E535 – Sodium ferrocyanide | anti-caking agent in salt and cyanide concern

Quick analysis summary about E535 – Sodium ferrocyanide food additive

Bottom line about E535

E535 is sodium ferrocyanide, an anti-caking agent used mainly in salt. It is graded GREEN – SAFE at permitted food-use levels because exposure is very low and the ferrocyanide complex is poorly absorbed.

Why this grade for E535

The cyanide groups in ferrocyanide are tightly bound to iron and are not equivalent to free cyanide in normal food conditions. EFSA found no safety concern at authorised uses and set a conservative group ADI for ferrocyanides.[1]

Who may want to limit or avoid E535

Most consumers do not need to avoid E535 itself. People who have been told to reduce salt intake should limit salty foods regardless of whether E535 is present.

Common uses and where E535 appears

E535 is mainly found in table salt, cooking salt, and salt substitutes. It helps salt crystals stay dry and free-flowing.

E535 source or origin

E535 is a synthetic inorganic salt, usually produced as sodium ferrocyanide or sodium hexacyanoferrate. Food-grade material must meet purity specifications.

Intake note for E535

EFSA set a group ADI (Acceptable Daily Intake) of 0.03 mg/kg body weight per day expressed as ferrocyanide ion for sodium, potassium, and calcium ferrocyanides. Estimated food-additive exposure was below this value in the refined exposure scenario.[1]

Is E535 banned anywhere?

E535 is authorised in the European Union for salt and salt substitutes, and the United States permits yellow prussiate of soda in salt up to 13 parts per million calculated as anhydrous sodium ferrocyanide. Codex and several other reviewed jurisdictions also list ferrocyanides for limited salt-related uses, so no clear major food-use ban was identified.

Safety grading GREEN – SAFE

E535 is graded GREEN – SAFE because the realistic dietary exposure from salt is very small and because ferrocyanide is much less hazardous than free cyanide. The main toxicological signal is kidney effects at much higher animal doses, not a recurring human effect from normal salt use. This grade does not mean unlimited salt is healthy, because the sodium in salt remains a separate dietary concern.[1,3]

Study basis or key toxicological reasoning for E535

EFSA identified the kidney as the target organ and used a chronic 2-year rat study in which 4.4 mg sodium ferrocyanide/kg body weight per day was the NOAEL (No Observed Adverse Effect Level) for renal effects. EFSA also reported low absorption, no human accumulation, no concern for genotoxicity or carcinogenicity, and refined exposure up to 0.003 mg/kg body weight per day in children and adolescents.[1] EFSA also summarizes older short-term feeding data, and an in vitro human lymphocyte genotoxicity study supports the absence of a clear genotoxicity signal. The human evidence base remains limited because food exposure is expected to be very low.[1,2]

Side effects of E535 – Sodium ferrocyanide food additive

Kidney effects at high dose: Animal studies identified kidneys as the main target at doses far above expected intake from salt.[1]
Salt-related health issues: Products containing E535 are usually salt, so high intake may increase sodium exposure rather than E535 exposure.
Free cyanide fear: The name sounds alarming, but the cyanide groups are strongly bound in the ferrocyanide complex under normal food-use conditions.
Possible impurity concern: Food-grade specifications matter because purity and metal impurities can influence safety margins.
Excessive intake: Very high intake of ferrocyanide salts is not a realistic food scenario, but would be more likely to increase renal stress.

Should You Avoid E535 – Sodium ferrocyanide food additive?

Most people do not need to avoid E535 when it appears in salt at permitted levels. The practical health decision is usually about total salt intake, not sodium ferrocyanide itself. People with hypertension, kidney disease, heart failure, or medical advice to reduce sodium should choose lower-salt eating patterns. E535 is not the same as free cyanide, but it is still reasonable to prefer products with shorter additive lists when salt intake is already high.

Common uses of E535 – Sodium ferrocyanide food additive

Table salt to prevent clumping during storage.
Cooking salt to keep crystals free-flowing.
Iodised salt where flowability must be maintained.
Salt substitutes in jurisdictions where ferrocyanides are authorised.
Industrial salt crystallisation as an adjuvant for dendritic salt crystals.
Dry savoury mixes only when permitted local rules allow the specific use.

Common names and synonyms of E535 – Sodium ferrocyanide food additive

Sodium ferrocyanide
E535
INS 535
Sodium hexacyanoferrate
Sodium hexacyanoferrate(II)
Yellow prussiate of soda
Yellow prussiate
Sodium ferrocyanide decahydrate
Anti-caking agent

What is E535 – Sodium ferrocyanide food additive?

E535 is the E-number for sodium ferrocyanide, an inorganic coordination compound used in food mainly as an anti-caking agent. Its job is physical rather than nutritional. It modifies the surface and shape of salt crystals so they do not stick together as easily in humid conditions.

The word ferrocyanide can be confusing because it contains cyanide ligands. In E535, those ligands are coordinated tightly to iron, forming a stable complex that behaves differently from free cyanide salts. Under normal food storage, cooking, and eating conditions, it does not act like cyanide poisoning agents. Strong acids or unusual chemical conditions can release hydrogen cyanide from ferrocyanides, but this is not the normal situation in table salt. Because E535 is used in very small amounts, regulation focuses on strict maximum levels, purity, and exposure margins.

Where is E535 – Sodium ferrocyanide food additive allowed (EU vs US)?

In the European Union, E535 is authorised as a ferrocyanide anti-caking agent in salt and salt substitutes under specific maximum levels. In the United States, FDA permits yellow prussiate of soda as an anti-caking agent in salt and as an adjuvant in dendritic salt production up to 13 parts per million calculated as anhydrous sodium ferrocyanide.

E535 – Sodium ferrocyanide