González-Torres et al. 2023 — Comparative review of heavy metals in edible vegetable oils (2015–2022)
This review synthesizes the scientific literature (2015–2022) on the presence of heavy metals in edible vegetable oils, analyzing more than 25 metals across 35 different oil types from 24 countries. The most studied oils are olive (14.4%), sunflower (13.8%), rapeseed (9.9%), and corn (9.9%); the most studied metals are Cd (14.6%), Pb (12.4%), Cu (12.0%), and Fe (9.5%). A key regulatory finding: cadmium — the most analyzed heavy metal in this matrix — has no specific international regulatory limit for edible vegetable oils, meaning oils with high Cd content (some exceeding 4 mg/kg in Iranian and Italian olive oils, and 0.88 mg/kg in Chinese rapeseed oil) are marketed without restriction. The review also highlights antimony (Sb) migration from PET packaging as an emerging concern.
Key numbers
Countries with most studies: Brazil 17.2%, Turkey 15.6%, China 10.9%, Iran 9.4%, India 6.3%.
Most studied metals by frequency: Cd 14.6%, Pb 12.4%, Cu 12.0%, Fe 9.5%.
Analytical techniques: ICP-OES/ICP-AES 25%, FAAS 17.7%, ICP-MS 16.2%, GF-AAS 14.7%.
Selected concentration data from cited primary studies (ranges or average values, mg/kg):
Cadmium (Cd):
- Chinese rapeseed oil: 0.88 mg/kg (ICP-OES)
- Iranian/Italian olive oil: 0.396–4.181 mg/kg (ICP-OES)
- Indian sunflower oil: up to 0.54 mg/kg
- Turkish olive oil: 0.026–0.097 mg/kg
- Iranian oils (olive, rapeseed, corn, sesame, sunflower): 0.090–0.100 mg/kg
Lead (Pb):
- Regulatory limit (Codex, EU 2021/1317, Spain RD 308/1983): 0.10 mg/kg for edible vegetable oils
- Pakistani olive oil: 8.546–18.783 mg/kg (ICP-OES) — greatly exceeds limit
- Pakistani rapeseed oil: 1.301–6.765 mg/kg
- Chinese rapeseed oil: 1.96 mg/kg
- Cypriot olive oil: 0.15–1.48 mg/kg (ICP-MS)
- UK sunflower oil: 0.274 mg/kg; UK rapeseed oil: 0.181 mg/kg; UK coconut oil: 0.158 mg/kg; UK olive oil: 0.143 mg/kg (all FAAS)
- Iranian oils (various): 0.092–0.100 mg/kg (near limit)
Copper (Cu):
- Spanish (Chinese export) limit for olive oil: 0.1 mg/kg; Spanish limit for others: 0.4 mg/kg
- Cypriot olive oil: 1.02–3.81 mg/kg (ICP-MS) — greatly exceeds limit
- Ukrainian olive oil: 0.355 mg/kg
- Brazilian rapeseed/sunflower oil: 0.81 mg/kg
Iron (Fe):
- No specific toxicological limit; Codex quality criteria: refined 1.5 mg/kg, virgin 5.0 mg/kg
- Saudi olive oil: up to 7.861 mg/kg (above Chinese 3.0 mg/kg export limit)
- Chinese walnut oil: up to 11.2 mg/kg (above Spanish 10 mg/kg limit)
Antimony (Sb):
- EU migration limit from plastic materials (food contact): 0.04 mg/kg
- Turkish walnut, sweet almond, soybean, bitter almond, coconut oils in PET: 1.02–1.66 mg/kg (ICP-OES) — greatly exceeds migration limit
- Italian extra virgin olive oil in PET: 7×10⁻⁵–4.50×10⁻⁴ mg/kg (ICP-MS)
Detection limits (selected): GF-AAS achieves lowest LODs — Cd 2.00×10⁻⁶ mg/kg, Pb 2.00×10⁻⁵ mg/kg in olive/sunflower/corn oils. ICP-OES LOD for Cd: 6×10⁻⁵ mg/kg (rapeseed).
Methods
Systematic literature review. Inclusion criteria: edible vegetable oils for consumption, 2015–2022 publication, concentration data for at least one heavy metal, LD reported. Excluded: crude/virgin oils unfit for consumption, fish oils, algae oils. Regulatory comparison uses: Codex Alimentarius (CX-A), WHO, EFSA, EU Regulation 2021/1317 (Pb), EU Regulation 2021/1323 (Cd), China GB/T23347-2021 (olive oil export), and Spain RD 308/1983.
Implications
Certification: This review is the most comprehensive available synthesis of Pb, Cd, Cu, and Fe data in edible vegetable oils globally. The absence of Cd limits for vegetable oils in Codex and EU regulation (as of 2022) is a regulatory gap with direct bearing on HMT&C standard setting — any HMT&C threshold for Cd in vegetable oil-derived products would be self-referential to literature rather than anchored to a regulatory floor. The EU 2023/915 regulation (now in force; post-dates this review) should be consulted for updated Pb limits.
Courses: Excellent reference for teaching the analytical technique landscape (ICP-OES vs. FAAS vs. GF-AAS vs. ICP-MS), regulatory patchwork, and the PET/antimony migration issue.
App: The compilation of literature ranges across 35 oil types and 24 countries is valuable for broad contextual framing but not for point-estimate ingredient contamination profiles — individual primary studies cited herein are the appropriate source for specific values.
Microbiome: Not applicable.