Registration Dossier

Administrative data

Description of key information

In-vivo corrosivity screening studies are available for chromium (VI) trioxide.  Non-standard in vivo studies of skin corrosivity and irritation are available for sodium chromate, sodium dichromate and potassium dichromate; the results of these studies are sufficient for classification.  Literature reviews of additional non-standard studies and the effects of human exposure are alos presented.

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.

Sodium chromate

Dry sodium chromate was not found to be a skin irritant in a guideline-compliant study (Dunn, 1984), however sodium chromate was found to be a skin irritant in the same study when moistened with physiological saline. There was no evidence of corrosivity. The results of this study therefore indicate that the skin irritancy of sodium chromate is a consequence of its low pH when in aqueous solution. In an additional study using a 24 -hour application period, signs of local dermal irritation were accompanied by systemic toxicity and mortality. The findings of irritancy in these studies are consistent with the results of other studies reported in the EU RAR. The results of the animal studies indicate that sodium chromate is classified as a skin irritant, however it is noted that this compound is classified as corrosive (R34) 'Causes burns' according to Directive 67/548/EEC.

No guideline studies for eye irritation are available. Based on the literature reports of non-standard studies, experience in humans and the R34 classification, testing is not considered to be scientifically justified and additionally cannot be supported on animal welfare grounds. Classification with (R41) 'Risk of serious damage to eyes' is implicit.

Sodium dichromate

Dry sodium dichromate was found to be a slight skin irritant in a guideline-compliant study (Dunn, 1984), however sodium dichromate was found to be a marked skin irritant in the same study when moistened with physiological saline. There was no evidence of corrosivity. The results of this study therefore indicate that the skin irritancy of sodium dichromate is a consequence of its low pH when in aqueous solution. In an additional study using a 24 -hour application period, signs of local dermal irritation were accompanied by systemic toxicity and mortality. The fiindings of irritation in these studies are consistent with the results of other studies reported in the EU RAR. The results of the animal studies indicate that sodium dichromate is classified as a skin irritant, however it is noted that this compound is classified as corrosive (R34) 'Causes burns' according to Directive 67/548/EEC.

No guideline studies for eye irritation are available. Based on the literature reports of non-standard studies, experience in humans and the R34 classification, testing is not considered to be scientifically justified and additionally cannot be supported on animal welfare grounds. Classification with (R41) 'Risk of serious damage to eyes' is implicit.

Potassium dichromate:

Dry potassium dichromate was not found to be a skin irritant in a guideline-compliant study (Dunn, 1984), however potassium dichromate was found to be a skin irritant in the same study when moistened with physiological saline. There was no evidence of corrosivity. The results of this study therefore indicate that the skin irritancy of potassium dichromate is a consequence of its low pH when in aqueous solution. In an additional study using a 24 -hour application period, signs of local dermal irritation were accompanied by systemic toxicity and mortality.  The findings of irritation these studies are consistent with the results of other studies reported in the EU RAR. The results of the animal studies indicate that potassium dichromate is classified as a skin irritant, however it is noted that this compound is classified as Corrosive (R34) 'Causes burns' according to Directive 67/548/EEC.

No guideline studies for eye irritation are available. Based on the literature reports of non-standard studies, experience in humans and the R34 classification, testing is not considered to be scientifically justified and additionally cannot be supported on animal welfare grounds. Classification with (R41) 'Risk of serious damage to eyes' is implicit.


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.

Sodium chromate

The available animal data are from non-standard studies, however they indicate that sodium chromate is classified as as skin irritant according to current EC criteria. However it is noted that sodium chromate is listed on Annex I of Directive 67/548/EEC and is classified as corrosive (R34) 'Causes burns'. No change to this classification is proposed.

Sodium dichromate

The available animal data are from non-standard studies, however they indicate that sodium dichromate is classified as as skin irritant according to current EC criteria. However it is noted that sodium dichromate is listed on Annex I of Directive 67/548/EEC and is classified as corrosive (R34) 'Causes burns'. No change to this classification is proposed.

Potassiun dichromate

The available animal data are from non-standard studies, however they indicate that potassium dichromate is classified as as skin irritant according to current EC criteria. However it is noted that potassium dichromate is listed on Annex I of Directive 67/548/EEC and is classified as corrosive (R34) 'Causes burns'. No change to this classification is proposed.