Toxic metals and metalloids in collagen supplements of fish and jellyfish origin: Risk assessment for daily intake

Summary

This is a primary occurrence survey of toxic metals and metalloids in collagen supplements of marine origin, covering both fish-derived and jellyfish-derived products. The authors measured arsenic, chromium, cadmium, lead, and mercury in 120 samples spanning 4 species-labeled brands (Atlantic cod, Pangasius, jellyfish Rhizostoma pulmo, Tilapia) sold on Italian e-commerce and retail channels during 2022–2023, plus a lab-extracted Scomber scombrus (mackerel) skin collagen for comparison. The load-bearing findings are that (1) arsenic is the dominant contaminant in fish-derived collagen — total arsenic (As) reached 1.11 mg/kg in the Atlantic cod brand and showed significant between-brand variation; (2) the Pangasius brand carried the highest mean concentrations of lead, cadmium, and chromium (with the highest lead (Pb) and cadmium (Cd) maxes; Tilapia held the chromium (Cr) max); and (3) the jellyfish-derived (R. pulmo) brand and the in-house S. scombrus skin extract showed non-detectable concentrations for every metal measured, identifying jellyfish and mackerel-skin substrates as potential low-contaminant alternatives. No sample exceeded EU Regulation 2023/915 maximum levels (Cd 3 mg/kg, Pb 3 mg/kg, mercury (Hg) 0.1 mg/kg for food supplements), and all estimated average daily intakes were below the relevant tolerable daily intakes used by the authors. For the Index, this establishes arsenic as the priority analyte for fish-derived marine collagen supplements, with the fish/marine origin as the plausible route for the arsenic burden, and identifies jellyfish-origin collagen as an empirically lower-contaminant substrate within the same product category.

Key numbers

ICP-MS for As, Cr, Cd, Pb on UltraWAVE-digested samples; direct mercury analyzer (DMA-80, atomic absorption) for Hg. Concentrations expressed as mg/kg wet weight of supplement. Arsenic is total As; the authors apply the EFSA inorganic arsenic (iAs) reference (0.3 µg/kg/day BMDL01) to the measured total As for the risk-assessment step but do not perform iAs speciation. Chromium is total Cr (no hexavalent chromium (Cr-VI) speciation).

Pooled totals across the dataset (Table 3, last row):

Between-brand pattern (Table 3, by labeled species):

• Atlantic cod (Gadus morhua, Brand 1): As mean 0.912 ± 0.16, max 1.11 mg/kg — significantly higher mean As than other brands (p = 3 × 10⁻⁷); Pb mean 0.123 ± 0.023, max 0.038 as printed in Table 3 (this value is internally inconsistent with the stated mean and the Figure 1 boxplot — see Verification notes); Cd mean 0.002 ± 0.002, max 0.006; Cr mean 0.054 ± 0.02, max 0.08.
• Pangasius (P. hypophthalmus, Brand 2): highest Pb (mean 0.136 ± 0.03, max 0.201), Cd (mean 0.003 ± 0.003, max 0.013), Cr (mean 0.053 ± 0.01, max 0.08), and the only brand with detectable Hg (max 0.0018 mg/kg in 2 samples); As mean 0.484 ± 0.16, max 0.64.
• Jellyfish (Rhizostoma pulmo, Brand 3): n.d. for all 5 metals measured.
• Tilapia (Tilapia spp., Brand 4): As mean 0.390 ± 0.2, max 0.71; Pb mean 0.125 ± 0.01, max 0.14; Cd mean 0.002 ± 0.001, max 0.011; Cr mean 0.040 ± 0.03, max 0.14.
• S. scombrus skin extract (in-house, not commercial): n.d. for all 5 metals measured.

Compliance and intake context:

• No sample exceeded EU Reg 2023/915 maximum levels for food supplements (Cd 3 mg/kg, Pb 3 mg/kg, Hg 0.1 mg/kg).
• Average daily intakes (ADDs) at 5 g and 10 g daily doses for a 67.7 kg adult woman were below the corresponding TDIs for iAs (0.3 µg/kg/day BMDL01, EFSA), Pb (0.5 µg/kg/day BMDL01, EFSA), and Cd (0.36 µg/kg/day from TWI 2.5 µg/kg/week, EFSA). Table 4 reports per-brand and pooled ADDs (e.g., total Pb ADD 1.4 × 10⁻² µg/kg/day; total iAs ADD 4.9 × 10⁻² µg/kg/day; total Cd ADD 3 × 10⁻⁴ µg/kg/day) and shows all ADD-as-percent-of-TDI values rounding to 0 at the precision printed. The authors qualitatively flag Pb as “alarming” in the Conclusions despite the formal compliance.

Methods (brief)

UltraWAVE microwave digestion (3 mL 60% HNO₃ + 5 mL ultrapure water; ~0.1 g supplement) followed by 0.45 µm filtration to 50 mL final volume. ICP-MS on Agilent 7700x for As, Cr, Cd, Pb; the LOD by 3σ and LOQ by 10σ approach. Hg measured separately by Milestone DMA-80 direct mercury analyzer (atomic absorption at 250 nm, no digestion required). 7-point calibration with r² > 0.999; CRM DORM-5 (fish protein) verified accuracy; recovery 96–105% across three concentration points. Repeatability and within-laboratory reproducibility assessed across three days with operator changes. Not-detected values imputed at LOQ/2 for statistical analysis (Shapiro–Wilk normality, Kruskal–Wallis between-brand). Risk step used EFSA inorganic-As assumption applied to total As; reference body weight 67.7 kg (woman).

Implications

• Establishes total arsenic as the priority toxic metal for fish-derived marine collagen supplements within Ingredient class — protein/collagen powders, with Atlantic cod showing the highest As burden and Pangasius the highest co-burden of Pb, Cd, and Cr. Complements the protein-powder cadmium signal from bandara2020-protein-powder-heavy-metals — collagen powders track arsenic (and a Pangasius-specific multi-metal burden), protein/whey powders track cadmium.
• Jellyfish-derived collagen (R. pulmo) and mackerel-skin (S. scombrus) extract show non-detectable toxic metals across the full panel, identifying jellyfish biomass as an empirically lower-contaminant substrate. Relevant to supply-chain screening for collagen sourcing and to any future product subcategory that distinguishes source-organism within collagen powders.
• Contributes occurrence evidence to Arsenic (1.11 mg/kg max, fish-marine route), Lead (0.201 mg/kg max, Pangasius-driven), Cadmium (low-level but near-ubiquitous in fish-derived; n.d. in jellyfish), Chromium (low-level, total Cr only, no Cr-VI speciation), and Mercury (largely absent except in Pangasius).

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