Regulatory status and the 2005 UK reclassification
Under UK and EU food law, E170 covers calcium carbonates as a group. The UK Miscellaneous Food Additives (Amendment) (England) Regulations 2005 explicitly merged the two historical sub-entries, E170(i) calcium carbonate and E170(ii) calcium hydrogen carbonate, into a single listing: 'Calcium carbonate'. Calcium hydrogen carbonate therefore no longer holds a separate regulatory code in UK law but is covered under E170. It is authorised under assimilated EU Regulation 1333/2008 and in many food categories at quantum satis (no fixed upper limit).
The UK 2005 amendment substituted the two-part entry 'Calcium carbonates (i) calcium carbonate (ii) calcium hydrogen carbonate' with simply 'Calcium carbonate', consolidating both forms under E170.
2005RegulatoryThe Miscellaneous Food Additives (Amendment) (England) Regulations 2005, SI 2005/1099
E170 is listed as authorised for Great Britain under assimilated Regulation (EC) No 1333/2008 Annex II, effective from 31 December 2020.
2020RegulatoryUK FSA Regulated Products database, E-170 entry
EFSA safety re-evaluations of E170
EFSA reviewed calcium carbonate (E170) in 2011 and again in 2023. Both reviews concluded there is no need for a numerical acceptable daily intake, and no safety concern from calcium carbonate itself at the use levels found in food. The 2023 opinion noted that calcium hydrogen carbonate is not separately addressed in these evaluations, as it is treated as part of the same E170 group.
The EFSA Panel concluded there is no need for a numerical ADI for calcium carbonate and no safety concern with respect to exposure to calcium carbonate per se at currently reported use levels, including for infants below 16 weeks.
2023Regulatory reviewEFSA Panel on Food Additives and Flavourings, re-evaluation of calcium carbonate (E 170), EFSA Journal 2023;21(7):8106
The earlier 2011 EFSA re-evaluation assigned 'ADI not specified', reflecting no toxicological concern for the calcium carbonate compound itself at food additive use levels.
2011Regulatory reviewEFSA ANS Panel, Scientific Opinion on re-evaluation of calcium carbonate (E 170), EFSA Journal 2011;9(6):2318
Aluminium as an unavoidable impurity in E170
Calcium carbonate is a mineral product and naturally contains trace impurities including aluminium, originating from clay in limestone. EFSA's 2023 opinion flagged this specifically: the aluminium present in commercially available E170 could, at the highest measured concentrations, exceed the tolerable weekly intake for aluminium many times over when dietary exposure from all sources is combined. EFSA recommended new maximum limits for aluminium in E170 specifications. This concern applies to the parent compound E170, not to calcium hydrogen carbonate as a distinct substance. Because calcium hydrogen carbonate exists only in dilute aqueous solution and is used at relatively low concentrations, its contribution to aluminium exposure would be lower than solid calcium carbonate uses.
EFSA found that the unavoidable presence of aluminium in E170 is of concern. At the highest measured values in commercial calcium carbonate (1,120 mg aluminium per kg), the tolerable weekly intake for aluminium could be exceeded by approximately 890% when combined with other dietary sources.
2023Regulatory reviewEFSA Panel on Food Additives and Flavourings, EFSA Journal 2023;21(7):8106
EFSA recommended new specification limits for aluminium, lead, cadmium, arsenic, and mercury in E170, noting that decontamination of aluminium from calcium carbonate at industrial scale is not currently available.
2023Regulatory reviewEFSA Panel on Food Additives and Flavourings, EFSA Journal 2023;21(7):8106
Chemical instability and practical food use
Calcium hydrogen carbonate cannot be isolated as a dry powder: heating or evaporation causes it to decompose into calcium carbonate, carbon dioxide, and water. This limits its practical application to liquid or aqueous food systems. It is not used as a standalone additive in the same way as solid calcium carbonate and is most commonly encountered as a naturally occurring component of hard water used in food and drink production.
Calcium hydrogen carbonate exists only in aqueous solution and decomposes on heating or evaporation to yield calcium carbonate, carbon dioxide, and water. It cannot be produced or stored as a stable solid.
EstablishedWikipedia, Calcium bicarbonate article; confirmed by EFSA and Codex Alimentarius substance definitions
