Egyptian Journal of Aquatic Research (2012) 38, 67–75
National Institute of Oceanography and Fisheries Egyptian Journal of Aquatic Research
http://ees.elsevier.com/ejar www.sciencedirect.com
FULL LENGTH ARTICLE Risk probability due to heavy metals in bivalve from Egyptian Mediterranean coast
Ahmed El Nemr *, Azza Khaled, Abeer A. Moneer, Amany El Sikaily
Environmental Division, National Institute of Oceanography and Fisheries, Kayet Bey, El-Anfoushy, Alexandria, Egypt
Available online 21 December 2012
KEYWORDS Abstract An assessment of marine contamination by eight heavy metals (Al, Cd, Co, Cr, Cu, Ni, Pb, Heavy metals; and Zn) made along the Egyptian Mediterranean coast. Also, risk probability due to heavy metals Mediterranean; contamination in bivalve was investigated. The bivalve samples collected in April 2007 from nine Bivalve; hot spot locations started at El-Mex and ended at Port-Said along Mediterranean coast. The recorded Health risk; average concentrations of Al, Cd, Co, Cr, Cu, Ni, Pb, and Zn were 137.8 ± 147.4, 0.09 ± 0.04, Egypt 2.45 ± 1.29, 8.49 ± 5.19, 3.82 ± 2.21, 10.28 ± 4.09, 0.24 ± 0.15, and 21.87 ± 21.38 lgg 1 dry weight, respectively. In spite of the mollusks species, El-Mex exhibited the highest metal pollution index (MPI), which is expected due to the presence of industrials and agriculture drain near El- Mex location, followed by Port-Said and Abu-Qir stations that suffer from many industrials, marine transportation, fisheries and human activities. Western Harbor and Damietta stations recorded the lowest MPI. Principal component analysis (PCA) and cluster analysis were applied to highlight the relationships between metals. The dendrograms of the cluster analysis confirm the results obtained with PCA. Indeed, depending on the statistical analysis, the studied metals were grouped into two groups, the first group contains Co, Pb, Zn, Cu, Cd and Ni, and the second group includes the remain- ing two studied metals (Al and Cr). Risk probability study showed that the risk quotients for Cd, Cu, Ni, Pb, and Zn in both the best-case and worst-case scenarios do not cause adverse effect for either low or high consumption groups. Only chromium recorded a risk quotient three times greater than the worst-case scenarios, which may associate health problem for the heavy shellfish consumers groups. ª 2012 National Institute of Oceanography and Fisheries. Production and hosting by Elsevier B.V. All rights reserved.
Introduction
* Corresponding author. The coastal zone can be considered as a geographic space of E-mail addresses: [email protected], ahmed.m.el- interaction between terrestrial and aquatic ecosystems that is [email protected] (A. El Nemr). of great importance for survival of a large variety of plants, Peer review under responsibility of National Institute of Oceanography animals and aquatic organisms (Castro et al., 1999; Usero and Fisheries. et al., 2005). In many countries, increasing of the industrializa- tion and agricultural activities contribute to an increasing of discharge of chemical pollutants into the ecosystem, which lead to increase in metals levels in the natural waters that caus- Production and hosting by Elsevier ing damage of fresh and marine habitats (Yu et al., 2011;
1687-4285 ª 2012 National Institute of Oceanography and Fisheries. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ejar.2012.11.001 68 A. El Nemr et al.
