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Comparative evaluation of heavy metal concentration in three commercially important fish: insights from organ-specific and interspecies variability

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Overview

Dinesh Kumar and colleagues compared heavy-metal concentrations across four organs (muscle, liver, intestine, gills) in three commercially important fish species landed at Ennore fishing port, Chennai (Bay of Bengal, India): Indian Oil Sardine (Sardinella longiceps, planktivorous), Indian Mackerel (Rastrelliger kanagurta, planktivorous), and Red Snapper (Lutjanus campechanus, carnivorous predator). The study is routeable for marine-fish occurrence context across both non-predatory and predatory product categories. The paper emphasizes organ-specific variation, so edible-muscle values must be separated from non-edible organ values during downstream extraction.

Key numbers

  • All concentrations are reported on a dry-weight basis in ppm (mg/kg dry tissue); the digestion procedure used 1 g of dried tissue.
  • Metals quantified (11): Cu, Cr, Al, Zn, Co, Hg, Pb, Ni, Fe, Cd, Mn, by inductively coupled plasma mass spectrometry.
  • Overall mean concentration ranking (Supplementary Table S1): Fe 525.23 ppm > Al 275.57 ppm > Zn 29.12 ppm > Mn 5.87 ppm > Cu 3.92 ppm > Cr 1.49 ppm > Ni 0.99 ppm > Co 0.25 ppm.
  • Fe ranged 4.05–4717.2 ppm and Al ranged 0.52–2663.81 ppm across organs.
  • Cd and Pb were often below the limit of quantification (BLQ). BLQ frequencies: Co 49/60 samples, Pb 34/60, Cd 32/60. Maximum observed concentrations: Cd 1.19 ppm, Pb 2.95 ppm.
  • Mean concentrations in muscle tissue (edible part): Cd 0.047 ± 0.05 ppm, Pb 0.084 ± 0.04 ppm (both dry weight).
  • Hg was consistently BLQ across all sampled tissues; the paper measured total Hg by ICP-MS and did not perform mercury speciation.
  • The authors compared muscle-tissue Cd and Pb means against WHO/FAO/Codex Alimentarius (2024) maxima of Pb 0.3 mg/kg, Cd 0.05–0.1 mg/kg, and Hg 0.5 mg/kg for methylmercury in fish.
  • Interspecies pattern: Snapper accumulated higher concentrations of most metals; Sardine carried elevated Fe, Al, and Zn; Mackerel showed the lowest levels.
  • Organ-level pattern: muscle consistently had the lowest values; liver was associated with Pb and Cu; intestine accumulated Fe, Al, Cr, and Ni; gills reflected waterborne exposure.

Methods (brief)

15 fish per species × 4 organs (muscle, liver, intestine, gills) = 60 organ samples. Tissues were dissected with sterile tools, stored at -20 °C, and 1 g of dried tissue digested at 140 °C with 5 mL concentrated nitric acid (Suprapur, Merck) in an Anton Paar microwave digestion system. Trace-element concentrations were quantified by ICP-MS (Agilent 7500). Analytical accuracy was validated against NIST CRM QC3163 (seawater). Results are total element concentrations in ppm on a dry-weight basis. The source measured total Hg by ICP-MS (consistently BLQ) and did not perform mercury speciation; report any downstream Hg routing as tHg, not MeHg.

Implications

Certification: Supports seafood metals context, but any benchmark extraction must isolate edible tissue from non-edible organs.

Courses: Useful for explaining why whole-organism or organ values cannot be silently pooled with fillet values.

App: Can inform seafood context if species and edible portion are retained.

Update history

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