Ormaza-Gonzalez et al. 2020 - Mercury, cadmium, lead in eastern-Pacific tuna products

Ormaza-Gonzalez and colleagues analyzed 8 years of regulatory testing records (2009-2016, n=2572) from the National Institute of Fisheries of Ecuador (INP), the ISO/IEC 17025 certified control laboratory for tuna products exported to the European Union. Samples were drawn from cannery production batches and covered canned tuna (solid pack, chunks, flake in water or oil) and pre-cooked frozen loins from skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares), and bigeye (Thunnus obesus) caught in the eastern Pacific. The reported wet-weight averages over the full period were 0.23 ± 0.14 mg/kg total mercury, 0.032 ± 0.027 mg/kg cadmium, and 0.058 ± 0.050 mg/kg lead - all well below the EU 1881/2006 maximum levels (Hg 1.0, Cd 0.1, Pb 0.3 mg/kg) used by the authors as comparators. A separate retail survey of 9 cans from 5 product groups purchased in Guayaquil returned still-lower means (Hg 0.043, Cd 0.012 mg/kg; Pb below the 0.01 mg/kg detection limit).

The dataset is one of the larger continuous-monitoring time series available for eastern-Pacific tuna product. The authors observe a slight downward drift in mean tHg over the study period, which they attribute to a rising proportion of skipjack (an epipelagic, lower-trophic species) in the Ecuadorean canning stream, and to improvements in on-board brine-freezing practices that reduce salt - and metal - uptake into the loins.

Key numbers

• Whole-period summary (2009-2016, n=2572 samples, wet weight; Table 1):
  • tHg mean ± SD: 0.23 ± 0.14 mg/kg; range 0.021-1.490 mg/kg.
  • Cd mean ± SD: 0.032 ± 0.027 mg/kg; range 0.007-0.210 mg/kg.
  • Pb mean ± SD: 0.058 ± 0.050 mg/kg; range 0.026-0.920 mg/kg.
  • (Abstract rounds these to 0.24 ± 0.14, 0.03 ± 0.03, 0.05 ± 0.05 mg/kg.)
• Concentration order across every year of record: Hg > Pb > Cd.
• Annual means (mg/kg wet weight; Table 1; cells left blank where the source reports no value for that year):
  • 2009 (n=34): Hg 0.30 ± 0.016; Cd —; Pb —.
  • 2010 (n=759): Hg 0.20 ± 0.15; Cd 0.034 ± 0.031; Pb 0.064 ± 0.117.
  • 2011 (n=562): Hg 0.27 ± 0.18; Cd 0.040 ± 0.030; Pb 0.046 ± 0.300.
  • 2012 (n=377): Hg 0.26 ± 0.18; Cd 0.021 ± 0.011; Pb 0.038 ± 0.005.
  • 2013 (n=377): Hg 0.25 ± 0.17; Cd 0.032 ± 0.037; Pb 0.060 ± 0.040.
  • 2014 (n=294): Hg 0.20 ± 0.11; Cd 0.044 ± 0.039; Pb 0.093 ± 0.072.
  • 2015 (n=89): Hg 0.21 ± 0.11; Cd 0.026 ± 0.011; Pb —.
  • 2016 (n=80): Hg 0.14 ± 0.08; Cd —; Pb —.
• Retail-survey samples (Guayaquil, 9 cans from 5 product groups, anonymized in the wiki): tHg 0.043 ± 0.004 mg/kg; Cd 0.012 ± 0.002 mg/kg; Pb < detection limit (0.01 mg/kg). Authors report these are 5.75x (Hg), 2.6x (Cd), and 5.8x (Pb) below the archival-set means.
• Comparator limits used by the authors (EU Commission Regulation 1881/2006): tHg 1.0 mg/kg; Pb 0.3 mg/kg; Cd 0.1 mg/kg. Whole-period archival means run 4.4x (Hg), 5.17x (Pb), and 3.1x (Cd) below those limits.
• Exceedances (over the EU comparator): 15 of 2572 samples (0.58%): 12 Cd (0.47%), 2 Pb (0.08%), 1 Hg (0.04%). Eight of the 15 were classified as statistical outliers by the authors (Hg 1, Cd 4, Pb 3).
• Notable maxima: tHg 1.49 mg/kg in 2010 (bigeye canned in oil); Pb 0.92 and 0.89 mg/kg in 2010 (bigeye pre-cooked loins). Cadmium over-limits were predominantly on skipjack product (11 of 12), with one bigeye pre-cooked loin.
• No statistically significant correlation was found between Hg, Cd, and Pb across the dataset; the authors interpret this as independent bioaccumulation pathways. The single year with a weak Hg-Pb linear relationship was 2010 (Pb = 0.424·Hg + 0.0062 mg/kg; r² = 0.128, p < 0.003).
• Theoretical bioaccumulation envelope the authors compute from published surface-water dissolved-metal ranges in the eastern Pacific (2-18 ng/kg) and a 2-6x bioaccumulation factor (Peterson et al. 1973): tuna-flesh end-concentrations of 0.012-0.042 (Hg), 0.036-0.108 (Cd), and 0.010-0.027 µg/kg (Pb) - one order of magnitude below the observed concentrations and well below safe-consumption limits.
• Ecuadorean tuna production context (IATTC 2018, cited in the introduction): annual processed volumes rose from ~200,000 mt in earlier years to 482,489 mt (2015), 471,423 mt (2016), and 477,113 mt (2017), with ~66% exported to the EU and ~8.7% to the US. Skipjack supplied roughly 44% of eastern-Pacific catches over 2009-2016; eastern-Pacific skipjack landings rose from 239,408 mt (2009) to 342,579 mt (2016).

