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Risk assessment of toxic residues among some freshwater and marine water fish species

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Overview

Hussein et al. measured lead (Pb), cadmium (Cd), total mercury (Hg), total arsenic (As), and aluminum (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, total arsenic (tAs), total mercury (tHg), and Al; relevant to the seafood ingredient for marine-species evidence on the same analytes.

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