Overview
This study measured Pb, Cu, Fe, Cd, Mn, and Zn in water, sediment, and five fish tissues (spleen, muscle, liver, intestines, gills) from polyculture aquaculture ponds in two Egyptian governorates — El-Sharkia (ES; n=7 ponds) and Kafr El-Sheikh (KES; n=8 ponds) — using ICP-OES. The two fish species were Bolti (Oreochromis niloticus, Nile tilapia) and Topara (Chelon ramada, thinlip mullet), which together represent the dominant species in Egyptian aquaculture. Heavy metal concentrations were significantly higher in ES ponds than KES ponds across all matrices. Human health risk assessment (EDI, THQ, HI, carcinogenic risk) based on muscle tissue showed non-carcinogenic risk within acceptable bounds for all metals, but cadmium poses a carcinogenic risk to children consuming Bolti muscle from ES ponds.
Key numbers
Water (ppb, µg/L) — KES vs ES fishponds:
- Fe: 320.67 (KES) vs 416.00 (ES)
- Zn: 68.49 (KES) vs 110.05 (ES); WHO limit 3000 ppb
- Pb: 10.72 (KES) vs 15.40 (ES); WHO limit 10 ppb — ES exceeds limit
- Cd: 2.94 (KES) vs 5.10 (ES); ES exceeds WHO limit
Sediment (ppm dw-b, µg/g) — ranges across sites:
- Fe: 21,312–60,332
- Mn: 846–1,058
- Zn: 58.33–160.00
- Pb: 10.56–18.06
- Cd: 2.31–2.76
Fish muscle (selected from Tables 2–3; ppm dw-b): Tissue concentrations were significantly higher in fish from ES ponds. Concentrations in liver and spleen exceeded muscle levels for all metals. Muscle Pb and Cd for both species were below EU/WHO permissible limits (Pb <0.3 ppm ww for fish; Cd <0.05–0.1 ppm ww per EU Reg 1881/2006 for seafood).
Metal pollution index (MPI-HMC): Water and sediment MPI >10 (heavily contaminated) in both sites; ES fishponds more contaminated than KES. Topara muscle was the only tissue not classified as heavily contaminated.
Human health risk assessment (USEPA 2018 methodology):
- Non-carcinogenic: THQ < 1 and HI < 1 for both species and both sites (EDI-based).
- Carcinogenic: Cd CR for children consuming Bolti muscle from ES ponds exceeded acceptable limits (CR > 10⁻⁴), constituting a warning-level carcinogenic risk.
- Adult carcinogenic risk: within acceptable range for both species and sites.
Haematological/biochemical effects: Hb, RBC, PCV, MCHC, MCH significantly lower in ES fish vs KES fish; WBC, MCV significantly higher. Serum proteins, albumin, globulin reduced. Lysozyme, total Ig, and complement C3 reduced in ES fish, indicating metal-driven immunosuppression.
Methods (brief)
ICP-OES (Perkin-Elmer 4300 DV). Sample preparation per AOAC. Tissues: spleen, muscle, liver, intestines, and gills. n=3 fish/pond. Metal concentrations expressed as ppm dry weight basis (dw-b) for sediment and tissues; ppb (µg/L) for water. HRA based on USEPA (2018) EDI, THQ, HI, and CR methodology.
Limitation: Total metals only (no As speciation; no MeHg/tHg reported — Fe, Cu, Mn, Zn are essential metals not HMT&C analytes). Small n per pond (n=3). Dry-weight basis values require wet-weight conversion for comparison with most food safety limits. Cd carcinogenic risk finding for children is based on USEPA cancer slope factor applied to estimated daily intake — regulatory context-specific.
Implications
Certification: Documents Cd carcinogenic risk to children consuming tilapia from more-contaminated Egyptian aquaculture ponds. Supports Cd as the primary concern for freshwater aquaculture fish. Pb in water exceeds WHO drinking water limits in ES ponds; muscle Pb and Cd remain below EU fish limits, illustrating how water contamination does not necessarily translate to exceedance of product-level food safety limits under normal commercial aquaculture conditions.
Courses: Strong case example for the aquaculture contamination pathway: agricultural drainage water → fishpond → fish tissue bioaccumulation → human health risk. MPI-HMC methodology illustrated for multi-metal contamination assessment.
App: Provides Pb and Cd concentration ranges for Nile tilapia and mullet muscle from Egyptian aquaculture. Wet-weight values must be derived from dry-weight data using moisture content (not provided in this paper); treat as indicative ranges only without that conversion.
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| Commit | Date | Change | Description |
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