Methods (brief)

The bulk of the dataset comes from quality-and-safety certificates issued by INP laboratories for production-batch traceability of tuna exported to the EU. Samples were drawn from canneries (skipjack, yellowfin, bigeye) and represent canned product (solid, chunks, flake in water or oil), pre-cooked frozen loins, and a small number of fresh-fish samples. Only white muscular tissue was analyzed. Drained weight was used for canned samples (oil or water removed before digestion). The retail survey purchased 9 cans from 5 product groups in Guayaquil; cans were de-labeled and coded before analysis.

Mercury was determined by microwave-assisted acid digestion (0.25 ± 0.05 g wet tissue, 10 cm³ 65% HNO3) followed by cold-vapor atomic absorption spectroscopy at 253.7 nm with stannous chloride dihydrate as reductant on a Varian SpectrAA 220z/220fs (Morgan et al. 1997; Evans et al. 2010). Calibration covered 0, 2.5, 5.0, and 10 µg Hg/dm³ in 1.5% HNO3 / 1.5% H2SO4.

Cadmium and lead were determined by AOAC Official Method 999.10 (atomic absorption spectrophotometry after microwave digestion). Sample aliquots of 0.2-0.5 g were digested in HNO3/H2O2 under pressure in a closed microwave vessel; analysis used graphite furnace AAS with background correction at 283.3 nm (Pb) and 228.8 nm (Cd) on the same Varian instrument. Reported analyte ranges were 0.1 mg/kg for Pb and 0.01 mg/kg for Cd. Cd calibration ran 0, 1, 3, 5 µg/dm³ and Pb 0, 50, 100, 200 µg/dm³ in 0.2% HNO3, with 1:4 sample dilution.

Quality control used IAEA-407 herring/capelin/anchovy fish-flesh certified reference material, plus LUTS-1 and TORT-2 reference materials. Reagent blanks, fortified (spiked) samples, and recovery tests fell within 100 ± 20%. When sample results exceeded the regulatory limits, stricter re-sampling and re-analysis were performed and the initial value was either validated or refused. Statistical analysis (means, SDs, ranges, regressions, box plots) was performed in Excel; correlation analysis was repeated year by year with Hg taken as the independent variable.

Speciation and interpretation notes

• The measured Hg analyte is total mercury (tHg); methylmercury was not speciated. The page therefore reports metals: [tHg] rather than MeHg, per CLAUDE.md Part 14.
• Cadmium and lead were quantified as total Cd and total Pb (no speciation reported); the page uses the umbrella Cd and Pb abbreviations accordingly.
• The retail-survey n=9 sample (5 product groups, brand names redacted by the original authors and additionally anonymized here) is markedly cleaner than the archival cannery-batch set. The authors do not propose a causal explanation; the difference may reflect product selection by retailers, batch heterogeneity, or sampling year (the retail survey was conducted in 2018, after the archival period). Treat the two datasets as separate occurrence strata, not as a paired comparison.
• The “tendency to decrease” in mean tHg over 2009-2016 (0.30 mg/kg in 2009 → 0.14 mg/kg in 2016) is the authors’ descriptive observation; they did not report a formal trend test with confidence intervals. Take it as a directional observation, not a statistically certified trend.
• The 2009 row reports only Hg (n=34, lab uncertainty rather than between-sample SD); Cd and Pb monitoring was not yet reported in the certificates for that year. The 2015 row lacks Pb and the 2016 row lacks both Cd and Pb in Table 1.
• The “bioaccumulation envelope” calculation (eastern-Pacific dissolved 2-18 ng/kg × 2-6x bioaccumulation) yields end concentrations one to two orders of magnitude lower than the observed tissue values. The authors note this mismatch but do not resolve it; possible explanations include higher near-coastal dissolved concentrations than the open-ocean literature values cited, dietary pathway concentration beyond simple BAF multiplication, or the conservative end of the BAF range being too low.

