Naz et al. 2025 — Cd, Cu, Pb, and Ni in freshwater fish from Punjnad headworks, Pakistan
This study measured cadmium, copper, lead, and nickel in the liver, gills, and muscle tissue of five freshwater fish species collected from the right and left banks of Punjnad headworks in Punjab, Pakistan, where five rivers (Beas, Sutlej, Ravi, Chenab, and Jhelum) converge and industrial and agricultural effluents contribute to elevated metal burdens. Wallago attu, a carnivorous catfish at the top of the local food chain, showed the highest accumulation across all four metals and all organs, with liver lead reaching 46.03 mg/kg in the right bank during winter; the right bank consistently showed higher metal concentrations than the left bank, consistent with differential industrial discharge patterns. Human health risk assessment using THQ found that Cd and Pb had THQ >1 for both mature and juvenile regular consumers, and the total target hazard quotient (TTHQ) exceeded 1 for all five species, indicating that fish from both banks were unsafe for consumption under routine intake scenarios. The study is one of the few to characterize Punjnad headworks specifically for multiple metals across seasons and banks, and provides baseline data for a heavily populated agricultural region of Pakistan with few prior contamination records at this site.
Key numbers
- Species: Rita rita, Sperata sarwari, Wallago attu, Mastacembelus armatus, Cirrhinus mrigala
- Sample size: 27 fish total; 3 fish per species per season; sampled November 2021–July 2022
- Method: AAS (Analytik Jena NovAA 400P), acetylene-air flame; LODs: Cd 0.10 mg/kg, Cu 0.05 mg/kg, Pb 0.5 mg/kg, Ni 0.5 mg/kg; validated against CRM IAEA 407, recovery 95–101%
- Analytes measured: Cd, Cu, Pb, Ni (mg/kg, wet weight)
- Organs analyzed: liver, gills, muscle (liver consistently highest, muscles lowest)
- Highest single value (liver, W. attu, winter, right bank): Pb 46.03 ± 10.56 mg/kg; Cd 15.25 ± 2.47 mg/kg; Cu 7.48 ± 1.81 mg/kg; Ni 11.68 ± 1.23 mg/kg
- Highest muscle Pb (W. attu, winter, right bank): 20.36 ± 2.48 mg/kg
- Lowest muscle concentrations (C. mrigala, winter, left bank): Cd 1.45 ± 0.30 mg/kg, Cu 0.57 ± 0.06 mg/kg, Pb 8.29 ± 1.65 mg/kg, Ni 1.48 ± 0.24 mg/kg
- THQ order: Cd > Pb > Ni > Cu across all species
- THQ >1 for Cd and Pb (all fish species, both consumer categories)
- TTHQ >1 for all five fish species (mature and juvenile, regular and seasonal consumers)
- MPI index: moderate to high contamination in all fish species
- Right bank > left bank for all metals in all fish species (statistically significant, p < 0.00)
- Seasonal pattern: summer > other seasons for TTE accumulation (p < 0.00)
- RfD values used: Cd 0.001, Cu 0.04, Pb 0.004, Ni 0.02 mg/kg/day (US EPA)
- Ingestion rates: mature 0.20 kg/day, juvenile 0.10 kg/day; exposure frequency regular 365 days/year, seasonal 150 days/year
Methods (brief)
Freshwater fish collected monthly from November 2021 to July 2022 at two sites 5 km apart (right bank: 29°23’46.9N, 71°01’48.7E; left bank: 29°23’01.0N, 71°05’34.8E). Non-metallic sampling equipment to prevent contamination. Three organs dissected: liver, gills, muscle. Acid digestion (HNO3:HClO4, 3:1, 100°C, 4–5 hours). AAS analysis at Central Laboratory, MNSUA, Multan. Statistical analysis: one-way ANOVA with Duncan multiple range test (α < 0.05), Pearson correlation, PCA, and HCA. Human health risk assessment: THQ and TTHQ for four consumer categories (mature/juvenile × regular/seasonal), plus Metal Pollution Index (MPI). Concentrations reported as mg/kg wet weight. Note: Cu is not a regulated heavy metal of toxicological concern at the levels reported here; Cd and Pb are the primary toxicological endpoints from this study.
Implications
Certification: Provides muscle-tissue concentration data for Pb and Cd in five freshwater fish species from an industrially impacted South Asian river system. The TTHQ >1 finding for all species supports the principle that origin-of-catch matters for freshwater fish safety assessments. Pb values in muscle tissue are high relative to regulatory thresholds (EU maximum level for muscle fish meat: 0.30 mg/kg for Pb; several species here are well above this in all seasons).
Courses: Useful case study for the bioaccumulation module: liver > gills > muscle hierarchy is clearly demonstrated across all five species, seasons, and banks. The right-bank vs. left-bank comparison illustrates how localized industrial discharge creates differential contamination even at the same geographic site.
App: Provides muscle-tissue Pb and Cd data for freshwater catfish and carp species from a contaminated South Asian site. Not generalizable to other geographies without caution, but informative for origin-of-catch risk framing.