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Ecotoxicological information

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:
other: Result based on an internationally accepted QSAR tool.
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Principles of method if other than guideline:
ECOSAR (Ecological Structure Activity Relationships) predicts the potential toxicity of industrial chemicals to organisms living in the water body to which the chemicals are discharged.
GLP compliance:
no
Details on sampling:
Sampling performed at the start and the end of the tests with ethyl, butyl and octyl lactate, in test media without algae. Samples of 50-100 ml volume were immediately extracted with 5 ml hexane adding n-dodecane as an internal standard.
Test organisms (species):
other: Green algae
Details on test organisms:
TEST ORGANISM
- Common name: S. capricornutum
- Strain: ATCC 22662, American Type Culture Collection, 12301 Parklawn Drive, Rockville. Maryland, U.S.A.
- Inoculum (at test initiation): 10E4 cells/mL
Water media type:
freshwater
Total exposure duration:
96 h
Hardness:
no data
Test temperature:
20 ± 1 °C
pH:
8.0 at the start of the tests
Dissolved oxygen:
Not relevant
Salinity:
Not relevant
Nominal and measured concentrations:
In algal test systems loss of test substance is possible by several mechanisms (e.g. volatilization,biodegradation). In this study, analytical confirmation was carried out in the tests with ethyl, butyl and octyl lactate in test media without algae. The initial measured concentrations varied considerably when compared to the nominal values, but at nominal concentrations of 32 mg/L or higher, at least 90% of the test substance was recovered analytically at the start of the test. At the end of the 72h tests with ethyl and butyl lactate, at least 80% of both substances was recovered analytically in a range relevant to the calculation of the EC50 values. The decrease of actual concentration was considerably higher in the 96h algal test with octyl lactate (EPA guideline), i.e. up to 50% at the EC50 level in test media without algae. The amount of loss tended to be proportional to the concentration of octyl lactate, possibly indicating a first order hydrolysis reaction. Octyl lactate had almost entirely depleted in 96h in test media from which the algal cells had been removed, possibly due to bacterial growth (and activity) which is almost always present in algal cultures.
Details on test conditions:
TEST SYSTEM
- Test vessel: 200 mL conical test flasks
- Fill volume: 100 mL
- Aeration: no
- Initial cells density: 10E4 cells/mL
- light intensity, 80-86 µmol/s/m²
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: amended with 150 mg/L NaHCO3 and 80 mg/L Fe-citrate.3H2O to increase its buffer capacity and prevent Fe limitation of growth.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: determined daily by electronic particle counting (Coulter Counter Model TAB, 100 pm aperture). A linear relationship between the particle counts and microscopic cell counts was established. The mean control growth rate of the algal cultures was 0.072 h-1
Reference substance (positive control):
not specified
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
0.378 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
dodecyl lactate
Basis for effect:
growth rate
Remarks on result:
other: ECOSAR Class Esters
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
0.63 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
dodecyl lactate
Basis for effect:
growth rate
Remarks on result:
other: Baseline Toxicity

dodecyl lactate:

                                                                                            Predicted

ECOSAR Class  Esters               Organism            Duration  End Pt  mg/L (ppm)

=========================== ================== ======== ======  ==========

Esters                                    : Green Algae          96-hr     EC50       0.378

=========================== ================== ======== ======  ==========

Neutral Organic SAR                : Green Algae          96-hr     EC50       0.630

(Baseline Toxicity)       

=========================== ================== ======== ======  ==========

------------------------------

Class Specific LogKow Cut-Offs

------------------------------

If the log Kow of the chemical is greater than the endpoint specific cut-offs

presented below, then no effects at saturation are expected for those endpoints.

 

Esters:

------

Maximum LogKow: 6.4 (Green Algae EC50)

 

Baseline Toxicity SAR Limitations:

---------------------------------

Maximum LogKow: 6.4 (Green Algae EC50)

Description of key information

Based on ECOSAR v1.1 Class-specific Estimations, the 96h-EC50 for Green Algae ranges from 0.378 based on grouping under esters to 0.630 mg/L (baseline toxicity). Extrapolation based on a trendline of alkyl lactates resulted in an EC50 of 0.21 mg/L. The experimental 72h-EC50 for Green Algae exposed to C12-15 alkyl lactates was > 1.8 mg/L based on measured concentrations. The key value is based on the lower value from the ECOSAR v1.1 Class-specific Estimations.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.38 mg/L

Additional information

Based on the analytical results of the 96h algal test with octyl lactate in the referred study, alkyl lactates with C-chains of 8 carbons or more, degrade rapidly due to hydrolysis and bacterial activity. The available data hold only very limited information about the NOEC/EC10 for growth rate, so no key values could be provided for the NOEC or EC10.