Muhammad et al., 2011; El Nemr, 2012). Metals differ from Principal component analysis (PCA) and cluster analysis were other toxic substances in that they are neither created nor de- applied to highlight the relationships between metals. Risk stroyed by human. Heavy metals discharged into the aquatic probability due to heavy metals contaminated in the studied environment can damage both of aquatic organisms and spe- bivalves has been investigated. cies diversity, due to their easy uptake into the food chain, tox- icity and accumulative behavior and bio-magnification in the Materials and methods food chain (Eisler, 1988; Matta et al., 1999; Islam and Tanaka, 2004; Yi et al., 2011). The accumulation patterns of heavy met- The bivalve samples were collected in April 2007 from nine als in fish and other aquatic organisms depend on their uptake locations along the Egyptian Mediterranean coast (Fig. 1). and elimination rates (Guven et al., 1999). The contamination The individuals were selected for a standard shell size levels of the aquatic environment by heavy metals can be esti- (30 ± 5 mm). At each location about 40 individuals of each mated by analyzing water, sediments and marine organisms. species were collected to prepare a pooled sample to reduce The levels of heavy metals in mollusks and other invertebrates individual variations in heavy metal concentrations (Daskala- are often considerably higher than in other constituents of kis, 1996; Szefer et al., 1997; El-Sikaily et al., 2004). marine environment due to their habitat and their feeding hab- The collected bivalves species belong to class Bivalvia are its (Amundsen et al., 1997; Romeoa et al., 1999; Canli and bivalves of stations Eastern Harbor (Tapes decussata, Linne, Atli, 2003; Sun et al., 2011). Compared to sediments, mollusks 1758), El-Dekheila (Paphia undulata, Born, 1778), Western exhibit greater spatial sensitivity and therefore, are the most Harbor (Venerupis decussata, Linnaeus, 1758) and El-Mex reliable tool for identifying sources of biologically available (Gafrarium pectinatum, Linnaeus, 1758) are belonging to order heavy metal contamination (Szefer, 1986; El-Sikaily et al., Veneroida and family Veneridae, while bivalves of stations Ro- 2004; Hamed and Emara, 2006). Under certain environmental setta (Donax venustus, Poli, 1795), El-Jamil (Donax trunculus, conditions, heavy metals might accumulate up to toxic concen- Linnaeus, 1758), Damietta (Donax semistriatus, Poli, 1795) trations and cause ecological damage (Guven et al., 1999; Riet- and Port-Said are belonging to order Veneroida and family zler et al., 2001; Bai et al., 2011). Metals such as iron, copper, Donacidae, while species of Abu-Qir station belongs to order zinc and manganese, are essential metals since they play impor- Pterioida and family Pteriidae. The wide variations between tant roles in biological systems (Hogstrand and Haux, 2001), the collected species are due to the environmental condition whereas non-essential metals such as Pb, Cd and Hg are usu- and the biodiversity of each station. ally potent toxins and their bioaccumulation in tissues leads The edible part of the meat from samples of each location to intoxication, decreased fertility, cellular and tissue damage, was carefully removed by shelling the bivalves with a plastic cell death and dysfunction of a variety of organs (Oliveira knife; they were then dried (El-Sikaily et al., 2004), homoge- Ribeiro et al., 2002; Damek-Proprawa and Sawicka-Kapusta, nized and ground to a fine powder in a mortar before analysis 2003). Only few metals with proven hazardous nature are to (Chiu et al., 2000; Ruelas-Inzunza and Pa´ez-Osuna, 2000). be completely excluded in food for human consumption. Thus, About 0.2 g from each sample was taken for analysis and only three metals, lead, cadmium and mercury, have been in- underwent microwave acid (HNO3 Suprapur, Merck) diges- cluded in the regulations of the European Union for hazardous tion (Camusso et al., 2001). The completely digested samples metals (EC, 2001), while the United States Food and Drug were allowed to cool at room temperature, filtered (glass Administration (USFDA) has included a further three metals wool), and made up to 25 ml. All digested samples were ana- chromium, arsenic