Implications for wiki use

This page contributes a large-n (2572) regulatory-grade occurrence dataset for canned and pre-cooked tuna product from the eastern Pacific, sampled under ISO/IEC 17025 conditions over 8 years. The dataset is especially useful as broad context for the canned-fish and marine-predatory-fish product categories: it documents that the central tendency of canned tuna in this region runs well below EU comparator limits, that the within-category spread reaches the comparator (Hg max 1.49 mg/kg; Pb max 0.92 mg/kg), and that exceedances are concentrated in bigeye (a mesopelagic species) for Hg and Pb but in skipjack for Cd. Because the dataset is product-level (canned, pre-cooked loins) rather than species-level for the majority of samples, the routing layer should treat this source as broad evidence for canned-fish / fish-marine-predatory occurrence and as exposure context for tHg, Cd, and Pb on the metal pages; it is not a species-resolved dataset of the kind needed to update species-specific contamination profiles.

The retail-survey subset (n=9, 5 anonymized product groups) is too small to anchor any percentile statement on its own but provides corroborating low-end context.

Wiki pages this source may touch

• canned-tuna
• fish
• seafood
• canned-fish
• fish-marine-predatory
• seafood
• mercury
• mercury-total
• cadmium
• lead
• eu-1881-2006-contaminants-superseded
• ecuador-nte-inen-184-2013-canned-tuna

Sources

• Ormaza-Gonzalez FI, Ponce-Villao GE, Pin-Hidalgo GM. 2020. “Low mercury, cadmium and lead concentrations in tuna products from the eastern Pacific.” Heliyon 6:e04576. DOI: 10.1016/j.heliyon.2020.e04576.
• Manual-fetch PDF: raw/manual-fetch/Kimi_Agent_Download Corruption Issue/seafood_papers/03_Marine_Predatory/Low Mercury, Cadmium and Lead Concentrations in Tuna Products from the Eastern Pacific.pdf (SHA-256 4e1bcae61ab033f68704f9d48c92ef4979ef5f927b074e58c6f6b756bc34cf28).

Verification notes

• 2026-06-03 Claude fresh ingest from manual-fetch/Kimi_Agent_Download Corruption Issue/seafood_papers/03_Marine_Predatory. Numbers cross-checked against Abstract, Table 1, Figure 2, and the exceedance counts paragraph in Section 3.
• Brand firewall (Part 12): the source mentions that the retail survey sampled “5 main brands” purchased in Guayaquil but does not name them; this page reports the retail-survey aggregate (n=9, 5 product groups) without brand attribution.
• Analyte speciation: Hg method is cold-vapor AAS on total digest (no MeHg speciation), so metals: [tHg] rather than [MeHg] or [tHg, MeHg].
• The paper’s filename mentions “Eastern Pacific” - the work is on Ecuadorean canneries processing eastern-Pacific catches; jurisdictions tag retains EC (Ecuador, production and retail) and EU (the regulatory comparator under which the dataset was generated for export QA).
• The paper engages only EU Commission Regulation 1881/2006 and FDA as comparator frameworks; it does not cite Ecuador NTE INEN 184:2013. The [[regulations/ecuador-nte-inen-184-2013-canned-tuna]] cross-link in the touch-points section is therefore jurisdictional context (this is the Ecuadorian rule that applies to the product category the paper studies), not a regulation the paper itself analyzes.
• 2026-06-03 Claude audit subagent (fresh context) verdict: PROMOTE. 5/5 checks clean. One minor polish applied: clarified NTE INEN 184 cross-link as jurisdictional context per the subagent’s Check 2 note.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.