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Measurement and risk assessment of heavy metals in the muscle tissue of long tail tuna (Thunnus tonggol) in Chabahar fishing ports- Sistan and Balouchestan province
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H. Taji1   , S. Sharifian1 |
| 1- Department of Fisheries, Faculty of Marine Sciences, Chabahar Maritime University, Chabahar, Iran |
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Abstract: (20 Views) |
Introduction
Fish and seafood are widely recognized as valuable components of a healthy diet because they provide high-quality protein, essential amino acids, omega-3 fatty acids, vitamins, and minerals. Despite these nutritional benefits, aquatic organisms can also accumulate environmental contaminants, particularly heavy metals. These contaminants enter marine ecosystems through both natural processes and human activities, including industrial effluents, municipal wastewater, and agricultural runoff. Owing to their persistence, non-biodegradable nature, and tendency to bioaccumulate, heavy metals may be transferred through the food chain and ultimately pose health risks to consumers of seafood (Ahmed et al., 2018).
Among commercially exploited marine fish, tuna species are of particular economic and nutritional importance. Longtail tuna (Thunnus tonggol) is one of the dominant tuna species in the northern Oman Sea and supports an important regional fishery. Given its widespread consumption and commercial significance, regular assessment of heavy metal contamination is essential to ensure its safety for human consumption. Accordingly, this study quantified the concentrations of Zn, Fe, Cu, Pb, Cd, Hg, As, Cr, Mn, and Ni in the muscle tissues of longtail tuna collected from the fishing ports of Chabahar, Beris, and Pasabandar in the northern Oman Sea. In addition, the potential human health risks associated with the consumption of this species were evaluated.
Methodology
A total of 60 longtail tuna specimens were collected from three fishing ports along the northern Oman Sea, including Chabahar, Beris, and Pasabandar. Muscle tissues were separated from the dorsal, abdominal, and caudal regions and homogenized. The samples were then dried in an oven at 70 °C for 48 hours. Approximately 0.5 g of each sample was digested using a microwave digestion system with concentrated nitric acid (HNO₃) and hydrogen peroxide (H₂O₂). Heavy metal concentrations were determined using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The concentrations of metals were expressed as micrograms per gram (µg/g) on a dry weight basis. Moisture content was determined according to standard AOAC methods (AOAC, 2000). Human health risk assessment was conducted using several indicators including estimated daily intake (EDI), estimated weekly intake (EWI), target hazard quotient (THQ), and cumulative hazard index (∑THQ). These indices were calculated using standard equations recommended by international health organizations (USEPA, 2015). Average fish consumption rates were assumed to be 33.6 g/day for adults and 13.1 g/day for children (IFO, 2020), with body weights of 70 kg and 16 kg, respectively. Statistical analyses were performed using SPSS software, and significant differences among sampling locations were evaluated using one-way ANOVA followed by Tukey’s post-hoc test at a significance level of 0.05.
Results
The results revealed variations in heavy metal concentrations in the muscle tissues of longtail tuna among the three sampling locations. In samples collected from Chabahar port, copper showed the highest concentration (15.63 µg/g), while lead had the lowest concentration (0.02 µg/g). In Beris port, copper again exhibited the highest level (17.19 µg/g), whereas chromium recorded the lowest concentration (0.04 µg/g). In Pasabandar port, iron showed the highest concentration (22.84 µg/g), while chromium remained the lowest among the analyzed metals. Overall, the pattern of metal accumulation in tuna muscle tissues across the sampling sites followed the order: Cu > Zn > Fe > Ni > Mn > As > Hg > Cd > Pb > Cr. The overall mean concentrations of Zn, Fe, Cu, Pb, Cd, Hg, As, Cr, Mn, and Ni were 16.63, 17.50, 18.39, 0.25, 0.27, 0.32, 0.55, 0.04, 1.73, and 8.30 µg/g dry weight, respectively. Risk assessment results indicated that the estimated daily intake (EDI) and estimated weekly intake (EWI) of all metals for both adults and children were significantly lower than the provisional tolerable intake limits established by international health organizations. Among the studied metals, nickel, cadmium, and mercury showed relatively higher intake contributions; however, their levels remained far below the safety thresholds. The calculated target hazard quotient (THQ) values for individual metals in adults ranged from 0.001 to 0.225. The cumulative hazard index (∑THQ) values for adults were 0.357, 0.447, and 0.278 for Chabahar, Beris, and Pasabandar, respectively. For children, the cumulative THQ values ranged between 0.052 and 0.072. In all cases, THQ values were lower than 1, indicating no significant non-carcinogenic health risk associated with the consumption of longtail tuna from the studied regions.
Discussion and conclusion
The findings of this study indicate that heavy metal accumulation in longtail tuna varies among the three fishing locations. Slightly higher concentrations of some metals were observed in samples collected from Pasabandar compared with those from Chabahar and Beris. These differences may be associated with environmental conditions, local pollution sources, and biological factors such as fish size and age that influence metal bioaccumulation (Mortazavi and Sharifian, 2012; Ahmed et al., 2018). Despite these variations, most heavy metal concentrations were within the permissible limits recommended by international food safety authorities (USEPA, 2015). Although cadmium concentrations were relatively higher than some guideline values, the overall risk assessment indicated that the exposure levels remain within safe limits. The calculated EDI, EWI, and THQ values demonstrated that the consumption of longtail tuna from the studied regions does not pose a significant health risk to either adults or children. The cumulative hazard index values were well below the critical threshold of 1, suggesting that long-term consumption of this species is unlikely to cause adverse health effects related to heavy metal exposure. In conclusion, longtail tuna harvested from the fishing ports of Chabahar, Beris, and Pasabandar can be considered safe for human consumption with respect to the heavy metals investigated in this study. Nevertheless, continuous monitoring of heavy metal contamination in marine ecosystems and commercially important fish species is recommended to ensure food safety and detect potential environmental changes that may influence contaminant levels in the future.
Conflicts of interest
There is no conflict of interest between authors.
Acknowledgments
We sincerely appreciate and thank all the experts at the Central Laboratory of Chabahar Maritime University who helped us in conducting this research. |
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| Keywords: Long tail tuna, Heavy metals, Health risks, Estimated daily intake, Oman Sea, Sistan and Balouchestan province |
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Full-Text [PDF 777 kb]
(9 Downloads)
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Type of Study: Research |
Subject:
آلودگي محيطهاي آبي
Received: 2026/03/21 | Accepted: 2026/09/1
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