Hussein et al. 2023 — Toxic residues in Egyptian freshwater and marine fish

Hussein et al. measured Pb, Cd, total Hg, total As, and Al in 120 fish from six freshwater and marine species collected at the El-Obour city fish market in Egypt. The study reports species-level mean concentrations in edible fish flesh, exceedance counts against European Commission maximum permissible limits for Pb, Cd, and Hg, and dietary exposure calculations for Egyptian adults. Arsenic was measured as total arsenic only; the risk assessment modeled inorganic arsenic as 10% of total. Mercury was likewise measured as total mercury without methylmercury speciation.

Key numbers

• 120 fish total, collected February-August 2022: 20 each of Oreochromis niloticus, Mugil cephalus, Lates niloticus (freshwater), Epinephelus tauvina, Plectropomus leopardus, Lethrinus nebulosus (marine).
• Detection limits (µg/g): Pb 0.01, Cd 0.005, As 0.02, Hg 0.01, Al 0.10. Reference material: NRCC DORM-3 Fish Protein. Measurements expressed in µg/g wet weight.
• Pb mean concentrations (mg/kg wet weight): L. niloticus 0.31 ± 0.04, E. tauvina 0.17 ± 0.03, M. cephalus 0.11 ± 0.03, O. niloticus 0.09 ± 0.02, L. nebulosus 0.08 ± 0.01, P. leopardus 0.06 ± 0.01 (Figure 2).
• Cd mean concentrations (mg/kg wet weight): L. niloticus 0.13 ± 0.02, E. tauvina 0.11 ± 0.02, M. cephalus 0.08 ± 0.02, P. leopardus 0.07 ± 0.01, O. niloticus 0.04 ± 0.01, L. nebulosus 0.03 ± 0.01 (Figure 3).
• Total As mean concentrations (mg/kg wet weight) in species order O. niloticus / M. cephalus / L. niloticus / E. tauvina / P. leopardus / L. nebulosus: 0.13 ± 0.01, 0.21 ± 0.02, 0.25 ± 0.04, 1.13 ± 0.06, 1.09 ± 0.07, 1.03 ± 0.04 (Figure 4). Marine species concentrations significantly higher than freshwater (P<0.05).
• Total Hg mean concentrations (mg/kg wet weight) in same species order: 0.07 ± 0.01, 0.27 ± 0.03, 0.42 ± 0.05, 0.12 ± 0.01, 0.19 ± 0.03, 0.13 ± 0.02 (Figure 5).
• Al mean concentrations (mg/kg wet weight) in same species order: 2.62 ± 0.18, 2.95 ± 0.26, 3.35 ± 0.19, 2.11 ± 0.29, 1.53 ± 0.11, 1.38 ± 0.12 (Figure 6).
• Pb exceedances above 0.30 mg/kg wet weight (EC limit) per Table 1: O. niloticus 2 (10%), M. cephalus 3 (15%), L. niloticus 5 (25%), E. tauvina 4 (20%), P. leopardus 3 (15%), L. nebulosus 5 (25%).
• Cd exceedances above 0.05 mg/kg wet weight (EC limit) per Table 1: O. niloticus 4 (20%), M. cephalus 13 (65%), L. niloticus 15 (75%), E. tauvina 13 (65%), P. leopardus 8 (40%), L. nebulosus 1 (5%). The Results paragraph (page 5) lists the same species order but reverses the counts (1 (5%), 8 (40%), 13 (65%), 15 (75%), 13 (65%), 4 (20%)); Table 1 is the canonical source.
• Hg exceedances above 0.50 mg/kg wet weight (EC limit) per Table 1: only L. niloticus, 6 (30%) samples. All other species 0%.
• Average EDI values (µg/kg body weight/day): Pb 0.095, Cd 0.052, As 0.392, Hg 0.139, Al 1.600. EDI/TDI%: 2.66%, 5.20%, 18.66%, 60.96%, 1.11% respectively (Table 2). FIR set at 48.57 g/day; BW set at 70 kg for Egyptian adults.
• Average THQ values: Pb 0.024, Cd 0.052, total As 1.307, inorganic As 0.13, Hg 0.278, Al 0.002. Average HI: 1.662 on total-As basis; 0.486 on inorganic-As basis (Table 3). Only total-As THQ exceeds 1.
• Average RI for Pb: Table 3 reports 0.0008; Results text reports 0.000806. Both fall in the 10⁻⁶-to-10⁻⁴ “tolerable” range per the authors’ classification.

