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EC number: 252-161-3
CAS number: 34708-08-2
Table 1. Test results
The authors of the study report determined the 96-h LC50 between 10-32
mg/l to be equivalent to 18 mg/l as the geometric mean of the
However, the current reviewers are of the opinion that 18 mg/l is not
correct because 85% mortality was determined at 18 mg/l. There are
insufficient data to calculate the LC50 for this study and the test
material contains a thiocyanate, considered to have a specific mode of
action. Substances with a specific mode of action often have sharp
dose-response curves, further increasing the uncertainty associated with
the derivation of an LC50 from the data.
96hr LC50: 10-18 mg/l (nominal)
A 96 hour LC50 value of between 10 and 18 mg/l and a NOEC of 10 mg/l
have been determined for the effects of the test substance on mortality
of Danio rerio (tested as Brachydanio rerio). The results
are interpreted with reference to nominal concentrations of the test
The test solution was prepared using tert-butyl alcohol (TBA) as a
solvent. The recommended solvent concentration (100 mg/l) was exceeded
during the test, with TBA at a concentration of approximately 250 mg/l
(based on a density of 0.781 g/ml). However, according to the REACH
registration dossier for TBA (2-methylpropan-2-ol), the lowest E(L)C50
value is 933 mg/l for invertebrates. It is therefore unlikely that TBA
significantly affected the results of the test.
The authors of the study report determined the 96 hour LC50 to be
between 10-32 mg/l and equivalent to 18 mg/l as the geometric mean of
the concentration ranges.
However, the current reviewers are of the opinion that 18 mg/l does not
represent the correct LC50 value because 85% mortality was
determined at 18 mg/l, while 0% mortality was reported at the 10 mg/l
concentration. There are insufficient data to calculate the LC50 for
this study and the test material contains a thiocyanate functional
group, considered to have a specific mode of action. Substances with a
specific mode of action often have sharp dose-response curves, further
increasing the uncertainty associated with the derivation of an LC50
from the data. For these reasons, the current reviewers are
choosing to set a conservative LC50 at 10 mg/l for the
purpose of deriving a PNEC.
addition, the test substance is susceptible to hydrolysis and it is
likely that the test organisms were exposed to a mixture of the parent
compound and the hydrolysis products of the substance.
A functional group associated with ecotoxicity by a specific mode
of action (thiocyanate) is present in both the registration substance
and the silanol hydrolysis product, and the effects seen are attributed
to this. It is therefore reasonable to conclude that both the parent and
hydrolysis product could contribute to any effects observed. Daily
renewal of test media was used and no undissolved material was observed
at the test concentrations from which the LC50 is calculated (some oily
droplets were observed after dosing at 100 mg/l). In the absence of
analytical monitoring, it is not possible to estimate with confidence
the concentrations of parent form or hydrolysis product in the test
It is therefore considered appropriate and conservative to use
this result without adjustment as the starting point for deriving
and PNECsediment (for registration substance)
and PNECsediment (for silanol hydrolysis product, by Equilibrium
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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