Potassium Ferrocyanide
The short version
The standard EU anti-caking agent for table salt — controversial in popular health narratives, regulated at very low residual.
It's permitted and generally considered safe, but there are a few reasons to be mindful — like sensitivities in some people, debated studies, or intake limits. The Safety section below explains the specifics.
Safety profile
JECFA (1974) set an ADI of 0–0.025 mg/kg body weight (calculated as sodium ferrocyanide). In 2018 EFSA set a group ADI for sodium, potassium and calcium ferrocyanide of 0.03 mg/kg body weight per day, expressed as ferrocyanide ion, and found no safety concern at the authorised uses and use levels. Despite the cyanide groups in the formula, absorption of ferrocyanides is low and they do not accumulate in the body; EFSA noted that the potential amount of free cyanide released at the ADI would not be of safety concern. Repeated misinformation panics around table salt do not reflect the actual chemistry. Banned in some countries (e.g., a few US states' organic standards) more on precautionary than evidence-based grounds.
Sources
- EFSA ANS Panel — Re-evaluation of sodium ferrocyanide (E 535), potassium ferrocyanide (E 536) and calcium ferrocyanide (E 538) as food additives (2018) — European Food Safety Authority (EFSA Journal 16(7):5374), via PubMed Central, 2018. safety: group ADI 0.03 mg/kg bw/day as ferrocyanide ion; free cyanide not of concern
- JECFA — Potassium ferrocyanide (INS 536), evaluation 1974 — WHO / Joint FAO/WHO Expert Committee on Food Additives, 1974. safety: JECFA ADI 0–0.025 mg/kg bw (as sodium ferrocyanide); synonym yellow prussiate of potash
- Regulation (EC) No 1333/2008 on food additives, Annex II, category 12.1 Salt and salt substitutes (consolidated text of 18.08.2026) — EUR-Lex, Publications Office of the European Union, 2026. usage/regulation: EU maximum 20 mg/kg in salt and salt substitutes
- 21 CFR 172.490 — Yellow prussiate of soda (sodium ferrocyanide) — US eCFR (Office of the Federal Register), 2026. regulation: the US lists the sodium salt (not potassium) for salt, max 13 ppm
Checked against these sources on .
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