GENERELLE ASPEKTE

Seasonal bioaccumulation of toxic trace elementsin economically important fish species from the Caspian Seausing GFAAS

Aziz A. Fallah • Fariba Zeynali • S. Siavash Saei-Dehkordi •

Mohammad Rahnama • Tina Jafari

Received: 23 October 2010 / Accepted: 8 December 2010 / Published online: 15 February 2011� Bundesamt fur Verbraucherschutz und Lebensmittelsicherheit (BVL) 2011

Abstract This study aimed to determine the con-centrations of aluminium, cadmium, lead and nickelin edible muscle of three commercially valuable fishspecies (Rutilus frisii kutum, Liza aurata and Cyprinuscarpio) from four fishing sites of Iranian coastal watersof the Caspian Sea during winter and summer. Thesamples were analyzed using graphite furnace atomicabsorption spectrometry (GFAAS) after wet-ashingdigestion. The results were expressed as lg/g of wetweight. The resulted range of metals in fish specieswas between 0.89–2.46 lg/g for aluminium,0.03–0.17 lg/g for cadmium, 0.21–0.38 lg/g for leadand 0.12–0.52 lg/g for nickel. Seasonal variationinfluenced concentration of the metals in fish sam-ples of some fishing sites. The highest concentrationsfound were 4.63 lg/g for aluminium in winter and0.82 lg/g for lead in summer in Cyprinus carpio; whilecadmium (0.49 lg/g) and nickel (1.14 lg/g) were the

highest in Rutilus frisii kutum in winter. This demon-strates that estimated daily and weekly intakes ofaluminium, lead and nickel and estimated monthlyintake of cadmium via consumption of fish flesh arebelow the established PTDI, PTWI and PTMI values.

Keywords Toxic elements � Food safety �Seasonal variation � Caspian Sea � GFAAS

1 Introduction

Owing to consumers demand for high-quality heal-thy food, seafood products play an important role ina balanced human diet. They are rich in protein andcontain high portions of valuable x-3 polyunsatu-rated fatty acids such as eicosapentaenoic acid (EPA)and docosahexaenoic acid (DHA) known to supportgood health (Polat et al. 2009; Kaya and Turan 2010).The American Heart Association (AHA) advocatesconsumption of fish at least twice a week for generalpopulation in order to prevent cardiovascular dis-eases (Kris-Etherton et al. 2002).

Agricultural, industrial and municipal wastes,vehicle emission via shipping traffic, geochemicalstructure and mining of metals can be a potentialsource of metals pollution in the aquatic environ-ment. The pollutants are bio-accumulated by aquaticinhabitants, and subsequently transferred to humanthrough the food chain. Hence, regular monitoringof chemical quality of aquatic organisms, speciallythe concentrations of toxic heavy metals, is veryimportant for human health (Demirak et al. 2006;

A. A. Fallah (&) � S. S. Saei-DehkordiDepartment of Food Hygiene and Quality Control,Faculty of Veterinary Medicine, Shahrekord University,Shahrekord 34141, Irane-mail: fallah.aziz55@yahoo.com

F. ZeynaliDepartment of Food Science and Technology,Faculty of Agriculture, Urmia University, Urmia 1177, Iran

M. RahnamaDepartment of Food Hygiene and Quality Control,Faculty of Veterinary Medicine, University of Zabol,Zabol 98615, Iran

T. JafariEsfahan University of Medical Sciences,School of Medicine, Esfahan 81745, Irane-mail: tinajafari1357@yahoo.com

J. Verbr. Lebensm. (2011) 6:367–374DOI 10.1007/s00003-011-0666-7

Journal fur Verbraucherschutz und LebensmittelsicherheitJournal of Consumer Protection and Food Safety

123

Erkan et al. 2010; Ozden et al. 2010). Fish have beenfound to be good indicators of heavy metal con-tamination in aquatic ecosystems because theyoccupy different trophic levels and are of differentsizes and ages (Burger et al. 2002). Studies demon-strated that the accumulation of heavy metals in fishtissues depends on many factors, such as environ-mental conditions (pH, salinity, temperature and,etc.), nourishment source, biological variations(species, sex, size and age) and seasonal changes(Carvalho et al. 2005; Zeynali et al. 2009).

