2-(1-(3',3'-dimethyl-1'-cyclohexyl)ethoxy)-2-methyl propyl propanoate

Endpoint summary

Description of key information

Aquatic datasets are presented for both the registered substance and the relevant transformation product.

For the registered substance, aquatic toxicity data are based on measured results and were used to derive the PNECs, while for the relevant transformation product, aquatic toxicity is based on QSAR predictions, and were used to conclude on the PBT Assessment.

Acute data based on international guidelines, are available to assess the short-term toxicity of the registered substance on three trophic levels: Algae, Invertebrates and Fish.

Among all the species tested, an acute toxic effect was found for aquatic invertebrates and fish, with a similar sensitivity. No toxicity was observed on the algae up to the highest attainable concentration, measured at 1.1 mg/L in this test. In addition, one chronic study is available to assess the long-term toxicity of the registered substance on aquatic invertebrates Daphnia magna. The study on the algae is also considered as a chronic study. These data are summarized in the table 6.1/1 below.

Table 6.1/1: Aquatic toxicity of the registered substance

Registered substance			Acute EC50/LC50 Experimental results	Chronic NOEC/EC10 Experimental results
	Algae	S. capricornutum	> 1.1 mg/L	≥ 1.1 mg/L
	Aquatic invertebrates	D. magna	3.3 mg/L	0.20 mg/L
	Fish	O. mykiss	3.6 mg/L	No data

To demonstrate that the transformation product (C6 and C7 isomers) of the registered substance is not Toxic (non-T) in the context of PBT assessment, the acute and chronic toxicity values on three aquatic trophic levels: Algae, Invertebrates and Fish, were estimated using two QSAR models: ECOSAR v1.11 and iSafeRat QSAR. Both QSAR results were considered reliable as the substances (C6 and C7 isomers) fall within the applicability domain of the models.

The QSAR results are summarized in the table 6.1/2 below.

Table 6.1/2: Aquatic toxicity of the transformation product

Transformation product		Acute EC50/LC50 Range of QSAR predictions	Chronic ChV/NOEC Range of QSAR predictions
	Algae	1.73-2.4 mg/L	0.73-0.84 mg/L
	Aquatic invertebrates	0.93-2.7 mg/L	0.17-0.23 mg/L
	Fish	1.31-2.2 mg/L	0.17-0.39 mg/L

The estimated lowest L(E)C50 values were 1.73 mg/L for algae, 0.93 mg/L for daphnids and 1.31 mg/L for fish. The estimated lowest chronic values were 0.73 mg/L for algae and 0.17 mg/L for daphnids and fish.

In addition, one experimental study performed to assess the acute fish toxicity of the major transformation product (C6 isomers) of the registered substance to Danio rerio is available. Even if this endpoint is considered not assignable due to lacking information, the experimental 96h-LC50 at 10.7 mg/L (nominal) supports the QSAR results purporting that the transformation product (C6 and C7 isomers) of the registered substance is not Toxic in the context of PBT assessment.

To assess the toxicity to microorganisms, one study was performed on the registered substance showing no reduction in biochemical oxidation of microorganisms up to 100 mg/L, the highest concentration tested. In addition, the toxicity of the transformation product (C6 and C7 isomers) of the registered substance, to microorganisms was evaluated. No toxicity of the transformation product (mixture of C6 and C7 isomers; tested at 104.5 mg/L) was observed in the available screening non-GLP biodegradation study (OECD 301F; Firmenich, 2013). The 30-180min EC50 value of the transformation product (C6 and C7 isomers) to activated sludge was predicted (by iSafeRat® High Accuracy QSAR v1.1) as greater than the water solubility value within the exposure period of the test. Therefore, no toxicity is predicted to sludge dwelling microorganisms.