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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
Study period:
from 1997-06-17 to 1997-06-20
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Good study conducted according to a guideline equivalent to OECD 201, with GLP, however no analytical monitoring was performed.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: A stock solution of 1 g/L in deionised water was prepared by stirring for 18 hours.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM

- Strain: CHODAT (SAG 86.81)

- Source (laboratory, culture collection): Institut fur Wassrer-, Boden- und Lufthygiene, Berling danach eigene Zucht

- Age of inoculum (at test initiation): 3 days old

- Method of cultivation: not reported


ACCLIMATION

- Acclimation period: not reported
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23 degrees C +/- 1
pH:
range beginning of the test: 7.8-7.9
range end of the test: 7.7-9.3
Nominal and measured concentrations:
Nominal concentrations: 0.021, 0.043, 0.085, 0.171, 0.342, 0.712, 1.424 mg/l
Measured concentrations 0 h: 1.06, 1.01, 0.71, 1.21, 1.29, 1.55, 2.28 mg/l
Measured concentrations 72 h: ND, ND, ND, ND, 1.07, 0.81, 1.33 mg/l (ND = not detectable)
Details on test conditions:
TEST SYSTEM

- Test vessel: Erlenemeyer flasks

- Initial cells density: 2 x 10^4 cells/ml

- Control end cells density: 106 x 10^4 cells/ml

- No. of vessels per concentration (replicates): 5

- No. of vessels per control (replicates): 5


GROWTH MEDIUM

- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: not reported

- Culture medium different from test medium: not reported

- Intervals of water quality measurement: not reported


OTHER TEST CONDITIONS

- Sterile test conditions: yes

- Adjustment of pH: sodium bicarbonate was added to the test medium

- Light intensity and quality: ca. 8000 lux, white


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

- Determination of cell concentrations: spectrophotometer, absorption 685 nm. Measured every 24 h.


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2

- Range finding study: none reported
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.33 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.66 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.085 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.27 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
- Exponential growth in the control (for algal test): yes
Reported statistics and error estimates:
Regression analsyis and Probit Analysis (Cavalli-Sforza 1972)

Table 1. Cell concentration during the 72 h exposure to dodecanol.

 

Nominal concentrations (mg/L)

Cell concentration (cells x 104/ml)

0 h

72 h

Control

2

106

0.021

2

114

0.043

2

107

0.085

2

110

0.171

2

97

0.342

2

42

0.712

2

25

1.424

2

2

 

Validity criteria fulfilled:
yes
Conclusions:
A reliable 72 h ErC50 of 0.66 an EbC50 value of 0.33 mg/l, an ErC10 of 0.27 mg/l and a NOEC of 0.085 mg/l have been determined for the effects of the dodecanol on the cell numbers of the algae Scenedesmus subspicatus (new name: Desmodesmus subspicatus).
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1992-08-28 to 1992-09-04
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
Not key study: Other studies (same reliability score) but showing greater toxicity are available
Qualifier:
according to
Guideline:
other: DIN 38412 Part 9
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
not applicable
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: from a stock solution of 1g/100 ml ethanol a dilution was made to form a stock solution of 10 mg/100 ml ethanol. From the second stock solution appropriate aliquots were pipetted into the test vessels to achieve nominal concentrations.

- Chemical name of vehicle (organic solvent, emulsifier or dispersant): ethanol

- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): stock solution 100 ml, final test solution concentration of vehicle is 10 ml.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM

- Strain: SAG 8681

- Source (laboratory, culture collection): University of Gottingen, Institut of Plant Physiology.

- Age of inoculum (at test initiation): 3 days

- Method of cultivation: not reported


ACCLIMATION - not reported
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Test temperature:
range: 22.5-24 degC
pH:
The pH ranged from 7.9 to 8.4 in the control, and from 7.9 to 9.9 in the lower treatment vessels and from 7.8 to 8.1 in the highest treatment vessels. No justification for the pH range seen in the lowest treatment levels is given by the authors. The controls were unaffected.
Nominal and measured concentrations:
Nominal concentrations: 0.01, 0.03, 0.1, 0.3, 1.0, 3.0 and 10 mg/L
Details on test conditions:
TEST SYSTEM

- Test vessel: Erlenmeyer flasks

- Type: open

- Size, fill volume: 300 ml flasks filled with 100 ml test solution

- Initial cells density: 1*10exp4 cells/ml

- Control end cells density: 1.9*10exp6 cells/ml

- No. of vessels per concentration: 3

- No. of vessels per control: 3


GROWTH MEDIUM

- Standard medium used: yes, Algae 10.10; TFB headquarters Microbiological Services (TFB-Zentrale Mikrobiologische Dienste)

- Intervals of water quality measurement: 24 and 72 h


TEST MEDIUM / WATER PARAMETERS

- Intervals of water quality measurement: pH and temperature were measured every 24 hours


OTHER TEST CONDITIONS

- Photoperiod: continuous illumination

- Light intensity and quality: 2000 Lux


EFFECT PARAMETERS MEASURED:

- Determination of cell concentrations: the cells were measured via the Thoma Kammer method; the cell counts were taken at 0, 24, 48, 72 and 96h.


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 3

- Range finding study: not reported
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
0.3 mg/L
Basis for effect:
other: growth rate and biomass
Duration:
96 h
Dose descriptor:
other: EbC0
Effect conc.:
0.3 mg/L
Basis for effect:
other: growth rate and biomass
Duration:
96 h
Dose descriptor:
other: EbC10
Effect conc.:
0.73 mg/L
Basis for effect:
other: growth rate and biomass
Duration:
96 h
Dose descriptor:
other: EbC50
Effect conc.:
0.97 mg/L
Basis for effect:
other: growth rate and biomass
Details on results:
- Exponential growth in the control (for algal test): yes

- Any stimulation of growth found in any treatment:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values:
- Effect concentrations exceeding solubility of substance in test medium:

Table 1: Effect of dodecanol on the cell density and growth rate of S. subspicatus.

