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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:
experimental study
Adequacy of study:
key study
Study period:
October 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
Samples of the test solutions were collected at approximately 0 and 72 hours to measure concentrations of the test substance. Samples at test initiation were collected from the individual batches of test solution prepared for each treatment and control group prior to distribution into the test chambers and prior to inoculation. At exposure termination, samples were collected from the pooled replicates from each treatment and control group. At each sampling interval, 20 mL of test solution was collected from mid-depth and transferred into glass scintillation vials. Samples were acidified with concentrated phosphoric acid upon collection.
Vehicle:
no
Details on test solutions:
A primary stock was prepared by dissolving 0.0118 g of the test substance in 1000 mL of freshwater AAP medium to achieve a nominal concentration of 10 mg a.i./L. The primary stock was inverted at least twenty times and stirred for five minutes prior to use and continued stirring while all subsequent dilutions were made. The primary stock appeared clear and colorless. Five additional test solutions were prepared at nominal concentrations of 0.10, 0.26, 0.64, 1.6, and 4.0 mg a.i./L by diluting aliquots of the 10 mg a.i./L primary stock with freshwater AAP medium. The 0.10, 0.26, 0.64, 1.6, and 4.0 mg a.i./L test solutions were mixed by inversion and appeared clear and colorless and were otherwise unremarkable at the time of preparation. The negative control solution consisted of freshwater AAP medium without test substance added.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Original algal cultures were obtained from the University of Texas at Austin, and have been maintained in culture medium at EAG Laboratories, Easton, Maryland since June 2017. Algal cells used in this test were obtained from EAG Laboratories – Easton cultures that had been actively growing in culture medium under similar environmental conditions as used in this test for at least two weeks prior to test initiation. Algal cells for this study were taken from a culture that had been transferred to fresh medium four days prior to test initiation.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
According to AAP medium
Test temperature:
23.8 - 24.15 °C
pH:
Day 0: 7.3 - 7.4
Day 3: 7.4 - 9.8
Salinity:
According to AAP medium
Conductivity:
According to AAP medium
Nominal and measured concentrations:
nominal concentrations: 0.10, 0.26, 0.64, 1.6, 4.0 mg and 10 mg a.i./L
geometric mean, measured concentrations were determined to be 0.050, 0.15, 0.40, 1.2, 3.6, and 9.0 mg a.i/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 250mL glass erlenmeyers plugged with foam stoppers
- Initial cells density: 10000 / mL
- Control end cells density: haemocytometer
- No. of vessels per concentration (replicates):3
- No. of vessels per control (replicates):6

GROWTH MEDIUM
- Standard medium used: yes AAP

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: purified well water
- Total organic carbon, Metals, Pesticides, Chlorine: checked December 7 , 2016
- Intervals of water quality measurement: not specified

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: yes
- Photoperiod:no
- Light intensity and quality: cool-white fluorescent 6,000 lux ± 10%.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: electronic particle counter (Coulter Electronics, Inc.)

Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1.8 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.81 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.05 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Details on results:
After 72 hours of exposure, inhibition of cell density in the 0.050, 0.15, 0.40, 1.2, 3.6, and 9.0 mg a.i./L treatment groups (based on geometric mean, measured concentrations) was 0, 19, 37, 82, 99, and 100%, respectively, relative to the negative control. Inhibition of growth rate in the 0.050, 0.15, 0.40, 1.2, 3.6, and 9.0 mg a.i./L treatment groups was 0, 4, 8, 30, 85, and 100%, respectively, relative to the negative control.
After 72 hours of exposure, adherence of cells to the test chambers was not observed in any of the control or treatment groups. Flocculation or aggregation of cells was not observed in any of the experimental groups. Cells in the 3.6 and 9.0 mg a.i./L treatment groups appeared enlarged when compared to cells in the negative control. Cells present in all other treatment groups appeared normal when compared to cells in the negative control.
Reported statistics and error estimates:
Dunnett’s test indicated mean growth rate and mean yield were significantly reduced (p < 0.05) in the 0.15, 0.40, 1.2, 3.6, and 9.0 mg a.i./L treatment groups when compared to the negative control. Dunnett’s test indicated mean cell density was significantly reduced (p < 0.05) in the 0.40, 1.2, 3.6, and 9.0 mg a.i./L treatment groups when compared to the negative control. The 72-hour NOEC was determined to be 0.050 mg a.i./L based on statistically significant reductions in growth rate and yield. The 72-hour NOEC for cell density was determined to be 0.15 mg a.i./L. The 72 hour EC50 values for cell density, growth rate, and yield were determined to be 0.52, 1.8, and 0.53 mg a.i./L, respectively.
Validity criteria fulfilled:
yes
Remarks:
Mean cell density control flasks increased by 318, 3 days, achieving the 16X growth criterion. CV av sp growth rates in control 0.76%,< 7% criterion. mean percent CV section-by-section specific growth rates in control replicates 30.9% < 35% criterion
Conclusions:
Toxicity of 1,3-Butylene Glycol Diacrylate to freshwater alga Pseudokirschneriella subcapitata (a.k.a. Raphidocelis subcapitata) was assessed using OECD Test Guideline 201. Growth rate inhibition was evaluated as being ErC50-72h = 1.8 mg/L and ErC10-72h = 0.81 mg/L, meaning that the substance can be classified as toxic to algae according to GHS rules.
Executive summary:

In agreement with the requirements od OECD TG 201, the freshwater alga, Raphidocelis subcapitata, was exposed to a series of six treatment levels of 1,3-Butylene Glycol Diacrylate ranging from 0.050 to 9.0 mg a.i./L, based on geometric mean, measured concentrations. The toxicity of 1,3-Butylene Glycol Diacrylate to Raphidocelis subcapitata was assessed based on effects on cell density, growth rate, and yield relative to the negative control. The 72-hour NOEC was determined to be 0.050 mg a.i./L based on statistically significant reductions in growth rate and yield. The 72-hour NOEC based on cell density was 0.15 mg a.i./L. The 72-hour EC10values for cell density, growth rate, and yield were determined to be 0.16, 0.81, and 0.18 mg a.i./L, respectively. The 72-hour EC50values for cell density, growth rate, and yield were determined to be 0.52, 1.8, and 0.53 mg a.i./L, respectively.

Description of key information

Toxicity of 1,3-Butylene Glycol Diacrylate to freshwater alga Pseudokirschneriella subcapitata (a.k.a. Raphidocelis subcapitata) was assessed using OECD Test Guideline 201. Growth rate inhibition was evaluated as being ErC50-72h = 1.8 mg/L and ErC10-72h = 0.81 mg/L, meaning that the substance can be classified as toxic to algae according to GHS rules.

Key value for chemical safety assessment

EC50 for freshwater algae:
1.8 mg/L
EC10 or NOEC for freshwater algae:
0.81 mg/L

Additional information