Fish: Safe Weekly Consumption Guidance

Overview

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Key numbers

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sampling in Lake Jugla (minimum length 75 cm) and is used consistently in tables and fig-
posites (n = 119 pooled composites). A predefined core nutrient panel was available for
coverage in the core nutrient panel were: fat (100.0%), protein (100.0%), metals (100.0%),
iodine (93.7%), fatty acids (91.0%), and PFASs (83.6%) (see Table S1, Supplementary Materials;
methylmercury (MeHg) was estimated conservatively as 95% of the total mercury content
extracted with 25% TMAH at 85 ◦ C for 3 h. Tellurium (Te) was used as an internal standard
ally evaluated LB (0), MB (LOQ/2), and UB (LOQ) substitution and summarized its effect
Table S6). Where Σ4 PFAS (Σ4 PFAS = PFOS + PFOA + PFNA + PFHxS; sum on wet weight
(e.g., Hg/MeHg in mg/kg ww; Σ4 PFAS in µg/kg ww) and Cons is weekly fish consump-
µg/kg bw/week; Σ4 PFAS TWI in ng/kg bw/week). Accordingly, the weekly intake per
the EFSA TWI for MeHg (1.3 µg/kg bw/week) (5). For PFASs, exposure was characterized
A nutritional index (0–1 scale) was calculated as the arithmetic mean of the capped
Left-censored sensitivity (iodine and Σ4 PFAS). Left-censored results (<LOQ) were
addressed in the main analysis using middle-bound substitution (MB = LOQ/2). To quan-
lower-bound (LB = 0) and upper-bound (UB = LOQ) substitution for iodine and Σ4 PFAS.
and limiting hazard). Results are summarized in Supplementary Table S6.
pends on the nutritional index specification and LC handling (Supplementary Tables S6 and S7).
MeHg risk ratio at 300 g/week ranged from 0.08 (well below the TWI) up to 3.48 in the
PFAS data were available) ranged from 0.06 to 0.66, meaning that none of the measured
single stratum (Usma–Roach) (Supplementary Table S6). At the lake level, total mercury
15–25% of the ~406 g/week protein reference for 300 g of fish consumption (reflecting the
with iodine contributing minimally across strata (Figure 4; Supplementary Table S6).
Supplementary Table S3 and visualized in Figure 5. In total, 20/30 strata were categorized
can be compared to European Union maximum levels for mercury in fish (0.5 mg/kg wet
for the sum of PFOS, PFOA, PFNA, and PFHxS. In our dataset, Σ4 PFAS median concen-
trations were far below these limits (the highest median Σ4 PFAS was <1 µg/kg), which
at 100% of daily needs. This was a conservative choice taken to avoid, for example, oily fish
(Supplementary Table S6). Seasonality is another representativeness constraint. Samples
(Supplementary Table S3). If those groups in fact had undetected PFASs, their true safe
Latvian dataset, PFOA showed low detection frequency and concentrations (45% detection;
mean 0.01 ng/g ww), whereas PFOS dominated the PFAS profile (~60% of total selected
range of foods (including freshwater fish) to support dietary exposure assessments (7). In
construction (Supplementary Tables S6 and S7). EFSA’s risk–benefit assessment guidance

Methods (brief)

pooled samples stratified by lakes and species. Risks were characterized for methylmercury,
ments were left-censored and constant after limit of quantification (LOQ) handling. This
assessment (RBA) for Latvian inland lake fish using pooled samples stratified by lake and
Fish samples were collected from five major inland lakes in Latvia: Burtnieks, Jugla,
threshold provides a policy-relevant ‘high-end’ stratum rather than a representative sample
collected across the five lakes, comprising 72 perch, 73 pike, 84 tench, 79 bream, 91 roach,
posite samples based on species and lake of origin. The pooled composites were prepared
number of available pooled composites differs by analyte. Each composite sample consisted
posites typically consisted of 5–7 individual fish samples. Where individual sub-samples
composites), noting that sub-sample documentation is incomplete for many composites.
Samples were collected during two distinct periods: Autumn (September–October
1. and Summer (July–August 2025). While 134 pooled composites were collected in
pooled sample counts by lake × species are summarized in Table S2).
plasma mass spectrometry (ICP-MS) following high-pressure digestion, according to LVS
EN 15763:2010 (15). Samples were digested with nitric acid (HNO3 ) and hydrogen peroxide
(H2 O2 ) in a microwave system. Gold (Au) was added to the standard and sample solu-
(LOQ) was sufficient to detect relevant environmental levels, and measurement accuracy
these analytes were below the method LOQs and therefore did not contribute meaningfully

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

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Verification notes

Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing wiki/sources/ pages before creation.
Full-PDF read: pdftotext -layout was run on the full PDF twice; extracted text hashes matched before the page was written.
Numeric verification: numeric/table-bearing lines were selected mechanically from the verified extraction and preserved without unit conversion or rounding.
Brand firewall: the worker skips PDFs when extracted numeric lines appear brand/manufacturer-sensitive; this page contains category-level or species-level evidence only.
HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and 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.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised