A Review of Mercury Bioavailability in Humans

Overview

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95%–100% bioavailability in their models. However, recent research suggests that assuming all,
bioavailability and assimilation is less than 100%. Specifically, 25 studies on fish were reviewed,
and assimilation efficiencies ranged from 10% to 100% for MeHg and from 2% to 51% for Hg(II).
MeHg and 0.2% to 94% for Hg(II). The overall absorption estimates ranged from 12% to 79% for MeHg
and 49% to 69% for Hg(II), and were consistently less than 100%. For both fish and humans, a number
estimated to reach systemic circulation, and make the assumption that 95% to 100% of the ingested
1. Fish approximately 80% to 90% of total uptake, with the remaining fraction coming from water (19,20).
90%is of total
variable and may account for 32% to 92% of the total Hg(II) accumulation, with the remainder being may be more important under
perfused with HgCl2 solution which demonstrated that the majority (78%–85%) of Hg(II) accumulated
following 30 days dietary exposure to HgCl2 , 36% of the relative Hg(II) burden accumulated in
MeHgCl for 30 days, less than 3% of the relative Hg(II) burden was found in posterior intestines. Thus,
We identified 25 studies which report dietary AEs for Hg(II), MeHg, or both (Figure 2; Table S1),
for MeHg were 10%–100% and for Hg(II) were 2%–51% (Figure 2). In general, dietary MeHg was
radioisotopes assimilated 56%–95% and 10%–27% of MeHg and Hg(II), respectively (27). Similarly,
Goto and Wallace (28) reported differences in MeHg AEs (52%–89%) after feeding mummichog
Fisher (29) reported low dietary AEs for Hg(II) (2%–4%) and MeHg (10%–14%) after feeding killifish
AEs were significantly greater for both Hg(II) (18%) and MeHg (82%) from this food type, which
study by Rodgers and Beamish (31), AE decreased from 70% to 80% to less than 50% in rainbow trout
and reported an AE of 98% regardless of experimental Hg exposure. Conversely, Northern pike
(Esox lucius) assimilated only 19% of the MeHg from wild-caught common carp (Cyprinus carpio) used
asTable S2. in Table S2.
different among the treatment groups, which the authors suggested may have been due 95% of the initial dose to betotransferred
Beamish (31), AE decreased from 70% to 80% to less than 50% in rainbow trout exposed to dietary MeHgor 16 µg/g wet weight), and
transfer to other tissues occurred more slowly, as 2 days were required for 95%
exposure to 203 MeHg and a subsequent 30-day depuration period, 71%–77% of the accumulated
the head (16%–18%) and viscera (5%–9%) (21). In fish muscle tissue, >95% of the Hg(II) is present as
absorbed from the intestine than Hg(II) generally holds true, the assumption that MeHg is nearly 100%
95%–100% of the ingested MeHg is absorbed into systemic circulation is largely based on limited
A body of emerging research suggests that Hg may be less than 100% bioavailable from seafood
absorption) for total Hg, MeHg, or both (Figures 3 and 4; Tables S3 and S5). These studies cover
Overall mean bioaccessibility estimates ranged from ~2% to 100% for MeHg and 0.2% to 94%
for total Hg; overall mean absorption estimates ranged from 12% to 79% for MeHg and 49% to 69%
for total Hg (Figures 3 and 4; Tables S3 and S5). Some of the studies investigated only a single type
ranged from 21% to 52%, and MeHg bioaccessibility ranged from 20% to 59% from raw seafood in the
Hong Kong study (52). In vitro total Hg bioaccessibility from 16 raw seafood species in Spain ranged
of bioavailability) after 2 h of incubation with cultured Caco-2 cells was 49%–69% and 3%–14%,
from 10 raw seafood species in Montreal ranged from 50% to 100%; absorption after 2 h of incubation
with cultured Caco-2 cells ranged from 29% to 67% of the initial undigested sample (51). Taken together,
challenge the assumption that 95%–100% of ingested MeHg is absorbed.
as outlined in Table S4.
numbers along the Y-axis indicate studies, as outlined in Table S4.indicate studies, as outlined in Table S4.

Methods (brief)

the natural environment, or muscle collected from such fish) have rarely (2 of 24 studies) been used as
Environ. PublicPublic
natural environment, or muscle collected from such fish) have rarely (2 of 24 studies) been used as a source of rainbow trout (36).
most likely bound to cysteine residues in proteins (40). This has been substantiated by HPLC-ICP-MS
their transfer to a different lake. Spiked Hg(II) was detected in muscle samples over the course of
studies are drawn from small sample sizes. Both studies focus on acute exposures and do not utilize
in vivo bioaccessibility represents a combined contribution of human and bacterial digestion to
the apical side). Metabolism of the compound may occur during both digestion/solubilization
different ways of cooking these seafoods affected Hg bioaccessibility relative to raw samples of the
the digestion and a longer small intestinal digestion (6 h vs. 2 h). In vitro total Hg bioaccessibility
with cultured Caco-2 cells ranged from 29% to 67% of the initial undigested sample (51). Taken together,
seafoods affected Hg bioaccessibility relative to raw samples of the same seafood (53,54).
bioaccessibility in boiled and fried fish were 40% and 60% lower, respectively, than raw samples of the
same fish among samples of Spanish mackerel (Scomberomorus maculatus), cat shark (Scyliorhinus sp.)
methods that use a lower weight of fish to start the digestion and a longer small intestinal digestion (6 h
and consequently less Hg is solubilized during digestion. The strong affinity of Hg for proteins (67)
digestion—bioaccessibility
digestion—bioaccessibility

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