and nickel in the list (USFDA, 1993). lyzed, in triplicate, using an atomic absorption spectrophotom- The Eastern Harbor, Western Harbor, El-Mex, El-Dekhila eter (flame for Zn and flameless for other metals) (Shimadzu, and Abu-Qir, which are located along the coast of the Alexan- AA-6800). The digestion and analytical procedures were dria city, are the major tourist attract locations due to their checked by analysis of standard reference material (IAEA- clean waters and coastal habits. These locations are also vital 407, International Atomic Energy Agency) in every batch for fisheries and marine activities. However, these coasts are digestion. Replicate analysis of the reference material showed under constant threats of petroleum pollution in the form of good accuracy, with metals recovery rates between 96% and heavy tar loads (El Nemr, 2003, 2005, 2008; El Nemr et al., 103% as illustrated in Table 1. Precision was verified by ana- 2012). This may result from untreated domestic sewage, oil lyzing a replicate sample in every batch digestion. The percent- transportation, oil spillage and ballast water from tankers, as age relation between the difference of the two values obtained well as industrial waste waters. Furthermore, the western re- and the mean value of these was lesser than 10% in most cases, gion of the coastal zone of Alexandria city is subjected to petroleum contamination from different sources including, the western desert oil field and the Suez Mediterranean pipe- line terminal (SUMED). Rashid, El-Jamil, Damietta and Port 32 Mediterranean Sea Said are exposed to agricultural drains contaminated with haz- 6 ardous industrial wastes, domestic sewage, organic matter, fer- 31.5 5 8 4 9 tilizers and pesticides, in addition to oil pollution from ships 1 El-Burullus lagoon and oil terminal as in Port Said and Damietta (El Nemr Manzala lagoon 31 Bardaweel lagoon 2 3 et al., 2007a,b; El Nemr, 2008, 2010; Khaled et al., 2010, 2012). Egypt
The primary purpose of this study was to obtain quantita- 30.5 tive information on some heavy metal concentrations in bi- 29 29.5 30 30.5 31 31.5 32 32.5 33 33.5 34 valves from nine hot spot stations along Egyptian Mediterranean coastal from Rosetta to Port Said cities and Figure 1 Map of the sampling locations along Egyptian Medi- to compare the total metal content at the different sites. terranean coast. Risk probability due to heavy metals in bivalve from Egyptian Mediterranean coast 69
Table 1 Heavy metals concentrations (lg/g dry weight) in reference material (IAEA-407, fish tissue) analyzed together with the mussels species. Elements (lg/g dry weight) Al Cd Co Cr Cu Ni Pb Zn Certified values 13.80 0.189 0.100 0.73 3.28 0.60 0.120 67.10 Found values 13.26 0.182 0.103 0.71 3.15 0.59 0.123 67.45 Standard deviation 1.25 0.012 0.008 0.20 0.26 0.16 0.034 1.87 Recovery (%) 96.1 96.3 103.0 97.5 96.1 98.2 102.5 100.5
and the precision was, therefore, considered satisfactory. The to 1.77 mg (Underwood, 1977). G. pectinatum collected from potential contamination of samples was evaluated analyzing El-Mex Bay was exhibited the highest concentration value of one acid blank in every batch. The results of the blanks were Co (4.25 lg/g dry weight) followed by D. trunculus (2.86 lg/ always below the methods detection limit. g dry weight) and D. venustus (3.64 lg/g dry weight) collected from El-Jamil and Port-Said stations, respectively. While the Results and discussion lower value was detected in D. venustus (1.02 lg/g dry weight) collected from Rashid as shown in Fig. 4. The cobalt concen- The concentration levels of studied heavy metals (Al, Cd, Cu, trations in the present study are higher than that reported by Co, Cr, Ni, Pb, and Zn) detected in bivalves samples from nine Sivaperumal et al. (2007) (nd–0.85 lg/g dry weight) but within hot spot stations from El-Mex to Port-Said cities are illus- the range recorded by de Mora et al. (2004) (0.12–12.9 lg/ trated in Table 2. Among the different metals analyzed lead, g dry weight) collected from the Arabian Gulf and Gulf of cadmium, chromium and nickel are classified as chemical haz- Oman. ards (FAO, 1983; EC, 2001; FDA, 2001). The highest concen- It has been estimated that the average daily human requires tration level of