Methods (brief)

Edible flesh samples were dissected, homogenized in a domestic blender, and 1 g digested in 3:2 nitric acid (65%) / perchloric acid (70%) for 12 h followed by 3 h at 70°C with stirring, diluted to 20 mL with DDW, and filtered. Pb, Cd, and Al were measured by graphite furnace AAS (PerkinElmer PinAAcle 900T). The extracted methods text does not specify a separate instrument for As or Hg. Quality control used NRCC DORM-3 Fish Protein reference material. Statistical analysis used ANOVA, post-hoc Turkey–Kramer HSD via JMP. Limitations the authors name: total-arsenic-only measurement (with inorganic As modeled at 10% of total for risk calculation); no methylmercury speciation.

Implications

Certification (HMTc): Contributes occurrence data for Pb, Cd, total As, total Hg, and Al in the fresh-fish and seafood product categories, with species-level means and EC-limit exceedance counts for Pb, Cd, and Hg. The total-arsenic finding (THQ > 1 for marine species) is informative for exposure framing but not directly substitutable for inorganic-arsenic threshold work per the wiki’s speciation rule.

Courses: Teachable case study for brand QA, regulatory affairs, and supply-chain audiences. Combines market sampling, species-level residue reporting, EC maximum-limit exceedance tables, EDI/THQ/HI exposure modeling, and explicit acknowledgement of the inorganic-arsenic speciation gap.

App: May contribute to the contamination_profile for fish and freshwater-fish on Pb, Cd, tAs, tHg, and Al; relevant to the seafood ingredient for marine-species evidence on the same analytes.

Wiki pages this source may touch

• fish
• freshwater-fish
• seafood
• fresh-fish
• seafood
• lead
• cadmium
• arsenic-total
• mercury-total
• aluminum

Verification notes

• Cross-vendor audit (Codex, 2026-05-17) caught noncanonical matrix terms freshwater-fish and marine-fish; collapsed matrices: to the broad controlled-vocabulary term fish per source scope.
• The paper cites European Commission Regulation (EC) No 1881/2006 as the source of the Pb (0.30 mg/kg), Cd (0.05 mg/kg), and Hg (0.50 mg/kg) limits for fish flesh. No regulation page for EC 1881/2006 currently exists in the wiki taxonomy. EC 1881/2006 was the operative EU contaminants framework before being recast by EU 2023/915 (May 2023). Worth adding eu-1881-2006-contaminants-superseded as a regulation page so that pre-recast literature has a citable target; flagged for Karen per Part 10.
• The Results paragraph on page 5 lists the species in the same order as Table 1 but reverses the Cd exceedance counts (paragraph reads 1, 8, 13, 15, 13, 4 against species O. niloticus → L. nebulosus, while Table 1 reads 4, 13, 15, 13, 8, 1 across the same species columns). Table 1 values are used in this source page; the discrepancy is a paper-internal error, not a transcription issue.
• The paper’s Abstract reports the Pb/Cd exceedance percentages for L. niloticus as “75 and 15%” — the Pb and Cd percentages are swapped relative to Table 1, which has L. niloticus at 25% Pb and 75% Cd. This is a third paper-internal inconsistency in addition to the Results-vs-Table-1 mismatch above. Table 1 values are canonical.
• The paper’s Methods §“Analytical procedures” specifies only that Pb, Cd, and Al were measured on a PerkinElmer PinAAcle 900T graphite-furnace AAS; it does not name the instrument or method used for As or Hg, even though the QA/QC paragraph reports detection limits for both (As 0.02, Hg 0.01 µg/g) and the Results sections report mean values. The wiki page reproduces the source’s instrument attribution as-given rather than inferring a method for As/Hg.
• The paper writes the post-hoc test as “Turkey–Kramer HSD” in the Statistical analysis paragraph; the intended test is “Tukey–Kramer HSD”. The wiki page faithfully reproduces the source’s spelling.
• This page was enhanced 2026-05-17 from a GPT-5.5 fast-mode draft via the verification pipeline. Prior version (2026-05-13) had invented ingredient slugs (tilapia, mullet, marine-fish), invented method detail (“Cold vapor AAS for Hg” — not in source), and a transposition of the L. niloticus Pb/Cd exceedance percentages. All three corrected in this revision.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.