E-numbers / Other additives / E552
also: Silicic acid calcium salt
A mineral powder used to stop salt, spices and supplements clumping. EU safety regulators reviewed it and concluded the current evidence is insufficient to confirm it is without risk.
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In a 2020 re-evaluation, EFSA concluded the safety of E552 cannot be confirmed: silicon accumulated in the kidneys and liver of rats at higher doses, particle sizes fall into the nanomaterial range under EU definitions, and key toxicology studies on chronic exposure and reproductive effects have never been done.
18
of the 43,325 UK supermarket foods we checked declare E552 in their ingredients
That is under 0.1%, counted by its code or its name.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Why it’s worth knowing. In a 2020 re-evaluation, EFSA concluded the safety of E552 cannot be confirmed: silicon accumulated in the kidneys and liver of rats at higher doses, particle sizes fall into the nanomaterial range under EU definitions, and key toxicology studies on chronic exposure and reproductive effects have never been done.
Calcium silicate is a white, odourless powder composed of calcium and silicon bound with oxygen. It occurs naturally in minerals but the food-grade form is synthetically produced. It is classified as an anti-caking agent and separating agent.
It absorbs moisture and oils on the surface of dry food particles, preventing them from sticking together and forming lumps. This keeps powders and granules free-flowing throughout shelf life.
Most common in table salt (the primary use), ground spices and seasoning blends, baking powder, dried powdered foods, chewing gum base, hard confectionery, some cheeses (as a separating agent on cut surfaces), food supplements in tablet form, and powdered flavourings. On a label it appears as calcium silicate or E552.
The European Food Safety Authority completed a full re-evaluation of E552 in 2020 and reached an unusually cautious conclusion: it could not establish an acceptable daily intake and stated that the safety of calcium silicate as a food additive cannot be assessed. The reason was a lack of adequate subchronic toxicity, chronic toxicity and reproductive toxicity studies, meaning the data needed to draw firm conclusions simply does not exist.
EFSA concluded that the safety of calcium silicate (E 552) cannot be assessed and set no acceptable daily intake, citing critical gaps in subchronic, chronic, and reproductive toxicity data.
Rat studies at higher doses found silicon accumulating in kidney and liver tissue. EFSA flagged this as a concern because chronic accumulation in organs could cause harm, but the studies were not adequate in design or duration to determine at what level of intake this becomes a problem for humans.
Accumulation of silicon from calcium silicate was reported in the kidneys and liver of rats at elevated doses in available animal studies, identified as a data concern by EFSA.
EFSA noted that calcium silicate as used in food contains particles below 100 nanometres when examined by electron microscopy, meaning it qualifies as a nanomaterial under EU definitions. The behaviour of nanoscale particles in the body can differ from larger particles of the same substance, and no specific nano-toxicology data was available for this additive.
Transmission electron microscopy detected particles below 100 nm in calcium silicate used as a food additive, meeting the EU nanomaterial definition and raising unanswered questions about nano-specific toxicity.
The permitted specifications for heavy-metal impurities in food-grade calcium silicate (arsenic, lead, mercury) were judged by EFSA to allow exposures significant enough to warrant tightening. The additive is mined or synthetically derived from mineral sources, and impurity levels in commercial batches vary.
EFSA recommended lowering the maximum permitted limits for arsenic, lead and mercury in E 552 specifications, noting that current limits could allow significant exposure to toxic elements.
No specific group is formally advised to avoid it under current UK rules. People who want to minimise exposure to additives with unresolved toxicology can look for products listing E552 or calcium silicate in the ingredients and choose alternatives, particularly in table salt (where potassium ferrocyanide E536 is the other common anti-caking option, itself with its own profile).
E552 is one of the more unusual cases in the approved-additives list: it remains fully legal but regulators themselves have put on record that they cannot confirm it is without concern. The EFSA 2020 opinion was not a ban or an alarm, but it was an acknowledgement that decades of use happened without the toxicology studies that would ordinarily be required today. The nanomaterial finding adds a layer of uncertainty that is not unique to this additive but has not been resolved. The European Commission has not acted on the opinion to restrict it; the UK FSA has not published a revised position. The practical exposure from salt and spices is low in absolute terms, but the honest assessment is that the data needed to draw a firm line does not exist.
No. E552 is authorised for use in the UK under the assimilated EU Regulation 1333/2008, carried over after Brexit. It remains on the FSA approved-additives list. However, the EU's food safety authority (EFSA) completed a re-evaluation in 2020 and concluded it could not confirm the additive's safety with the available data. No ban or restriction has followed from that finding as of mid-2026.
EFSA found that the toxicology studies needed to establish an acceptable daily intake, specifically adequate subchronic (90-day), chronic (lifetime), and reproductive toxicity studies, had never been done. Animal studies that did exist showed silicon accumulating in kidneys and liver at higher doses. The Panel also found that commercial calcium silicate contains nano-sized particles, which raises questions about behaviour in the body that standard studies do not address.
Table salt is the most common source. It also appears in ground spices and seasoning blends, baking powder, dried powdered foods, hard confectionery, chewing gum base, food supplements in tablet form, and some cheeses (applied to cut surfaces to prevent sticking). Look for calcium silicate or E552 in the ingredients list.
Yes. Calcium silicate is a mineral-derived or synthetically produced inorganic compound with no animal-derived ingredients.
Last reviewed: 20 June 2026
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