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Health hazard assessment and cooking effects on toxic metals in marine fish from the mediterranean sea at the Damietta Coast, Egypt

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Overview

Makroum and colleagues determined arsenic, mercury, lead, and cadmium concentrations in dorsal muscle tissue of three commercially consumed marine fish species (thinlip grey mullet, sardines, sand smelt) collected from the Mediterranean Sea at the Damietta Coast, Egypt. Ninety raw samples per species were analysed, and sub-sets of 30 samples each were subjected to grilling (15 specimens per species) and frying (15 specimens per species) to assess cooking effects. 100% of samples exceeded the permissible maximum level (ML) for arsenic. Frying and grilling significantly reduced metal levels in all species. The Total Target Hazard Quotient (TTHQ) exceeded 1 in all tested fish samples for arsenic and lead, indicating probable non-carcinogenic chronic health risks under the assumed Egyptian consumption scenario.

Key numbers

  • Mean concentrations in raw fish (mg/kg wet weight, mean +/- SE): thinlip grey mullet: arsenic 2.29 +/- 0.22; mercury 0.119 +/- 0.019; lead 0.651 +/- 0.131; cadmium 0.042 +/- 0.009. Sardines: arsenic 1.68 +/- 0.18; mercury 0.098 +/- 0.018; lead 1.011 +/- 0.169; cadmium 0.049 +/- 0.008. Sand smelt: arsenic 1.87 +/- 0.16; mercury 0.055 +/- 0.057; lead 0.965 +/- 0.186; cadmium 0.052 +/- 0.009.
  • 100% of fish samples exceeded the permissible ML for arsenic. Mercury levels were within safe limits for all tested samples.
  • TTHQ exceeded approved limits for arsenic and lead in all fish species.
  • Cooking effects: frying and grilling significantly reduced metal concentrations in cooked vs raw muscle; risk assessments based on raw fish overestimate risk for cooked fish consumers.
  • Cancer slope factors (CSF) used: arsenic 1.5, cadmium 0.38 (mg/kg/day)^-1 (USEPA values). No CSF recorded for mercury or lead.
  • Reference doses (RfD) used: arsenic 3 x 10^-4 and 1 x 10^-3 mg/kg/day for methylmercury and cadmium respectively; lead 4 x 10^-3 mg/kg/day.
  • Exposure scenario: average adult body weight 70 kg; daily fish ingestion rate 57.1 g (0.0571 kg/day) per FAOSTAT data for Egypt; BMDL for arsenic (EFSA, cardiovascular) 0.63 micrograms/kg body weight/day.
  • Analytical method: AAS (Atomic Absorption Spectrophotometer, Buck Scientific USA 210 VGP) for lead and cadmium (oxidising air-acetylene flame); mercury hydride cold vapour technique for mercury and arsenic. LODs: arsenic 0.033 mg/L, mercury 0.017 mg/L, lead 0.007 mg/L, cadmium 0.005 mg/L. LOQs: arsenic 0.067 mg/L, mercury 0.067 mg/L, lead 0.017 mg/L, cadmium 0.017 mg/L.
  • Validation: certified reference material (CRM) Dogfish liver (DOLT-4, National Research Council of Canada) used. Recovery for cadmium 96.3%; lead not stated for the CRM (CRM values below method LOD for arsenic (As), mercury (Hg), Pb). Spike recovery for arsenic 98.2%, cadmium 94.4%, mercury 96.6%, lead 94.4% (Table 2).
  • Calibration curves prepared with standards at 0.01, 0.02, 0.1, 0.5, 5, and 20 mg/L for cadmium and arsenic; 0.005, 0.01, 0.05, 0.25, 2.5, and 10 mg/L for lead; 0.01, 0.05, 0.1, 0.5, 2, and 5 mg/L for mercury.

Methods (brief)

Two grams of dorsal muscle from each specimen were digested in a mixture of 12 mL concentrated HNO3, 8 mL concentrated HClO4, and 4 mL HCl in a water bath at 53 degrees Celsius overnight. Digests were filtered through Whatman Filter Paper Grade 42, made to 50 mL with deionised water. Blank solutions and matrix-matched standard solutions were run in parallel. Precision criteria followed AAS-specific instrumental guidelines (Table 2 of source). Sampling sites at 3 locations between 31 degrees 34 minutes N and 31 degrees 47 minutes E; 31 degrees 30 minutes E and 31 degrees 56 minutes E on the Egyptian Mediterranean coast. Fish identified to species and body weight/length measured. Cooking sub-sets (15 specimens per species per method) were raw vs grilled or fried (not boiled); cooked samples taken from the same muscle on the opposite side of the fish.

Implications

  • Certification (HMTc): Very high arsenic concentrations (mean thinlip grey mullet 2.29 mg/kg, sardines 1.68 mg/kg, sand smelt 1.87 mg/kg) in these Egyptian Mediterranean fish samples substantially exceed EU maximum levels for fish (1 mg/kg total arsenic for certain species under Regulation (EU) 2023/915). However, the paper reports total arsenic without speciation; inorganic arsenic fractions would need to be measured or estimated before HMTc-row application. Lead concentrations in sardines (mean 1.011 mg/kg) and sand smelt (0.965 mg/kg) also exceed the EU ML of 0.30 mg/kg for fish.
  • Courses: Useful demonstration that cooking (frying and grilling) can materially reduce metal concentrations in fish muscle, and that risk assessments conducted on raw fish may overstate exposure for typical consumers of cooked fish.
  • App: Concentration values are specific to the Damietta Coast Mediterranean environment. Regional industrial and agricultural discharge patterns influence these values and they should not be treated as globally representative baselines for these species.
  • Microbiome: No microbiome data.

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