J. Appl. Environ. Biol. Sci., 8(12)15-22,2018 | ISSN: 2090-4274 |
Journal of Applied Environmental | |
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a LaboratoryofEnvironmentandAquaticBiology,DepartmentofSciencesandEnvironment Management,NanguiAbrogouaUniversity,Abidjan,Côted’Ivoire
Received: October 5, 2018 Accepted: November 30, 2018
Thepresentstudyaimatassessingthecontamination offish fromriverswherechemicalsusedin goldextraction byartisanalminersaredischarged.Thestudywasconductedon in thetownofHiréin thesouth ofCôted'Ivoire. Thistownisdominated bytheartisanalgold mining activities.Furthermore,thehealth risksassociated withthis contamination werealsobeassessed. Thesamplesoftwo fishes(Tilapia zilii and Oreochromis niloticus)were collected along threeriverscourse(Agbalé,TchebiandAkississo). Thesefishesarethemost consumed bythe population. Samples were persevered and taken tothelaboratoryfor analysis. Musclesand gills wereused for analysis. Thesamplefish tissues were analyzed byinductivelycoupled plasmamass spectrometry(copper and zinc);bycold vaporatomicfluorescencespectrometry(mercury)andbyultravioletdigestion (totalcyanide). The results obtained showed in the organs of the fish, a strong accumulation of pollutants (copper, zinc, total cyanide),preferentiallyin thegills,on allsites.Thecontentofthesepollutantsgenerallyexceedsthethreshold value tolerated for fish but also for humans. This isa limiting factor in the protein of the population of Hiré. Long-term consumption risks expose the population to contamination and therefore to the effects of these pollutants. KEY WORDS:artisanalgold mining,fishcontamination,health risks,heavymetals
Development ofeconomicsactivitiesofCôted’Ivoiretothemining sector hasled totheincreased of artisanalgold mining.Theseactivitiesarefrequentlyaccompaniedbyextensiveenvironmentaldegradation and deplorable socio-economic conditions, both during operationsand well after mining activitieshave ceased [1]. Indeed, artisanal miners employ rudimentary techniques for mineral extraction and often operate under hazardous, labour intensive, highly disorganized and illegal conditions. Human health impacts resulting from chemicals (mercury, cyanide, zinc, copper, etc.) use to extract gold. These chemicals polluted water and soils around sites and subsequently the food chain [2]. These pollutants are thus found in the tissues of plants and aquatic organisms. These fish, when ingested by man, contaminate it and expose it to the effects of the said pollutants. Trace elements (copper and zinc) play a biological role at low concentrations but become toxic at high levels. Others (cyanide and mercury) are considered to be trace pollutants of the environment and have deleteriousbiologicaleffectsevenatlowconcentrationson human health [1-3].
In Côte d'Ivoire, few studies have been carried out concerning the characterization of environmental pollution and the health impacts of artisanal and small-scale gold mining activities. The present study aim at assessingthecontamination offish fromriverswherechemicals(copper,mercury,zincandtotalcyanide)used in gold-washing are discharged. Furthermore, the health risks associated with this contamination will also be assessed.In ordertoachievetheseobjectives,thetown ofHiréwaschosen becauseoftheintensityofartisanal and small-scale gold mining activities in this zone compared to the other mining zones [4]. Specifically, measurementsofcopper,mercury,zincand totalcyanideconcentrationsin thegillsand muscletissuesofTilapia zilii andOreochromis niloticus, which werethemostconsumed fishes,and analysisoftherisksassociated with theirconsumption.
Study area
Thestudywascarriedin thetown ofHiré(06°15'08.6and06°10'00.0 Nand05°23'44.8to05°16'32.1
W) [5]. The sampling stations are the streams bordering gold mining sites of Tchebi, Agbalé and Akississo (Figure1).
*Corresponding author: Aman MESSOU, LaboratoryofEnvironment andAquaticBiology, Department of Sciences and EnvironmentManagement,NanguiAbrogouaUniversity,Abidjan,Côted’Ivoire. Email:messouaman@gmail.com/(225)07442995
Citation: Amenan Lydie Clarisse MANGOUA-ALLALI, Aman MESSOU, Tiangoua KONE, Lacina COULIBALY; 2018, Fish Contamination on Artisanal Gold Mining Area and Health Risks in Hiré, CôteD’ivoire; Journal of Applied Environmental and BiologicalSciences,8(12)15-22,2018.
Figure 1. Sampling sites
Collection and preparation of fish samples
Three specimensof Tilapia zilii and Oreochromis niloticus were fishing from each sampling stations. Theywereconsideredasrepresentativeoffish speciescommonlyconsumedin theareaunder study. Fish were then identified accordingtotheidentification keysof[6-7]andwerepreserved in an icebox andtransferredto thelaboratory,wherethesampleswerefrozen.Atlaboratory,eachspecimenwasweighed andmeasured bytotal length.
