The levels of heavy metals found in fish species in various studies generally vary depending on the various factors such as fish species, size, age, the region where fish was caught, seasonal changes, analytical methodology etc. Thus, the mean values obtained in the present study were compared with other literature data referring to the same species of fish in Turkey.
Cadmium is one of the most toxic metals for human and may cause kidney dysfunction, skeletal damage and reproductive deficiencies22. Common carp samples analyzed in this study showed 3.2 fold higher levels than the limit accepted in Turkish Food Codex, and gilthead seabream and sea bass were 2.6 and 2.2 fold higher, respectively. Our finding regarding Cd concentration in rainbow trout is in agreement with the findings of Şireli et al.23 and Çelik et al.24, who found lower concentration of Cd in rainbow trout than the maximum acceptable limit. Göksu et al.25 reported the Cd level of common carp as 0.46 mg kg-1, which is higher than our result. In a study carried out by Türkmen et al.26, the levels of Cd in gilthead seabream and sea bass were determined as 0.30 and 0.10 mg kg-1, respectively. These results are above the maximum acceptable limit similar to those in our study.
It is known that lead is a health-endangering metal for human. The average levels of Pb in common carp and sea bass samples were found above the maximum acceptable limit, while rainbow trout and gilthead seabream were in the permissible levels for human consumption in terms of Pb level. Our findings for common carp and sea bass were higher than the findings of Ersoy et al.27, Mendil et al.28 and Türkmen et al.26 who found lower Pb concentration than the legal limits. In another study carried out by Mol et al.29, it was reported that Pb did not determined in the muscle of common carp. As for rainbow trout and gilthead seabream, our Pb values were lower than the findings of Çelik et al.24 and Türkmen et al.26 who found higher Pb concentration than the legal limits.
Copper is an essential micro-nutrient and not toxic for humans in low levels30. Cu levels presented in this study are in agreement with values reported by many researchers12,26,28,29,31. Their findings regarding the levels of Cu in rainbow trout, common carp, gilthead seabream and sea bass have showed that Cu levels in fish samples is quite below the maximum acceptable limit, similar to those in our study.
Zinc is found in almost every cell and in a wide variety of foods, and it is known to be involved in most metabolic pathways in humans28. Among the fish species analyzed in this study, the highest Zn content was found in common carp, with 14.13 mg kg-1. This finding is quite higher than the finding of Göksu et al.,25 who found 0.84 mg kg-1 Zn level in common carp. Our findings for rainbow trout, gilthead seabream and sea bass were close to the findings of Gokoglu et al.,12, Çelik and Oehlenschläger31, Çelik et al.24 and Türkmen et al.26.
Iron is an essential mineral for life. It is known that adequate iron in a diet is very important for normal regulation of various metabolic pathways28,30. In our study, the highest Fe level was found in common carp. This level is 6.5 fold higher than the finding of Göksu et al.25, who found 1.93 mg kg-1 Fe level in common carp caught from the Seyhan Dam Lake in southern of Turkey. Our finding regarding the concentration of Fe in rainbow trout was close the finding of Gokoglu et al.12 and Çelik et al.24. In a study carried out by Türkmen et al.26, the average levels of Fe in gilthead seabream and sea bass were reported as 38.9 and 28.9 mg kg-1, respectively. These levels are higher than our results.
It has been reported that the recommended daily intake is 15 mg for Zn for adult males, 12 mg for adult females; 1.5-3 mg for Cu for adults; 15 mg for Fe, for adult females and 10 mg for adult males30. Compared the our levels to these levels, it can be said that common carp is a good source for Zn, Cu and Fe whereas Zn, Cu and Fe contents of rainbow trout, gilthead seabream and sea bass are notably below the recommended daily intake limits.
According to our results, the average levels of Cd in common carp, gilthead seabream and sea bass considerably exceeded the maximum acceptable limits established in the Turkish Food Codex. In addition, Pb levels in common carp and sea bass were also found higher than the legal limit. In this instance, it can be speculated that consumption of these fish species in long time period can constitute a hazard for public health. Fish sold in Elazig should be controlled periodically to avoid excessive intake of heavy metals by people, and to monitor the pollution of Keban Dam Lake and Euphrates.
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