Ulusoy 2023 — Toxic Metals in Canned Tuna: 36-Country Survey with Health Risk Assessment
This peer-reviewed study measured cadmium, lead, mercury (total), and total/inorganic arsenic in 222 canned tuna samples purchased from supermarkets in 36 countries (19 developed, 17 developing) during 2017–2019, using ICP-MS (Perkin Elmer Nexion 1000). Health risk was assessed via target hazard quotient (THQ) for non-carcinogenic risk and target cancer risk (TCR) for carcinogenic risk from inorganic arsenic. The main findings are that Hg THQ values exceeded the safe limit (>1) for consumers eating canned tuna more than once per week, and TCR for iAs showed carcinogenic risk when consuming more than one meal per week. All Cd and Pb concentrations were well below regulatory limits.
Key numbers
Toxic metals in canned tuna from developed countries (mean ± SD, µg/g wet weight, Table 4):
- Cd: 0.022 ± 0.01 µg/g (permissible limit 0.10 mg/kg EU)
- Pb: 0.12 ± 0.06 µg/g (permissible limit 0.30 mg/kg FAO/WHO)
- Hg (total): 0.09 ± 0.09 µg/g (permissible limit 1.0 mg/kg FAO/WHO)
- Total As: 0.64 ± 0.28 µg/g
- Inorganic As (estimated as 3% of total): 0.047 ± 0.01 µg/g
Toxic metals in canned tuna from developing countries (mean ± SD, µg/g ww, Table 5):
- Cd: 0.017 ± 0.01 µg/g
- Pb: 0.10 ± 0.20 µg/g
- Hg (total): 0.13 ± 0.22 µg/g
- Total As: 0.13 ± 0.22 µg/g
- Inorganic As (estimated): 0.042 ± 0.01 µg/g
Notable outliers (from Tables 4–5):
- Holland (developed): Total As = 1.28 ± 0.64 µg/g — highest in developed group
- England (developed): Pb = 1.28 ± 0.06 µg/g — exceeded limit; highest in study
- Russia (developing): Pb = 0.83 ± 0.01 µg/g — exceeded limit
- Saudi Arabia (developing): Pb = 0.29 µg/g — above limit
- Croatia: Total As = 1.19 ± 0.04 µg/g
Statistically significant differences between developed and developing countries: iAs (p < 0.05) and Cd (p < 0.05) were significantly different; Pb and Hg were not (p > 0.05).
Health risk (Table 6 summary):
- Cd: EDI 0.037 µg/kg bw/day (developed), 0.030 (developing); THQ << 1; safe at any frequency
- Pb: EDI 0.197 µg/kg bw/day (developed), 0.179 (developing); THQ << 1
- Hg: EDI 0.156 µg/kg bw/day (developed), 0.220 (developing); THQ > 1 when eating 7×/week; permissible at 1–3×/week
- iAs: TCR (carcinogenic) exceeded 10⁻⁴ threshold when consuming >1 meal/week in some scenarios
ICP-MS LODs: As 0.025 ppb, Cd 0.18 ppb, Pb 0.15 ppb, Hg 0.05 ppb.
Fish species: primarily Katsuwonus pelamis (skipjack tuna) and Thunnus albacares (yellowfin); some Thunnus alalunga (albacore) and Thunnus tonggol.
Methods (brief)
222 canned tuna samples from 36 countries, 34 brands, purchased 2017–2019. 3 cans per country per brand. Meal size 120 g (whole can). Microwave digestion (Milestone Ethos D Plus 1): HNO₃ 65% (7 mL) + H₂O₂ 30% (1 mL); program to 220°C. ICP-MS (Perkin Elmer Nexion 1000 NexION 1000, USA). iAs estimated as 3% of total As (Okati et al. 2021). THQ calculated per EPA/FAO WHO RfDs: Cd 0.3 µg/kg bw/day, Pb 0.10 µg/kg bw/day, Hg 1.0 µg/kg bw/day. Analysis per AOAC 999.10. CRM ERM-CE278k validated (recovery 98.17–108.45%).
Limitations
Inorganic arsenic is estimated as 3% of total As rather than directly speciated — this is a significant limitation given that most arsenic in fish muscle is organic (arsenobetaine) and essentially non-toxic. The iAs carcinogenic risk estimates are therefore conservative and may substantially overestimate risk. The England and Russia Pb exceedances warrant follow-up but are based on n=3 samples each. The iAs 3% assumption is a methodological shortcut that overstates risk; direct speciation would likely show iAs < 1% of total As in skipjack tuna.
Implications
- Certification: Confirms that Cd and Pb in canned tuna are consistently well below regulatory limits across all 36 countries tested. Mercury in canned tuna from high-frequency consumers (7×/week) warrants attention but is below limits at 1–3 servings/week — relevant for any HMT&C program extension to seafood.
- Courses: Excellent example of why total arsenic is not the appropriate risk metric for seafood — the 3% iAs assumption illustrates the problem and directly supports the wiki’s non-substitution rule (tAs ≠ iAs).
- App: Provides global canned tuna concentration baseline: Cd mean ~0.02 µg/g ww; Pb mean ~0.10 µg/g ww; Hg mean ~0.10 µg/g ww; total As ~0.30–0.65 µg/g ww.
- Microbiome: Not applicable.