Heavy metals such as aluminium (Al), cadmium(Cd), lead (Pb) and nickel (Ni) are readily transferredthrough food chains while do not serve any essentialbiological function. They are harmful for humanwhen ingested over a long time period (Liu 2003;Çelik and Oehlenschlager 2007). Prolonged or highdose exposure of Al may induce lung fibrosis, osteo-malacia in adults and defective bone mineralizationin children, dialysis dementia, and ferric-indepen-dent microcytic anaemia (Reilly 2002; Barton 2008).Accumulation of Cd in the human body may induceskeletal damage, kidney dysfunction and reproduc-tive deficiencies. Intake of Pb may increase bloodpressure and cardiovascular disease in adults; andcause reduced cognitive development and intellec-tual performance in children (Uluozlu et al. 2009).Acute Ni exposure is associated with a variety ofclinical symptoms including gastrointestinal distur-bances (nausea, vomiting, abdominal discomfortand diarrhoea), visual disturbance (temporary lefthomonymous hemianopia), headache, giddiness,wheezing and cough. Chronic intake of Ni and itscompounds are associated with an increased risk oflung cancer (EVM 2003).

The Caspian Sea is the largest enclosed body ofwater in the world with a surface area of about436,000 km2. The coastlines of the Caspian Sea areshared by Iran, Azerbaijan, Kazakhstan, Russia andTurkmenistan (Mora et al. 2004; Zeynali et al. 2009).Referring to scientific literature, very few data havebeen published about the accumulation of toxicelements in fish of the Caspian Sea. Additionally, fishhas an important role as a source of protein in thediet of people in northern states of Iran. Therefore,this study was aimed to determine the concentra-tions of Al, Cd, Pb and Ni in edible muscle offrequently consumed fish species, namely Caspianwhite fish (Rutilus frisii kutum), golden gray mullet(Liza aurata) and common carp (Cyprinus carpio),collected from different fishing sites of Iraniancoastal waters of the Caspian Sea in two separateseasons.

2 Materials and methods

2.1 Reagents

All reagents were of analytical grade unless other-wise stated. Nitric acid (67–69 %) and hydrogenperoxide (30 %) were of suprapure quality andobtained from Romil Ltd. (Cambridge, UK) and Merck(Darmstadt, Germany), respectively. Stock standardsolutions of Al, Cd, Pb and Ni were purchased fromMerck (Darmstadt, Germany) in concentrations of1,000 mg/l. Double distilled deionised water (Milli-QMillipore 18.2 X/cm resistivity) was used in theexperiment. All glassware were soaked overnight indiluted nitric acid (1/9, v/v), and rinsed carefully withdouble deionised water prior to use.

2.2 Apparatus

A PerkinElmer model 4100 atomic absorption spec-trometer (Norwalk, CT, USA) equipped withdeuterium background corrector and HGA graphitefurnace was used in this study. Pyrolytic-coatedgraphite tubes (PerkinElmer Part No. 091504) with anintegrated platform were employed. High purityargon was used as inert gas. Samples were injected tothe furnace using a PerkinElmer AS-800 automaticsampler. The experimental analytical conditions fordetermination of Al, Cd, Pb and Ni by graphite fur-nace atomic absorption spectrometry (GFAAS) aredepicted in Table 1.

