A Novel Approach to Estimate Mercury Exposure Risks Through

Overview

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Key numbers

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mercury and selenium concentrations in samples (n = 309) of fish tissues and analyzed
positive HBVSe values were found in 42% of the fish samples (n = 131). As a result, we
This article is an open access article table (1). Se is essential for the enzymatic activity of many proteins (selenoproteins) that act
herbivores (n = 60), detritivores (n = 77), planktivores (n = 61), carnivores (n = 47), and
5.0 mL of potassium permanganate (KMnO4 at 5% w/v, Merck® ), again at 70 ◦ C, for
(NH2 OH.HCl 12% w/v, Merck® ). The samples were adjusted to a final volume of 14 mL
About 0.5 mL of hydrogen peroxide (H2 O2 30%, Merck® ) was added to each sample and
then another 4.0 mL of 5.0 mol−1 nitric acid (HNO3 65%, Merck® ). After 30 min in the
(HCl 37%, Merck® ) was added. Then after 30 more minutes in the digester block, the
(BCR-463, Joint Research Center) was used, with recovery of 97.7 ± 0.5% for THg (n = 8,
(DORM-2, National Research Council Canada) was used, with recovery of 102.5 ± 0.6%
(n = 3, LOD = 0.005 mg kg−1 , and LOQ = 0.015 mg kg−1 ). The glassware was previously
decontaminated with HNO3 (3%, Merck ® ), and analytical blanks were used to guarantee
The Hg concentrations in all samples (n = 309) were compared directly with the
concentrations of Hg relative to Se) (n = 178, Table S3).
The variables were classified into five risk levels (Table 1). Total Hg, Se:Hg, and
(Table 1). Harmony degrees (HDs) were then calculated for both risk and benefit indicators,
Table 1. Classification of input variables for normalization by harmony degrees and calculation of
evaluated using the Kruskal–Wallis test, followed by Dunn’s post hoc test (n = 309). The
test (n = 178). Kendall’s non-parametric correlation was employed to assess the relation-
these associations was weak to moderate (Table S4). Therefore, THg and Se concentrations
models (traditional and Se-inclusive) (n = 178). A significance level of p < 0.05 was adopted
species of the five trophic guilds evaluated, namely Mylossoma aureum (herbivore, n = 29),
Hemiodus unimaculatus (detritivore, n = 34), Hypophthalmus marginatus (planktivore, n = 37),
Cichla pleiozona (carnivore, n = 36), and Serrasalmus rhombeus (piscivore, n = 38) (Table S5).
guilds (p < 0.05, Table S6). Hg concentrations were above those recommended by
rous (0.188 ± 0.060 mg kg−1 ) species (Figure 2b, Table S7). Principal component analysis
explained 85.1% of the variation in the data. Axis 1 (61.1%) revealed a high dissimilarity
Molar ratios greater than one and positive HBVSe values were found in 42% of the
and planktivorous species (n = 34), along with a small number of carnivores (n = 3)
species (KW = 146.5; p < 0.0001) (Figure 4a, Table S7). Similarly, HBVSe values were
and carnivores (−0.0157 ± 0.0142) (KW = 139; p < 0.0001) (Figure 4b, Table S7).
nivores (Table 2). All trophic guilds showed average Hg consumption above that recom-
(p < 0.05, Table S6). Mean Hg intake ranged from 0.43 ± 0.36 to 4.86 ± 2.93 µg kg−1 day−1
for herbivores and carnivores, respectively (Table 2). Despite the reduction in estimated
threshold of 0.57 µg kg−1 day−1 , representing a 73% reduction compared to model I. The
smallest decreases in EDI between models were observed for carnivorous (41.8 ± 19.4%)
samples (n = 26) exhibited EDI values below the safety threshold, mainly herbivorous
(n = 10) and planktivorous (n = 10) species, with lower occurrences among carnivorous
Table 2. Descriptive statistics of the estimated daily intake (EDI) of Hg using the traditional approach
and fuzzy logic revealed that most fish samples posed a low (33.7%) or moderate (24.7%)
risk (1.1%) (Figure 5, Table S8). In addition, over half of the individuals who presented a

Methods (brief)

mercury and selenium concentrations in samples (n = 309) of fish tissues and analyzed
positive HBVSe values were found in 42% of the fish samples (n = 131). As a result, we
(RW), high water (HW), falling water (FW), and low water (LW). The fish samples were
collected using nets with mesh between 30 and 70 mm. The individuals were identified
dorsal muscle was collected and stored in a freezer (−20 ◦ C) until Hg and Se quantification.
region (36). A total of 309 individuals from 17 species and 5 trophic guilds were collected:
FishBase platform (55). The data on sample size, trophic level, habitat, total weight, and
To quantify total Hg (THg), samples of dorsal muscle weighing 200 mg (wet weight) were
obtained from predatory fish and 400 mg from non-predatory fish. The samples were subjected
Merck® ). These samples remained for 30 min in a digester block (TE-007MP, Tecnal,
Piracicaba, Brazil) at 70 ◦ C. After the samples had cooled to room temperature, we added
another 20 min in the digester block. The cooled samples were reserved overnight, and
(NH2 OH.HCl 12% w/v, Merck® ). The samples were adjusted to a final volume of 14 mL
atomic absorption spectrophotometry with cold vapor generation (CV-AAS, FIMS-400,
About 0.5 mL of hydrogen peroxide (H2 O2 30%, Merck® ) was added to each sample and
samples were filtered and transferred to falcon tubes, to which ultrapure water (Milli-Q)
using inductively coupled plasma-optical emission spectrometry (ICP-OES, Optima 8300
LOD = 0.001 mg kg−1 , and LOQ = 0.005 mg kg−1 ). For Se determination, dogfish muscle

Implications

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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