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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
For details on endpoint specific justification please see read-across report in section 13 or find a link in cross-reference “assessment report”.
Reason / purpose:
read-across source
Reason / purpose:
assessment report
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
73.2 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
54.4 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Validity criteria fulfilled:
yes
Conclusions:
Derived effect concentrations were: 72h-ErC50 (Pseudokirchneriella subcapitata, growth rate) = 73.2 mg/L, NOErC (Pseudokirchneriella subcapitata, growth rate) = 54.4 mg/L.
Executive summary:

The study used as source investigated toxicity to aquatic algae. The study results of the source compound were considered applicable to the target compound. Justification and applicability of the read-across approach (structural analogue) is outlined in the read-across report in section 13 or find a link in cross reference “assessment report”.

Description of key information

Derived effect concentrations were: 72h-ErC50 (Pseudokirchneriella subcapitata, growth rate) = 73.2 mg/L, NOErC (Pseudokirchneriella subcapitata, growth rate) = 54.4 mg/L (mean measured, OECD 201, 2003).

Key value for chemical safety assessment

EC50 for freshwater algae:
73.2 mg/L
EC10 or NOEC for freshwater algae:
54.4 mg/L

Additional information

A key study is available for the assessment of aquatic toxicity of the submission substance towards green algae (RL1; read-across from isopentanoic acid). The study was performed according to OECD 201 (1984) and in compliance with GLP. The freshwater alga Pseudokirchneriella subcapitata was exposed to seven nominal test concentrations of 1.56, 3.13, 6.25, 12.5, 25.0, 50.0 and 100 mg/L and a medium control over a 96-hour period in static test conditions. The study was performed with three replicates per treatment group (n=3). Test concentrations were analytically verified. Deviation from nominal concentrations was <20%. Nonetheless, effect concentrations were based on mean measured values.

The pH values in the test solutions ranged from 4.8 to 7.7 at test initiation, from 4.7 to 9.6 in replicates with algae at test termination, and from 4.7 to 7.5 in blank replicates without algae at test termination. The decrease in pH was related to the test substance itself, which is an acid. Therefore, observed may be related to pH-effects rather than inherent toxicity of the test substance. The derived effect concentrations were: 72h-ErC50 (Pseudokirchneriella subcapitata, growth rate) = 73.2 mg/L, NOErC (Pseudokirchneriella subcapitata, growth rate) = 54.4 mg/L.

Preliminary testing with and without pH adaption to neutral allowed to conclude that approximately 35% of observed inhibitory effect at nominal 100 mg/L were due to the acidic pH, only. As such, the derived effect values represent a worst case approach integrating both, purely pH related effects as well as adverse effects caused due to intrinsic toxicity of the test item.

The study fulfilled the validity criteria of the guideline (OECD 201 adopted 1984 and 2011). The study was considered reliable and adequate for the environmental hazard and risk assessment for aquatic organisms.