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Ecotoxicological information

Long-term toxicity to aquatic invertebrates

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Description of key information

For this endpoint information from a structural similar compound is available. This study for this similar compound was performed according to GLP and the methods applied are fully compliant with OECD TG  211. The NOEC of the study was at 13 µg/L and thus in the range of the water solubility limit. 

Key value for chemical safety assessment

Additional information

Justification for read across

Type of read across:one-to-one

Target compound (without data):

CAS: 82991-48-8
Smiles Code: CCCCC[C@H]1CC[C@@H](CC1)C1=CC=C(CCC)C=C1

Source Compound (with data):

CAS: 81936-32-5
Smiles Code: CCC[C@H]1CC[C@@H](CC1)C1=CC=C(OC)C=C1

Based on:
(1) chemical similarity:
Both compounds share a cyclohexyl-phenyl-core structure. The cyclohexyl ring shows an alkyl substitution in para-postionto the phenyl ring. Comparing the source and the target compound the chain lenght of this alkyl chain is different; i.e. n=3 for source and n=5 for target molecule. The phenyl ring of both molecules is substuituted in para postion with a methoxy group (source compound) and propyl chain (target compound). The structural similarity measure in terms of a Tanimoto Score is 0.7.

(2) physicochemical parameters:
Both compounds show a very low water solubility and a high logP value as determined experimentally. This leads to a low bioavailability and thus a low exposure in the aqueous system.

(3) biological response:
Both compounds show similar response in relevant higher TIER Ecotox Assays (i.e. fish long term toxicity): NOEC > limit of water solubility.


Assay
Target Compound
CAS: 82991-48-8
Source Compound
CAS 81936-32-5
cyclohexyl phenyl core
yes
yes
Terminal alkyl chain at the cyclohexyl ring yes (C3)
yes (C5)
Terminal substituent at the phenyl ring
propyl
methoxy
Liquid crystalline properties
yes
yes
Water solubility
46 µg/L (GC FID)
25 µg/L (GC FID)
logP
> 6.5 (OECD 117, EU A.8)
> 6.5 (OECD 117, EU A.8)
Fish long term (28 d) from GLP compliant OECD TG 305 study
NOEC > 0.02 mg/L (LOD)
NOEC > 0.1 mg/L (LOD)
Daphnia Reproductive Toxicity (GLP, OECD TG 211)
no data
NOEC > 13 µg/L (measured)


Justification

The Target Compound shows a data gap for Daphnia Reproductive Toxicity, however a chemical analogue provides data for this endpoint. Both the Target Compound (without data) and the Source Compound (with data) show a very high chemical similarity and almost identical physicochemical parameters. The response in ecotoxicological assays is comparable.

Based on these finding it is justified to use the data from the source compound  (Daphnia Reproductive Toxicity (GLP, OECD TG 211)) to fill the data gap for the target compound.