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The acute oral LD50 of dichromium tris(chromate), tested as a water dilution (25% corresponding to 23.6% active ingredient) was between 50 and 300 mg active ingredient/kg bw in female rats in a recent GLP guideline study. The acute dermal LD50 of dichromium tris(chromate) 25% solution was found to be greater than 2000 mg active ingredient/kg bw in rats, in a recent GLP guideline study. No data are available for inhalation toxicity; the EU RAR (2005) reviews the data regarding the inhalation toxicity of other Cr (VI) compounds, reported LC50 values range from 99 to 217 mg/m³. 

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Additional information

Acute toxicity: oral

The acute oral toxicity of dichromium tris(chromate) 25% solution was evaluated in female rats, in a GLP study according to the acute toxic class method OECD 423 (Tavaszi, 2010). The test substance was administered as a single oral dose by gavage, rats were observed for 14 days post-administration and necropsies were performed on all animals. The first group of 3 females were dosed with 300 mg active ingredient/kg bw. All 3 rats died within 6 hours of dosing, therefore the second group was dosed with 50 mg active ingredient/kg bw. No deaths occurred, so a confirmatory group was also dosed with 50 mg/kg bw. Clinical signs observed in all 3 rats administered 300 mg/kg were decreased activity, hunched posture, dyspnoea, piloerection, soft faeces and death. No mortalities occurred in the animals administered 50 mg/kg, and no clinical signs were observed in these animals.

Necropsy of the animals dosed with 300 mg/kg revealed dark/brown discolouration of the oesophagus, stomach and/or digestive content, as well as dark/brown discolouration of the lungs associated with yellow liquid in the trachea or nasal cavity. There were no abnormal findings in the 50 mg/kg animals.

The acute oral LD50 of dichromium tris(chromate) 25% solution was found to be between 50 and 300 mg active ingredient/kg bw in female rats.

Acute toxicity: inhalation

No data are available for dichromium tris(chromate). Further testing is not required due to the corrosive nature of Cr (VI) compounds, and on the basis that acute toxicity data for the oral and dermal exposure routes are available. Information regarding the inhalation toxicity of a number of other Cr (VI) compounds is available in the EU RAR (2005), and is presented here in a weight of evidence approach in support of proposed changes to the classification of dichromium tris(chromate):

The EU RAR (2005) reviews the available data for a number of Cr (VI) compounds, which indicates that this group of chemicals are toxic by inhalation. The EU RAR states that potassium dichromate aerosols (mass median aerodynamic diameter 1-2 microns) were toxic when inhaled by rats, deaths occurring following a 6-hour exposure to 37 mg/m³ (13 mg Cr (VI)/m³) and above. There were no deaths at 31 mg/m³ (11 mg Cr(VI)/m³). Decreased body weight gain and increased lung weight were observed following 2 -hour exposure to 20 mg/m³ (7 mg Cr(VI)/m³). LC50 values of 99 mg/m³ (potassium dichromate) (35 mg Cr(VI)/m³), 200 mg/m³ (sodium and potassium dichromate) (70 mg Cr(VI)/m³) and 104 mg/m³ (sodium chromate) (33 mg Cr(VI)/m³) have been reported for male rats with a 4-hour aerosol exposure period. Signs of toxicity included reduced body weight, respiratory distress and irritation of the respiratory tract. Lung oedema, inflammation and tracheal epithelium necrosis were seen in rats following inhalation of 28 mg/m³ sodium chromate (9 mg Cr(VI)/m³) for 24 hours; minimal lung effects (reduction in glycoprotein secretion in the trachea) were seen at 8 mg/m³ (3 mg Cr(VI)/m³) for 24 hours. Intratracheal instillation of potassium dichromate at 1.14 mg (0.4 mg Cr(VI)) produced lung inflammation in rats. An LC50 value of 217 mg/m³ (113 mg Cr(VI)/m³) for chromium (VI) trioxide (presumably aerosol) has been reported for rats with a 4-hour exposure period. It is predicted that severe damage to tissues of the respiratory tract would occur at low concentrations due to the corrosive nature of this substance. In the case of all the Cr (VI) compounds under consideration, depending upon the pH of the Cr (VI) solution, corrosive effects can occur on contact.

Acute toxicity: dermal

The acute dermal toxicity of dichromium tris(chromate), tested as a water dilution (25% corresponding to 23.6% active ingredient) was evaluated in male and female rats, according to OECD 402 (Zelenak, 2010). The test material was applied to the shaved intact dorsal skin at doses of 175, 350, 850, 1400 and 2000 mg active ingredient/kg bw, and held in place using a semi-occlusive dressing for 24 hours. The rats were observed for 14 days following removal of the dressings, and were necropsied at the end of the observation period. There were no mortalities, no clinical signs were observed, and no abnormalities were detected at necropsy. Discolouration of the hair and skin at the test site was noted. It was concluded that the acute dermal LD50 of dichromium tris(chromate) 25% solution is >2000 mg active ingredient/kg bw in rats.

Justification for classification or non-classification

The acute oral LD50 of dichromium tris(chromate) was between 50 and 300 mg active ingredient/kg bw in female rats. Based on the results of the acute oral study, dichromium tris(chromate) should be classified as Toxicity Category 3 according to UN GHS and Regulation (EC) No 1272/2008. The acute dermal LD50 of dichromium tris(chromate) 25% solution was greater than 2000 mg active ingredient/kg bw in rats. The substance is not classified as acutely toxic by the dermal route according to UN GHS and Regulation (EC) No 1272/2008 criteria, and no changes to this classification are proposed. Based on information available regarding other soluble Cr (VI) compounds, dichromium tris(chromate) should be classified as toxic by inhalation Toxicity Category 2 according to UN GHS and Regulation (EC) No 1272/2008.