aluminum was recorded in Port-Said (503.5 lg/ of chromium is 1 lg(Mertz, 1969). Deficiency of chromium re- g dry weight) while the lowest concentration was observed at sults in impaired growth and disturbances in glucose, lipid, and Abu-Qir Bay (15.2 lg/g dry weight) as illustrated in Fig. 2. protein metabolism (Calabrese et al., 1985). Chromium is Traces of cadmium were detected in all collected samples, among a group of hazardous metals notified by the USFDA the highest concentration was recorded at Abu-Qir Bay (1993). Chromium was detected in all the studied samples (0.14 lg/g dry weight) followed by that detected in species col- and the concentrations were fluctuated between 3.72 and lected from El-Dekhila and El-Mex stations. The lowest cad- 18.58 lg/g dry weights. The highest Cr concentration was de- mium concentration was observed at Western Harbor and tected in D. venustus collected from Port-Said station. All the Damietta stations (0.04 and 0.03 lg/g dry weight, respectively), collected bivalve samples showed Cr concentrations below or while moderate values were scattered between Rashid, El-Ja- within the range of FDA (2001), except Port-Said station mil, and Port-Said stations as given in Fig. 3. Cadmium con- which exhibits a relatively higher Cr concentration than the tents of all species under investigation were much below the permissible level as shown in Table 2. Bivalves collected from legal limits of EC (2001), FDA (2001) and FAO (1983) as re- all stations in the current study exhibited higher values than ported in Table 2. The threshold for acute cadmium toxicity that reported in southern Spain by Usero et al. (2005) (0.24– would appear to be a total ingestion of 3–15 mg. Severe toxic 1.22 lg/g dry weight). However, Cr concentrations reported symptoms are reported to occur with ingestions of 10–326 mg. in this study were comparable with that observed in Arabian Fatal ingestions of Cd, producing shock and acute renal fail- Gulf and Gulf of Oman by de Mora et al. (2004) (0.01– ure, occur by ingestions exceeding 350 mg (NAS–NRC, 3.76 lg/g dry weight); in marketable shellfish from India by 1982). The concentration level of Cd in all collected bivalve Sivaperumal et al. (2007) (0.18–3.65 lg/g dry weight); in Gulf species was lower than that reported by Hamed and Emara of Suez by Hamed and Emara (2006) (2.34–7.99 lg/g dry (2006) (0.64–2.13 lg/g dry weight) in Gulf of Suez and by Use- weight), except Port-Said station, which recorded relatively ro et al. (2005) in southern Spain (0.29–0.38 lg/g dry weight). higher value. It is also much lower than that observed by de Mora et al. Copper is an essential part of several enzymes and it is nec- (2004) in Arabian Gulf and Gulf of Oman (1.17–21.9 lg/g dry essary for the synthesis of hemoglobin (Underwood, 1977). weight), and that reported by Sivaperumal et al. (2007) in Copper concentrations were ranged from 1.54 to 11.85 lg/g dry marketable shellfish from India (1.17–24.1 lg/g dry weight). weight in all the analyzed samples (Fig. 4). The results revealed However, the reported Cd concentrations in this study are that there is a high contamination by copper at El-Mex Bay due comparable with that detected by Sankar et al. (2006) from to El-Mex Pumping Station, which discharges mixed wastewa- Kerala, India (0.1 lg/g wet weight). ter of industry, agriculture and sewage. It also receives waste Cobalt is an essential nutrient for man, and is an integral effluents from oil refineries (SUMED) and power station. The part of vitamin B12. Cobalt has also been implicated in blood concentrations of Cu in all studied samples were below the toxic pressure regulation (Perry et al., 1954), and has been found to limit (30 lg/g) (FAO, 1983). The present concentrations of Cu be necessary for proper thyroid function (Blakhima, 1970). in all collected samples were much lower than that recorded by Excessive ingestion of Co is reported to cause congestive heart Usero et al. (2005) in southern Spain (9.2–90 lg/g dry weight) failure and polycythemia and anemia (Alexander, 1972). The and by de Mora et al. (2004) in the Gulf of Oman (60.9– average daily intake of cobalt, in all forms ranged from 0.3 210 lg/g dry weight). However, the Cu concentrations reported 70 A. El Nemr et al.
