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Organ-specific bioaccumulation and deterministic health risk assessment of selected heavy metal(loid)s in commercial fish from a southern harbor region (Nagapattinam)

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Overview

Ray and Vashishth profiled arsenic, cadmium, chromium, mercury, lead, strontium, and vanadium in three organs (liver, gills, and muscle tissue) of three commercially important fish species (Nemipterus japonicus, Oreochromis mossambicus, and Lates calcarifer) from the Nagapattinam coastal fish market in Tamil Nadu, India. Analysis used ICP-MS. Metal concentrations in fish were in the range 0.025-21.53 micrograms/g (dry weight). Non-carcinogenic THQ was below 1 for all species under both adult and child consumption scenarios. However, the cancer risk (CR) for chromium in Nemipterus japonicus was elevated under the worst-case conservative assumption that all chromium is hexavalent (children 1643.58 x 10^-6; adults 939.19 x 10^-6), well above the acceptable threshold of 1 x 10^-4. The authors note this assumption substantially overstates risk for fish where chromium is predominantly trivalent.

Key numbers

  • Sample set: 9 fish (3 replicates per species) collected January-February 2024 from Nagapattinam local fish markets (10.7672 degrees N, 79.8449 degrees E). Mean lengths: Nemipterus japonicus 16.1 +/- 0.72 cm, Oreochromis mossambicus 16.9 +/- 0.30 cm, Lates calcarifer 15.9 +/- 0.24 cm.
  • Analytical method: ICP-MS (PerkinElmer NexION 1000, Vellore Institute of Technology). Three organs (liver, gill, muscle) desiccated in laboratory oven at 40 degrees Celsius to consistent weight, ground to fine powder. Acid digestion: 25 mg dry weight sample, 8 mL 30% hydrogen peroxide and 8 mL laboratory-grade 67% nitric acid, 220 degrees Celsius on a hot plate for 8 h (approximate). Transferred to 10 mL volumetric flask with 2% HNO3. R-squared calibration values 0.9981-1.00.
  • LOD (micrograms/g): 0.001-0.010; LOQ (micrograms/g): 0.005-0.030 depending on element. Percentage recoveries 90-105% from spiked matrix samples.
  • Metal concentration ranges in all fish (all organs combined): 0.025-21.53 micrograms/g (dry weight). Values not separately tabulated for each species/organ combination in the pages reviewed.
  • PTWI values used (micrograms/kg body weight/week, citing FAO/WHO and Scientific Opinion on Lead in Food 2010): arsenic (inorganic) 15; cadmium 7; lead 25; mercury 4; strontium 7000; vanadium 7.
  • Reference doses used (RfD, mg/kg/day): arsenic 0.0003; cadmium 0.001; lead 0.0035; mercury 0.0001; strontium 0.6; vanadium 0.009; chromium (Cr-III) 1.5; chromium hexavalent chromium (Cr-VI) 0.003.
  • Ingestion rates: 75 g/day (children, body weight 20 kg) and 150 g/day (adults, body weight 70 kg) standardised fish consumption values used for EDI calculation.
  • THQ values below 1 for all species under both adult and child consumption scenarios, indicating no significant non-carcinogenic risk under assumed intake scenario.
  • Cancer risk (CR) for chromium: Nemipterus japonicus children 1643.58 x 10^-6, adults 939.19 x 10^-6; under conservative worst-case assumption all total chromium is Cr-VI. Authors note this assumption inflates CR estimates for fish (dietary chromium is predominantly Cr-III).
  • DIL (Daily Intake Limit) and MDI (Maximum Daily Intake) also calculated for each metal; CRlim (Concentration Risk Limit) derived for comparison with measured values.

Methods (brief)

A purposive sampling technique with 3 replicates per species was employed, all fish purchased as dead from local landing batches. Fish were dissected using Teflon knives; liver, gill, and muscle tissues excised using metal-free instruments; isolated organs desiccated to constant weight at 40 degrees Celsius, ground to fine powder using mortar and pestle. 25 mg dry weight per sample subjected to acid digestion in a closed heat-resistant receptacle (specifically, Teflon tubes) using 8 mL 30% hydrogen peroxide (H2O2) and 8 mL 67% nitric acid (HNO3, Nice Chemicals) at approximately 220 degrees Celsius on a hot plate for 8 h. Mineralized samples transferred to 10 mL volumetric flask with 2% HNO3, tenfold dilution prepared. All samples analysed in triplicate. External calibration used multi-element standard solutions in the same acid matrix. Internal standards corrected for instrumental drift and matrix effects. Helium collision mode (He KED) with triple cone interface. No certified reference material for fish tissues was analysed in the study. The study represents a cross-sectional assessment from a single seasonal sampling period (dry season south-east coast of India, January-February 2024) at a single harbor.

Implications

  • Certification (HMTc): Total chromium in Nemipterus japonicus exceeded WHO limits under the conservative worst-case Cr-VI assumption used by the authors. For HMTc purposes, chromium speciation (Cr-III vs Cr-VI) is essential before any certification-related action on this finding; applying a Cr-VI cancer slope factor to unspeciated total chromium in fish is a known methodological limitation.
  • Courses: Useful case study for teaching organ-specific bioaccumulation patterns and the methodological significance of chromium speciation in cancer risk assessment. Illustrates why THQ < 1 (no non-carcinogenic concern) and elevated CR can co-exist for the same food.
  • App: Concentration data are from a single seasonal cross-sectional study at one harbor in Tamil Nadu. Insufficient sampling depth to represent population-level contamination baselines for these species in India or globally.
  • Microbiome: No microbiome data.

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