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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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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  201.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
130 µg/L

Additional information

Justification for read across

Endpoint:Toxicity to aquatic algae

Type of read across:one-to-one

Test Compound (with data):CAS: 174350-05-1

Dossier Compound (without data):CAS:
82991-48-8

The read across is based on the following similarity measures:

(1) Chemical similarity

The test compound (CAS: 174350-05-1) provides the main chemical features present in the dossier compound (CAS: 82991-48-8). Both substances share typical structural features for liquid crystals, i.e. one phenyl ring coupled via single bond to a cyclohexyl ring.

The phenyl ring of the test compound shows a flour substitution (n=2) that is not present in the dossier compound. The cylohexyl ring of both compounds shows a para alkyl substitution of different chain length (dossier cpd.: n=5; test cpd.: n=3). The phenyl ring of the dossier compound shows an ethyl substitution while the test compound exhibits a methoxy substituent at the para position.

(2) Physicochemical similarity
The high chemical similarity yields almost identical physicochemical key parameters relevant for bioavailability as listed in the table below.


(3) Similar Effects in Biological Systems

Both, the dossier compound and the test compound have been evaluated for bioaccumulation and short-term fish toxicity. The GLP compliant studies were performed according to the relevant OECD guidelines, i.e. OECD 203 and OECD 305. In all assays performed from short-term exposure up to 28 days, no toxic effects were obtained up to the limit of water solubility.

The table below lists the similarity measures applied for this read across.

Table 1. Comparison of the similarity measures applied for Test and Dossier compound

Assay

Test Compound
CAS: 174350-05-1

Dossier Compound
CAS: 82991-48-8

Cyclohexyl phenyl core

yes

yes

Terminal substitution at the cyclohexyl ring

propyl

pentyl

Terminal substitution at the phenyl ring

ethoxy

ethyl

Liquid crystalline properties

yes

yes

Fluor Substitution at the phenyl ring

yes (n=2)

no

Water solubility

130 µg/L (EU A.6)

46 µg/L (EU A.6)

logP

> 5.7 (OECD 117, EU A.8)

> 6.5 (OECD 117, EU A.8)

Short term aquatic toxicity to fish

(96h) EC50 > 86.4 mg/L
(OECD 203, with SPAN-60)

(96h) EC50 > 100 mg/L
(OECD 203, with SPAN-60)

Long term aquatic toxicity to fish

NOEC > 0.02 mg/L
(OECD 305, with SPAN-20)

NOEC > 0.02 mg/L
(OECD 305, with SPAN-20)

Read Across

Toxicity to aquatic algae

EC10 > 130 µg/L = water solubility limit
(OECD 201)

EC10 > water solubility limit
(Read Across)

 

Conclusion

The Dossier Compound shows a data gap for toxicity to aquatic algae; however, a chemical analogue provides data for this endpoint. Both the Dossier compound and the Test compound show a very high chemical similarity and almost identical physicochemical parameters leading to similar bioavailability.

Both compounds have been tested for acute and long-term toxicity to fish in GLP compliant OECD guideline tests. The response (e.g. EC10, NOEC) in these biological systems was comparable, i.e. no effects up to the limit of water solubility.

Based on these finding it is justified to use the data from the chemical analogue (Toxicity to aquatic algae (GLP, OECD TG 201), NOEC > 130 µg/L) to fill the data gap for the dossier compound.

 

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