Najem et al. 2024 — Lead, arsenic, and mercury bioaccumulation in common carp from Baqubah, Iraq
This study measured total arsenic (tAs), lead (Pb), and total mercury (tHg) in liver, gills, and dorsal muscle of 10 common carp (Cyprinus carpio L.) from Baqubah market fish, sourced from aquaculture in Diyala province, Iraq. Analysis by flame atomic absorption spectrometry (FAAS). Key finding: As and Pb concentrations in all three tissues were below WHO permissible limits (As: 0.5 ppm; Pb: 1.5 ppm), while Hg exceeded the WHO permissible limit (0.14 ppm) in 60% of liver samples, 100% of gill samples, and 90% of muscle samples, indicating significant Hg contamination of freshwater systems in Diyala province (Tigris and Diyala rivers). Histopathological lesions in gills and liver were documented alongside the chemical findings.
Key numbers
Values in ppm (mg/kg wet weight), FAAS, n=10 specimens:
Liver (mean ± SE):
- tAs: 0.07021 ± 0.006983; range 0.0127–0.132
- Pb: 0.320693 ± 0.027842; range 0.1002–0.6455
- tHg: 0.214123 ± 0.013867; range 0.1123–0.3211
Gills (mean ± SE):
- tAs: 0.1331 ± 0.03408; range 0.06–0.70
- Pb: 0.7135 ± 0.01590; range 0.60–0.90
- tHg: 0.5496 ± 0.00856; range 0.48–0.63
Muscle (mean ± SE, n=10; one outlier M8 Hg value of ~1034 ppm appears in the raw data, likely a transcription error — see original table):
- tAs: not exceeding 0.071 ppm across samples
- Pb: 0.202–0.736 ppm per sample
- tHg: 0.145–0.476 ppm (excluding apparent M8 anomaly)
WHO permissible limits applied: As 0.5 ppm, Pb 1.5 ppm, Hg 0.14 ppm. All As and Pb values were within WHO limits; Hg exceeded limits in 60% of liver samples, 100% of gill samples, and 90% of muscle samples.
Note: Arsenic is measured as total arsenic by FAAS without speciation; values should not be interpreted as inorganic arsenic. The paper identifies tHg as “mercury” without MeHg speciation.
Methods (brief)
Ten fresh carp randomly selected from Baqubah local markets, September 2022–January 2023. Fish dissected; dorsal muscle, liver, and gills collected and stored at −20°C. FAAS at the Ministry of Industry and Minerals, Ibn Sina Center, Iraq. Calibration curves established per analyte. Histopathological sections prepared in 10% formalin and evaluated for pathological changes. Statistical analysis by SPSS 17.0; ANOVA significance at p < 0.05.
Implications
Certification: Common carp from Diyala province (Iraq) show systemic Hg exceedance above WHO limits in most tissue compartments, consistent with documented Tigris River contamination. Pb levels approach but do not exceed WHO limits in gill tissue (mean 0.71 ppm vs. 1.5 ppm limit), warranting attention.
Courses: Illustrates tissue-specific metal distribution in freshwater fish (gills > liver for Pb and Hg; liver as first-pass accumulation organ). Documents mercury contamination in Middle Eastern freshwater fish supply chains.
App: tAs/Pb/tHg occurrence data for farmed common carp from Tigris River aquaculture system; Iraq jurisdiction.