Preparation of samples and analysis were made according to FAO technical paper [8]. For metal analysis,frozenfish werepartiallythawed,and eachfishwasdissected using stainlesssteelinstruments.Muscles and gillsweretakenout;compositesamplesof25 to100g,respectivelyforsmall-sizeand large-sizeindividuals, wereused foranalysis.Thesamplefishtissueswereanalyzed byinductivelycoupled plasmamassspectrometry (copper (Cu)and zinc(Zn)); bycold vapor atomicfluorescencespectrometry(mercury(Hg) and byultraviolet digestion (totalcyanide(CNT)).
Thenormalityofthedatawasverified usingtheShapiro-Wilktest(softwareR) andhomogeneitywas verified by Levene's test (STATISTICA 7.1). The variation of the chemicals parameters measured between organs fishes was compared using ANOVA of Kruskal-Wallis. The Mann Whitney test was employed to indicate significant differences between both organs fishes. The statistical program used for both tests was R software3.1.1.Thesignificancelevelwasp<0.05.
Theevaluationofthehealth risktolocalpeoplein theareaofstudyposed bytheconsumption offishes wasbased onthedatafromthemusclesamples.Thecontentsofthepollutantscontained inthemusculartissues havebeenused forrisksassessment.
The daily dose of exposure (DDE) to chemical pollutants following consumption of fresh fish per individualwasdeterminedaccordingtotheequation 1[9-10].
J. Appl. Environ. Biol. Sci.,8(12)15-22,2018
CP | CCP*R | (1) | |||
---|---|---|---|---|---|
DDE | = | = | |||
BW | BW |
Where DDE(mg/kg/d):dailydoseofan individual'sexposuretochemicalpollutantsfromfish consumption ; CP(mg/kg/d):chemicalpollutantintakeperdayaftertheconsumption offishbyan individual; BW(kg):bodyweightofthefishconsumer(60kg)overtheentirelifetimealsoestimated at60years[11]; CCP(mg/kg):concentration ofchemicalparameterin fish ; R:yearlyfishconsumptionperperson,whichis14.45kgforCôted’Ivoire[12].
The methodology of estimating hazard quotient (HQ) provides indications of the human health risk level due to exposure to pollutants [10]. HQ is the ratio between daily dose of an individual's exposure to chemical pollutants from fish consumption and tolerable daily dose. If the HQ > 1, there is a potential risk related tothestudied metal[13].Thefollowingequation wasused toestimaterisk:
DDE (2)
HQ= TDD
Where HQ:Hazard quotient DDE(mg/kg/d):dailydoseofan individual'sexposuretochemicalpollutantsfromfish consumption; TDD(mg/kg/d):tolerabledailydose
Quantity of fish(QF) to be consumed for exposure to chemical pollutants QF is the maximum quantityoffish can be eating to attack tolerable dose [14]. The equation (3) was used to estimateQF.
TDD*BW*FBM
(3) QF =
CCP*R
Where QF(kg):Maximumquantityoffishcan beeatingbydaywithoutrisk; TDD(mg/kg/d):tolerabledailydose; BW(kg):bodyweightofthefishconsumer(60kg)overtheentirelifetimealsoestimated at60years[11]; FBM:Fish bodymass(kg); CCP(mg/kg):concentration ofchemicalparameterin fish; R:yearlyfishconsumptionperperson,whichis14.45kgforCôted’Ivoire[12].
RESULTS
The concentrationsof mercury, copper, zincand total cyanide in thegillsand muscular tissues of the speciesTilapia zilii and Oreochromis niloticus caughtintheAgbalé,TchebiandAkississoriversareillustrated inTable1.
Whatever theorgan, fish and sampling site, mercuryconcentrationsarewell belowtherecommended threshold(0.5mg/kg)foranyorgan,fish andsamplingsite.In fact,mercuryconcentrationsarebetween1.1*10-5 and 6*10-5 mg/kg. For Tilapia zilii from Akississo and Agbalé, and Oreochromis niloticus from Agbalé, the results indicate that Hg accumulates preferentially in the gills comparatively to Tilapia zilii and Oreochromis niloticus from Tchebi. The Kruskal-Wallis test showed no difference (p> 0.05) between the concentrations of mercuryobtained in thegillsandin muscle.