2.3 Collection of the samples

In this study, 120 fresh samples of three most dietaryand economically important fish species, namelyCaspian white fish (Rutilus frisii kutum), golden graymullet (Liza aurata) and common carp (Cyprinus car-pio), were collected from four fishing sites (Chaloos,Anzali, Roodsar and Fereidonkenar; Fig. 1) of Iraniancoastal waters of the Caspian Sea during winter (asrainy season) and summer (as dry season) in 2008.The samples were brought to the laboratory on iceinside an ice chest. Then, the muscle samples weretaken, packed in polyethylene pouches and stored at-20 �C prior to analysis.

2.4 Digestion procedure

Digestion of fish samples was carried out by usinghigh-pressure decomposition vessels, known asdigestion bomb, according to the method of ourprevious study (Saei-Dehkordi et al. 2010) with some

368 A. A. Fallah et al.

123

modifications. Briefly, a homogenized sample (1 g)was mixed with 6 ml of concentrated nitric acid and2 ml of hydrogen peroxide in a Teflon container. Thesystem was heated up to 130 �C for 120 min. Aftercooling to ambient temperature, the solution wasfiltered through a 0.22 lm acid-resistant cellulosenitrate membrane, followed by transfer to a 25 mlvolumetric flask and made up to volume with doubledeionised water. Blank digest was also carried out inthe same way. The metals were determined againstaqueous standards.

2.5 Validation of analytical methods

Homogenized samples of different fish species werespiked with various metal concentrations for therecovery repeatability tests and verification of theanalytical methodology. All runs were carried out in

triplicate. The results revealed good recoveries ofspiked samples and demonstrated the accuracy of theanalytical methods (Table 2).

2.6 Determination of detection limit

The detection limit of each method was defined asthe concentration corresponding to three times thestandard deviation of ten reagent blanks (Mendilet al. 2010). The values were found to be 0.57 lg/l(0.014 lg/g) for Al, 0.12 lg/l (0.003 lg/g) for Cd,0.44 lg/l (0.011 lg/g) for Pb and 0.38 lg/l (0.009 lg/g)for Ni.

2.7 Statistical analysis

The data were statistically analyzed using the t test ofGraphPad Prism software (version 3) to evaluate dif-ferences between element concentrations in winterand summer. The levels were considered significantlydifferent at p\0.05.

Table 1 Working conditions for the determination of metals by GFAAS

Al Cd Pb Ni

Wave length (nm) 309.3 228.8 283.3 232.2

Slit width (nm) 0.5 0.7 0.5 0.2

Lamp current (mA) 25 8 10 18

Argon flow (ml/min) 250 250 250 250

Modifier Mg(NO3)2 Pd (NO3)2 ? Mg(NO3)2 NH4H2PO4 Mg(NO3)2Sample volume (ll) 20 20 20 20

Modifier volume (ll) 5 10 5 5

Replicate injections 3 3 3 3

Fig. 1 The fishing sites of Iranian Coastal waters of the CaspianSea

Table 2 Recoveries of the metals spiked to fish samples(mean ± SEM; n = 3)

Element Spikedconcentration(lg/g)

Recoveryconcentration(lg/g)

Percentage ofrecovery (%)

