Shaalan 2024 — Heavy metals in Nile tilapia muscle, Eastern Delta Egypt
This 2024 study measured concentrations of eight metals (Mg, Cd, Hg, Cr, Cu, Ni, Pb, Zn) in muscle tissue of 120 Nile tilapia collected from two sites in the Eastern Nile Delta: the Damietta branch of the River Nile (n=60) and El-Rayah El-Tawfeeky canal in Benha City (n=60). Metal concentrations were significantly higher in El-Rayah El-Tawfeeky fish across all analytes; hazard index calculations showed that habitual fish consumers at the El-Rayah El-Tawfeeky site face unacceptable non-carcinogenic risk from Cd, Hg, Ni, Pb, and Zn, while habitual consumers at the Damietta site exceed HI=1 for Ni, Mg, and Pb.
Key numbers
Muscle tissue concentrations (mg/kg, mean ± SD), wet weight, by site:
El-Rayah El-Tawfeeky canal:
- Mg: 74.533 ± 0.075
- Cd: 2.286 ± 0.115 (HI habitual: 4.651; HI normal: 1.019)
- Hg: 10.360 ± 0.075 (HI habitual: 3.512; HI normal: 0.770)
- Cr: 63.020 ± 0.346 (HI habitual: 0.051)
- Cu: 54.406 ± 0.116 (HI habitual: 0.790)
- Ni: 23.560 ± 0.019 (HI habitual: 3.993; HI normal: 0.875)
- Pb: 33.403 ± 2.068 (HI habitual: 2.718; HI normal: 0.595)
- Zn: 212.086 ± 4.328 (HI habitual: 2.016; HI normal: 0.441)
Damietta River Nile branch:
- Mg: 59.146 ± 0.980
- Cd: 0.270 ± 0.053 (HI habitual: 0.549)
- Hg: 1.500 ± 0.030 (HI habitual: 0.508)
- Cr: 38.853 ± 0.449 (HI habitual: 0.031)
- Cu: 38.986 ± 0.991 (HI habitual: 0.566)
- Ni: 20.823 ± 0.106 (HI habitual: 3.530; HI normal: 0.773)
- Pb: 14.673 ± 0.723 (HI habitual: 1.193; HI normal: 0.261)
- Zn: 99.930 ± 0.370 (HI habitual: 0.949)
Ingestion rate assumptions: habitual fish consumers = 0.1424 kg/day; general population = 0.0312 kg/day; BW = 70 kg; ED = 70 years.
All metal concentrations in El-Rayah El-Tawfeeky fish were statistically significantly higher than Damietta fish (p < 0.05). Cd and Ni in El-Rayah El-Tawfeeky exceeded WHO maximum allowable concentrations for fish.
Water concentrations (mg/L): Pb at both sites (0.146–0.152 mg/L) exceeded WHO limit of 0.1 mg/L. Hg (0.135–0.153 mg/L) far exceeded limit of 0.002 mg/L.
Methods (brief)
ICP-OES (Perkin Elmer Optima 4100DV) after nitric acid digestion and 0.45 µm filtration. LOD/LOQ: Cd/Zn 0.003/0.01; Hg 0.020/0.080; Cr 0.0033/0.011; Cu/Ni 0.006/0.02; Pb 0.0012/0.004 mg/L. Recovery 94–103%. Results expressed as µg/kg dry weight in text, mg/kg in tables. Human risk assessment used ADD and HI methodology per US EPA oral RfD values. Histopathological analysis and RT-qPCR gene expression of MyoD, IGF-1, TNFa, IL6 genes also conducted; severe pathological changes observed in El-Rayah El-Tawfeeky fish. Paper license is CC BY-NC-ND 4.0.
Implications
Certification: Provides context for freshwater fish contamination levels from heavily polluted Nile Delta sites; values are very high (Pb up to 33 mg/kg in muscle) compared to EU limits for fish (typically 0.3 mg/kg Pb wet weight), indicating severe pollution. These are not representative of commercially traded tilapia.
Courses: Demonstrates the range of contamination possible in fish from industrial/agricultural waste discharge zones; useful for illustrating why source-water monitoring matters.
App: Not directly applicable to commercial fish products; these represent extreme pollution scenarios.
Microbiome: Not addressed.