Dichromium tris(chromate)

Endpoint summary

Description of key information

Dichromium tris(chromate), tested as a water dilution (25% corresponding to 23.6% active ingredient), was found to be non-corrosive in the in vitro EPISKIN assay. However, dichromium tris(chromate) is classified as Skin Corrosion Category 1A according to Regulation (EC) No 1272/2008. The substance is however, also classified according to additional note T "The substance may be marketed in a form which does not have the physical hazards as indicated by the classification...". The EU RAR summarises the data for other Cr (VI) compounds, and concludes that these substances are irritating and corrosive to skin.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (corrosive)

Additional information

Skin irritation / corrosion

The corrosive properties of dichromium tris(chromate) 25% solution were evaluated in the EPISKIN reconstituted human epidermis in vitro assay, according to OECD 431 (Ágh, 2010). The positive control (glacial acetic acid) showed zero viability. The test item did not show significantly reduced cell viability in comparison to the negative control. All test item results were above 35% of the mean negative control value. All validity criteria were within acceptable limits. It was concluded that a water based solution of dichromium tris(chromate) (23.6% active ingredient) is not corrosive to skin when tested in vitro with the EPISKIN assay.

No in vivo data are available for dichromium tris(chromate), further testing is not required and cannot be justified on animal welfare grounds as the substance is classified as corrosive to skin. The EU RAR (2005) summarises a number of non-standard studies in animals which indicate that water-soluble Cr (VI) compounds (sodium chromate, sodium dichromate and potassium dichromate) are likely to be skin irritants. Single applications of sodium chromate, sodium dichromate or potassium dichromate to rabbit skin for 4 hours resulted in irritant responses of erythema and oedema of grade 3 or less, when the compounds were in solution or moistened with saline. Reactions appeared to subside but irritation was still present at 6 days after application.

In terms of human experience, direct accidental contact with very acidic or high temperature solutions of highly water-soluble Cr (VI) compounds has resulted in severe burns to human skin. It is not clear from the available reports whether intact skin is damaged by single contact with neutral solutions of such compounds. In one patch test study, some volunteers responded to 0.5% aqueous potassium dichromate with mild irritation, especially around the hair follicles.

Aqueous chromium (VI) trioxide is a corrosive substance due to its low pH. Studies in guinea pigs have demonstrated concentration-dependent erythema, reactions were dependent on the degree of trauma (abrasion) to the skin before application.

In workers regularly exposed to highly water-soluble Cr (VI) in solution, chrome ulcers develop after some initial damage to the skin. This has been described for dye workers handling sodium or potassium dichromate solutions and frequently in exposed workers in the chromate production and chrome plating industries. The severity of the ulcer depends upon the frequency and duration of skin contamination. Small papules develop initially, progressing to an ulcer which penetrates gradually to deeper skin layers. Typically, chrome ulcers have a hard circular periphery and a cavity leading to a base covered with exudate or a crust.

Eye irritation

There are no studies available for dichromium tris(chromate), further testing is not required and cannot be justified on animal welfare grounds as the substance is classified as corrosive to skin. The EU RAR (2005) reports that a neutralised sodium chromate solution was not irritating to the rabbit eye. In contrast, repeated administration of potassium dichromate in powder form daily for 7 days caused severe irritation including necrosis of the conjunctivae and ulceration of the cornea.

In occupational settings, accidental splashing of highly water-soluble Cr(VI) compounds in solution into the eye has resulted in damage to the human eye. A number of case reports have detailed both inflammation of the cornea and conjunctivae and in more severe cases, corneal erosion and ulceration. The severity of response is increased by low pH or high temperature.

Effects on skin irritation/corrosion: highly corrosive

Justification for classification or non-classification

Dichromium tris(chromate) is classified as Skin Corrosion Category 1A according to Regulation (EC) No 1272/2008. The substance is however, also classified according to additional note T "The substance may be marketed in a form which does not have the physical hazards as indicated by the classification...". No change to this classification is proposed.