Nominal concentrations (mg/L)

Rep

Initial cell density (cells/ml)

Cell density at
96 h

Treatment
Mean cell density cells/ml)

% Inhibition of cell density

Treatment
Mean growth  rate (24-96 h)

% Inhibition of growth rate

 Control

1

 1*10^4

 161*10^4

 

 1.9*10^6

 

 -

 

 

 0.051

 

 

 

 

2

  1*10^4

193*10^4

3

  1*10^4

 212*10^4

0.01

1

  1*10^4

 196*10^4

1.9*10^6

 

 

 0

 

 

0.049 

 

 

3.2 

 

 

2

  1*10^4

 179*10^4

3

  1*10^4

 188*10^4

0.03

1

  1*10^4

 180*10^4

 1.9*10^6

 

 

 0

 

 

0.052 

 

 

 

 

2

  1*10^4

 201*10^4

3

  1*10^4

 179*10^4

0.1

1

  1*10^4

 187*10^4

1.9*10^6 

 

 

 0

 

 

0.049 

 

 

5.2 

 

 

2

  1*10^4

 193*10^4

3

  1*10^4

 179*10^4

0.3

1

 1*10^4

 212*10^4

 2*10^6

 

 0

 

 0.053

 

 0

 

2

  1*10^4

 198*10^4

3

  1*10^4

 190*10^4

1.0

1

 1*10^4

58*10^4

 5.7*10^5

 70

0.037 

28 

2

  1*10^4

63*10^4

3

  1*10^4

50*10^4

 3.0

1

 1*10^4

71*10^4

7*10^5

63

0.042

17

2

  1*10^4

80*10^4

3

  1*10^4

59*10^4

10

1

 1*10^4

32*10^4

3*10^5

84

0.036

31

2

  1*10^4

27*10^4

3

  1*10^4

31*10^4

 

RESULTS: EXPOSED
Biomass
EbC10 (0-72h) = 0.79 mg/l
EbC10 (0-96h) = 0.73 mg/l
EbC50 (0-72h) = 6.02 mg/l
EbC50 (0-96h) = 0.97 mg/l

Validity criteria fulfilled:
no
Remarks:
pH changes more than 1.5 units, but thought to not have affected outcome
Conclusions:
A 96 h EbC50 value of 0.97 mg/L and a NOEC of 0.3 mg/L have been determined for the effects of the test substance on biomass of the freshwater alage S. subspicatus.

Description of key information

Toxicity to aquatic algae: 72 hour EC50 0.66 mg/l, EC10 0.27 mg/l and NOEC 0.085 mg/l (nominal) for the effects of dodecanol on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus) in accordance with test guideline EU Method C.3 (Algal Inhibition test).

Key value for chemical safety assessment

EC50 for freshwater algae:
0.66 mg/L
EC10 or NOEC for freshwater algae:
0.27 mg/L

Additional information

Reliable values for toxicity to aquatic algae are available. These data indicate an EC50 in the range 0.3-2.6 mg/l, and NOECs/EC10s in the range 0.085-0.45 mg/l. The lowest reliable result is a 72 h EC50 value of 0.66 mg/L, EC10 value of 0.27 mg/l and a NOEC value of 0.085 mg/l for the effects of dodecanol on the growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus). This value has been selected as key.

These results are supported by consistent values in other aquatic algae species:

96 h EC50 (Scenedesmus subspicatus (new name: Desmodesmus subspicatus)) = 0.97 mg/l and EC10 = 0.73 mg/l (growth rate and biomass) [Henkel KGaA, 1992].

96 h EC50 (Scenedesmus subspicatus (new name: Desmodesmus subspicatus)) = 2.6 mg/l (growth rate) and EC0 = 0.4 mg/l (biomass) (nominal concentrations) (no EC10 was reported) [Henkel KGaA, 1994].

96 h EC50 (Pseudokirchneriella subcapitata) = 1.29 mg/l (growth rate) and EL10 = 0.45 mg/l (growth rate) (nominal concentrations) [Fraunhofer-Institute, 2003].

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

The data for single carbon chain length LCAAs show toxicity to increase from an ErC50 of 80 mg/L for C6 to 0.33 mg/L for C12. The C14 and C16 LCAAs were not toxic to algae, indicating a toxicity cut-off at C14 and above. Two of the studies determined NOECs that are suitable for assessing long-term toxicity. A NOEC of 11 mg/L has been reported for hexan-1-ol based on measured exposure concentrations. A test with dodecanol resulted in a 72-h EC0 (equivalent to a NOEC) value of 0.085 mg/L.

Other algal studies used a WAF methodology and/or used test concentrations greater than the limit of water solubility and/or did not report a NOEC or equivalent statistic.

The data for mixed carbon chain length LCAAs (commercial products) shows that substances containing LCAAs with carbon numbers in the ranges of C7-9 to C12-15 exerted toxicity at concentrations of between 3.1 and 0.043-0.092 mg/L. At these concentrations all the constituents are likely to have been fully dissolved. For the C12-18 and C14-15 multi-constituent substances there was evidence of toxic effects in tests conducted on water-accommodated fractions prepared at loading rates that will have exceeded the solubility of some constituents.