Nazari et al. 2023 — Heavy metals in seed crops and oil products: impacts on human health (review)
This Iranian-led review summarises the published literature on heavy metal contamination (As, Pb, Cd, Hg, Ni, and Cr) in oilseeds and their derived vegetable oils, covering sources, occurrence data, effects on nutritional quality, regulatory maximum residue levels, and human health impacts. The review compiles concentrations from a range of studies on oils including olive, sunflower, rapeseed/canola, hazelnut, and linseed, and identifies Pb and Cd as the most frequently documented concerns. A key synthesis point is that coexistence of multiple metals in oils can produce synergistic toxic interactions, and that the current regulatory landscape leaves many oil and seed categories without specific MLs.
Key numbers
No original data; values synthesised from cited literature:
Cd in oilseeds (from cited studies):
- Sunflower seeds: elevated Cd relative to other oil crops; linseed Cd noted
- Olive oil: Cd typically low
- Hazelnut oil: Cd noted as highest among surveyed oils in one cited study
Pb in oilseeds (from cited studies):
- Linseed oil and rapeseed oil: Pb concentrations investigated in cited studies
- Sunflower: Pb and Cd both in seeds
- One Nigerian study: concentrations of Fe, Mn, Zn, Cu, Pb, Co, Cd, Na, K, Ca, Mg in oils from Zaria; Pb, Co, Cd elevated in margarine; sunflower oil elevated for Ca
Cd in hazelnut oil: cited as highest Cd among tested oils in one reference (Dhiman et al. 2017 cited in review)
Typical metals detected in oils: Fe, Mn, Zn, Cu, Pb, Co, Cd, Na, K, Ca, Mg per cited literature
Regulatory context: EU regulation establishes MLs for some contaminants in food; as of the review date, maximum levels for heavy metals in oilseeds and most vegetable oils were limited (only Cd in a few oil categories). Authors recommend revising permissible levels and increasing surveillance.
Note: this review lists “chromium (Cd)” in its abstract metal list — this is an apparent typographical error; the review discusses Cr (chromium) and Cd (cadmium) separately in the body.
Methods (brief)
Narrative review. No systematic search methodology described. Iranian institutions; likely reflects Iranian and globally published literature with some selection bias toward available studies. No primary data; all values are from cited secondary sources.
Implications
Certification: Useful as a general orientating document for oilseed heavy metal coverage but should not be used as a primary quantitative source for any specific value. The synthesis reinforces that Cd and Pb are the priority concerns in oilseeds. For HMT&C products containing seed oils, the ingredient profiles on specific oil seeds (sunflower, flax, sesame, rapeseed) should draw primarily on primary occurrence studies.
Courses: Provides a usable overview of contamination routes and health effects for oilseeds and oils for educational modules. The point on synergistic metal interactions in co-contaminated oils is relevant to cumulative exposure discussions.
App: Low utility for direct app-facing exposure modelling given lack of n, specific matrices, and methods. Use as background orientation only; populate ingredient pages from primary occurrence studies.