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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification
Justification for type of information:
The supporting QMRF report has been attached
Reference:
Composition 1
Qualifier:
according to
Guideline:
other: as mentioned below
Principles of method if other than guideline:
The data is predicted using the OECD QSAR toolbox version 3.3 with logKow as the primary descriptor.
GLP compliance:
not specified
Test material information:
Composition 1
Specific details on test material used for the study:
- Name of test material: 1,1-diethoxy-3,7-dimethylocta-2,6-diene
- Molecular formula : C14H26O2
- Molecular weight : 226.357
- Smiles notation : C(\C=C(\CC\C=C(/C)C)C)(OCC)OCC
- InChl : 1S/C14H26O2/c1-6-15-14(16-7-2)11-13(5)10-8-9-12(3)4/h9,11,14H,6-8,10H2,1-5H3/b13-11+
- Substance type:Organic
- Physical state: Liquid
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Test type:
static
Water media type:
freshwater
Total exposure duration:
72 h
Test temperature:
24+/- 1ºC
pH:
at the start of test - 7.9 - 8.1
at the end of test - 8.2 - 10.1
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
4.892 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
growth rate

The prediction was based on dataset comprised from the following descriptors: EC50
Estimation method: Takes average value from the 5 nearest neighbours
Domain  logical expression:Result: In Domain

(((((((("a" or "b" or "c" or "d" or "e" )  and "f" )  and ("g" and ( not "h") )  )  and "i" )  and ("j" and ( not "k") )  )  and ("l" and ( not "m") )  )  and ("n" and ( not "o") )  )  and ("p" and "q" )  )

Domain logical expression index: "a"

Referential boundary: The target chemical should be classified as Neutral Organics by US-EPA New Chemical Categories

Domain logical expression index: "b"

Referential boundary: The target chemical should be classified as Acetal OR Alkene OR Alkoxy OR Allyl OR Ether by Organic Functional groups ONLY

Domain logical expression index: "c"

Referential boundary: The target chemical should be classified as Acetal OR Alkoxy OR Allyl OR Overlapping groups by Organic Functional groups (nested) ONLY

Domain logical expression index: "d"

Referential boundary: The target chemical should be classified as Aliphatic Carbon [CH] OR Aliphatic Carbon [-CH2-] OR Aliphatic Carbon [-CH3] OR Alpha-diether [C-O-C-O-C] OR Olefinic carbon [=CH- or =C<] OR Oxygen, aliphatic attach [-O-] by Organic functional groups (US EPA) ONLY

Domain logical expression index: "e"

Referential boundary: The target chemical should be classified as Dialkylether AND Ether by Organic functional groups, Norbert Haider (checkmol)

Domain logical expression index: "f"

Referential boundary: The target chemical should be classified as No alert found by DNA binding by OECD ONLY

Domain logical expression index: "g"

Referential boundary: The target chemical should be classified as Non binder, non cyclic structure by Estrogen Receptor Binding

Domain logical expression index: "h"

Referential boundary: The target chemical should be classified as Non binder, impaired OH or NH2 group OR Non binder, MW>500 OR Non binder, without OH or NH2 group OR Weak binder, OH group by Estrogen Receptor Binding

Domain logical expression index: "i"

Referential boundary: The target chemical should be classified as Class 1 (narcosis or baseline toxicity) by Acute aquatic toxicity classification by Verhaar (Modified) ONLY

Domain logical expression index: "j"

Referential boundary: The target chemical should be classified as No alert found by in vivo mutagenicity (Micronucleus) alerts by ISS

Domain logical expression index: "k"

Referential boundary: The target chemical should be classified as H-acceptor-path3-H-acceptor by in vivo mutagenicity (Micronucleus) alerts by ISS

Domain logical expression index: "l"

Referential boundary: The target chemical should be classified as Not known precedent reproductive and developmental toxic potential by DART scheme v.1.0

Domain logical expression index: "m"

Referential boundary: The target chemical should be classified as Beta alkyl substituted alcohols- sub category (25b) OR C1 to C4 non-branched alkyl alcohols- sub category (25a) OR Known precedent reproductive and developmental toxic potential OR Multi-halogenated alkyl ethers (23b) by DART scheme v.1.0

Domain logical expression index: "n"

Referential boundary: The target chemical should be classified as No alert found by Carcinogenicity (genotox and nongenotox) alerts by ISS

Domain logical expression index: "o"

Referential boundary: The target chemical should be classified as Structural alert for nongenotoxic carcinogenicity OR Substituted n-alkylcarboxylic acids (Nongenotox) by Carcinogenicity (genotox and nongenotox) alerts by ISS

Domain logical expression index: "p"

Parametric boundary:The target chemical should have a value of log Kow which is >= 3.22

Domain logical expression index: "q"

Parametric boundary:The target chemical should have a value of log Kow which is <= 5.19

Validity criteria fulfilled:
not specified
Conclusions:
The median Effective concentration (EC50) value for 1,1-diethoxy-3,7-dimethylocta-2,6-diene on Desmodesmus subspicatus in a 72 hour study was estimated to be 4.89 mg/L on the basis of effects on growth rate.
Executive summary:

Using the OECD QSAR toolbox version 3.3 with log kow as the primary descriptor and considering the five closest read across substances, the short term toxicity on aquatic algae and cyanobacteria was predicted for target substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene

(CAS no. 7492 -66 -2). EC50 value was estimated to be 4.89 mg/l for Desmodesmus subspicatus for 72 h duration. Based on this value it can be concluded that the substance 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene is considered to be toxic to aquatic environment and can be considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.

