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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
Not applicable, computer calculated
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This summary has a reliability of 2 because the results are estimated using a computer model that is appropriate for use with this hydrocarbon substance.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose:
read-across: supporting information
Qualifier:
no guideline followed
Principles of method if other than guideline:
The aquatic toxicity was estimated by a QSAR, the Petrotox computer model. This model combines a partitioning model used to calculate the aqueous concentration of hydrocarbon components with the Target Lipid Model used to calculate acute and chronic toxicity of non-polar narcotic chemicals. Petrotox computes toxicity based on the summation of the aqueous-phase concentrations of hydrocarbon block(s) that represent a hydrocarbon substance and membrane-water partition coefficients (KMW) that describe the partitioning of the hydrocarbons between the water and organism.
GLP compliance:
no
Remarks:
Data Calculated by computer model
Analytical monitoring:
not required
Vehicle:
no
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
other: QSAR model
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Key result
Duration:
21 d
Dose descriptor:
EL50
Effect conc.:
1.085 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
0.074 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Executive summary:

The aquatic toxicity was estimated using the Petrotox computer model, which combines a partitioning model used to calculate the aqueous concentration of hydrocarbon components as a function of substance loading with the Target Lipid Model used to calculate acute and chronic toxicity of non-polar narcotic chemicals. Petrotox computes toxicity based on the summation of the aqueous-phase concentrations of hydrocarbon block(s) that represent a hydrocarbon substance and membrane-water partitioning coefficients (KMW) that describe the partitioning of the hydrocarbons between the water and organism. The estimated algal LL50 = 1.085mg/L and 21-day NOELR (No Observed Effect Loading Rate) value is 0.074 mg/l based on growth rate.

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1995
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The study was given a reliability rating of 1 because it followed a standard test guideline, which describes a procedure to evaluate this endpoint, and the results were reviewed for reliability and assessed as valid. The study was also conducted under GLP.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose:
read-across: supporting information
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
An equilibration trial was performed to determine the time required for the components of the test substance to achieve maximum aqueous solubility. Five glass aspirators were each filled with 22L of main dechlorinated water, leaving a small headspace of air. The test substance was added to four of the vessels at a loading rate of 1000 mg/L, and the contents of the fifth aspirator served as the control. All five vessels were then sealed, and stirred as vigorously as possible without creating a dispersion in the sealed vessels, which contained a small headspace of air to permit stirring. After nominal stirring periods of 24, 48, 72, 96 and 198 hours, the WAF solutions were allowed to settle for 1-3 hours, after which a sample of the aqueous layer was extracted and analyzed by GC/FID. The results of the equilibration study showed that equilibrium between the test substance components and the aqueous phase at a loading of 1 g/L was reached in about 72-96 hours.

Samples from each of the tests were analyzed at the start of the test and at 72 hr using hexane extraction and GC/FID analysis.
Vehicle:
yes
Details on test solutions:
The toxicity to algae of WAFs of the test substance was determined in two 72 hr growth inhibition test in sealed test vessels without renewal, the second because the first failed to determine a highest no observed effect level. WAFs were prepared at loading rates of 1, 3 ,10 , 30, 100 , 300 and 1000 mg/L for the first test and at loading rates of 0.1, 0.3 ,1, 3, 10, 30 and 100 mg/L for the second test. The test material was dissolved in acetone first in order to prepare the WAFs for the second trial. Acetone concentrations in the final medium were 0.1ml/L. Control and dilution water were laboratory prepared algal nutrient medium.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Axenic strain of R. subcapitata 9ATCC 22662) was obtained from the American Type Culture Collection, Maryland, Ohio, U.S. Axenic cultures were maintained on agar plates, and used to inoculate liquid cultures which, while in exponential phase growth, are in turn used to inoculate test media.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
no data
Test temperature:
Temperature of 25.1-25.7 (test 1) or 23.1 - 24.5 (test 2) degrees C.
pH:
The pH for test 1 was 6.9-9.0 and 6.9-8.6 for test 2.
Dissolved oxygen:
n/a
Salinity:
freshwater
Nominal and measured concentrations:
Nominal Loading Measured concentration (mg/L)
(mg/L) time 0 72 hr
Test 1
Control <0.2 <0.2
1 0.02 <0.02
3 0.04 0.03
10 0.22 0.16
30 0.37 0.20
100 0.32 0.19
300 0.34 0.29
1000 0.62 0.30