here was comparable with the data reported by Sivaperumal et al. (2007) (1.17–24.1 lg/g dry weight); Sankar et al. (2006) (1.5–6.5 lg/g dry weight) and by Hamed and Emara (2006) (1.6–12.17 lg/g dry weight). The essential function of nickel, for example, in enzymes such as urease and hydrogenase, in most plants and some microorganisms is well-known. On the other hand, nickel is a carcinogenic metal and overexposure to it can cause de- creased body weight, heart and liver damage and skin irrita- tion (Homady et al., 2002). The nickel concentration in studied samples showed wide variation where the higher con- centration was detected at Abu-Qir station (15.02 lg/g dry weight), while the lower was observed at Damietta station (3.42 lg/g dry weight). The present study reveals that the nickel concentrations are relatively lower than that reported by Usero et al. (2005) in southern Spain (66.0–92.0 lg/g dry weight) but higher than that recorded by Sivaperumal et al. (2007) in marketable shellfish from India (nd–0.89 lg/g dry weight). The nickel concentration in all bivalves under inves- tigation was lower than the permissible limit for shellfish as shown in Table 2 (FDA, 2001). G. pectinatum (El-Mex), Pa- phia undulate (El-Dekhila) and Veneroida species (Port-Said) showed relatively higher nickel concentrations (14.95, 13.7, and 12.08 lg/g dry weight respectively) as illustrated in Fig. 4. Lead is the second element (after arsenic) on the top 20 list of the most poisoning heavy metals. Its target organs are bones, brain, blood, kidneys, reproductive and cardiovascular sys- tems, and thyroid gland (Homady et al., 2002; Massadeh et al., 2004). The accumulation of lead in mussels fluctuated be- tween 0.05 lg/g dry weight at Western Harbor to 0.49 lg/g dry weight at Abu-Qir Bay with mean 0.24 ± 0.15 lg/g dry weight. The concentration of Pb found in the present work was compa- rable with those in the literature (0.48–1.18, 0.12–1.09, 0.01– 1.18, 0.44–0.67 lg/g dry weight) (Favretto et al., 1987; Majori et al., 1991; Widdows et al., 1997; Conti and Cecchetti, 2003, g/g dry weight) collected along the Egyptian Mediterranean coast.
l respectively) in Italy but lower than that reported by Usero et al. (2005) in southern Spain (0.74–1.92 lg/g dry weight). High levels of zinc cause pancreatitis, anemia, muscle pain, and acute renal failure (Pais and Benton Jones, 1997). The concentration range of Zn in the studied mussels was 8.35– 66.05 lg/g dry weight with the lowest value at West Harbor and the highest at Abu-Qir station. A relatively high value of Zn was noticed at El-Mex station as showed in Fig. 5. Comparison of the obtained results with those previously re- ported, Zn is within the range reported by Hamed and Emara (2006) (56.5–191.4 lg/g dry weight) in Red Sea and Campa- nella et al. (2001) (5–31 lg/g dry weight) in Favignana Island, Sicily (Italy). It is also comparable with the marketable shell- fish from India (3.8–165 dry weight) (Sivaperumal et al.,
– 1.0––––1.0–– –– 4.0 0.52007), – but – relatively 13 lower – than that – observed 30 by 80Widdows – – 0.5 – 40 – – et al. (1997) (82–185 lg/g dry weight) in Venice Lagoon, Italy (Conti and Cecchetti, 2003) (98–152 lg/g dry weight).
Metal pollution index (MPI)
Regardless the type of species, the overall metal content of bi- valves at the investigated locations in the current study, was Mean concentration and stander deviations of metals in mussels ( compared using the metal pollution index (MPI) calculated with the following formula (Usero et al., 1996, 1997).
