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Short-term toxicity to aquatic invertebrates

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Description of key information

The 48 h-EC50 (immobilisation) to Daphnia magna is 3.67 mg/L under static conditions (95% CI 3.02 to 4.62 mg/L) in accordance with OECD 202 under GLP. 

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
3.67 mg/L

Additional information

The key study was conducted in accordance with OECD 202 under GLP to determine the aquatic acute toxicity of the test substance potassium isopentyl dithiocarbonate (PIAX) to Daphnia magna. The observed 48 h-EC50 (immobilisation ) to Daphnia magna was 3.67 mg/L (95% CI 3.02 to 4.62 mg/L) based on nominal concentrations. Potassium dichromate was used as a reference substance. The stability of PIAX was monitored as TOC, and as 94 % was recovered after 48 hours, the substance was concluded to fulfil the stability criteria of the method. Therefore it was concluded that the nominal concentrations could be used instead of measured concentrations to verify the effect levels of the study. The study was considered as reliable without restrictions and hence used as a key value for hazard assessment and classification and labelling of the substance. The study was considered as reliable without restrictions and hence can be used as a key value for hazard assessment and classification and labelling of the substance.

A 24 -h EC50 to Daphnia magna was determined for PIAX also by Xu et al. (1988) to be 3.0 mg/L at 20 oC at pH of 8.4 in accordance with OECD 202. In that study potassium PIAX and the other two xanthates tested were 10 times less toxic than potassium ethyl xanthate. As the results are taken from a peer reviewed publication with basic information on test materials and methods, they are rated as scientifically acceptable, and support the result of the key study.

Hawley (1977) reviewed older acute toxicity data of short term bioassays. The 96-h median tolerance level in Daphnia magna was expected to lie in the range 0.1 - 1.0 mg/L on a read-across substance PAX. Leduc et al. (1974) reported a single 48-h LC50value to Daphnia magna in the range 0.01 - 0.16 mg/L in a static system also on PAX, and compared it to other acute aquatic toxicity values obtained. As the details of the test materials, methods and study results, including statistics and controls are not available in the both of these reports,the results obtained are rated as not reliable, but suggest daphnids being the most sensitive species regarding the acutely toxic aquatic effects.

Available EC/IC50 -values of degradation products 3-methylbutan-1 -ol and pentanol are > 100 mg/L for daphnids and freshwater ciliata. For CS2, a 48 -h EC50 on Daphnia magna (immobilisation) was 2.1 mg/L in a semi-static acute immobilisation test.