Al 0.50 0.48 ± 0.01 96

1.00 0.93 ± 0.03 93

3.00 2.81 ± 0.02 94

Cd 0.025 0.023 ± 0.002 92

0.50 0.048 ± 0.003 96

0.100 0.095 ± 0.005 95

Pb 0.150 0.140 ± 0.021 93

0.300 0.273 ± 0.040 91

0.450 0.432 ± 0.031 96

Ni 0.060 0.057 ± 0.003 95

0.120 0.111 ± 0.002 92

0.240 0.223 ± 0.005 93

Toxic elements in fish from the Caspian Sea 369

123

3 Results and discussion

3.1 Concentrations of Al, Cd, Pb and Ni in fishsamples

Without taken into account the fishing sites, theaverage concentrations of the Al, Cd, Pb and Ni infish species caught from Iranian coastal waters of theCaspian Sea are depicted in Table 3. The highest andlowest mean concentrations of Al were observed inCyprinus carpio (2.47 lg/g of wet weight) and Lizaaurata (0.89 lg/g of wet weight), respectively. Agahet al. (2009) reported the Al content of different fishspecies from the Persian Gulf between 1 and 3 lg/g ofwet weight which is comparable with the findings ofthe present study. In a previous survey (Ranau et al.2001), the majority of fish species caught from NorthSea contained Al contents close to 0.1 lg/g of wetweight. Muller et al. (1998) determined the Al con-centrations of four fish species from German market,between 2.1–7.6 lg/g of wet weight (herring),1.5–5.8 lg/g (trout), 2.4–7.3 lg/g (mackerel) and2.2–7.2 lg/g (sardine).

The mean concentrations of Cd in fish samplesfrom the Caspian Sea ranged between 0.04 lg/g ofwet weight in Liza aurata to 0.17 lg/g of wet weightin Rutilus frisii kutum (Table 3). In a previous study(Anan et al. 2005), the mean contents of Cd in fishspecies sampled at 2000 and 2002 from the Iraniancoastal waters of the Caspian Sea were 0.008 lg/g inRutilus rutilus caspius, 0.002 lg/g in Neogobius sp.,0.013 lg/g in Clupeonella delicatula and 0.001 lg/g inRutilus frisii kutum. Also, Agusa et al. (2004) reportedthat the concentration of Cd in muscle of sturgeonscollected from Caspian Sea during 2000–2001 wasbetween BDL (below detection limit) and 0.002 lg/g.The aforementioned results reveal remarkably lowerCd contaminations compared with our findings.Mendil et al. (2010) determined the Cd contents infish species from the Yesilırmak River in Tokat(Turkey) ranging from lower than 0.54 lg/g forunpolluted areas to 0.75 lg/g for polluted areas.

The mean concentrations of Pb in fish species fromthe Caspian Sea were 0.38, 0.21 and 0.38 lg/g of wetweight in Rutilus frisii kutum, Liza aurata and Cyprinuscarpio, respectively (Table 3). In previous studies onfish species from the Caspian sea (Agusa et al. 2004;Anan et al. 2005), the concentrations of Pb in Aci-penser persicus, Rutilus rutilus caspius, Neogobius sp.,Clupeonella delicatula and Rutilus frisii kutum were0.006, 0.005, 0.007, 0.015 and 0.008 lg/g, respec-tively, which are notably lower than results of thepresent survey. Juresa and Blanusa (2003) reported Ta

ble

3Conce

ntrations(lg/g

ofwet

weight)ofAl,Cd,Pb

andNiin

fish

spec

iesfrom

Iran

ianco

astalwatersoftheCaspianSea

Spec

ies

na

Al

Cd

PbNi

Winter

Summer

Mea

nb

Winter

Summer

Mea

nbWinter

Summer

Mea

nb

Winter

Summer

Mea

nb

Rutilusfrisii

kutum

201.53

±0.23c

0.97

±0.08d

1.25

±0.13

0.27

±0.07c

0.07

±0.01d

0.17

±0.04

0.52

±0.04c

0.22

±0.04d

0.38

±0.04

0.54

±0.13

0.49

±0.11

0.52

±0.09

Liza

aurata

201.34

±0.17c

0.45

±0.06d

0.89

±0.11

0.03

±0.00

0.04

±0.00

0.03

±0.00

0.25

±0.03

0.17

±0.03

0.21

±0.02

0.15

±0.03

0.10

±0.02

0.12

±0.02

Cyp

rinus

carpio

203.62

±0.43c

1.31

±0.18d

2.46

±0.29

0.13

±0.03c

0.05

±0.01d

0.09

±0.02

0.39

±0.04

0.36

±0.07

0.38

±0.04

0.48

±0.08

0.39

±0.07

0.44

±0.05

aNumber

ofsamplesin

each

season

bMea

nsofwinteran

dsummer

c,d

Mea

ns

±SEM

indicatesignificantdifferen

ces(p

\0.05)betwee

nwinteran

dsummer

370 A. A. Fallah et al.

123

that Pb contents in fish species from the Adriatic Searanged between 0.007 and 0.150 lg/g of wet weight.In another study (Ozturk et al. 2009), mean Pb con-centration in muscle of Cyprinus carpio from AvsarDam Lake in Turkey was 2.14 lg/g of wet weight,which is notably higher than our results.

