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In total 3 studies (Klimisch 1) are available for the assessment of DEC. One fish, one Daphnia and one activated sludge study. A fourth study (algae) was considered to be nor reliable (Klimisch 4) since the validity criteria were not met.

The acute toxicity of P5524 (which contains 99.9% DEC) to rainbow trout (Oncorhynchus mykiss) was determined in a semi-static GLP compliant test according to EU method C.1 and OECD 203 (Bell 1996). The test was started with a Control (0), 10, 22, 46, 100, and 220 mg test item/L. Dose verification at hour 0 and hour 72 confirmed that the test solutions were correctly dosed (recoveries of the biologically relevant concentrations in general within 80 - 120%. For each test concentration and the control, 1 replicate with 7 fish (mean total length 5.5 cm, average weight 2.16 g/fish) each were set up in 18 L test solution (glass vessels). The test was performed in a 16:8 h light dark cycle. The concentrations were reported as nominal concentrations. After 96 hours of exposure, 0, 0, 0, 0, 0, 0, and 100 % of the daphnids were immobilized at Control, 10, 22, 46, 100, and 220 mg test item/L. The corresponding 96 h LC50 value is 150 mg test item/L.

The acute toxicity of P5524 (which contains 99.9% DEC) to Daphnia magna was determined in a static GLP compliant test (Bell 1996). The test was performed according to guidelines OECD 201 and EU C.2. The test was started with a Control (0), 1.0, 2.2, 4.6, 10, 22, 46, and 100 mg test item/L. Dose verification at hour 0 confirmed that the test solutions were correctly dosed (recoveries of the biologically relevant concentrations > 80%. For each test concentration and the control, 2 replicates with 10 daphinds each were set up in 200 mL test solution (glass vessels). The test was performed in a 16:8 h light dark cycle. The concentrations were reported as nominal concentrations. After 48 hours of exposure, 0, 0, 0, 0, 5, 100, 100 and 100 % of the daphnids were immobilized at Control, 1.0, 2.2, 4.6, 10, 22, 46, and 100 mg test item/L. The corresponding 48 h EC50 value is 14 mg test item/L

The inhibitory effect of P5524 (which contains 99.9% DEC) to activated domestic sludge was determined in a static GLP compliant test according to OECD 209 (Bell 1995). The test was started with a Control (0), 10, 22, 46, 100, and 220 mg test item/L and a reference substance (3,5-dichlorophenol). Dose verification was not performed. two control replicates were set up. For each test concentration 1 replicate was set up. The test solutions were incubated for 3 hours. After 3 hours of exposure, 8, 16, (66), 38 and 46 % inhibition were recorded at, 10, 22, (46), 100, and 220 mg test item/L, respectively. The inhibition value for 46 mg/L was considered to be an outlier due to technical failure.The corresponding 3 h IC20 and IC 50 values are 33 and > 220 mg test item/L.

These three studies were performed according to international guidelines and under GLP and fulfilled the validity criteria. Therefore, this studies were considered to be Klimisch 1 studies. The obtained results are considered as relevant for the risk assessment.

 

The growth inhibition of P5524 (which contains 99.9% DEC) to Pseudokirchneriella subapitata (reported as Selenastrum capricornutum) was determined in a 72 h static GLP algae growth inhibition test (Bell, 1995). The test design was based on the OECD 203 guideline and the EU method C.3.Tthe study was performed under GLP and according the guideline. From 48 to 72 hours, the control cultures showed only limited or even negative growth rates. Consequently, the growth of the 3 replicates of the control cultures did not fulfil the CV- section-by section growth rate as outlined in the updated OECD 201 guideline (2006). The other two quality criteria (CV Average specific growth rate and Increase >16 times) were fulfilled. The nominal test concentrations were Control (0), 1.0, 2.2, 4.6, 10, 22, 46, and 100 mg test item/L. Three control replicates and 3 replicates from each test solution were set up. Dose verification analysis was performed but was not able to verify correct dosing. In order to determine the growth of the cultures, the cells were counted electronically. The test was started with about 12000 cells/mL. The cell density was determined at 24, 48 and 72 hours. For hour 0, analytical dose verification confirmed that the 100 mg/L test solution was correctly dosed (recovery > 90%). Analytical verification at hour 0 was not able to verify the nominal concentrations for test solutions with 46 mg/L or less. For these concentrations a recovery of about 40 % was obtained (except at nominal 1 mg/L where 75.1 % recovery was found). The rational for this discrepancy was not reported. All results are expressed in terms of nominal concentration. Measured concentrations could not be thoroughly verified due to difficulties with the analytical method. As outlined above, the growth of the control cultures has not fulfilled the validity criteria from OECD 201 (2006). The 72 -hour ErC50 is 59 mg/L based on the nominal concentration. Based on these shortcomings (mainly for not meeting the validity criterion for the section-by section growth rate), this study is considered to have a Klimisch 4 score.

Since this study is a Klimisch 4 study, the results are considered to be not relevant for the assessment of the substance.

Conclusion on classification

Relevant EC50/LC50 values > 1 mg/L.

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