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EC number: 695-097-5
CAS number: 15789-90-9
on valid algal inhibition studies for two closely related structural
analogues, the toxicity to freshwater green algae of
(E)-3-methyl-4-(2,6,6-trimethylcyclohex-2-en-1-yl)but-3-en-2 -one has
72h ErC50 value
of >5.1 and <= 7.47 mg/L and NOEC of 1.68 to 2.3 mg/L. The EC50 value of
> 5.1mg/L represents the fact that only 33% inhibition was observed at
the highest test concentration of 5.1
Ionone Alpha Iso 60 source
study). Therefore the determined value of 7.47 mg/L (Raldeine
A GD source
study) has been chosen as the key value for chemical safety assessment.
Out of the two reliable NOEC values, the lowest and more conservative
NOEC of 1.68 mg/L has been selected.
study to assess the toxicity to aquatic algae and cyanobacteria is not
available for the registration substance. However, valid algal
inhibition studies exist for two analogue substances; Methyl Ionone
Alpha Iso 60 and Raldeine A GD. Both studies are GLP compliant,
conducted to OECD 201 guidelines, covered the required exposure duration
of 72 hours and included sufficient dose levels to enable the relevant
determination of potency. Read-across from these two analogue substances
is considered to give a reliable estimate of the toxicity of
freshwater green algae 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 (both
the target and source substance consist of isomers), the same mode of
action and similar physicochemical properties. A detailed justification
for the proposed read-across in-line with the ECHA RAAF guidelines is
provided in the target endpoint record.
study performed on Methyl Ionone Alpha Iso 60 (Study No AL/N51/02)
employed a static design and used conventional loosely stoppered test
vessels. The test material (53 -58% main isomer, tested as 100% active)
is representative of the source substance. Analysis of the test
solutions was performed at 0, 24, 48 and 72 hours by a gas
chromatographic and mass spectrometric method. The initial measured
concentrations of the test item solutions were 1.1, 1.4, 3.1, 5.3 and 12
mg/L, which gradually declined throughout the 72 hour exposure period to
0.27, 0.31, 0.44, 0.87 and 1.9 mg/L (14-25% initial). Therefore the
effect data were calculated based on the geometric mean of the 0, 24, 48
and 72 hour measured concentrations i.e. 0.49, 0.61, 1.1, 2.3 and 5.1
mg/L. The study was considered reliable with no restrictions
(reliability 1). The 72 hr EC50 based on growth rate was reported to be
> 5.1mg/L (33% inhibition seen at highest test concentration) and the
NOEC based on both growth and inhibition was determined to be 2.3 mg/L.
study performed on Raldeine A GD (Study No 2470-FF) was conducted under
static conditions using test material (94.4% sum of isomers) which is
representative of the source substance. The study was considered
reliable with no restrictions (reliability 1). The test was performed in
sealed containers from which all air space had been removed to minimize
the potential loss of test substance from the test solutions to the
atmosphere. Nominal concentrations of test substance were: 0 mg/L
(control), 0.50, 1.0, 2.0, 4.0, 8.0, and 16 mg/L. Analytical
confirmation of the test substance (derivatized using
2,4-dinitrophenylhydrazine) was performed at 0 and 72 hours by HPLC.
Samples collected at the start of the toxicity test were collected from
test solutions just prior to the addition of algae and distribution of
the test solutions to sealed test vessels. Samples collected at the end
of the toxicity test were centrifuged to remove algal cells from pooled
replicate test vessels. Initial measured concentrations of test
substance were: ND (none detected at or above the limit of quantitation;
control), 0.404, 0.954, 1.68, 2.94, 6.74, and 14.0 mg/L. The final
measured concentrations ranged from 51 to 62% of the initial
concentrations. A stability sample, prepared with a nominal
concentration of 16 mg/L and not inoculated with algae, was incubated
among the test vessels during the 72 hour exposure. The final measured
concentration in this stability sample was 56% of the initial measured
concentration. The latter is in the same range of the 51-62% obtained
for the test samples, indicating that the decrease in measured
concentrations in the test samples with algae is not attributable to
adsorption to the growing algal biomass. However, the test substance was
stable in laboratory control samples (4mg/L standards prepared in
dilution water) where 72 h measured concentrations were 83-94% initial.
Thus losses seen in the test samples after 72 hours could be a result of
differences in sample work up (e.g. centrifugation) and/or storage
conditions. Taking this into consideration and also the fact that the
test vessels were sealed to minimise any loss due to volatility, it is
considered justifiable to base the biological effects on the initial
measured concentrations. The 72 h EC50 based on growth rate was
determined to be 7.47 and the corresponding 72h NOEC to be 1.68 mg/L.
72h EC50 and NOEC values 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 toxicity to freshwater green algae of
is a 72h ErC50 of > 5.1 and <= 7.47 mg/L and a 72h NOEC of 1.68 to 2.3
mg/L. The read-across is justified and considered adequate for the
purposes of classification and risk assessment.
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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