Hussein et al. 2024 — Toxic metals in canned fish from Mansoura, Egypt
This Egyptian food safety study determined residual concentrations of Cd, Pb, As, Hg, Al, and Sn in 100 canned fish products (five species, 20 samples each) purchased from Mansoura city retail markets between May and September 2023. Detection used atomic absorption spectroscopy (AAS) with hydride generation and cold vapor for As and Hg respectively. The study found that sardine and tuna had the highest rates of EU limit exceedance across multiple metals, with sardine exceeding EU limits for Pb in 35% of samples, Cd in 30%, and Hg in 45%; tuna exceeded Pb limits in 25%, Cd in 25%, and Hg in 40% of samples. The estimated daily intake of Hg exceeded the tolerable daily intake for all species tested. The hazard index for canned tuna and sardines exceeded 1.0, indicating non-negligible health risk.
Key numbers
Percent of samples exceeding EU maximum limits by species (Pb / Cd / Hg):
- Herring: 20% / 10% / 10%
- Mackerel: 15% / 5% / 20%
- Salmon: 0% / 5% / 0%
- Sardine: 35% / 30% / 45%
- Tuna: 25% / 25% / 40%
Estimated daily intake of Hg: mean EDI 0.265 µg/kg body weight/day, exceeding the TDI of 0.228 µg/kg BW/day (based on FAO food ingestion rate for adults 48.57 g/day, body weight 70 kg). Al and Sn were measured; exact concentration values for Al and Sn were not fully extracted from the available text, but all Al samples were reported within acceptable limits. Sn exceedances were not reported as significant.
Analytical method: flame AAS (Perkin Elmer PinAAcle 900T) for Pb, Cd, Al, Sn; hydride generation AAS for As; cold vapor AAS for Hg. LODs (µg/g): Pb 0.01, Cd 0.005, As 0.02, Hg 0.01, Al 0.1, Sn 0.02. Reference material: DORM-3 fish tissue (NRC). Values reported in µg/g wet weight.
Note: “As” in this paper is total arsenic (tAs) measured by hydride generation AAS without speciation; inorganic arsenic fraction is not reported.
Methods (brief)
Samples purchased from normal-condition cans at retail. Digestion: 1 g flesh in 60% HNO3/40% HClO4, heated at 70°C. Health risk assessment: estimated daily intake and hazard index calculated using USEPA framework (2017) with Egyptian adult body weight 70 kg and FAO adult fish ingestion rate 48.57 g/day. Hazard quotient computed per metal; hazard index summed across metals.
Limitation: Egyptian market sample; Mansoura city only. All products were commercially canned; mix of domestic and imported brands not distinguished. Seasonal sampling (May–September) may not represent year-round market stock.
Implications
Certification: Sardine and tuna from Egyptian retail show the highest rates of Hg, Pb, and Cd exceedance in this study. The Hg EDI exceeding the TDI is a significant finding for any certification program incorporating canned fish; tHg and Hg speciation (MeHg) are both relevant but only tHg is reported here.
Courses: Useful for modules on canned fish safety, demonstrating that processing (canning) does not eliminate heavy metal contamination and that species selection significantly affects exposure.
App: Species-level risk differentiation is well supported here: sardine and tuna > mackerel > herring > salmon for Pb/Cd/Hg in Egyptian retail canned fish. Supports separate ingredient-level flagging for canned tuna and canned sardine.