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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Based on valid algal inhibition studies for two closely related structural analogues, the algae 72 hour ErC50 for (E)-dec-4-enal is estimated to be 1.1 - 4.5 mg/L. The corresponding NOEC is estimated to be 0.34 – 0.76 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
1.1 mg/L
EC10 or NOEC for freshwater algae:
0.34 mg/L

Additional information

A study to assess the toxicity to aquatic algae and cyano bacteria is not available for the registration substance, (E)-dec-4-enal. However, valid algal inhibition studies exist for two analogue substances, nonanal and undec-10 -enal. Read-across from these two analogue substances is considered to give a reliable estimate of the toxicity of (E)-dec-4 -enal to aquatic algae and cyanobacteria and is justified based on the hypothesis that the target substance and two source substances will have similar ecotoxicological properties as a result of structural similarity, the same mode of action and similar physicochemical properties. A detailed justification for the proposed read-across is provided in the document "Aquatic Toxicity Read-Across Justification for (E)-DEC-4 -ENAL", which is attached in section 13.

The effect of the source substance, nonanal, on the growth of the green alga,Selenastrum capricornutum,was determined according to OECD guideline 201 (T.R. Wilbury Study No. 2468-FF). It is a GLP compliant study conducted with a test material (98% pure) representative of the source substance. The study was considered valid and reliable without restrictions but because it is being used in a read-across approach it is rated reliability 2 (the maximum for read-across). The test was performed under static conditions in sealed containers from which all air space had been removed to minimize the potential loss of test substance from test solutions to the atmosphere. Analysis of test samples at 0 and 72 hours showed a decline in measured concentrations, with the final measured concentrations being < 7% of the initial measured concentrations. However, stability samples incubated with test material but not inoculated with algae showed a final measured concentration that was 79% of the initial measured concentration indicating that the decrease observed in the test samples with algae was predominantly due to adsorption to the increasing algal biomass. Given that disappearance of the test substance from solution by adsorption to the algal biomass does not mean that it is lost from the test system and that the algae are still exposed to the test substance, and given that the measured decline in the stability sample was only just below the allowed deviation of ± 20 %, it is considered appropriate to base the analysis of the results on the initial measured concentrations. The study design covered the required exposure duration of 72 hours and included sufficient dose levels to enable the relevant determination of potency.  Thus the results are adequate for the purpose of classification and labelling and/or risk assessment.The 72 h ErC50 and NOEC were determined to be 4.5 mg/L and 0.76 mg/L respectively (based on initial measured concentrations).

The effects of the source substance, undece-10-enal (trade name: Aldehyde C11 Undecyclenic), on the growth of the green alga,Pseudokirchneriella subcapitata, was determined during a 72-hour growth inhibition toxicity test, conducted in accordance with OECD guideline 201 (Smithers Viscient Study Number 3200013). It is a GLP compliant study conducted with test material (98%) representative of the source substance. The study was considered valid and reliable without restrictions but because it is being used in a read-across approach it is rated reliability 2 (the maximum for read-across). The test was performed under static condition using conventional test vessels. Analysis of the test media samples was conducted at 0, 24, 48 (with algae) and 72 hours (with and without algae). In the test samples with algae, a gradual decline in measured concentration was observed from the 24, 48 and 72 hour analysis. In the 72 hour stability samples without algae, the measured concentrations were significantly higher indicating that the decrease observed in the test samples with algae was predominantly due to adsorption to the increasing algal biomass. The final measured test concentrations in the stability samples were 75 to 78% of the initial measured concentration. However, since the measured test concentrations in the 72 hour samples without algae were <80% of the 0 hour measured concentration, it was considered appropriate to base the results on the geometric mean measured test concentrations in order to give a worst case analysis of the data. Given that concentrations below the limit of detection were observed at 48 and 72 hours it was not possible to calculate the geometric mean measured concentrations over the 72 hour period. It was therefore considered justifiable to base the results on the geometric mean measured concentrations of the 0 and 24 hour results. The study design covered the required exposure duration of 72 hours and included sufficient dose levels to enable the relevant determination of potency. Thus the results are adequate for the purpose of classification and labelling and/or risk assessment.The 72 h EC50 and NOEC (based on growth rate) were determined to be 1.1 mg/L and 0.34 mg/L respectively (based on geometric mean measured concentrations).

The results for the two source substances are similar and within the same environmental classification band. Used in a weight of evidence approach, they are considered to give a reliable estimate of the algae 72h ErC50 for (E)-dec-4-enal, which is a value of 1.1 – 4.50 mg/L. The corresponding NOEC is estimated to be 0.34 – 0.76 mg/L.

The read-across is justified and considered adequate for the purposes of classification and labelling and/or risk assessment.