Registration Dossier

Administrative data

Description of key information

A valid test on acute inhalation toxicity of another sparingly water soluble chromate, strontium chromate, exists and is utilised for read-across. In acute oral toxicity, a poorly described study on strontium chromate is notified but the LD50 is based on read-across from a sparingly water soluble chromate. There is no non-human information on acute dermal toxicity of zinc potassium chromate. Human information on zinc potassium chromate is also lacking. 

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Dose descriptor:
LD50
327 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion
Dose descriptor:
LC50
270 mg/m³

Additional information

According to REACH guidelines with>1,000 t/a substances, two toxicity tests are required (oral and inhalation or dermal acute toxicity tests) for showing acute toxicity of a substance. Based on the assumptions made in the toxicokinetics of the bioavailability, exposure via inhalation route is relevant for chromates. As zinc potassium chromate is a sparingly water soluble chromate, read-across from other sparingly water soluble chromates as strontium chromate is the priority when regarding the acute toxicity of zinc potassium chromate. In a well-performed acute inhalation toxicity test with strontium chromate, the LD50 was between 0.27 and 0.51 mg/L air, suggesting category 2 in classification. There are two other studies on acute toxicity of strontium chromate. In these, the substance was orally or intratracheally administered in rats, giving a LD50value of 3,118 mg/kg bw (795 mg Cr/kg) and 16.6 mg/kg (4.2 mg Cr/kg), respectively. According to this acute oral toxicity study and read-across approach from strontium chromate, there would not be classification for zinc potassium chromate. There is no non-human information on acute dermal toxicity of zinc potassium chromate. Human information on zinc potassium chromate is also lacking..

Data with highly water soluble chromates exist, but this data can be regarded as worst case scenario. This is because both the well-documented inhalation study (LC500.27-0.51 mg/L) and the supporting oral toxicity study (LD503,118 mg/kg bw) with strontium chromate give evidence on the lower acute toxicity also for zinc potassium chromate compared to the results received in studies with highly water soluble hexavalent chromium compounds (e.g. in Gad et al. 1986: LC50for acute inhalation toxicity 0.094-0.158 mg/L, and LD50for acute oral toxicity 51.1-57.2 mg/kg bw). For acute inhalation toxicity, classification of zinc potassium chromate into category 2 is justified. Furthermore, it is reasonable to judge acute oral toxicity of zinc potassium chromate to category 4 as a study with sparingly soluble calcium chromate suggest. This is milder classification than with highly water soluble chromates but tighter than in the poorly described study with strontium chromate.

Justification for classification or non-classification

Conclusion: Zinc potassium chromate is classified for acute oral toxicity as 'harmful if swallowed' (category 4), and for acute inhalation toxicity 'fatal if inhaled' (category 2). No further testing is suggested.