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Experimental results are available from studies conducted in fish with the substance methyl chloroacetate. However, no analytical monitoring was conducted during the studies. Therefore, there is no evidence that the concentration of the substance was maintained during the tests. ECOSAR calculations were conducted for both methyl chloroacetate and the analogue ethyl chloroacetate. The outcome of this calculations is that the LC50 values for fish for both substances are below 1 mg/l. These results support the classification for methyl chloroacetate as Hazardous for the Aquatic Environment, Acute Category 1.

The analogue ethyl chloroacetate which shares the same functional group with methyl chloroacetate, also has comparable values for the relevant molecular properties for the aquatic toxicity endpoint. These properties are:

- a low log Pow value which is 0.94 -1.12 for ethyl chloroacetate and 0.63 for methyl chloroacetate,

- a high water solubility which is 20 g/l at approximately 20 ºC for ethyl chloroacetate and 51.6 g/l for methyl chloroacetate and

- similar molecular weights which are 122.55 for ethyl chloroacetate and 108.52 for methyl chloroacetate.

The analogue ethyl chloroacetate is included in the list of harmonised classifications and labellings and it is classified as Hazardous for the Aquatic Environment, Acute Category 1.

Experimental results are available from a study conducted in Daphnia with the substance methyl chloroacetate. The EC50 for Daphnia was concluded to be 5.5 mg/l. However, no analytical monitoring was conducted during the study. Therefore, there is no evidence that the concentration of the substance was maintained during the test. A QSAR prediction conducted with the Multicase model and reported in the Danish EPA database, provides a 48 -h LC50 for methyl chloroacetate of 1.66 mg/l. The data used in the model come from an EC50 for the analogue ethyl chloroacetate which is reported in a publication with a value of 1.6 mg/l. Using the read-across approach based on the analogue ethyl chloroacetate, an EC50 value of 1.42 mg/l is calculated for methyl chloroacetate on Daphnia magna.

Based on the QSAR prediction for the analogue ethyl chloroacetate (48 h EC50 = 20.8 mg/l; Multicase model; Danish EPA) and the molecular weights, the read-across approach is applied and for algae the EC50 for methyl chloroacetate is calculated to be 18.33 mg/l.