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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC50 (72 hours): >1 mg/l (nominal concentration) based on growth rate
EC50 (72 hours): 0.38 mg/l (nominal concentration) based on biomass
NOEC (72 hours): 0.016 mg/l (nominal concentration) based on growth rate
LOEC (72 hours): 0.031 mg/l (nominal concentration) based on growth rate
EC10 (72 hours): >0.063-0.125 mg/l (nominal concentration) based on growth rate
EC10 (72 hours): 0.02 mg/l (nominal concentration) based on biomass
(EU Method C.3, static test)

Key value for chemical safety assessment

EC50 for freshwater algae:
1 mg/L
EC10 or NOEC for freshwater algae:
0.016 mg/L

Additional information

GLP-guideline study with algae (Desmodesmus subspicatus) was performed according to the European Directive 67/548/EWG, C.3 “Algal inhibition test”, comparable to OECD TG 201. In a growth inhibition test a 72 h-EC50r of > 1 mg/L for the growth rate and 0.38 mg/L for the integral of biomass was determined (Bayer AG, 1992b). The corresponding 72 h-NOEC was 0.016 mg/L and the 72 h-LOEC was 0.031 mg/L for the growth rate and for biomass 72 h EC10 was 0.2 mg/L.

As the detection limit of the analytical method was 0.5 mg/L, only the highest test concentrations were analysed. The recovery rate was in the range of 76 % to 110 %. For the determination of the effect values the nominal concentrations were used.

For algae the following results were derived from another GLP toxicity study with Pseudokirchneriella subcapitata (= Selenastrum capricornutum) according to OECD TG 201 (EA Japan, 1999d): For growth rate, the 72 h-ErC50 was 23 mg/L and the NOEC 2.0 mg/L (all dicyclohexylamine concentrations measured). For biomass, the 72 h- EbC50 was 9.1 mg/L (95 % confidence limits: 8.4-9.8 mg/L) and the NOEC was 2.0 mg/L.

Although the inhibition rate by the growth rate method was less than 50 % at the highest concentration, the toxicity value was determined as 23 mg/L by extrapolation.