1=8 Table 2 LocationEl-MexWestern HarborEl-DekhilaEastern 2 HarborAbu-Qir WH 1Rashid 4 3El-Jamil 53.06 EM (±0.83) EHDamietta EDPort Al Said 127.18 5 (±1.93) 0.036 24.36 (±0.003)Min (±0.73) value 115.40 (±0.82) 6Max AQ 0.131 value (±0.001) 7 1.13 (±0.02)EC 0.115 8 0.133 (2001) (±0.002) (±0.002) Ra 15.22 4.25 EJ (±1.01) 9 (±0.04) 11.03 Da 2.45 1.53 (±0.41) (±0.02) (±0.01) 173.37 (±0.65) PS Cd 0.144 12.25 82.73 (±0.001) (±0.21) (±0.73) 1.54 145.15 (±0.12) (±3.29) 5.24 4.18 (±0.32) (±0.64) 0.072 (±0.002) 3.93 503.53 11.85 (±0.03) (±4.92) (±0.32) 0.083 0.028 (±0.003) 10.21 (±0.002) (±0.33) 1.02 3.46 1.92 (±0.002) (±0.32) (±0.32) 0.087 14.95 15.22 (±0.004) (±0.25) 12.02 2.86 1.21 (±0.52) (±0.03) 0.05 (±0.014) 503.53 (±0.004) 5.00 (±0.61) 9.02 13.70 Co 3.64 0.43 (±0.25) (±0.23) (±0.04) (±0.002) 5.97 4.42 (±0.35) 8.35 (±0.21) 3.72 (±0.06) (±0.12) 3.40 0.14 51.83 (±0.23) (±0.003) 0.29 (±0.02) 18.58 (±0.003) (±0.32) 15.02 1.59 (±0.25) 1.87 (±0.27) 1.91 0.028 (±0.32) 9.72 0.144 6.57 (±0.06) 8.70 14.13 2.77 (±0.26) (±0.02) (±0.24) 0.49 (±0.001) 3.42 Cr (±0.12) 5.43 (±0.23) 2.87 2.78 0.12 66.05 12.08 (±0.004) (±0.04) (±0.35) 0.19 (±0.003) 0.19 (±0.002) 12.34 4.84 1.02 0.28 (±0.02) (±0.01) 4.25 10.41 (±0.03) 11.43 (±0.06) 2.69 12.60 (±0.05) Cu 1.98 2.52 4.93 3.72 18.58 Ni 1.54 11.85 Pb 15.02 3.42 Zn 0.49 0.048 66.05 MPI 8.35 – – FDA (2001) FAO (1983) MPI ¼ðAl Cd Co Cr Cu Ni Pb ZnÞ Risk probability due to heavy metals in bivalve from Egyptian Mediterranean coast 71
600 Al In spite of the bivalve species, at El-Mex station bivalve exhibited the highest MPI (6.56), which may be attributed to 500 the presence of El-Mex Pumping Station, which discharges 400 mixed wastewater of industry, agriculture and sewage. Bivalve
300 from Port-Said (4.93) and Abu-Qir stations (4.84), which suf- fer from different types of wastes due to marine transporta- 200 tion, fisheries, industrial and human activities showed the 100 Conc (ppm, dry weight) dry Conc (ppm, next MPI after El-Mex bivalve. Western Harbor and Damietta
0 bivalves recorded the lowest MPI as showing in Table 2. EM WH ED EH AQ Ra EJ Da PS Location Normalization
Figure 2 Concentration of Al in studied bivalves along Egyptian Normalization of heavy metals in the environmental samples to Mediterranean coast. Fe, Li, and Al seemed to be a good tool to study the compari- son of metal concentrations (Kouadio and Trefry, 1987; Van der Weijden, 2002; El-Sikaily et al., 2004). The use of normali- 0.6 Cd Pb zation overcome the difference between metals comes from size, 0.5 species, and regional difference of studied mollusks samples. 0.4 Table 3 illustrated the Pearson correlation between the metals
0.3 in the bivalves under investigation. There were a good positive correlation between cobalt and each of copper, lead and Zinc; 0.2 cadmium and nickel; copper and zinc; lead and each of cad-
