Pawlaczyk et al. 2020 - mercury in canned fish from Polish retail

Pawlaczyk and colleagues measured total mercury in 84 canned fish products (plus seafood comparators and the non-fish packaging matrices) purchased in Lodz, Poland in 2019-2020, using cold-vapor atomic absorption spectrometry on an MA-3000 gold-amalgamation analyzer. The study compared mercury content across fish species, predatory versus non-predatory groupings, country of production, and packaging matrix, and used the standard Burger 1.12 division factor to estimate methylmercury from total mercury for the exposure assessment. None of the 489 individual analytical samples exceeded the EU regulatory ceilings, but tuna - and one Bonito-in-oil product in particular at 336 µg/kg - drove both the highest mean concentrations and the only meaningful share of the modeled tolerable weekly intake.

Key numbers

All concentrations are total mercury (Hg_tot) in µg/kg on a wet-weight basis unless noted. The authors do not report basis explicitly in every table; methods describe analysis of drained fish meat without reconstitution, consistent with as-consumed wet weight. The estimated methylmercury column in the exposure table is computed by dividing measured total mercury by 1.12 per Burger et al. 2004 (reference [8] in the paper).

Whole-study summary (all 489 individual samples, Table 2)

Note on Table 2 typo: the printed “Max = 35” disagrees with the printed Range = 351 and with the box-and-whisker text on the same page describing whiskers reaching ~351 µg/kg. The narrative and Tables 3-4 confirm the true study maximum is 351.3 µg/kg (one Bonito-in-oil tuna sample), so the consistent reading is Max ~351 µg/kg with the tabulated “35” being a missing-digit typo.

Top ten highest mean Hg results (Table 3, n=3 cans per product)

The paper reports per-product means under anonymised letter codes (HH, OO, ZZ, GG, TT, MM, FF, AA) that the authors use as a deliberate anti-attribution device; the table identifies product form, declared species, predatory or non-predatory classification, packaging matrix, and country of production but not the manufacturer name. The wiki carries the form/species/matrix/country columns and omits the producer codes.

The paper classifies tuna, salmon, cod, and mackerel as predatory (PR), and sprat, herring, sardine, and pollock as non-predatory (NPR). The text flags pollock at rank 4 as an exception worth noting: pollock is classified non-predatory yet appears in the top-ten with the same magnitude as predatory tuna and cod, with the authors offering bottom-feeding behaviour and fishing area as candidate explanations.

Canned tuna only (n=57, Table 4)

Predatory vs non-predatory fish (Figure 4, n=252)

Analysis of variance gave a statistically significant difference between predatory and non-predatory groups.

Origin: domestic Polish production vs imported (Figure 3, n=252)

No statistically significant difference between domestic and imported cans.

Per-species mean mercury (canned fish, narrative summaries pages 14-16)

Non-predatory fish:

Predatory fish:

Herring species split: Atlantic herring mean 61.7 µg/kg (n=33) versus Baltic herring mean 16.9 µg/kg (n=9). Cod species split: Atlantic cod mean 82.4 µg/kg versus Black cod mean 8.20 µg/kg. The paper attributes both splits to fishing-area effects (Atlantic Ocean carrying higher Hg than the Baltic Sea or coastal/closed seas).

Packaging matrix in the non-fish liquid or solid medium

Mercury was not detected (results below LOQ) in any of the analysed packaging media themselves (oils, tomato sauce, jelly, own juice, brines, vinegar, sauces). The authors interpret this as evidence that mercury bound to fish-muscle proteins does not migrate appreciably into the canning medium.

Exposure assessment (Table 5, 70 kg adult, 200 g can)

The exposure calculation uses MeHg estimated as total Hg / 1.12 (Burger 2004). For the highest-Hg product (Bonito tuna in oil, 336 µg/kg Hg_tot, ~300 µg/kg MeHg-equivalent), the modelled real MeHg intake for a 70 kg adult eating one 200 g can per week is 858 µg per person per week, equal to 53.6 percent of the JECFA provisional tolerable weekly intake of 1.6 µg/kg b.w./week. Reaching the full PTWI would require 1.88 cans per week of that single highest product.

Table 6 extends the exposure calculation to subpopulations (children >= 6 years old, women of childbearing age) using WHO consumption data and a separate Skipjack reference value of 0.14 mg/kg mean and 0.49 mg/kg max. Assessed dietary exposure for the “eaters only” subgroup exceeded the 1.6 µg/kg b.w./week PTWI in all WHO scenarios and in the children’s group when applying this study’s maximum tuna concentration.

EU regulatory comparison

Commission Regulation (EC) 1881/2006 sets the mercury maximum at 1.0 mg/kg wet weight for the listed predatory species and 0.5 mg/kg wet weight for other fishery products. None of the 489 individual samples in this study exceeded the applicable ceiling on a per-sample basis; the highest single sample at 351.3 µg/kg sits at roughly 35 percent of the 1.0 mg/kg predatory ceiling.