Test 2
Control <0.2 <0.2
Acetone Control <0.2 <0.2
0.1 0.03 <0.02
0.3 0.08 0.10
1.0 0.20 0.16
3.0 0.20 0.19
10 0.21 0.24
30 0.26 0.22
100 0.23 0.21
Details on test conditions:
Test vessels were Erlenmeyer flasks which were completely filled with WAF. In each test there were four replicates per loading rate, and seven control flasks containing algal growth medium and in test 2 there were also seven replicates for the algal growth medium that contained acetone at 0.1ml/L. Three of the four treatments and six of the seven control flasks were inoculated with algal cells to yield an initial concentration of 5000 cells/ml. Uninoculated flasks were used to determine particle counts without algal cells. Two marbles were placed in each flask to aid in mixing, and the flasks were then sealed and incubated in cooled orbital incubators (100 cycles/min) under constant illumination (4500-5200 lux) at a temperature of 25.1-25.7 (test 1) or 23.1 - 24.5 (test 2) degrees C. The pH for test 1 was 6.9-9.0 and 6.9-8.6 for test 2. At the start of the test and then at approximately 24 hours cell counts were made on each sample flask using a Coulter Multisizer. Biomass was calculated as area under the growth curve.
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
0.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
0.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
Based on nominal loading rates:
Test 1
Nominal 72 hr Mean Cell Conc. % Inhibition
Conc. (mg/L) (million cells/ml) biomass growth rate
Control 0.12 na na
1 0.058 48 17
3 0.058 53 22
10 0.072 43 14
30 0.059 55 19
100 0.02 82 57
300 0.048 62 28
1000 0.069 48 13

Test 2
Nominal 72 hr Mean Cell Conc. % Inhibition*
Conc. (mg/L) (million cells/ml) biomass growth rate
Control 0.088 na na
Acetone Control 0.13 na na
0.1 0.11 13 2.4
0.3 0.09 27 11
1.0 0.092 31 15
3.0 0.11 24 6.4
10 0.076 45 17
30 0.14 22 -0.4
100 0.08 38 12
*determined using acetone control data

72-hr NOELB (no observed effect loading rate, biomass) <0.1 mg/L
72-hr NOELR (no observed effect loading rate, growth rate) = <0.1 mg/L
72-hr EL50B (50% inhibition effect loading rate, biomass) >1000 mg/L
72-hr EL50R (50%inhibition effect loading rate, growth rate) >1000 mg/L
Reported statistics and error estimates:
EL50 values estimated by visual inspection of the data

The results of both tests demonstrated an absence of clear loading rate/response relationship over the complete range of test loading rates (0.1 -1000 mg/L) precluding determination of EL50 and NOEL values. The results showed that at all test loading rates there was insufficient test material to consistently inhibit growth by >50%. This value is representative of aquatic algal toxicity for those C14-C20 (high aromatics) aliphatic category members having an initial minimum boiling point range of 263C. The hydrocarbon constituents for these category members with boiling point values greater than 263 deg C did not show adequate water solubility in equilibrated aqueous solutions to cause 50% inhibition acute aquatic toxicity effects.

Validity criteria fulfilled:
yes
Conclusions:
The toxicity of Hydrocarbons, C16-C20, n-alkanes, isoalkanes, cyclics, aromatics (2-30%), as measured by biomass and growth rate to the green alga (Pseudokirchneriella subcapitata formerly Selenastrum capricornutum) was evaluated in freshwater. Under the conditions of this study, Hydrocarbons, C16-C20, n-alkanes, isoalkanes, cyclics, aromatics (2-30%) did not produce a significant effect on biomass or growth rate at 1000 mg/l, based on nominal loading of the test substance in water.
Executive summary:

The toxicity of Hydrocarbons, C16-C20, n-alkanes, isoalkanes, cyclics, aromatics (2-30%), as measured by biomass and growth rate to the green alga (Pseudokirchneriella subcapitata formerly Selenastrum capricornutum) was evaluated in freshwater. Under the conditions of this study, Hydrocarbons, C16-C20, n-alkanes, isoalkanes, cyclics, aromatics (2-30%) did not produce a significant effect on biomass or growth rate at 1000 mg/l, based on nominal loading of the test substance in water.

Description of key information

Water accommodated fractions of hydrocarbons, C16 -C20, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%) did not cause acute toxicity to the freshwater green algae, Pseudokirchneriella subcapitata, at a nominal loading of 1000 mg/l. These data are used as read-across data to hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%).

Key value for chemical safety assessment

Additional information

Water accommodated fractions of hydrocarbons, C16 -C20, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%) did not cause acute toxicity to the freshwater green algae, Pseudokirchneriella subcapitata, at a nominal loading of 1000 mg/l. These data are used as read-across data to hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%).