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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 based on grouping of substances (category approach)
Adequacy of study:
key study
Justification for type of information:
The justification document on the read across category approach is included in IUCLID section 13.
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
47.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
127.9 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
2.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Conclusions:
No algae study with the target substance is available. Data generated with the category substance LABS Na is considered pivotal to this endpoint and this is the most conservative approach. Scenedesmus subspicatus was exposed to concentrations of 0, 0.6, 2.4, 10, 40, or 160 mg/L of test substance for 72 hrs. The cell concentration was measured at 24, 48, and 72 hrs. The 72-hr NOEC for algae was 2.4 mg/L. The 72-hr EbC50 was 47.3 mg/L, and the 72-hr ErC50 was 127.9 mg/L for algae. The 72-hr NOEC for algae was 2.4 mg/L. The 72-hr EbC50 was 47.3 mg/L, and the 72-hr ErC50 was 127.9 mg/L for algae.

Description of key information

No data on acute toxicity to aquatic algae are available for the target substance. Data from a category member LABS Na (CAS no: 68411-30-3) was used to understand the acute and chronic toxicity profile of substance to algae. The 72-hr EbC50 was 47.3 mg/L, and the 72-hr ErC50 was 127.9 mg/L for algae. The 72-hr NOEC for algae was 2.4 mg/L. The 72-hr ErC50 and EbC50 are greater than the water solubility of the target substance. Due to the extremely low water solubility, the acute and chronic toxicity is above the water solubility. As a consequence,   the target substance does not demonstrate acute and chronic aquatic toxicity at water soluble concentrations. 

Key value for chemical safety assessment

EC50 for freshwater algae:
127 mg/L
EC10 or NOEC for freshwater algae:
2.4 mg/L

Additional information

the target substance is an UVCB. Based on the structural and functional similarities, data on LABS Na (CAS no: 68411-30-3) being registered under REACH are considered suitable in case where specific data on the the target substance is lacking.

To assess the acute toxicity profile of the substance to aquatic algae, data was used from LABS Na (CAS no: 68411-30 -3). The acute toxicity to algae of LABS Na was determined in 88/302/EWG guideline study. The 72-hr NOEC for algae was 2.4 mg/L. The 72-hr EbC50 was 47.3 mg/L, and the 72-hr ErC50 was 127.9 mg/L for algae. The 72-hr ErC50 and NOEC are therefore greater than the water solubility of the target substance.

The EPISUITE QSAR modelling was used to predict the acute and chronic toxicity profile of the target substance. Modelled toxicity values for the target substance confirmed that the aquatic acute and chronic toxicity value exceeds (i) the predicted water solubility, indicating the substance is not soluble enough to measure the predicted effect and (ii) the log Kow cutoff value of 6.4 and 8.0 for acute and chronic toxicity to green algae, respectively.

According to data from analogue substance and QSAR modelling of the target substance, the substance does not demonstrate acute and

chronic aquatic toxicity at water soluble concentrations.

 

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