Possible Metal Burden of Potentially Toxic Elements in Rainbow Trout (Oncorhynchus mykiss) on Aquaculture Farm

Overview

Lehel and colleagues measured arsenic, cadmium, mercury, and lead by inductively coupled plasma optical emission spectrometry (ICP-OES) in the flesh of 40 farmed rainbow trout (Oncorhynchus mykiss) purchased at a Hungarian fishery market but originating from an aquaculture farm in Treviso County, Veneto Region, Italy. Mean total arsenic was 1.65 ± 0.49 mg/kg, but the authors note total As cannot be evaluated against a regulatory limit because none exists; estimating inorganic As as 5% of total As gave a mean of 0.08 ± 0.02 mg/kg, with estimated daily intake (EDI) and target hazard quotient (THQ) below reference values. Cadmium exceeded the EU maximum level in 30% of samples, but its EDI and THQ stayed below recommended limits. Mercury was below the limit of detection in all samples. Lead exceeded the EU maximum level in 10% of samples, while its EDI and THQ remained below the reference dose. The hazard index (HI) was below 1 for adults (0.86) but above 1 for children (1.22), so the authors concluded the fish is safe for adult consumption but poses a slight risk to children, particularly during long-term intake.

Key numbers

All concentrations are mg/kg wet weight in fish flesh (muscle) unless noted. Where a metal fell below the limit of detection (LOD), half the LOD value was substituted for statistical evaluation (text §2.2.4). Maximum levels (ML) referenced are EU Commission Regulation 2023/915.

Measured concentrations (Table 3, mg/kg ww):

Total As: mean 1.65 ± 0.49; min 0.54; max 2.79; 100% above LOD (LOD 0.50); no ML exists
Inorganic As (estimated as 5% of total As): mean 0.08 ± 0.02; min 0.03; max 0.14
Cd: mean 0.03 ± 0.02; detectable min 0.05; max 0.07; 30% above LOD and 30% above ML (LOD 0.05; ML 0.05)
Hg: all <0.50 (below LOD); 0% above LOD; 0% above ML (LOD 0.50; ML applied 0.50)
Pb: mean 0.16 ± 0.16; detectable min 0.24; max 0.85; 15% above LOD; 10% above ML (LOD 0.20; ML 0.30)

Exceedance detail (text §3.1–3.4):

Cd: 12 of 40 samples (30%) at or above the 0.05 mg/kg LOD; the same 30% were at or above the 0.05 mg/kg ML; the other 70% were below LOD and entered the calculation at half-ML (0.025)
Pb: 6 of 40 samples (15%) exceeded the 0.2 mg/kg LOD, highest 0.85 mg/kg; 4 of those 6 (10% of total) exceeded the 0.3 mg/kg ML
Hg: none of the 40 samples exceeded the 0.50 mg/kg LOD, so all were under the ML

Estimated daily intake (Table 3, µg/kg bw/day):

Total As: mean 1.55 ± 0.46; min 0.51; max 2.62 (no reference dose exists)
Inorganic As: mean 0.08 ± 0.02; min 0.03; max 0.13; RfD 0.3; 0% above reference
Cd: mean 0.03 ± 0.01; min 0.05; max 0.06; RfD 1; 0% above reference
Hg: <0.47 (below LOD); RfD 0.3; 0% above reference
Pb: mean 0.15 ± 0.15; min 0.23; max 0.80; RfD 0.16 (adult) / 0.26 (children); 10% above adult reference, 15% above children reference

Target hazard quotient (text §3.1–3.4):

Inorganic As: 0.26 (mean)
Cd: 0.03
Hg: not calculated (all below LOD; deemed not relevant)
Pb: 0.93 (children), 0.57 (adults)

Hazard index (text §3.5):

HI = 1.22 (children); HI = 0.86 (adults)

Provisional tolerable intake for Cd (text §3.2):

PTMI 0.90 ± 0.39 µg/kg bw vs WHO recommended 25 µg/kg bw (≈28× lower)
PTWI 0.23 ± 0.10 µg/kg bw vs WHO recommended 2.5 µg/kg bw (≈10× lower)

Validation parameters (Table 1, mg/kg):

