the metalloidAs as the highest priority pollutants for control in the ldquo12th5-year plan for comprehensive prevention and control ofheavy metal pollutionrdquo [26] Some other heavy metals arealso hazardous to living organisms depending upon doseand duration of exposure For example Mansouri et al [27]have found Ag as more toxic than Hg to a freshwater fish

24 Sources of Heavy Metals in the Environment Sources ofheavy metals in the environment can be both naturalgeogeniclithogenic and anthropogenic e natural orgeological sources of heavy metals in the environment in-clude weathering of metal-bearing rocks and volcaniceruptions e global trends of industrialization and ur-banization on Earth have led to an increase in the an-thropogenic share of heavy metals in the environment [28]e anthropogenic sources of heavy metals in the






































Cabioticmedium (1)




BAC Cplant

Csoil (2)





3rd trophic level

2nd trophic level

1st trophic level

Preyfood


Preyfood


Bioaccumulation


Bioconcentra

tion

HMs

Sediments


Cd Pb Hg As

Biod

ilutio

n

Biom

agni

ficat

ion

Trophic transfer

Trophic transfer

HMs

HMs





























(3)





















Heavy metals(HMs)


Cr

Pb NiHMs

Cd

HMs



C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls








































Cabioticmedium (1)




BAC Cplant

Csoil (2)





3rd trophic level

2nd trophic level

1st trophic level

Preyfood


Preyfood


Bioaccumulation


Bioconcentra

tion

HMs

Sediments


Cd Pb Hg As

Biod

ilutio

n

Biom

agni

ficat

ion

Trophic transfer

Trophic transfer

HMs

HMs





























(3)





















Heavy metals(HMs)


Cr

Pb NiHMs

Cd

HMs



C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls





























Cabioticmedium (1)




BAC Cplant

Csoil (2)





3rd trophic level

2nd trophic level

1st trophic level

Preyfood


Preyfood


Bioaccumulation


Bioconcentra

tion

HMs

Sediments


Cd Pb Hg As

Biod

ilutio

n

Biom

agni

ficat

ion

Trophic transfer

Trophic transfer

HMs

HMs





























(3)





















Heavy metals(HMs)


Cr

Pb NiHMs

Cd

HMs



C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls






















Cabioticmedium (1)




BAC Cplant

Csoil (2)





3rd trophic level

2nd trophic level

1st trophic level

Preyfood


Preyfood


Bioaccumulation


Bioconcentra

tion

HMs

Sediments


Cd Pb Hg As

Biod

ilutio

n

Biom

agni

ficat

ion

Trophic transfer

Trophic transfer

HMs

HMs





























(3)





















Heavy metals(HMs)


Cr

Pb NiHMs

Cd

HMs



C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls









Cabioticmedium (1)




BAC Cplant

Csoil (2)





3rd trophic level

2nd trophic level

1st trophic level

Preyfood


Preyfood


Bioaccumulation


Bioconcentra

tion

HMs

Sediments


Cd Pb Hg As

Biod

ilutio

n

Biom

agni

ficat

ion

Trophic transfer

Trophic transfer

HMs

HMs





























(3)





















Heavy metals(HMs)


Cr

Pb NiHMs

Cd

HMs



C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls






























(3)





















Heavy metals(HMs)


Cr

Pb NiHMs

Cd

HMs



C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls




















(3)





















Heavy metals(HMs)


Cr

Pb NiHMs

Cd

HMs



C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls









(3)





















Heavy metals(HMs)


Cr

Pb NiHMs

Cd

HMs



C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls














Heavy metals(HMs)


Cr

Pb NiHMs

Cd

HMs



C

H

C N

O H

C

C

H

H H

S

M

S

C HH

CN C

H

C

H

O

CH2CH2

CH2CH2

C

COOH

H

H2N

H2N

COOH

C N

O

CH2

CH2

H

C OO

H

O

N

H

C O

O

H










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls










References































































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls






































































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls





































































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls








































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls









Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls




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EnvironmentalChemistryandEcotoxicologyofHazardous …downloads.hindawi.com/journals/jchem/2019/6730305.pdftence, bioaccumulation, and toxicity (Figure 2). Toxic substances which are