The concentrations of copper are above the threshold value (0.3 mg/kg) at any site. These concentrations recorded in the gills are higher to those of the muscle excepted Oreochromis niloticus from Akississo. In the gills, the minimum concentrations (0.53 mg/kg) of copper are recorded at Agbalé in Oreochromis niloticus, while the maximum concentrations (12.27 mg/kg) of copper in the same organ are recorded in Tilapia zilii fromTchebi.Atthemuscle,thelowconcentrations(0.36mg/kg)ofcopper in both fish speciesarerecorded atAgbalé.UnlikeintheTchebiTilapiazilii muscles,wherethehighestconcentrations(0.82
Citation: Amenan Lydie Clarisse MANGOUA-ALLALI, Aman MESSOU, Tiangoua KONE, Lacina COULIBALY; 2018, Fish
Contamination on Artisanal Gold Mining Area and Health Risks in Hiré, CôteD’ivoire; Journal of Applied Environmental and
BiologicalSciences,8(12)15-22,2018.
mg/kg)ofcopperarenoted.TheKruskalWallistestshowsadifference(p˂0.05)betweencopperconcentrations ingillsand muscle.
The Zn concentrations in the two organs of the different fish exceeded FAO and WHO limit (0.5 mg/kg).Itisalsonoted thatthezincconcentrationsrecorded in thegillsaresignificantlyhigherthan thoseofthe muscletissuesforallsites(Mann-Withney:p˂0.05).Inthegills,themaximumZnconcentration observed was 40.99mg/kgatAkississoin Tilapia zilii andtheminimumof7.93mg/kgfor Oreochromis niloticus collected at Akississo. At the muscle, the concentration of zinc is lowest (6.75 mg/kg) of Tilapia zilii from Tchebi, but, highest(9.40mg/kg)of Tilapia zilii atAgbalé.
The total cyanide concentrations at thetwo organs of the different fish are above the threshold value
(0.05 mg/kg). The total cyanide concentration accumulates preferentially in the gills than muscle. The low concentrations of total cyanide (0.72 mg/kg) are recorded at the muscle of Tilapia zilii from Agbalé, and the highest CNT concentrations content of Oreochromis niloticus from Tchebi was (4.81 mg/kg). The Kruskal Wallis test showed no difference (p> 0.05) between the total cyanide concentrations obtained in the gill and muscle.
Table 1.Heavy metals concentration in fish organs
TheDDEtoHg (Figure2A),Cu(Figure2B) arewell belowtolerabledailydose0.0002mg/kg/d,0.5 mg/kg/drespectively.ButtheDDEtoCNT(Figure2C)werehigherthan tolerabledailydose(0.056mg/kg/d).
J. Appl. Environ. Biol. Sci.,8(12)15-22,2018
Figure 2. Dailydose of exposure (DDE) andtolerable dailey dose toHg (A),Cu (B) and CNT(C)
Hazard quotient (HQ)
In thepresentstudy,theresultsofHQcalculated foreachoftheheavymetals(Hg,Cu and CNT)intwo fish species (Tilapia zilii and Oreochromis niloticus) are given in Table 2. The HQ to fish consumption is generallybelow1 for Hg and Cuin all fish at sampling points.UnlikeHQvalues for CNT in Akississofish’s exceeds1.
Parameter Havy Sampling points Threshold metals
value
Agbalé Tchebi Akississo
The QFrecorded from Agbalé siteranged from 0.59 for CNT to 539.31 (kg/day) for Hg with T. zilii (0.0085 kg), and from 0.35 for CNT to 162.22 (kg/day) for Hg with O. niloticus (0.0075 kg). The two fish species from Tchebi sitepresented high QF(803.02 kg/day) for Hg with T. zilii (0.0152kg)and lowQF(0.34 kg/day) for CNT with O. niloticus (0.00135 kg). T. zilii (0.00306 kg) and O. niloticus (0.00278 kg) showed higher QF(41.4 and 50.09 kg/dayfor Hg) and lower QFvalue(0.639 and 1.02kg/dayfor CNT) on Akississo site.
Table 3.Maximum quantity of fish to be consumed by day without risk (QF)
Concerning the level of contamination of fish Tilapia zilii and Oreochromis niloticus, analyzes of pollutants in the organs (muscular tissues and gills) showed strong accumulations of copper, zinc and total cyanide in these organs. What would mean that the fish would have accumulated these pollutants follows a contamination.Fish gillsaccumulated morepollutantsthan muscletissue.Thesesameobservationswerenoted by[15-16].These authorsshowed thatan accumulation ofchemical pollutantsin fish organs, especiallyatthe
Citation: Amenan Lydie Clarisse MANGOUA-ALLALI, Aman MESSOU, Tiangoua KONE, Lacina COULIBALY; 2018, Fish
Contamination on Artisanal Gold Mining Area and Health Risks in Hiré, CôteD’ivoire; Journal of Applied Environmental and
BiologicalSciences,8(12)15-22,2018.
gill,wasindicativeofthehigh presenceofthesepollutantsin theirlivingenvironmentorintheirdiet.However, theconcentrationsofHg, Cu, Zn and CNTin fish organsdiffer markedlyfrom sitetositeand from speciesto species.Thedifferencebetweensitesisduetothefrequencyofuseofchemicalstoextractgold[17].
