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Toxicity to aquatic algae and cyanobacteria

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Description of key information

A 72-h EC50 of >220 mg/l and NOEC of 10 mg/l (OECD 201), RL2

Key value for chemical safety assessment

Additional information

Measured data was not available for [3 -(triethoxysilyl)propyl]urea (CAS 23779-32-0), therefore read across of data from the comparable substances ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters (CAS 116912-64-2) was deemed acceptable for assessment.

The influence of the test item ureidopropyltrialkoxysilane, mixed methoxy and ethoxy ester

on the growth of the freshwater algae species Selenastrum capricomutum was investigated in a 72 -hour static test according to OECD 201 and GLP (NOTOX, 2000f).The batch tested was a colourless viscous liquid consisting of three major components (NOTOX identification M2, M3 and M4) and completely soluble in test medium at the concentrations tested.

After two pilot tests, a final test was performed exposing exponentially growing algal cultures to test item concentrations ranging from 10 to 220 mg/l, increasing by a factor 2.2. The initial cell density was 104 cells/ml. The total test period was 72 hours. Samples were taken from three concentrations, i.e. 10, 46 and 220 mg/l and the blank control at T=0 h, t=6 h and T=27 h.

Analysis of the samples taken during the limit test showed that the concentrations based on component M2 were in agreement with nominal at the start of the test period (84% and 97%). Concentrations based on components M3 and M4 were significantly below nominal at 77 to 90% and 64 to 76% of nominal, respectively. All three components degraded rather rapidly with degradation of M4>M3>M2. Within 6 hours of exposure the concentrations of all three components had decreased by more than 30%. After 27 hours of exposure the concentration of M2 had decreased by > 80%, the concentration of M3 by 99%. And the concentration of M4 had totally disappeared. Since these results indicated an exponential decrease of actual concentrations during the first 27 hours of exposure, further analysis was not considered to be relevant.

Test item reduced growth rate of the freshwater algae species Selenastrum capricomutum significantly at concentrations prepared at 46 and 220 mg/l.


The EC50for cell growth inhibition (EBC50: 0-72h) and The EC50 for growth rate reduction (ERC50: 0-72h) were both beyond the range tested, i.e. > 220 mg/l.


The NOEC corresponded with a prepared concentration of 10 mg/l. Considering the high rate of hydrolytical degradation of the three components, exposure to the possible degradation products did not induce additional effects on algal growth.

The results are considered to be reliable. The test organisms were exposed primarily to the hydrolysis products of the substance.

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