Eccles et al. 2024 — Metals in polar bear tissues as traditional food for Inuit, Canadian Arctic
This study measured 32 metals in feces, muscle, liver, and fat of 49 polar bears harvested through community-based monitoring programs across six Canadian Arctic subpopulations (2016–2019). The primary goal was to develop predictive models converting fecal metal concentrations to internal tissue concentrations for non-invasive biomonitoring. The paper also includes a human health risk screening for Inuit consumption of polar bear muscle, using methylmercury as the example analyte. Polar bear liver shows very high total mercury (mean 45.86 µg/g dw), and MeHg in muscle (mean 0.43 µg/g dw) is relevant to Inuit traditional food exposure.
Key numbers
Mean concentrations in polar bear tissues (µg/g dry weight, n=49 bears unless noted):
| Metal | Fat mean ± SD (range) | Feces mean ± SD | Liver mean ± SD (range) | Muscle mean ± SD (range) |
|---|---|---|---|---|
| As (total) | 1.00 ± 0.79 (0.25–4.60) | 2.50 ± 3.29 | 1.39 ± 1.32 (0.25–6.50) | 1.49 ± 1.55 (0.25–5.20) |
| Cd | 0.04 ± 0.11 (0–0.78) | 1.59 ± 2.37 | 2.07 ± 1.24 (0.46–7.80) | 0.07 ± 0.05 (0.01–0.25) |
| Pb | 5.83 ± 39.98 (0.03–280) | 449.55 ± 3144.01 | 0.37 ± 0.55 (0.05–3.50) | 0.18 ± 0.42 (0.03–2.10) |
| THg | 5.55 ± 23.79 (0.01–147) | 2.69 ± 3.52 | 45.86 ± 41.89 (6.05–158.33) | 0.59 ± 0.44 (0.16–2.70) |
| MeHg | 0.03 ± 0.03 (0–0.12) | 0.31 ± 0.33 | 2.37 ± 2.50 (0.48–13.58) | 0.43 ± 0.33 (0.10–1.53) |
| Ni | 0.05 ± 0.05 (0.03–0.35) | 0.36 ± 0.69 | 0.05 ± 0.07 (0.03–0.52) | 0.05 ± 0.06 (0.03–0.30) |
Note: Al, Cr, Sb, Sn were excluded from predictive models because >60% of fecal samples were below detection limit. Pb in fat and feces showed extreme high-end outliers (Pb feces max 22,008.50 µg/g dw — likely environmental contamination).
Inuit consumption of polar bear meat: mean 9.7 ± 68 g/week (Inuit Health Survey 2007–2008).
MeHg ratio to THg in feces: approximately 29%.
Methods (brief)
Samples from legal community hunts under Government of Nunavut and Government of Northwest Territories quotas; 36 adults (30M, 6F), 12 subadults (6M, 6F), 1 unknown age. Tissue analysis: ICP-MS (Agilent 7700X) and ICP-OES (Varian Vista axial) for most metals; cold vapor atomic absorption for THg (Milestone DMA-80); Tekran 2700 Methyl Mercury Auto-Analysis System for MeHg. CALA-accredited laboratory. Values below detection limit replaced with ½ LOD. All values reported in µg/g dry weight. No speciation of arsenic (total As only); tHg and MeHg treated as distinct analytes per standard methods.
Implications
Certification: Polar bear meat is not in scope for HMT&C certification programs, but the data is relevant for understanding MeHg and THg exposure routes for high-consumption traditional food populations. Liver THg (mean 45.86 µg/g dw, max 158.33) is among the highest concentrations observed in any commonly consumed meat tissue. Muscle MeHg (mean 0.43 µg/g dw) is the relevant dietary exposure route.
Courses: Illustrates bioaccumulation and biomagnification at apex predator level in Arctic food web. Useful case study for MeHg, where muscle is the relevant dietary tissue and liver concentrations are much higher. The tHg/MeHg distinction is critical here: muscle MeHg/tHg ratio approximates 0.43/0.59 ≈ 73%, consistent with fish-like speciation in a fish-eating apex predator.
App: Not directly applicable (polar bear meat not a standard commercial food product). However, relevant as a data point for characterizing wild game organ meat risk.
Microbiome: Not addressed.