Zitronensäure und ihre Alkalisalze
MAK-Begründung, Nachtrag
Andrea Hartwig1 (Vorsitz der Ständigen Senatskommission zur Prüfung gesundheitsschädlicher Arbeitsstoffe, Deutsche Forschungsgemeinschaft)MAK Commission2
1 Institut für Angewandte Biowissenschaften, Abteilung Lebensmittelchemie und Toxikologie, Karlsruher Institut für Technologie (KIT), Adenauerring 20a, Geb. 50.41, 76131 Karlsruhe, Deutschland
2 Ständige Senatskommission zur Prüfung gesundheitsschädlicher Arbeitsstoffe, Deutsche Forschungsgemeinschaft, Kennedyallee 40, 53175 Bonn, Deutschland
Abstract
The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated citric acid [77‐92‐9] and its alkali metal salts, considering all toxicological endpoints.
The critical effect of citric acid is the irritation of the respiratory tract with an acute LOAEC of 225 mg/m3 in humans and 81 mg/m3 in guinea pigs. At this concentration coughing is induced due to the lowering of the pH value. The NOAEC in guinea pigs is 31 mg/m3, the corresponding NOAEC in humans is not known. Studies with repeated inhalation are not available. Therefore, the maximum concentration at the workplace (MAK value) has been set by analogy with the MAK value for phosphoric acid of 2 mg/m3 as inhalable fraction. Since a local effect is critical, Peak Limitation Category I is designated. The excursion factor of 2 is set by analogy with phosphoric acid.
The alkali metal salts of citric acid are not irritating, which precludes setting the same MAK value for the salts as for citric acid. However, a higher MAK value cannot be established because the systemic NOAEL is unclear. Therefore, no MAK value can be set for the alkali metal salts of citric acid.
The oral NOAEL for developmental toxicity in rats, mice, rabbits and hamsters is higher than 200 mg citric acid/kg body weight, which after toxicokinetic scaling corresponds to more than 200 mg/m3 at the workplace. Therefore, damage to the embryo or foetus is unlikely when the MAK value is observed and citric acid is assigned to Pregnancy Risk Group C.
Citric acid does not possess a relevant genotoxic potential in vivo. The same is assumed for its alkali metal salts. There are no valid carcinogenicity studies with citric acid. A tumour promoting effect of sodium citrate but not citric acid in the rat urinary bladder is due to excessively high sodium concentration in the urine and is therefore not relevant for humans at the workplace.
According to skin absorption models, percutaneous absorption of citric acid does not contribute significantly to systemic toxicity. The same is assumed for its alkali metal salts. Citric acid and its alkali metal salts are not sensitizing to skin or airways.