The mean concentration levels of Ni in fish speciesfrom Caspian Sea were found to be 0.52, 0.12 and0.44 lg/g of wet weight in Rutilus frisii kutum, Lizaaurata and Cyprinus carpio, respectively (Table 3). Inthe literature Ni levels have been reported in therange of 0.73–6.11 lg/g of dry weight in tropicalmarine fish species from the Bay of Bengal (Sharifet al. 1993), 0.54–1.84 lg/g of wet weight in demersalfish species from Iskenderun Bay, Turkey (Yilmazet al. 2010) and 1.1–10.2 lg/g of wet weight in fishspecies from polluted and unpolluted areas ofYesilırmak River in Tokat, Turkey (Mendil et al. 2010).

As seen above, the level of metals (Al, Cd, Pb andNi) in fish is different from one study to another.These variations may be ascribed to different factorssuch as geographical or geological differences, ana-lytical techniques employed and differences inpollution. Moreover, the possible high number ofmud volcanoes in the Caspian Sea could be a naturalsource of variations in pollution.

3.2 Effect of season on metal concentrations

Referring to scientific literature, no data has beenpublished on the concentration of the elements Al,Cd, Pb, Ni and other heavy metals in aquatic organ-isms from the Caspian Sea concerning seasonalvariations. Several studies conducted in other aquaticzones of the world indicated the seasonal changes ofmetal concentration levels in tissues of aquaticorganisms (Yilmaz and Yilmaz 2007; Ersoy and Çelik2009; Erkan et al. 2010; Ozden et al. 2010; Saei-Dehkordi et al. 2010). It has been stated that seasonalvariation of metal concentrations might be due toeither internal biological cycles of the organisms(growth and reproductive cycles) or changes in tem-perature and availability of the metals in the aquaticenvironment (Yilmaz and Yilmaz 2007; Ersoy andÇelik 2009). The high level of metals in aquaticorganisms in rainy seasons may be caused by con-siderable rainfall which rinses pollutants into thewater and increases metal concentrations (Duralet al. 2007; Ersoy and Çelik 2009).

According to Table 4, the highest Al content wasobserved in Cyprinus carpio (4.63 lg/g of wet weight)from Chaloos fishing site at winter, while the lowestlevel belonged to Liza aurata (0.28 lg/g of wet Ta

