Bioaccumulation and Biomagnification of Mercury Along the

Overview

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Key numbers

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levels. Indeed, MeHg constitutes 75–100% of the total mercury (THg) present in the tissues
vegetable ingredients has led to a substantial reduction in risk (11). Therefore, ensuring
The categories were as follows: (a) 0.4–0.59 mg/Kg of THg; (b) 0.60–1 mg/Kg of
THg; (c) 1.01–1.49 mg/Kg of THg; (d) above 1.5 mg/Kg of THg (exceeding the legal limit).
to geographic distribution and time trend. Between 2000 and 2012, 33.33% of analyzed
percentage of exceedance decreased, stabilizing at 28% (Table 1).
residue values in category d) (≥1.5 mg/Kg) are the large predators Thunnus thynnus (tuna),
benthic Mullus barbatus (mullet). The highest recorded value (3.37 mg/Kg) was found in
Table 1. Hg-contaminated samples between 2000–2011 and 2012–2024, divided per level of exceedance
Samples exceeding EU legal limits 27 (34.18%) 65 (28.51%)
Table 2. Summary of Hg contamination in selected fish species, with consistent exceedances of the
1 Legal limit 0.5 mg/Kg Commission Regulation (EU) 2023/915; 2 Legal limit 1.0 mg/Kg Commission Regulation
merluccius showed conflicting results (Table 3).
Table 3. Summary of Hg contamination in fish species exceeding ML, including median values,
Approximately 30% of studies (18 studies out of 60) concerning the Mediterranean area
genus exhibiting exceptionally high levels of Hg (up to 4.40 mg/Kg d.w.) (21,36) and
species from the Lophius genus displaying contamination values ranging from 0.68 mg/Kg
to 1.26 mg/Kg (n = 615) (16). Regarding apex demersal predators, the Thunnus genus
had 632 samples that exceeded the limits, showing Hg levels ranging from 1.02 mg/Kg to
3.37 mg/Kg (4,23). Xiphias gladius exhibited Hg levels above the legal limit, ranging from
fish (56). Similarly, the THg/MeHg ratio is lower in mussels than in fish (from 20% to 60%),
whereas in fish it ranges from 80% to 100% (57). In some cases, bivalve mollusks and
bivalve mollusk samples generally contain less Hg than the legal limit (59,60) (Table S1).
Hg concentrations, reaching 2.57 mg/Kg and 1.71 mg/Kg, respectively (65,66). Detailed
sharks exceeding 250 cm surpass the regulatory threshold of 1 mg/Kg established by the
have the highest Hg concentrations, with greenish (Prionace glauca) averaging 0.97 mg/Kg
and species of the genus Thunnus, such as Thunnus thynnus (0.71 mg/Kg) and Xiphias
up to 1.74 mg/Kg. Overall, 22% of examined shark and swordfish samples (n = 37) exceeded
the 1 mg/Kg Hg limit (27). Other commercially important species, such as tuna and conger
species, constituting an average of 88.1% of total Hg in the considered species (61,68–71)
revealed that 40% of muscle tissue samples from farmed specimens contained Hg levels
exceeding the European Commission’s maximum allowable limit of 1 mg/Kg (77). Ap-
proximately 38% of Thunnus samples showed Hg concentrations above legal thresholds
processes. For example, Milatou et al.’s study found that 40% of analyzed species exceeded
Between 2000 and 2012, 26.92% of analyzed samples recorded Hg levels exceeding
28.5%. During the time frame under consideration, the approval of well-defined policy
//www.mdpi.com/article/10.3390/foods14213752/s1, Table S1: Data extraction table. All references
Dwelling Omnivorous Fishes: The Case of Diplodus sargus (L.) (Osteichthyes: Sparidae). Mar. Pollut. Bull. 2018, 136, 10–21.
1. Wilman, B.; Bełdowska, M.; Normant-Saremba, M. Labile and Stable Mercury in Harris Mud Crab (Rhithropanopeus harrisii) from

Methods (brief)

Supplementary Table S1: first author, publication year; products; sample size; sampling
location/sample origin; product’s part; total Hg min (mg/kg); total Hg max (mg/kg); total
mulation studies, when multiple samples were available for the same species and location
or when samples differed only in sex or preservation method, the highest analytical value
captured and/or sampled, including specimens sold at fish markets. Sixty studies were
of sample sizes in most studies investigating Hg bioaccumulation in non-Mediterranean
samples recorded Hg levels exceeding legal limits. In the following years, up to 2024, this
Table 1. Hg-contaminated samples between 2000–2011 and 2012–2024, divided per level of exceedance
Level of Exceedance in Respect to EU Legal Limits: n. of Samples (%)
Samples exceeding EU legal limits 27 (34.18%) 65 (28.51%)
Overall analyzed samples 79 228
Reference (Year) Sampling Location Species Analyzed Sample Size THg Level (mg/Kg ww)
studies with positive results, and percentage of samples above limits.
Overall Sample Median Studies with Positive No. of Samples
had 632 samples that exceeded the limits, showing Hg levels ranging from 1.02 mg/Kg to
bivalve mollusk samples generally contain less Hg than the legal limit (59,60) (Table S1).
up to 1.74 mg/Kg. Overall, 22% of examined shark and swordfish samples (n = 37) exceeded
bluefin tuna) specimens. Three of these studies found that none of the samples surpassed

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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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