Description of key information

Using the OECD QSAR toolbox version 3.3 (2017) with log kow as the primary descriptor and considering the five closest read across substances, the short term toxicity on aquatic algae and cyanobacteria was predicted for target substance 1,1-diethoxy-3,7-dimethylocta-2,6-diene (CAS no. 7492 -66 -2). EC50 value was estimated to be 4.89 mg/l for Desmodesmus subspicatus for 72 h duration. Based on this value it can be concluded that the substance 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene is considered to be toxic to aquatic environment and can be considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
4.89 mg/L

Additional information

Predicted data for the target chemical 1,1-diethoxy-3,7-dimethylocta-2,6-diene(CAS No. 7492-66-2) and various weight of evidence studies for its closest read across substance with logKow as the primary descriptorwere reviewed to summarize the following information:

 

Short term toxicity on aquatic algae and cyanobacteria of target chemical1,1-diethoxy-3,7-dimethylocta-2,6-diene(CAS No. 7492-66-2) is predicted using the OECD QSAR toolbox version 3.3 with log kow as the primary descriptor and considering the five closest read across substances (2017).EC50 value was estimated to be 4.89 mg/l for Desmodesmus subspicatus for 72 h duration. Based on this value it can be concluded that the substance 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene is considered to be toxic to aquatic environment and can be considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.

 

In a weight of evidence study from secondary source (HPVIS, 2016) of the read across chemical 1,1 -methyldodecan-1 -ol (CAS no. 68526 -86 -3),short term toxicity to Pseudokirchnerella subcapitata (green algae) study was carried out for 72 hrs. The study was performed according to OECD Guideline 201 (Alga, Growth Inhibition Test). The study was based on the effects of the read across compound 11 -methyldodecan-1 -ol (CAS no. 68526 -86 -3) on Pseudokirchnerella subcapitata in a static fresh water system under a continuous illumination with a light intensity of 7600 to 7800 Lux., at a temperature of 23.1°C, pH ranges from 6.8 to 7.4 respectively. Pseudokirchnerella subcapitata was used as a test organism. Test chemical concentration used for the study was0,1.5, 3.0, 8.0, 20 and 61mg/L (nominal concentration) and1.5, 2.2, 2.2, 2.5, 3.0 mg/l (measured concentration), respectively. Individual Water Accomodated Fractions (WAFs) were prepared for each test treatment. The test substance was added volumetrically, via a syringe, to 2L of dilution water in a 2L glass bottle. The solution was mixed for 23 hours at a vortex of 8% of the total depth. Mixing temperature was approximately 23 Deg C. After a 1 hour settling/cooling period, the aqueous portions were transferred to the test chambers via the port at the bottom of the mixing vessel and used for testing. Test vessels were 125 ml glass Erlenmeyer flasks that were filled with approximately 60 ml of treatment solution and inoculated with algae. Samples were taken daily for cell counts. Four replicates were prepared for each treatment level. The initial algal concentration was 1.0 x 104cells/ml. All test replicates were placed on a shaker table at 100 oscillations per minute during the study. Biomass was calculated as the area under the growth curve. Based on effect on growth rate of the test organism Pseudokirchnerella subcapitata, the 72 hr NOEC and EC50 value was determined to be 2.2 and 3.2 mg/l and on the basis of effect on biomass, the 72 hr NOEC and EC50 value was determined to be 1.5 and 2.6 mg/l, respectively. Thus, based on the EC50 value, it can be concluded that the substance 11 -methyldodecan-1 -ol can be considered as toxic to aquatic organisms and thus can be considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.

 

Another short term toxicity to algae study was carried out for 72 hrs (OECD SIDS, 2006). The study was based on the effects of the read across compound 7 -methyloctan-1 -ol (CAS no. 27458-94-2) on algae in a static fresh water system. After 72 hours of exposure to 7 -methyloctan-1 -ol, the EC50 value was determined to be ranges from 1.6 to 19.0 mg/l. Thus, based on the EC50 value (1.6 mg/l), it can be concluded that the substance 7 -methyloctan-1 -ol can be considered as toxic to algae at environmentally relevant concentrations and can be considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.

 

Thus, based on the overall reported results for target chemical1,1-diethoxy-3,7-dimethylocta-2,6-diene(OECD QSAR toolbox version 3.3, 2017) and for its read across substance (fromsecondary source HPVIS and OECD SIDS),it can be concluded that the test substance 1,1 -diethoxy-3,7 -dimethylocta-2,6 -diene can be considered as toxic to aquatic environment and can be considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.