Lead is limited because its developmental neurotoxicity in young children has no demonstrated threshold — no agency can identify an intake or blood-lead level below which harm does not occur — so the governing frame is to minimize exposure as far as practicable, not to stay below a "safe" dose.

Cadmium is limited because it is a cumulative nephrotoxicant with a biological half-life of 10 to 30 years that concentrates in the renal cortex, is classified by IARC as a Group 1 human carcinogen, and has no effective clinical treatment, so control is a prevention problem addressed by capping dietary intake.

Inorganic arsenic is limited because it is an IARC Group 1 human carcinogen for which the major assessment bodies have declined to set any safe intake threshold, and current dietary exposures already sit at or above the cancer reference point EFSA derived in its 2024 reassessment.

Methylmercury crosses the blood-brain barrier and the placenta and accumulates in developing neural tissue, so with the prenatal and early-postnatal windows the most vulnerable and no safe threshold established for developmental neurotoxicity, dietary exposure is limited to protect the developing brain.

Nickel is limited because EFSA's 2020 reassessment set a chronic tolerable daily intake of 13 µg Ni/kg body weight/day on a reproductive-developmental endpoint that mean European dietary intake already exceeds, and because sensitized individuals react to oral doses far below that; contamination is largely controllable through sourcing and process control.

Inorganic tin migrating from tinplate cans produces only an acute gastrointestinal effect, with a wide margin between regulated canned-food concentrations and the dose that reliably irritates the gut in controlled human challenge, so its maximum level functions chiefly as a sentinel for can-lining integrity rather than a guard against chronic or cumulative toxicity.

Aluminium is limited because chronic dietary intake accumulates against a low tolerable weekly intake derived from animal neurotoxic, reproductive, and developmental endpoints — corroborated in humans by dialysis encephalopathy and osteomalacia — with renally impaired people, frequent antacid users, and formula-fed infants the most exposed; the resulting body burden is controllable through water treatment and process controls.

Trivalent chromium is a low-toxicity form assumed to dominate in food and long treated as an essential trace element, whereas hexavalent chromium is an IARC Group 1 carcinogen (established on occupational-inhalation evidence and assessed by US EPA as likely carcinogenic by the oral route), so chromium is limited only where a credible hexavalent-chromium pathway exists.