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Ecotoxicological information

Toxicity to aquatic plants other than algae

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Reference
Endpoint:
toxicity to aquatic plants other than algae
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
C12 LAS; Linear Alkylbenzene Sulfonate (LAS)) is a very close analogue of Calcium dodecylbenzenesulfonate (CAS No 26264-06-2, EC Number; 247-557-8) ) and read-across is valid.
Reason / purpose for cross-reference:
read-across source
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition Test)
Principles of method if other than guideline:
A 7-day flow-through growth inhibition test was developed using duckweed (Lemna minor). Control water (carbon and reverse osmosis filtered well water) and five concentrations of test material were delivered from diluter mixing chambers to Pyrex glass exposure chambers at a rate of 1.5 L every 16 minutes (approximately 14 replacement volumes per day). At time 0, each chamber received seven 2-frond, root excised duckweed colonies (four replicates per treatment level). Plants were given continuous illumination at 3875 lux (360 foot candles) and temperature was maintained between 21 and 23oC.
GLP compliance:
not specified
Analytical monitoring:
yes
Details on sampling:
Not reported
Vehicle:
no
Test organisms (species):
Lemna minor
Details on test organisms:
TEST ORGANISM
- Common name: Duckweed
- Strain: Not reported
- Source: The test species was originally collected near Boca Raton, Florida, and has been in continuous culture at the EPA Environmental Research Laboratory, Duluth, Minn., since 1971.
- Age of inoculum (at test initiation): Not reported
- Method of cultivation: Test species stocks were maintained in X0.01 Hutner's solution in a flow through system

ACCLIMATION
- Acclimation period: Not reported
- Culturing media and conditions (same as test or not): Not reported
- Any deformed or abnormal cells observed: Not reported
Test type:
flow-through
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Post exposure observation period:
None
Hardness:
120-130 (as CaCO3 ) mg/L
Test temperature:
21-23 °C
pH:
7.2-7.6
Dissolved oxygen:
8.5 mg/L
Nominal and measured concentrations:
Nominal concentration: Not specified in the study report. All results are based on measured active ingredient. Details of analytical results are not provided in the study report. The test concentrations, based on measured active components, were: 0, 2.1, 3.8, 8, 17 and 34 mg/L.
Details on test conditions:
TEST SYSTEM
- Incubation chamber used: Incubators were not used. However, the test chambers were placed in environmental control housing with a removable front cover for servicing.
- Test vessel: Pyrex glass test chambers
- Type: Open
- Material: All glass test chambers were separated into four individual compartments, each measuring 1.5 x 10.8 x 6.8 cm. Water volume in each compartment was regulated to approx. 400 mL
- Type of cover: Not reported
- Aeration: No (flow-through test)
- Agitation: No
- Type of flow-through: Proportional diluter
- Renewal rate of test solution: Water flow into the diluter was 1.5 L every 16 minutes, which was mixed with 6 mL nutrient stock to give the final concentration of 0.01X Hutner's solution in the test chambers. The flow rate through the individual test chambers was approximately 14 replacement volumes/day.
- Control end cells density: Not reported
- No. of colonies per vessel: Seven (two-frond, root-excised duckweed colonies)
- No. of fronds per colony: Two
- No. of vessels per concentration (replicates): Four
- No. of vessels per negative control (replicates): Four

GROWTH MEDIUM
- Standard medium used: No
- Detailed composition if non-standard medium was used: Nutrient stock solution used was X2.5 Hutner's solution which was mixed with dilution water to give the final concentration of X0.01 in the test chambers. Detailed composition of growth medium is not reported in the study.

