Statement on the findings presented in the Toxicological

Overview

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Key numbers

The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:

the tolerable weekly intake (TWI) of 4 μg/kg body weight (bw), expressed as mer-
than the TWI (1.3 μg/kg bw per week, expressed as mercury) established by EFSA
The CONTAM Panel established a tolerable weekly intake (TWI) for inorganic mercury of 4 μg/kg bw, based on a BMDL10
of 0.06 mg/kg bw per day (expressed as Hg), for increase in kidney weight in male rats (NTP, 19932), applying an UF of 100
and converted to a weekly basis expressed as mercury. For methylmercury, a TWI of 1.3 μg/kg bw, expressed as mercury,
was established based on a NOEL for neurodevelopmental effects from the Seychelles nutrition cohort of 11 mg/kg mater-
nal hair (Lynch et al., 20113) and on a BMDL05 for neurodevelopmental effects from the Faroese cohort 1 of 12 mg/kg in
maternal hair (FAO/WHO, 20044), resulting in 11.5 mg/kg maternal hair concentration causing no appreciable adverse ef-
This was converted to a maternal blood mercury concentration of 46 μg/L and, using a toxicokinetic model, further con-
verted to a dietary mercury intake of 1.2 μg/kg bw. An UF of 2 for variation in the hair to blood ratio and a standard factor
in consequence a daily dose of 0.19 μg/kg bw that was converted to a weekly basis.
In the EFSA (2012) assessment, mean dietary exposures across age groups did not exceed the TWI for methylmercury
food (EFSA CONTAM Panel, 2012), a tolerable weekly intake (TWI) for inorganic mercury of 4 μg/kg body weight (bw), ex-
For methylmercury, a TWI of 1.3 μg/kg bw, expressed as mercury, was established based on neurodevelopmental effects
In 2012, the EFSA CONTAM Panel established a TWI for inorganic mercury of 4 μg/kg bw, expressed as mercury, thus follow-
kidneys. Doses of 0.312, 0.625, 1.25, 2.5 or 5 mg/kg bw/day were tested in the 6-month study administered 5 days/week
and 0.625 (females) mg/kg mercuric chloride, respectively, accompanied by minimal to mild nephropathological find-
male rats in this study as the pivotal effect for deriving a HBGV. Based on the BMDL10 of 0.06 mg/kg bw/day, expressed
weekly basis and rounding to one significant figure, the Panel established a TWI for inorganic mercury of 4 μg/kg bw,
in adult albino Wistar rats. Six animals per group either received distilled water as control or 0.02 mg/kg bw/day mercury
stantiate their findings. Therefore, EFSA does not consider the study by Apaydın et al. (2016) suitable to derive a reference
mercury is not needed based on the results presented by ATSDR from 2024. The TWI for inorganic mercury of 4 μg/kg bw,
11 mg/kg, ‘the beneficial effects associated with maternal n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFAs)29 no longer
imately 11 mg/kg as an ‘apparent NOEL’. However, it was noted that the number of observations at higher exposure levels
BMDL05 of 12 mg/kg methylmercury in maternal hair that had previously been established from this study by JECFA (FAO/
BMDL05 value of 12 mg/kg methylmercury in maternal hair.
EFSA then used the maternal hair mercury concentrations from the Seychelles and Faroese studies (mean of 11.5 mg/
netic model yielded a corresponding steady-state intake of 1.2 μg/kg bw/day. A composite uncertainty factor of 6.4 was
intake (TWI) of 1.3 μg/kg bw, expressed as mercury.
corresponds to a maternal hair concentration of 5.56 mg/kg. This value was converted to an intake of 0.41 μg/kg/day using
the TWI (of 1.3 μg/kg bw, expressed as mercury) established by EFSA in 2012.
approximately 5 points). These small decrements may represent meaningful intellectual and economic achievement at a popu-
et al., 1997; US EPA, 2001). Using a benchmark response (BMR) of 5%, the resulting BMDL05 values ranged approximately
from 10 to 15 mg/kg methylmercury in maternal hair. EFSA adopted the value of 12 mg/kg methylmercury in maternal hair
For the Seychelles cohort, EFSA identified an ‘apparent NOEL’ of 11 mg/kg methylmercury in maternal hair based on the
estimated slopes ranging from 140 to 370 and a mean of approximately 250, and notes that the World Health Organization
factor of 3 for human variability’, but no UF was applied for hair to blood conversion (see Table A2 in Appendix 1).
11.5 mg/kg methylmercury in maternal hair, recruited approximately 300 pregnant women in 2001 and followed offspring
Zealand), a reference point of 5.56 mg/kg methylmercury in maternal hair was derived.
• EFSA, in contrast, derived a reference point of 11.5 mg/kg methylmercury in maternal hair based on cohorts from the
values that differ by approximately a factor of two on a weekly basis (0.7 vs. 1.3 μg/kg bw/week).
the current EFSA TWI of 1.3 μg/kg bw per week, expressed as mercury, remains valid.

Methods (brief)

minated diphenyl ethers (PBDEs), inorganic arsenic, dimethylarsinic acid (DMA), inorganic mercury and methylmercury.
acid (DMA), inorganic mercury and methylmercury13 in fish. For these contaminants, except mercury, the assessments were
tested, small sample size (6 instead of 10 animals tested per dose as suggested in respective guidelines) and no information
kidney is given, and it is not reported whether or not sample blinding was implemented prior to evaluation, which would
DMA dimethylarsinic acid
Hack, M., Taylor, H. G., Drotar, D., Schluchter, M., Cartar, L., Wilson-Costello, D., Klein, N., Friedman, H., Mercuri-Minich, N., & Morrow, M. (2005). Poor pre-

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

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Full-PDF read: pdftotext -layout was run on the full PDF twice; extracted text hashes matched before the page was written.
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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