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Description of key information

No reliable repeated dose studies are available. It is however clear that exposure to sodium carbonate will not result in increased systemic levels of sodium and carbonate due to the homeostatic regulation of both ions. Hence, no further studies are considered necessary for this endpoint.

Key value for chemical safety assessment

Additional information

Repeated dose toxicity: oral

No animal data are available on repeated dose toxicity studies by oral route for sodium carbonate. As side information from a developmental toxicity study, the oral repeated dose toxicity of sodium carbonate has been described already on page 14 of the OECD SIDS dossier (2002). Please find hereafter the text

A study on developmental toxicity has been reported by the FDA (1974). Although this study covers a different endpoint, it provides some information on repeated dose toxicity as well. Aqueous solutions of sodium carbonate were administered daily via oral intubation to pregnant mice at doses ranging from 3.4 to 340 mg/kg bw during days 6-15 of gestation. The test substance did not affect the survival, body weight, number of implantations and litter size and weight of dams but the reporting of the study was limited. Similar negative results were reported for rats and rabbits for daily doses from 2.45 to 245 mg/kg bw and 1.79 to 179 mg/kg bw, respectively (FDA, 1974).

Repeated dose toxicity: inhalation

A repeated dose inhalation study has been reported by Reshetyuk and Shevchenko (1966) but this study was not reported in sufficient detail. Histopathological changes were found in the lungs but the study was not considered reliable and therefore it is not further described here.

Summary and discussion of repeated dose toxicity

The repeated dose toxicity of sodium carbonate has been summarized already on page 14 of the OECD SIDS dossier (2002). Please find hereafter the text:

A repeated dose inhalation study, which was not reported in sufficient detail, revealed local effects on the lungs which could be expected based on the alkaline nature of the compound. A good quality oral, dermal or inhalatory repeated dose study is not available. However, the long-term hazard of sodium for humans is well known and has been focused on the effects of sodium on the prevention and control of hypertension.

Recommendations on daily dietary sodium intake were reported to be 2.0-3.0 g for a moderately restricted intake and 3.1-6.0 g

was considered to be a normal intake (Fodor et al., 1999). Carbonate would be neutralised in the stomach by the low pH of the gastric juice. Furthermore, sodium carbonate is not expected to be systemically available in the body due to neutralisation by gastric acid or by blood (see also 5.1). Therefore, additional testing for repeated dose toxicity is considered unnecessary for sodium carbonate. Implicitly this has been recognised in the past, because sodium carbonate is considered ‘GRAS’ in food with no limitation other than current good manufacturing practice (CFR, 1999).

Furthermore sodium carbonate is used as a food additive which confirms that the substance has a low repeated dose toxicity. The Joint FAO/WHO Expert Committee on Food Additives considered it not necessary to derive an Acceptable Daily Intake (ADI) for the food additive sodium carbonate (JECFA, 1965).

Justification for classification or non-classification

Based on the available information, no classification for repeated dose toxicity is required in accordance with EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.

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