2-benzyl-4-methyl-4a,5,6,7,8,8a-hexahydro-4H-benzo[d][1,3]dioxine

Endpoint summary

Description of key information

Reliable QSAR results are available to assess the aquatic toxicity of the registered substance, on aquatic invertebrates, algae for acute.

The QSAR predictions (iSafeRat models) have been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004) and predict the ecotoxicological values which would be expected when testing the substance under experimental conditions in a laboratory following OECD Guidelines. The ecotoxicological predictions were determined using validated QSAR models for the Mechanism of Action (MechoA) in question (MechoA 1.1, i.e. non-polar narcosis). QSAR models are based on validated data for training sets for which the concentrations of the test substance had been determined by chemical analyses over the test period.

 

According to these predictions :

- The acute 48-EC50 value for aquatic invertebrates, based on mobility, was determined to be 6.4 mg/L (95% CL: 5.7 -7.1mg/L);

- The acute 72h-ErC50 value for algae, based on growth rate, was determined to be 5.7 mg/L (95% CL: 4.8 - 6.7 mg/L);

- The chronic 72h-NOECr value for algae, based on growth rate, was determined to be 2.0 mg/L (95% CL: 1.6 - 2.4 mg/L);

 

Experimental studies are available to assess the aquatic toxicity of the registered substance, on fish, for acute exposure and on aquatic invertebrate for chronic exposure.

 

To assess the long-term toxicity of the registered substance to aquatic invertebrates, one experimental key study (Envigo, 2015)  is available. The chronic toxicity of the test item to Daphnia magna was conducted according to OECD 211 and EU Method C.20, "Daphnia magna Reproduction Test" and EPA OPPTS 850.1300 (Daphnid Chronic Toxicity Test). The chronic 21d-EC10 value for aquatic invertebrates, based on reproduction, was determined to be 1.0 mg/L based on mean measured test concentrations.

 

To assess the short term toxicity of the registered substance to fish, one experimental key study  (phytosafe, 2012) is available. The acute toxicity of the test item to zebra fish was conducted according to OECD 203 "Fish acute toxicity test". Under the test conditions, the 96 hour LC₅₀and NOEC for test substance is 5.7 and 3.4 mg/L in zebra fish (Brachydanio rerio), respectively.

 

 Experimental studies are available to supporting data on the aquatic toxicity of the registered substance, on aquatic invertebrates and algae for acute exposure.

 

In addition, an experimental study (phytosafe, 2012)  is available as supporting data point to assess the toxicity of the registered substance to aquatic algae. In an algal growth inhibition study performed according to OECD Guideline 201 and in compliance with GLP, the freshwater green algae species Desmodesmus subspicatus was first exposed to test item for 72 h, under semi-static conditions.

Under the test conditions, the ErC50 (growth rate) was 22.7 mg/L (95% CL: 3.3-157.4 mg/L); and EyC50 (yield) was 17.1 (95% CL: 11.8-24.9 mg/L) of the test item to Desmodesmus subspicatus. The NOEC was 9.0 mg/L based on measured concentrations.

 

All validity criteria were fulfilled. This study is considered reliable with restrictions as a high 95% CL was determined for the ErC50 value and acetone was used as solvent in this study. Because of the potential for interaction with the test chemical resulting in an altered response in the test, solvent use should be restricted to situations where no other acceptable method of test solution preparation is available. The use of solvent is not the best method at the time being. The concentration/quantity of solvent used in the treatment solutions was 0.5 mL/L, corresponding to 395 mg/L (with a density of 0.79), which is 5 times higher than the recommended maximum level of solvent (below 0.1 mL/L; OECD No. 23) but is below the NOEC of acetone (which was reported in the ECHA disseminated dossier at 530 mg/L).

 

 

In addition, an experimental study (phytosafe, 2012)  is available as supporting data point to assess the toxicity of the registered substance to aquatic invertebrate.. A Study was performed according to OECD Guideline 202 with GLP statement, to determine the treatment concentrations liable to immobilize 50 % of the daphnids (EC50) after 24 and 48 h exposure of the test item to Daphnia magna, under static conditions.

Under the test conditions, 48h-EC50 (Daphnia magna) = 0,38 mg/L (95% CL: 0,12-1,20 mg/L) based on analytically confirmed nominal concentrations (recovery of the substance at the end of the test: 95.7-100.9 %).

 

However, this study is not reliable due to high concentration of solvent used. Indeed, a large quantity of acetone was used as solvent in this study. Because of the potential for interaction with the test chemical resulting in an altered response in the test, solvent use should be restricted to situations where no other acceptable method of test solution preparation is available. The use of solvent is not the best method at the time being. Then, the concentration/quantity of solvent used in the treatment solutions was 5 mL/L, corresponding to 3.95 g/L (with a density of 0.79), which is 50 times higher than the recommended maximum level of solvent (below 0.1 mL/L; OECD 23) and represent almost half of the EC50 of acetone (which was reported in the ECHA disseminated dossier at 8.8 g/L). Acetone is suspected to have affected the definitive results. Some solvent/substance interactions may have occurred in this study with this high concentration of acetone.