Methods (brief)

Eighty-four canned fish products were purchased from local markets in Lodz, Poland over 2019-2020, covering 25 brands across 19 canned-fish brands and six seafood/sushi brands. Each can yielded triplicate analytical samples; the non-fish packaging matrix from each can was measured separately in duplicate (with a third only if the first two disagreed). Total 489 individual analytical samples.

Total mercury was determined by an MA-3000 automatic mercury analyser (Nippon Instruments Corporation, Tokyo, Japan), a cold-vapor AAS with a gold-amalgamation pre-concentration step at 253.7 nm. No wet pre-digestion was used; the gold-trap thermal-decomposition design lets the instrument accept raw fish-tissue aliquots directly. Each analytical aliquot was 0.05-0.10 g of drained fish muscle taken from different locations within the can. The calibration range used standards of 0, 1, 2, 5, and 10 ng Hg in L-cysteine matrix; the working range was the lower-than-10-ng cell.

Quality control used two certified reference materials produced under the Polish MODAS project: M-3 HerTis (MODAS-3 Herring Tissue, certified 227 +/- 21 µg/kg) and M-5 CodTis (MODAS-5 Cod Tissue, certified 310 +/- 22 µg/kg). Across 27 measurements of each CRM the mean recoveries were 99.9 percent (HerTis) and 99.6 percent (CodTis). The reported method limit of quantification was 0.24 µg/kg.

Methylmercury was not measured directly; the paper applies a division factor of 1.12 (Burger 2004) to total mercury for the exposure assessment, with explicit acknowledgement that MeHg-to-tHg ratios in the literature range from approximately 75 to 100 percent. Statistical analysis used STATISTICA 12; group comparisons used the Kruskal-Wallis non-parametric test because the data failed Kolmogorov-Smirnov and Shapiro-Wilk normality tests.

The drained-fish-muscle analytical basis means the values are most directly comparable to as-consumed wet weight after the consumer drains the can.

Implications

Certification: This is direct as-purchased Polish-retail canned-fish total-mercury occurrence evidence, with usable per-species and per-form breakdowns for the certification-relevant categories (canned tuna, canned herring, canned mackerel, canned sardine, canned sprat, canned salmon, canned cod, canned pollock, canned octopus, canned crab, canned mussel). The mercury values reported are total mercury by direct CV-AAS, not measured methylmercury; the paper’s MeHg numbers in the exposure table are an algebraic estimate using the 1.12 division factor and should not be promoted to wiki cells as if they were measured MeHg. The dataset is broad in coverage but per-species n is modest (e.g., 57 tuna, 33 Atlantic herring, 9 Baltic herring); the highest-form rank of Bonito-in-oil tuna at 336 µg/kg is a useful upper-tail data point against the 1.0 mg/kg EU ceiling. The pollock-as-non-predatory contradiction with the rank-4 magnitude is a useful counterexample when explaining why predator-status proxies alone do not predict canned-fish mercury risk.

Courses: Compact case study for explaining (a) why fishing area and species often outweigh the predator-vs-prey heuristic in canned-fish mercury risk, (b) how regulatory compliance (“no sample exceeded the EU limit”) and consumer-facing exposure messaging (“vulnerable subpopulations can exceed the methylmercury PTWI”) can coexist on the same dataset, and (c) how MeHg estimates from total Hg via a fixed correction factor differ from direct speciation analysis.

App: Values feed canned-fish and canned-tuna tHg occurrence cells with as-consumed wet-weight semantics. Do not propagate the algebraic MeHg-equivalent column to the MeHg cell; that field requires directly measured MeHg per the wiki’s speciation-distinction rule.

Microbiome: Not addressed.

Verification notes

PDF read in full across pages 1-27 of the published Molecules 25:5884 article (DOI 10.3390/molecules25245884). All numerical tables (Table 1 CRM statistics; Table 2 study-wide statistics; Table 3 top-ten ranking; Table 4 canned-tuna statistics; Table 5 PTWI exposure; Table 6 subpopulation exposure; Table 7 sample-type characterisation) were transcribed against the PDF. The Table 2 Max = 35 versus Range = 351 internal disagreement is documented above; the wiki carries the Range-consistent reading of ~351 µg/kg.

Brand-firewall handling: The paper uses two-letter anonymised producer codes (HH, OO, ZZ, GG, TT, MM, FF, AA, EE, NN) in place of brand names; these are explicitly the authors’ anti-attribution device, not real brand identifiers. The wiki carries the per-product mercury values with product form, declared species, predatory classification, packaging matrix, and country of production, and omits the producer letter codes to keep this page firmly inside the brand-firewall posture. Country-of-production codes (POL, GER, UK, TH, MA, PH, NOR, IT, EC, LV) are origin-of-manufacture, not brand identifiers, and are retained.

Speciation: The paper measured total mercury by CV-AAS and estimated methylmercury by dividing total Hg by 1.12 (the Burger 2004 correction factor). The metals frontmatter carries tHg and MeHg so the source routes to both metal pages, but the wiki narrative explicitly distinguishes measured tHg from estimated MeHg-equivalent throughout to satisfy the iAs/tAs/MeHg/tHg speciation discipline.

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.