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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The 72 -h EC50 (growth rate) of potassium isoamyl xanthate (PIAX) to Desmodesmus subspicatus is 10.51 mg/L  (95 % CI 9.85 - 11.24 mg/L) under static conditions in accordance with OECD 201 and GLP.

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
10.51 mg/L
EC10, LC10 or NOEC for freshwater algae:
1 mg/L

Additional information

The key study of Ležovičová, V. (2012b) was conducted in accordance with OECD 201 under GLP to determine the aquatic acute toxicity of the test substance potassium isopentyl dithiocarbonate (PIAX) to algae. The observed 72-h EC50 (growth rate) to Desmodesmus subspicatus was 10.51 mg/L (95% CI 9.85 to 11.24 mg/L) based on nominal concentrations. The substance was assessed as stable during the 72 hours by TOC monitoring. The calculated 72-h NOEC was 1 mg/L. This study is selected as the key study, as it was assessed as valid without restrictions.

The supporting studies for CSA are reported for the minor constituent of the target substance, potassium amyl xanthate (PAX). The read-across justifications are presented in the Annex of the CSR. Bertills et al. (1986) assessed acute toxicity of four xanthates to phytoplankton in a static freshwater system. The 72-h EC50 on phytoplankton (Monoraphidium griffithii) obtained with a read-across substance PAX was 0.1 mg/L, based on inhibition of growth rate at 20 deg. C and pH 6.5. The study was regarded as reliable with restrictions as no standard methods were used, and insufficient details on test results, statistics and controls were reported.

As the target substance is hydrolytically unstable, the results of the main degradation products were included in CSA as supporting information. The 8-d EC5 (growth rate) of 260 mg/l to Scenedesmus quadricauda for pentan-1-ol has been reported by Bringmann & Kuhn (1977). According to van Leeuwen et al. (1985), the 96-h EC50 (growth rate) of carbon disulphide to green algae Chlorella pyredoinosa is 21 mg/L.