ble

4Conce

ntrations(lg/g

ofwet

weight)ofAl,Cd,Pb

andNiin

fish

spec

iesfrom

differen

tfishingsitesoftheCaspianSea

Fishingsite

Spec

ies

na

Al

Cd

PbNi

Winter

Summer

Winter

Summer

Winter

Summer

Winter

Summer

Chaloos

Rutilusfrisiiku

tum

52.82

±0.55b

0.94

±0.25c

0.36

±0.11b

0.05

±0.01c

0.44

±0.03b

0.10

±0.02c

0.39

±0.13

0.43

±0.16

Liza

aurata

51.19

±0.44

0.62

±0.11

0.04

±0.01

0.03

±0.01

0.35

±0.05b

0.09

±0.03c

0.09

±0.04

0.06

±0.03

Cyp

rinusca

rpio

54.63

±0.88b

1.76

±0.63c

0.21

±0.05b

0.04

±0.02c

0.38

±0.04b

0.09

±0.02c

0.45

±0.16

0.37

±0.15

Anzali

Rutilusfrisiiku

tum

51.35

±0.23b

0.74

±0.09c

0.06

±0.01

0.04

±0.01

0.53

±0.10

0.39

±0.10

1.14

±0.38

0.98

±0.33

Liza

aurata

52.01

±0.37b

0.54

±0.14c

0.02

±0.01

0.02

±0.01

0.15

±0.04

0.10

±0.02

0.09

±0.03

0.12

±0.05

Cyp

rinusca

rpio

53.93

±0.65b

1.59

±0.24c

0.04

±0.01

0.04

±0.01

0.37

±0.10

0.44

±0.11

0.41

±0.22

0.39

±0.20

Roodsar

Rutilusfrisiiku

tum

50.76

±0.09c

1.21

±0.12b

0.04

±0.00c

0.14

±0.03b

0.71

±0.05b

0.31

±0.09c

0.13

±0.04

0.12

±0.03

Liza

aurata

50.95

±0.13b

0.28

±0.10c

0.02

±0.01c

0.07

±0.01b

0.12

±0.05c

0.38

±0.06b

0.11

±0.06

0.14

±0.04

Cyp

rinusca

rpio

51.30

±0.25

0.99

±0.07

0.01

±0.00c

0.09

±0.01b

0.39

±0.07c

0.82

±0.11b

0.48

±0.15

0.63

±0.18

Fereidonkenar

Rutilusfrisiiku

tum

51.20

±0.27

0.97

±0.10

0.49

±0.14b

0.06

±0.01c

0.43

±0.10b

0.08

±0.01c

0.50

±0.14

0.43

±0.17

Liza

aurata

51.19

±0.23b

0.35

±0.08c

0.06

±0.01b

0.01

±0.00c

0.36

±0.08b

0.10

±0.01c

0.29

±0.05b

0.07

±0.02c

Cyp

rinusca

rpio

54.61

±0.59b

0.91

±0.19c

0.25

±0.07b

0.04

±0.02c

0.43

±0.07b

0.11

±0.02c

0.59

±0.11b

0.18

±0.04c

aNumber

ofsamplesin

each

season

b,c

Mea

ns

±SEM

indicatesignificantdifferen

ces(p

\0.05)betwee

nwinteran

dsummer

Toxic elements in fish from the Caspian Sea 371

123

weight) from Roodsar fishing site at summer. There isno information about maximum allowable limit of Alin Iranian and international standards. Our resultsdemonstrated that about 66.6 % of the samples fromdifferent fishing sites had significantly higher(p\0.05) Al content in winter comparing tosummer.

For Cd contents, the highest and lowest levelsbelonged to Rutilus frisii kutum (0.49 lg/g of wetweight) at winter and Liza aurata (0.01 lg/g of wetweight) at summer, respectively, which both of thespecies were from Fereidonkenar fishing site(Table 4). Considering the maximum permissiblelimit of the European Commission (EC 2006) for Cd inFish, i.e. 0.05 lg/g of wet weight, 41.6 % of the sam-ples from different fishing sites had higherconcentration of Cd than EC regulation. Table 4shows that Cd content was significantly higher(p\0.05) in winter comparing to summer for about41.6 % of the samples from different fishing sites.

The highest level of Pb in analyzed samples per-tained to Cyprinus Carpio (0.82 lg/g of wet weight)from Roodsar fishing site at summer, while the leastlevel was found in Rutilus frisii kutum (0.08 lg/g ofwet weight) from Fereidonkenar fishing site at sum-mer (Table 4). Considering the maximum permissiblelimit of European Commission (EC 2006) for Pb(0.3 lg/g of wet weight), 62.5 % of the analyzedsamples exceeded the limit. The results showed thatthere was significant difference (p\0.05) betweenwinter and summer concentration levels of Pb in 75 %of the fish samples from different fishing sites(Table 4).