Concerning the degree of accumulation of pollutants in fish species, Tilapia Zilii accumulated more pollutants than Oreochromis niloticus,irrespective ofthe sampling siteand theanalyzed organ. This could be explained bythefact that these fish not the same feedingmode. Thefish studied belong totrophic levels in a food chain. According to [18], this chain includes primaryconsumers who directlyharvest food from primary producers(vegetation, etc.)andsecondaryconsumerswhofeed on primaryconsumers(invertebratesand small crabs, etc.). Indeed according to a study conducted by [19], Oreochromis niloticus feeds mainly on phytoplankton.Hefilterstheseseedlingsintothewatercolumn.AsforTilapia zilii,ithasalarger dietin thatit feedsoninsects,molluscs,zooplankton,fish,macrophytes[20].Asaresult,thevarietyofthedietofTilapia zilii isoneofthefactorscontributingtoastrongaccumulation ofchemicalpollutantsbythisfish.Furthermore,[2122]showed thattheaccumulation ofchemicalpollutantsin fishorgansalsodepended on factorssuchasthelevel of water and sediment contamination, diet, size, sex, Behavior, eating habits and the reproductive cycle. Moreover,accordingto[23-24], benthicspeciesaccumulated morepollutantsbecausetheyliveinthesediments thatarethereservoirsofmanychemicalpollutants.
Theresultsindicatethattheriskofdanger fromfish consumption islessthan 1for Hg andCu, butis verycriticalregarding totalcyanide.Contamination oftheconsumer bypolluted fish shouldbetaken seriously. Accordingto[25],fishremainsan importantsourceofproteinforpopulations.Itshould berecalled thatfeeding populations is the source of their exposure to chemical pollutants [26]. For [27], due to their resistance to biodegradation,theirpersistenceand toxicity,chemicalpollutantscanbeconcentrated in themusculartissuesof living organismsand causeconsiderableecologicaland publichealth damage.
ThequantitiesofO. niloticus fromTchebiandthetwofishspeciescaughtinAkississohavethelowest amountinrelationtotheestimated quantityoffishtobeconsumed perdayperindividualregarding tomercury. Thosesmallamountsarerelated tothefactthatthosefisheshaveaccumulatedhigh concentrationsofmercury. Asfor contamination bycopper,allfishescaughtin Tchebiand Agbaléhavethelowestquantitiesoffish tobe consumed. This would mean that the fish in these sites were more impacted by copper, so an uncontrolled feedingoffish fromthesesiteswould exposetheconsumer more.For totalcyanidecontamination,fishesfrom theTchebiandAgbaléstreamshavethelowest amountsoffish tobeconsumed.Thatquantitymightbedueto theaccumulation oftotalcyanidein thefishmuscles.For[3],thesesmallamountsoffishtoconsumereflectthe high toxicity of these pollutants to which consumers are exposed. There is then a relationship between the exposure ofthe populations and the heavy metals concentration in the flesh of the fish to be consumed [28]. Moreover,thosemaximumquantitiesoffisharehigherthan thetotalnationalaveragedailyconsumptioninCôte d'Ivoire. These quantities of fish that should not be exceeded in consumption are a limiting factor to the consumptionoftheHirépopulation,eveniftheprobabilityofconsuming such aquantityoffishperdayislow.
Chemical pollutants preferentially concentrate in the gills than the muscle. In addition, Tilapia zilii concentrated morepollutantsofOreochromis niloticus.Thehazardsquotientdeterminedclearlyshowsthatthe dailyconsumption of fish exposes consumerstohigh health risksbecause thelevels of these metalsareabove standards.Theriskofaccumulationofthesepollutantsin thebodyisrealand theadverseeffectstobefeared.In view of all the above, we recommend that the Hiré population not consume Tilapia zilii and Oreochromis niloticus fish from Tchebi and Akississo, to the competent authorities in this area, to regulate gold-washing activitiesin order topreservethewater and thefishing resourcesofthepollution ofthechemicalsused in this activity.
Thisstudyhasbeen supported bySida-UNESCOproject onabandoned minesin sub-Saharan African countries. We are very grateful to the Minister in charge of Mines for data, permission to access and sampling.Wethank theSanitationand EnvironmentalEngineering researchteammembersfor theirhelpduring thefield datacollecting.
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