Heavy Metals in Food: Lead, Cadmium, Mercury, Arsenic

Heavy Metals in Food

They don’t break down, they don’t cook out, and they accumulate — in the environment, in the food chain, and in us. Lead, cadmium, mercury, and arsenic are the “big four” heavy metals in food safety: different sources, different toxicities, one shared trait of persistence.

The big four

• Lead: neurodevelopmental toxin, especially harmful to children. Sources: old pipes and solder, contaminated soil, lead-shot game, some traditional products and ceramics. No safe exposure level is considered to exist for neurodevelopmental effects.
• Cadmium: kidney toxin, accumulates over a lifetime. Sources: phosphate fertilizers (uptake into cereals, potatoes, leafy vegetables), shellfish, offal.
• Mercury: methylmercury in fish is the concern — neurotoxin affecting fetal development. Predatory fish (tuna, swordfish, shark) accumulate the most; advisories target pregnant women.
• Arsenic: inorganic arsenic is the carcinogenic form. Rice is the notable accumulator (paddy-field chemistry favors uptake); also some water supplies and seaweed (mostly organic, less toxic forms).

Key facts

• Controls are agricultural and sourcing-based: soil testing, water quality, fertilizer choice, fishing-area selection, supplier specifications.
• Regulatory limits exist worldwide (EU Regulation 2023/915 sets maximum levels for these metals across food categories; Codex CXS 193 covers them; the US FDA monitors via the Total Diet Study).
• Processing rarely removes them — peeling and washing help marginally for surface contamination; for systemic uptake (cadmium in grain, arsenic in rice), the control is upstream.
• Testing: ICP-MS is the standard analytical method for multi-element quantification.

Why it matters

Heavy metals are the slow-burn chemical hazard — no dramatic outbreak, just chronic exposure shaving IQ points and kidney function across populations. The controls are unglamorous: know your soil, know your water, know your fishing grounds. For manufacturers, it means specifications on raw materials from risky origins and periodic testing — not because every batch is contaminated, but because the contamination, when present, never announces itself.

Sources: FDA; Codex CXS 193-1995.