The highest content of Ni was detected in Rutilusfrisii kutum (1.14 lg/g of wet weight) from Anzalifishing site at winter, while the lowest level was

measured in Liza aurata from Chaloos fishing site atsummer (Table 4); however, these are far below theaccepted limit of 76 lg/g of wet weight (FDA 1993).Also in most of the samples (83.3 %) from differentfishing sites, no significant difference (p[0.05) wasobserved between winter and summer levels of Ni.

3.3 Evaluation of exposure to the metals

The annual fish consumption per capita in Iran hasbeen reported as 7.62 kg in 2009 (Annual FisheryStatistics 2010). Therefore, the average daily fishconsumption in Iran is 21 g/person, which is equiva-lent to 147 g/week. In order to evaluate the potentialhazardous human exposure to the toxic trace metalsthrough the consumption of fish flesh, the estimateddaily/weekly intakes (EDI/EWI) of Al, Pb and Ni; andestimated monthly intake (EMI) of Cd were comparedwith provisional tolerable daily/weekly intake (PTDI/PTWI) and provisional tolerable monthly intake(PTMI) of the metals, respectively (Table 5). Accordingto Joint FAO/WHO Expert Committee on Food Addi-tives (JECFA), the PTWI of Al is 1 mg/kg of bodyweight (European Food Safety Authority 2008). ThePTWI for Pb and Cd were 25 and 7 lg/kg of bodyweight established by FAO/WHO (2004). But in viewof the long half-life of Cd, in the meeting that washeld in Geneva (Switzerland) at June 2010, JECFAannounced that the tolerable intake of Cd should beassessed over a period of at least 1 month; andestablished a PTMI of 25 lg/kg of body weight (FAO/WHO 2010). For Ni, WHO (1993) recommends a PTWIof 35 lg/kg of body weight. As can be seen in Table 5,the calculated EDI and EWI values of Al, Pb and Ni;and calculated EMI value of Cd for fish samples inpresent survey are far below the established limits.

Table 5 The estimated daily and weekly intakes of Al, Pb and Ni and estimated monthly intake of Cd for the fish samples from theCaspian Sea

Element PTWIa PTWIb PTMIc PTMId PTDIe EDIf EWIg EMIh

Winter Summer Winter Summer Winter Summer

Al 1,000 70,000 – – 10,000 45.43 19.11 318.01 133.77 – –

Cd – – 25 1750 – – – – – 90.30 33.60

Pb 25 1,750 – – 250 8.12 5.25 56.84 36.75 – –

Ni 35 2,450 – – 350 8.19 6.86 57.33 48.02 – –

a Provisional tolerable weekly intake (lg/week/kg body weight)b PTWI for an adult person (lg/week/70 kg body weight)c Provisional tolerable monthly intake (lg/month/kg body weight)d PTMI for an adult person (lg/month/70 kg body weight)e Permissible tolerable daily intake (lg/day/70 kg body weight)f Estimated daily intake (lg/day/70 kg body weight

372 A. A. Fallah et al.

123

4 Conclusions

This study determined the concentrations of Al, Cd,Pb and Ni in edible muscle of three commerciallyimportant fish species captured from different fish-ing sites of Iranian coastal waters of the Caspian Sea.The results indicate that: (a) more than 60 % of theanalyzed fish samples would not be marketable inthe EU and (b) the metal content (except Ni) variessignificantly as a function of season. However, itshould be considered that although the EWI of Al, Pband Ni and EMI of Cd are lower than the legislatedlimits; the role of the lower consumption of fish percapita per year in Iran should not be overlooked. Themain reason for the high concentration of toxic tracemetals (according to EC regulation) seems to be thedisposal of wastes from different sources (industrialunits, marine traffic and, etc.) to aquatic ecosystemsof the studied regions. Therefore, to improve theconditions to a safer level for human consumption,regular monitoring programs should be conductedin future.

Acknowledgments A special thank goes to Mr. Aman A. Ja-fari for his help in editing the manuscript. This study wasfinancially supported by Urmia University.

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