Conc (ppm, dry weight) Conc (ppm, 0.1 mium, copper and zinc. On the other hand, there was no corre- 0.0 lation between all metals under investigation and aluminum. EM WH ED EH AQ Ra EJ Da PS Normalization [i.e. divide metal concentration by normalize Station metal concentration (such as Al, Fe or Li) for each species], of- ten used to demonstrate correlations between elements. The Figure 3 Concentrations of Cd and Pb in studied bivalves along uncorrelated single concentrations are converted into highly Egyptian Mediterranean coast. correlated normalized concentrations Table 4, which reveals that by overcoming the different factors (size, species, food ha- bit, habitat, etc...), metals under investigation had the same source of pollution. The MPI values in Table 2 exhibited that Co Cr Cu Ni 20 Abu-Qir station receives huge amount of pollutants followed 18 by the Eastern Harbor station for all metals under investiga- 16 tion. El-Mex station takes the third position after Abu-Qir 14 and Eastern Harbor, and exhibited higher values for Zn, Co, 12 10 Cu, and Pb. Western Harbor station exhibited the highest val- 8 ues for Ni and Cr. These high values reflecting the huge amount 6 of industrial, agricultural and domestically drainage in Abu- 4 Qir, Eastern Harbor, El-Mex Bay and Western Harbor. Conc dry weight) (ppm, 2 0 EM WH ED EH AQ Ra EJ Da PS Risk assessment protocols Location
Figure 4 Concentrations of Co, Cr, Cu and Ni in studied In the present study, risk quotient (RQ) was calculated to as- bivalves along Egyptian Mediterranean coast. sess the environmental status as represented by the concentra- tions of investigated metals in mussels and threshold values likely to cause adverse effects in human consumers. Concentration of metal X in mussels 70 Zn RQ ¼ Level of concern for metal X 60 A level of concern is a ‘‘threshold concentration’’ of a 50 chemical above which a hazard to human health may exist, 40 and can be calculated by the following equation: 30 Tolerable Daily Intake Level of concern ¼ 20 Rate of shellfish consumption
Conc (ppm, dry weight) dry Conc (ppm, 10 The consumption rate for mussels was obtained from a 0 study performed on Egypt (FAO, 2002; Khairy et al., 2009). EM WH ED EH AQ Ra EJ Da PS In the current study, 1.5 g/person/day was used to calculate Location the level of concern for the low shellfish consumption group Figure 5 Concentrations of Zn in studied bivalves along while the maximum consumption rate of 30 g/person/day Egyptian Mediterranean coast. was employed to deduce the level concern for the high 72 A. El Nemr et al.
Table 3 Correlation between metals in the studied mollusks on the Egyptian Mediterranean samples. Al Cd Co Cr Cu Ni Pb Zn Al 1.000 Cd 0.163 1.000 Co 0.187 0.652 1.000 Cr 0.584 0.148 0.613 1.000 Cu 0.098 0.573 0.698* 0.366 1.000 Ni 0.054 0.761* 0.554 0.578 0.600 1.000 Pb 0.039 0.700* 0.885** 0.438 0.753* 0.535 1.000 Zn 0.265 0.640 0.733* 0.392 0.796* 0.637 0.885** 1.000 * Correlation is significant at the 0.05 level (2-tailed). ** Correlation is significant at the 0.01 level (2-tailed).
Table 4 Correlation between normalized metals against aluminum in the studied mollusks on the Egyptian Mediterranean samples. Cd/Al Co/Al Cr/Al Cu/Al Ni/Al Pb/Al Zn/Al Cd/Al 1.000 Co/Al 0.990* 1.000 Cr/Al 0.941* 0.967* 1.000 Cu/Al 0.975* 0.988* 0.963* 1.000 Ni/Al 0.981* 0.986* 0.987* 0.979* 1.000 Pb/Al 0.989* 0.997* 0.962* 0.990* 0.984* 1.000 Zn/Al 0.935* 0.969* 0.973* 0.971* 0.967* 0.972* 1.000 * Correlation is significant at the 0.01 level (2-tailed).
