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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
other: DIN 38412, part L9
GLP compliance:
no
Specific details on test material used for the study:
- Name of test material (as cited in study report): N-Hexylglykol
- Purity: no data given
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Strain: SAG 86.81
- Source (laboratory, culture collection): Algensammlung Goettingen, Germany
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Test temperature:
21.6 °C
pH:
- At start: 7.77 - 7.84
- At termination: 7.55 - 9.15
Nominal and measured concentrations:
- Nominal concentrations. 0 (control), 5, 10, 25, 50, 100 and 250 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: no data given
- Initial cells density: ca. 12 000 (N/mL)
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

GROWTH MEDIUM
- Standard medium used: no data given

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: fluorimeter after 0, 24, 48, 72 and 96 hours


Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
198.31 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% C.L.: 40.71 - >500 mg/L
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
23.43 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% C.L.: 8.71 - 63.03 mg/L
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
97.58 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 95% C.L.: 38.05 - 250.26 mg/L
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
11.08 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 95% C.L.: 4.22 - 29.14 mg/L
Details on results:
See 'Any other information on results incl. tables'.

ADDITIONAL REPORTED EFFECT CONCENTRATIONS:
- 96-h ErC50 (growth rate): 147.1 mg/L (95% C.L.: 76.3 - 283.6 mg/L)
- 96-h ErC10 (growth rate): 89.3 mg/L (95% C.L.: 85.8 - 151 mg/L)
- 96-h EbC50 (biomass): 69.6 mg/L (95% C.L.: 26.7 - 180.3 mg/L)
- 96-h EbC10 (biomass): 12.36 mg/L (95% C.L.: 4.3 - 35.5 mg/L)

Table: Cell density

 Nominal concentrations (mg/L)  0  24 48  72  96 
   (n/ml) (*10^3)   (n/ml) (*10^3)   (n/ml) (*10^3)   (n/ml) (*10^3)      (n/ml) (*10^3)
0   12  41  147  409  918
 5 000   12  48  138  362  928
 10 000   12  47  132  341  911
 25 000   12  46  129  330  918
50 000   12  46  122  274  839
100 000   12  42  91  205  520
250 000   12  26  33  25  19

Table: Cell growth and biomass after 72 h and 96 h respectively

Nominal concentrations (mg/l)  72 h  96 h      
   growth rate   Biomass inhibition (%)  inhibition rate (%)  growth rate    Biomass inhibition (%)   inhibition rate (%)
0   1.18  -  -  1.08 -  -
5 000   1.09  6.4 -0.2 1.14 6.8  3.5
10 000   1.08  10.4  0.2  1.12 11.4  5.2
25 000   1.08  12.0  0 1.10  13.8  6.1
50 000   1.06 23.2  2.1  1.04  22.1  11.4
100 000   0.94  46.5  13.1  0.95  41.8  19.6
250 000 0.11 94.6  89.4  0.24  85.4  79.2
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
algae were exposed 96 hours instead of 72 hours. Only 96-h effect concentrations are reported.
GLP compliance:
yes
Remarks:
UK
Specific details on test material used for the study:
- Name of test material (as cited in study report): Diethylene glycol monobutyl ether
- Physical state: liquid
- Analytical purity: 98%
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION OF TEST SOLUTION
200 mg of test material was dispersed in 1 litre of test medium to give a stock solution for further dilution.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Source: Culture of algae and protozoa from the Institute of Freshwater ecology, Cumbria, UK
- Method of cultivation: Sterile culture medium was inoculated from a master culture and incubated under continuous illumination (7000lux) and aeration at 21 °C to give an algal suspension in log phase growth characterised by an absorbance of 0.952 at 665nm.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
96 h
Hardness:
No details reported. However, refer to study on daphnia magna which was carried out by the same laboratory at the same time and contains water analysis details.
Test temperature:
24 °C
pH:
Test medium pH=8
Dissolved oxygen:
not reported
Nominal and measured concentrations:
- Nominal concentrations: 0 (control) and 100 mg/L
Details on test conditions:
TEST SYSTEM
- Type: closed
- Material, size, headspace, fill volume: 250 mL conical flasks containing 100mL test medium
- Aeration: no, but flasks mixed with orbital shaker.
- Initial cells density: 2.17x10E4 cells/mL
- Control end cells density: 1.14x10E4 cells/mL
- No. of organisms per vessel: 500 mL algal pre-culture added to 500 mL sterile nutrient containing the test material at the appropriate concentration.
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 3
- No. of vessels per vehicle control (replicates): not relevant

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
No details reported. However, refer to study on daphnia magna which was carried out by the same laboratory at the same time and contains water analysis details.

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: not reported as being performed
- Photoperiod: continuous
- Light intensity and quality: 7000 lux

EFFECT PARAMETERS MEASURED
- Determination of cell concentrations: spectrophotometer ,with measurements (665nm) every 24 hours. Cell densities of the control cultures at initiation and termination measured using a haemocytometer.
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
The substance showed no evidence of toxicity up to the maximum tested concentration of 100 mg/L.
Reported statistics and error estimates:
Not applicable from a limit test study which showed no response.

Description of key information

DGHE is with high probability acutely not harmful to alga.

Based on read-across to data available for the close structural analogue 2-(hexyloxy)ethanol, the 72 -h ErC50 and ErC10 values are determined at 258 mg/L and 31.7 mg/L, respectively in freshwater algae (D. subspicatus).

Key value for chemical safety assessment

Additional information

No studies on DGHE are available with alga. A read-across to CAS 112 -25 -4 and CAS 112-34 -5 was performed (see read-across justification in chapter 13). As additional supporting information a QSAR calculation (ECOSAR) was performed.

Also, the toxicity of Ethanol, 2-(hexyloxy)- (CAS 112 -25 -4) towards freshwater algae was determined in a study according to DIN 38412, part L9. In this study, exponentially growing freshwater alga (Desmodesmus subspicatus) were exposed to nominal test substance concentrations of 0, 5, 10, 25, 50, 100 and 250 mg/L for 96 hours under static conditions. The test was performed in 4 replicates per test concentration. At the start of the test and after 24, 48, 72 and 96 hours exposure duration, the cell concentrations were determined and growth rates at the different tested concentrations calculated. The 72-h ErC50 and ErC10 values are reported to be 198.3 mg/L and 23.4 mg/L, respectively. When correction for difference in molecular weight between the source chemical and target chemical, the 72 -h ErC50 and ErC10- values are

The limited toxicity towards freshwater algae is supported by a study with Ethanol, 2 -(2 -butoxyethoxy)- (CAS 112-34-5) which was performed according to OECD TG 201 and in compliance with GLP criteria. In this study, exponentially growing freshwater alga (Desmodesmus subspicatus) were exposed in a Limit test to a substance concentration of 100 mg/L under static conditions. The test was performed in 6 replicates per test concentration. The 96-h EC50 and NOEC values for growth rate and biomass corrected for molecular weight were determined at 100 mg/L and ≥100 mg/L, respectively (nominal). As no effect were seen up to the highest concentration tested, and in addition the information is supporting, no correction for molecular weight diference was performed.

Assessment of algae toxicity is further supported by QSAR prediction for CAS 112 -59 -4 resulting in an 96 -h EC50 value of 111.9 mg/L.