SEDIMENT USED: Sediment was not used as the test species is a floating plant

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The dilution water was carbon- and reverse osmosis filtered well water, with added nutrients.
- Total organic carbon: Not reported
- Particulate matter: Not reported
- Metals (mg/L): Mercury = <0.005, Cadmium = <0.005, Zinc = <0.001, Lead = <0.005, Copper = <0.001, Iron = <0.05, Sodium = 11.6, Nickel = <0.033
- Pesticides (mg/L): Chlorinated insecticides= <0.00005, Organophosphate insecticides = <0.0005
- Nitrite: <0.05 mg/L
- Nitrate: <0.05 mg/L
- Chlorine: Not reported
- Alkalinity: Not reported
- Ca/mg ratio: Not reported
- Conductivity: Not reported
- Culture medium different from test medium: No
- Intervals of water quality measurement: Not reported

OTHER TEST CONDITIONS
- Sterile test conditions: Not reported
- Adjustment of pH: Not reported
- Photoperiod: Continuous illumination
- Light intensity and quality: 3875 lux (360 foot candles) fluorescent lights

EFFECT PARAMETERS MEASURED
- Determination of frond number: Number of fronds in each replicate chamber was recorded once every 24 h for 7 d. Every frond visibly projecting beyond the edge of the parent frond was counted manually.
- Determination of biomass: Dry weights were determined at the end of exposure period.
- Determination of frond area: Not determined
- Other: The root lengths were determined at the end of the exposure period. Where possible, 15 to 20 roots from each replicate weremeasured to the nearest 0.5 cm and the ten largest values were selected for statistical analysis. All plant material from each replicate was placed in a tared aluminum dish and dried at 103°C for 3 h. Since the growth rates stabilized by the Day 4, only frond count data from Days 4 through 7, and Day 7 root length and dry weight data were used for statistical analysis. From the frond count data, two other parameters growth rate and doubling time were computed or Day 4 through 7.

NEGATIVE CONTROL PERFORMED: Yes (received only carbon and reverse osmosis filtered well water)

RANGE-FINDING STUDY: No
Reference substance (positive control):
no
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
2.7 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
act. ingr.
Basis for effect:
other: frond count
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
0.9 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
act. ingr.
Basis for effect:
other: frond count
Details on results:
A 7 d EC50 of 2.7 mg/L has been determined for frond count effects to Lemna minor of the test substance.
The 7d NOEC of C12LAS (linear alkylbenzene sulfonate) to Lemna minor was 0.9 mg/L, based on frond count in a flow through test. The result is based on measured concentration.
Validity criteria fulfilled:
yes
Conclusions:
A 7 d EC50 of 2.7 mg/L has been determined for frond count effects to Lemna minor of the test substance.
The 7d NOEC of C12LAS (linear alkylbenzene sulfonate) to Lemna minor was 0.9 mg/L, based on frond count in a flow through test. The result is based on measured concentration.

Description of key information

A 7 d EC50 of 2.7 mg/L has been determined for frond count effects to Lemna minor of the test substance.
The 7d NOEC of C12LAS (linear alkylbenzene sulfonate) to Lemna minor was 0.9 mg/L, based on frond count in a flow through test. The result is based on measured concentration.

Key value for chemical safety assessment

EC50 for freshwater plants:
2.7 mg/L
EC50 for marine water plants:
0.27 mg/L
EC10 or NOEC for freshwater plants:
0.9 mg/L
EC10 or NOEC for marine water plants:
0.09 mg/L

Additional information

A 7 d EC50 of 2.7 mg/L has been determined for frond count effects to Lemna minor of the test substance.

The 7d NOEC of C12 LAS (linear alkylbenzene sulfonate) to Lemna minor was 0.9 mg/L, based on frond count in a flow through test. The result is based on measured concentration.

The available data for saltwater aquatic plants other than algae are limited and to obtaine the value for PNECs for saltwaters is taken account a assesment factor 10 to extrapolate to LC50 following the “Guidance on Information Requirement and Chemical Safety Assessment R.10: Characterisation of dose [concentration]- response for environment”and “Table R.10-5 Assessment factors proposed for deriving PNEC water for saltwater for different data sets”, to account for the possibility that greater taxonomic diversity in the marine environment makes it likely that some marine taxa may be more sensitive than the most sensitive freshwater taxa

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