Groleau et al. (2025) analyzed heavy metal, trace element, and nutrient concentrations in a broad panel of traditional Inuit country foods consumed in Nunavik, northern Quebec, with particular focus on assessing risks and benefits for pregnant women. The study finds that large lake trout (>0.5 kg) pose an unacceptable mercury risk to pregnant women: more than 67% of large specimens exceed the Canadian RMRV of 0.5 µg/g for tHg, with maximum values of 4.5 µg/g, and mercury is >93% methylmercury. Arsenic in fish tissues is dominated by organic arsenobetaine (85-88% AsB in fish broth), with inorganic arsenic below 6% of total arsenic, substantially reducing the arsenic risk compared to what total-arsenic concentrations alone would suggest. Cadmium and lead are below regulatory thresholds in all fish and marine mammal samples except isolated seaweed samples, while fish broth provides substantial contributions to pregnant women’s daily intakes of potassium (26-53%), selenium (89-93%), and iron (27% from unfiltered lake trout broth).
Key numbers
Mercury in lake trout by size class:
| Size class | n | Proportion above 0.5 µg/g RMRV | Max tHg (µg/g) | MeHg (%) |
|---|---|---|---|---|
| Large (>0.5 kg) | 43 | >67% | 4.5 | >93% |
| Small (<0.5 kg) | Not specified separately | Lower prevalence | <0.5 typical | >93% |
Arsenic speciation in fish broth:
- Total arsenic in fish broth: multiple species exceeded 10 µg/L RMRV for total As
- Inorganic arsenic fraction in fish tissue: <6%
- Arsenobetaine (AsB) in fish broth: 85-88% of total As
- Risk interpretation: iAs exposure substantially lower than total As metrics suggest
Cadmium and lead:
- All fish and marine mammal samples: Cd and Pb below RMRV
- Exceptions: 1 seaweed sample Cd=1.6 µg/g (above RMRV); 1 seaweed sample Pb=0.57 µg/g (above RMRV)
Nutrient contributions to pregnant women’s daily intake (% of DRI):
- Potassium from fish broth: 26-53%
- Selenium from fish broth: 89-93%
- Iron from unfiltered lake trout broth: 27%
Lucky Iron Fish (iron supplementation device):
- At pH 4.5-6.5 (broth conditions): Fe release only 2-4 mg/L
- Marketed claim (6-8 mg/L) not reproduced in this experimental context
Methods (brief)
Analytical method: ICP-MS/MS (Agilent 8900 Triple Quadrupole) for multi-element analysis including As speciation. Total mercury by direct mercury analyzer (DMA-80). Methylmercury by cold-vapor atomic fluorescence spectrometry (CVAFS) after alkaline digestion. Arsenic speciation by HPLC-ICP-MS. CRM validation with DORM-4 and DOLT-5. Broth preparation protocol: traditional Inuit preparation methods (boiling, simmering). Lucky Iron Fish iron release tested at pH 4.5, 5.5, and 6.5 using simulated broth matrices. Nutrient contributions calculated against Health Canada DRIs for pregnant women aged 19-50.
Implications
Certification: Not directly applicable to HMT&C food product certification. However, this study is a methodological exemplar for arsenic speciation in fish matrices: it quantifies the iAs/tAs split in fish broth (iAs <6% of tAs), which is directly relevant to HMT&C’s non-substitution rule for iAs vs tAs. For seafood-adjacent products (fish-based baby food, fish oils, fish broths), tAs concentrations cannot be used as proxies for iAs exposure without speciation data.
Courses: The risk-benefit trade-off for country foods in Indigenous pregnant populations is a compelling teaching case. Selenium and potassium benefits from fish broth are nutritionally substantial; MeHg from large lake trout is a genuine risk. The Lucky Iron Fish finding (iron release much lower than marketed) is a cautionary note on non-validated supplementation devices.
App: Arsenic speciation data (85-88% AsB in fish broth; <6% iAs) provides a reference split factor for the app’s fish-broth and fish-product risk models. MeHg dominance (>93%) in freshwater fish tissue confirms that tHg-to-MeHg conversion factors at ~0.93 are appropriate for lake trout in this context.
Microbiome: Not directly addressed in this paper.