As: LOD 0.50, LOQ 1.67, precision 12.7%, trueness 13.6%
Cd: LOD 0.05, LOQ 0.17, precision 8.4%, trueness −10.9%
Hg: LOD 0.50, LOQ 1.67, precision 12.3%, trueness 8.1%
Pb: LOD 0.20, LOQ 0.67, precision 3.5%, trueness −8.4%

QC recovery (Table 2):

ERM-CE278k mussel tissue: As 102.5%, Cd 106.5%, Pb 91.7%
ERM-CE464 tuna fish: Hg 98.1%

Exposure parameters: average EU fish consumption 23.97 kg/year → 65.7 g/day/person; average adult body weight 70 kg.

Methods (brief)

Flesh samples (10 g) from 40 rainbow trout (Oncorhynchus mykiss) were ground, homogenized, bagged, and frozen at −70 °C. A 0.5 g aliquot was microwave-digested (CEM MARS 6) in 5 mL nitric acid (69 m/m%) and hydrogen peroxide (30 m/m%), made up to 25 mL with deionized water and analysed after twofold dilution. Arsenic, cadmium, mercury, and lead were determined by inductively coupled plasma optical emission spectrometry (ICP-OES; Perkin Elmer Optima 8300 DV). Yttrium (1 mg/L) and gold (0.25 mg/L, to stabilize mercury) served as internal standards; argon purity 4.6. Certified reference materials mussel tissue ERM-CE278k and tuna fish ERM-CE464 (EC Joint Research Centre, Geel) were used for quality control (the source prints the mussel material as ERM-CE278k in its Methods text but as ERM-CE287k in its Table 2 header; the Methods form is used here). LOD and LOQ were three and ten times the SD of blank samples. Statistical analysis used Microsoft Excel and R 3.3.2; half the LOD was substituted for below-LOD samples. Arsenic was measured as total As — ICP-OES does not speciate — so inorganic As was estimated as 5% of total As rather than measured; mercury was measured as total Hg without methylmercury speciation. Note: the EU maximum level for mercury in Oncorhynchus muscle is 0.3 mg/kg ww (Reg. 2023/915), but the authors compared against 0.50 mg/kg (the fishery-product limit, equal to their Hg LOD); since all samples were below the LOD this does not affect the reported outcome.

Implications

Certification: provides total-As, Cd, total-Hg, and Pb occurrence data (wet weight, muscle) for farmed freshwater rainbow trout from an Italian aquaculture region. Cadmium exceeded the EU maximum level in 30% of samples and lead in 10%, while estimated daily intakes for all four metals stayed below reference doses; relevant occurrence and provenance data for farmed freshwater fish product categories.

Courses: useful for illustrating the distinction between exceeding a per-sample regulatory maximum level and exceeding an exposure-based reference dose, the total-vs-inorganic arsenic estimation problem in fish, and the adult-vs-children hazard-index divergence (HI 0.86 vs 1.22).

App: total-As, Cd, total-Hg, and Pb data for farmed freshwater rainbow trout contribute to species- and product-level contamination profiles; values are wet-weight muscle from a single Italian aquaculture source.

Wiki pages updated on ingest

Verification notes

Fresh-context audit subagent (2026-05-30) verdict PROMOTE; all five checks clean against the source PDF. Two ⚠️/optional items resolved as follows:

Audit noted the bottom heading is “Wiki pages updated on ingest” rather than the audit-prompt’s expected “Wiki pages this source may touch”; verified — “Wiki pages updated on ingest” is the current template heading (docs/page-templates.md) used across the corpus. False positive; no change.
Audit noted the source prints its mussel reference material inconsistently (ERM-CE278k in the Methods text, ERM-CE287k in the Table 2 header); verified against PDF p6 vs p7 — correct, this is a typo in the source itself. Added a clarifying parenthetical to the Methods section so future readers do not flag the page’s “278k” as an error. The wiki follows the Methods-prose form.
Numerical fidelity (Tables 1–3, text §3.1–3.5), speciation (tAs total with iAs estimated at 5%; tHg with no MeHg speciation), Methods, Part 12 brand firewall, and Part 2 wiki/HMTc firewall all confirmed clean.

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