Overview
This study assessed methylmercury (MeHg) health risk from fish consumption among adult residents of Qatar, combining a dietary survey (n=600) with chemical analysis of 65 composite samples spanning seven commercially important species. Total mercury (T-Hg) was measured in all samples by ICP-MS following microwave acid digestion, with LOD 1 µg/kg and LOQ 10 µg/kg. MeHg concentrations were derived from T-Hg using species-specific literature conversion factors. The mean T-Hg across all fish was 0.077 µg/g wet weight (range: 0.001 µg/g in rabbitfish to 0.422 µg/g in imported grouper), well within the EU maximum of 0.5 µg/g for most species, though the finding that average estimated weekly MeHg intakes exceed the EFSA tolerable weekly intake (TWI) of 1.3 µg/kg bw/week for high-protein diet consumers and females of childbearing age raises concern about regular high-consumption patterns.
Key numbers
Fish species sampled (codes, scientific names):
- HM (grouper, Epinephelus coioides): local 0.161±0.06 µg/g ww; imported 0.422±0.04 µg/g ww; range 0.089–0.443 µg/g ww
- CH (narrow-barred Spanish mackerel, Scomberomorus commerson): 0.091±0.04 µg/g ww; range 0.06–0.161
- SH (spangled emperor, Lethrinus nebulosus): 0.064±0.01 µg/g ww; range 0.042–0.076
- TU (local tuna, Euthynnus affinis): 0.040±0.01 µg/g ww; range 0.032–0.052
- TU (canned tuna, multiple species): 0.092±0.07 µg/g ww; range 0.015–0.255
- SF (rabbitfish, Siganus rivulatus): 0.001±0.0002 µg/g ww; below LOQ in most samples
- SM (salmon, Salmo salar): fresh 0.008±0.004 µg/g ww; canned 0.023±0.01 µg/g ww
- SB (European seabass, Dicentrarchus labrax): 0.021±0.007 µg/g ww
MeHg-to-T-Hg conversion factors used (from literature): HM 97.3%, CH 97.6%, SH 94.1%, SF 94.5%, TU mackerel 93.0%, TU yellowfin 96.3%, canned TU 90.5%, SM 80.5%, SB 81.1%.
Average weekly fish consumption for all participants: 736 g/week (Qatari cohort 858 g/week; high-protein diet group 880 g/week; females of childbearing age 822 g/week).
MeHg estimated weekly intake (EWI) scenario 2 (species-specific conversion): average all participants 0.74 µg/kg bw/week, p75 1.07 µg/kg bw/week, p95 1.91 µg/kg bw/week. EFSA TWI = 1.3 µg/kg bw/week. At p95, EWI exceeds TWI.
n=65 composite samples; n=600 survey participants (336 Qatari, 264 non-Qatari; 56% female).
Methods (brief)
ICP-MS (Perkin Elmer NexION 350) after microwave acid digestion (ultra-WAVE); 1% HNO3 blank; LOD 1 µg/kg; LOQ 10 µg/kg; CRMs: CRM 7279 canned crab meat and CRM 7271 canned fish; recovery 95.07–115.3%; RSD 3.32%. T-Hg in dried samples back-calculated to wet weight using measured moisture content per species. Results expressed as µg/g wet weight. Non-detects in SF set to LOQ/2. MeHg derived from T-Hg using scenario-based approach; three scenarios including worst-case (100% as MeHg), species-specific conversion (Table 2 of paper), and regulatory maximum levels scenario. Deterministic disaggregated exposure assessment.
Speciation note: T-Hg only measured directly; MeHg concentrations are calculated estimates, not independently speciated. This is standard for country-level fish risk assessments but means iHg contribution cannot be independently verified.
Implications
Certification: Grouper (HM), particularly imported, is the most contaminated of the sampled species (0.422 µg/g), approaching the EU non-predatory limit of 0.5 µg/g. Canned tuna shows wide variability (0.015–0.255 µg/g). Salmon and seabass are low-tHg matrices (<0.025 µg/g ww). Context for HMT&C seafood criteria and for fish-containing product formulations (protein powders, meal-replacement products) using canned tuna.
Courses: Illustrates the population-specific risk dynamic: average intakes appear acceptable (HQ<1 at mean), but high-protein diet consumers and females of childbearing age can exceed the TWI at P75–P95 with common consumption patterns. Good case study for dose-response communication.
App: Species-specific T-Hg values directly usable for fish-containing product risk scoring; HM (grouper), CH (mackerel), SH (emperor), and canned TU are the species driving MeHg exposure. SF (rabbitfish) is low-risk.
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Update history
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| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 6 sections added; narrative text revised |