Overview
This study measured methylmercury in fish and used those values in a risk-benefit assessment for pregnant and infertile women in Taiwan.
Key numbers
Fish MeHg values are reported as mean ± SD across triplicate samples per species in mg/kg wet weight (Table 3, body text page 6). Hair MeHg values are geometric mean ± standard error in mg/kg (Table 1 footnote e, body text page 6).
Fish MeHg by species (mg/kg wet wt., n = 3 per species):
- Swordfish (Xiphias gladius): 0.28 ± 0.23.
- Tuna (Thunnus alalunga): 0.14 ± 0.13.
- Cod: 0.130.
- Greater amberjack: 0.110.
- Salmon: 0.097.
- Hairtail: 0.065.
- Tilapia: 0.050.
- Mackerel: 0.017.
- Milkfish: 0.006.
- Anchovy: 0.002.
Diet-group aggregates (mg/kg wet wt.):
- Carnivorous fish: 0.11 ± 0.13.
- Omnivorous fish (milkfish only): 0.006 ± 0.01.
- Filter-feeding fish (anchovy only): 0.002 ± 0.001.
All measured fish MeHg concentrations were below the Codex guideline level of 1 mg/kg (CAC/GL 7, FAO/WHO 1991).
Hair MeHg (mg/kg, geometric mean ± SE):
- Infertile women (n = 162): 1.82 ± 0.14.
- Pregnant women (n = 62): 1.24 ± 0.18.
- P = 0.01 (Wilcoxon rank-sum).
- 80% of infertile women and 68% of pregnant women had hair MeHg exceeding the USEPA reference-dose hair concentration of 1 mg/kg.
Daily MeHg exposure dose (µg/kg body weight/day, arithmetic mean ± SD):
- Pregnant women: 0.34 ± 0.34.
- Infertile women: 0.51 ± 0.49.
- 76.7% of pregnant women and 90.9% of infertile women exceeded the USEPA RfD of 0.1 µg/kg/day.
Methods
Hair samples (~2 cm, occipital scalp, stainless-steel surgical scissors) and 1-g fish muscle samples were prepared for MeHg analysis following the Brooks Rand BRL Method BR-0011 and USEPA Method 1630 with minor modifications. Hair was sonicated 30 min in neutral detergent, rinsed three times with deionized water, and oven-dried at 37 °C for 24 h. Fish was alkaline-digested in 25% KOH/methanol at 75 °C for 5.5 h, then liquid-liquid extracted with CH2Cl2 and HCl, filtered, and purged. Sodium acetate buffer and 1.0% NaBEt4 were added for ethylation prior to analysis on a MERX integrated automated MeHg analyzer (Brooks Rand). Quality control used IAEA-085 (human hair) and BCR-465 (tuna fish) certified reference materials; average recovery 94.7%, coefficient of variation 4.27%, accuracy 89.2%. Each sample was analyzed in triplicate.
The daily MeHg exposure dose was estimated from a species-weighted intake calculation referencing USEPA Eq. 1, with hazard quotient and allowable-daily-intake calculations against the USEPA MeHg RfD of 0.1 µg/kg/day. Statistical analysis used SPSS version 17.0; Wilcoxon rank-sum, chi-square, Fisher exact, Kruskal-Wallis, and Spearman rank correlation tests as appropriate.
Implications
Per-species MeHg values for all 10 species are routeable to seafood occurrence context, with the predatory species (swordfish, tuna, cod, greater amberjack, salmon, hairtail) most relevant to fish-marine-predatory occurrence routing. Human hair MeHg and daily-exposure-dose values are biomonitoring/exposure context for Taiwanese women of childbearing age, not product occurrence.
Related evidence
- Swordfish
- Fish
- Seafood
- Fresh Fish
- Fish — marine, predatory (tuna, swordfish, shark, king mackerel)
- Methylmercury
Update history
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