Table 5 Risk analysis for the metals present in mussel samples expressed along Egyptian Mediterranean coast. Metals Cd Cr Cu Ni Pb Zn
RQbcs 0.00012 0.31903 0.00001 0.00293 0.00006 0.00004 RQwcs 0.01234 3.18463 0.00203 0.25754 0.01171 0.00566
consumption group (Fishermen community). The tolerable respectively) indicated that these chemicals were probably not daily intake (TDI, lg/person/day) for heavy metals established of great health concern for either the low consumption or high values by FAO/WHO (2004), WHO (1993), EPA (2008) were consumption groups (lower than one) as shown in Table 5. used to calculate the relevant level of concern for each metal. The relevant risk quotient best-case scenario (RQbcs) and Statistical analysis risk quotient worst-case scenario (RQwcs) were calculated for the low and high consumption groups respectively as follows: Multivariate analysis (principal component analysis, PCA) has Esimated Daily Intake of metal X for low consumption group been applied on the data set of nine sampling and eight variables RQ ¼ bcs Tolerable Daily Intake for metal X (Al, Cd, Co, Cr, Cu, Ni, Pb, and Zn). In this way, the number of variables under investigation was reduced and inter-element Esimated Daily Intake of metal X for high consumption group associations might be assessed in detail (Bakac¸, 2000; El Nemr RQ ¼ wcs Tolerable Daily Intake for metal X et al., 2006, 2007a). R-mode factor analysis with varimax rota- tion was applied to the heavy metal concentrations in mussels.
The risk quotients (RQbcs and RQwcs) were calculated for Two principal components have been extracted by covering Cd, Cu, Cr, Ni, Pb and Zn as established health guidelines 80.03% of the cumulative variance (Table 6). Loading of the are available only for these contaminants as promulgated by variables on the two principal components showed that Cd, the food and drug administration of the United States (US- Co, Cu, Ni, Pb, and Zn are the dominant variables on the FAD). The concentration ranges of various metal contami- PCF1 (0.78, 0.83, 0.82, 0.71, 0.91, and 0.93, respectively), while nants present in mussels from all stations were used to Al (0.79) and Cr (0.85) are the dominant variables on the PCF2. estimate levels. It is noteworthy that RQwcs for Cr was three Hierarchical cluster analysis (HCA) was carried out using times greater than unity, suggesting that probable health asso- average linkage clustering applied on the Pearson correlation ciated problems might be encountered in heavy shellfish con- for the eight metals under investigation. This dendrogram sumers. The risk quotients for Cd, Cu, Ni, Pb, and Zn in was confirmed by applying two other clustering methods: (1) both the best-case and worst-case scenarios (RQbcs and RQwbs, single linkage using cluster method nearest neighbor with Risk probability due to heavy metals in bivalve from Egyptian Mediterranean coast 73
stations recorded levels lower than the acceptable limit except Table 6 Varimax normalization rotated factor loading for for the species collected from Port-Said and Abu-Qir, which two factors obtained for heavy metals in the mussels samples exhibited higher values for Cu and Zn, respectively. The ratio along Egyptian Mediterranean coast. of normalization revealed that Abu-Qir station receives huge Variable Factor 1 Factor 2 amount of all metals under investigation followed by the East- Al 0.158 0.789 ern Harbor location. El-Mex station takes the third position Cd 0.781 0.085 after Abu-Qir and Eastern Harbor, and exhibited high values Co 0.830 0.345 for Zn, Co, Cu, and Pb, while Western Harbor location exhib- Cr 0.413 0.850 ited high values for Ni and Cr. These high values reflecting the Cu 0.816 0.042 huge amount of industrial, agricultural and domestically Ni 0.709 0.225 drainages in Abu-Qir, Eastern Harbor, El-Mex Bay, and Wes- Pb 0.914 0.100 tern Harbor locations. The calculated risk quotients for Cd, Zn 0.934 0.062 Cu, Ni, Pb, and Zn in both the best-case and the worst-case Variance (%) 59.59 20.45 scenarios do not cause adverse effect for either low or high Cumulative (%) 59.59 80.04 consumption groups. Only chromium exhibited risk quotient Bold values are dominant variables in each factor. three times greater than the worst-case scenarios, which may associate health problem for the heavy shellfish consumers groups.
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