Registration Dossier

Administrative data

Description of key information

In-vivo corrosivity screening studies are available for chromium (VI) trioxide.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (corrosive)

Eye irritation

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Additional information

Chromium (VI) trioxide ['chromic acid']

A corrosivity screen in the rabbit in vivo (Cuthbert, 1983) showed that chromic acid (aqueous chromium trioxide) is corrosive to the skin. The results of a briefly reported screening study (Thyssen, 1979) also indicate severe skin and irritation. The EU RAR (2005) does not include any studies but states that 'aqueous chromium (VI) trioxide is a corrosive substance due to its low pH'. Further testing in vivo for skin or eye irritation (i.e. in guiideline and GLP-compliant studies) is therefore not required and is not justifiable both on scientific grounds or for reasons of animal welfare. The EU RAR (2005) states that symptoms of sensory irritation of the respiratory tract are known to occur among chrome plating workers exposed to a mist of aqueous chromium (VI) trioxide. Since this material is corrosive, such symptoms are to be expected. No quantitative data on such irritation are available from studies of workers.

Chromium trioxide is markedly more corrosive to skin than other water-soluble hexavalent chromium compounds, as a consequence of its low pH when mixed with water or moisture to form chromic acid. Read-across between chromium trioxide and other water-soluble hexavalent chromium compounds is therefore not appropriate for skin and eye irritation/corrosion.


Effects on skin irritation/corrosion: corrosive

Effects on eye irritation: corrosive

Effects on respiratory irritation: irritating

Justification for classification or non-classification

Chromium trioxide

The results of a screening studies in the rabbit in vivo clearly show that chromic acid (aqueous chromium trioxide) is corrosive. Further testing in vivo for skin and eye irritation is therefore not required and cannot be justified on animal welfare grounds. According to EU criteria, chromium (VI) trioxide is classified as (R35) 'Causes severe burns';. The risk of severe damage to eyes is considered implicit and therefore classification with (R41) 'Risk of serious damage to eyes' is not required.