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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:
13th-16th April 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
Samples of the test solutions were collected to measure concentrations of the test substance at 0 (test initiation, Day 0) and 72 hours (exposure termination, Day 3). Duplicate samples were collected at approximately 0 and 72 hours with one set of samples processed immediately for analysis and the other set stored refrigerated for potential future analysis if deemed necessary by the Study Director. Samples collected at test initiation (0 hour) were collected from the individual batches of test solution prepared for each treatment and control group prior to distribution into the test chambers.
At exposure termination (72 hours), samples were collected from the pooled replicates from each treatment and control group. At each sampling interval, 8.0 mL of test solution was added to 20 mL glass scintillation vials containing 2.0 mL of 0.5% formic acid in methanol.
Vehicle:
no
Details on test solutions:
A primary stock was prepared at a nominal concentration of 100 mg a.i./L by diluting 0.1002g of 2 (2-methoxyethoxy) ethyl methacrylate to a final volume of 1000 mL with freshwater AAP medium. The 100 mg a.i./L primary stock was stirred with a Teflon-coated stir bar and magnetic stir plate for twenty minutes and inverted at least twenty times to mix. The 100 mg a.i./L primary stock appeared clear and colorless with foam on the surface and continued stirring while all subsequent dilutions were made. Aliquots of the 100 mg a.i./L primary stock were diluted with freshwater AAP medium to prepare test solutions at nominal concentrations of 6.3, 13, 25, and 50 mg a.i./L. All test solutions appeared clear and colorless and otherwise unremarkable at the time of preparation.
Test organisms (species):
other: Raphidocelis subcapitata
Details on test organisms:
Algal cells for this study were taken from a culture that had been transferred to fresh medium four days prior to test initiation.The algal cells were cultured and tested in freshwater AAP medium (3). Stock nutrient solutions were prepared by adding reagent-grade chemicals to purified EAG Laboratories-Easton well water (NANOpure® water). The test medium then was prepared by adding appropriate volumes of the stock nutrient solutions to NANOpure® water. The pH of the medium was adjusted to 7.5 ± 0.1 with 10% hydrochloric acid and/or 0.1N sodium hydroxide at the time of preparation. The medium was sterilized by filtration (0.22 µm) and stored refrigerated prior to use.

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
Not stated
Test temperature:
Temperatures remained within the 24 ± 2°C range established for the test.
pH:
The pH of all test solutions at test initiation was 7.3. At test termination, pH in the pooled biotic replicates of each respective treatment and control group ranged from 8.2 to 9.9. The observed increase in pH is typical for tests conducted with R. subcapitata and is attributed to the photosynthetic activity of the algae.
Dissolved oxygen:
Not stated.
Salinity:
Not stated.
Conductivity:
Not stated.
Nominal and measured concentrations:
Nominal test concentrations used in the definitive test were 6.3, 13, 25, 50, and 100 mg/L and were based upon the results of the range-finding test. Measured concentrations of 2-(2-methoxyethoxy) ethyl methacrylate were determined from samples of test medium collected from each treatment and control groups at 0 and 72 hours of the test.
Details on test conditions:
Test chambers were held in an environmental chamber at a temperature of 24 ± 2ºC. The temperature of a container of water adjacent to the test chambers in the environmental chamber was measured continuously using an Amega Scientific Corporation centralized monitoring system. The algae were held under continuous cool-white fluorescent lighting throughout the test. The target light intensity was 6,000 lux ± 10%. Light intensity was measured at test solution level at five locations surrounding the test flasks at test initiation using a SPER Scientific 840006C light meter. The pH of the medium in each treatment and control group was measured at test initiation and exposure termination using a Thermo Orion A214 pH meter. At test initiation, pH was measured in the individual batches of test solution prepared for each treatment and control group. At exposure termination, pH was measured in pooled samples of test solution collected from each of the replicates of each treatment and control group.

Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 99 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
47 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Key result
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
> 99 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 99 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Details on results:
Conditions for the Validity of the Test
1) The mean cell density in the negative control replicates increased by a factor greater than 16 within three days. The factor was 343.

2) The coefficient of variation of the average specific growth rate in the negative control replicates during the whole test period did not exceed 7%. It was 1.55%.

3) The mean coefficient of variation for section by section specific growth rates (days 0 1, 1 2, and 2 3) in the negative control replicates did not exceed 35%. It was 13.3%.


Validity criteria fulfilled:
yes
Conclusions:
The objective of this study was to determine the toxicity of 2-(2-methoxyethoxy) ethyl methacrylate, to the freshwater alga, Raphidocelis subcapitata, over a 72-hour exposure period using a study method based on OECD TG 201. The 72hour EC50, EyC50, and ErC50values were all estimated to be >99 mg a.i./L. The 72-hour NOEC was determined to 47 mg a.i./L.
Executive summary:

In accordance with  OECD TG 201 following GLP conditions, the freshwater alga, Raphidocelis subcapitata, was exposed to a geometric series of five mean, measured concentrations of2-(2-methoxyethoxy) ethyl methacrylateranging from 5.8 to 64 mg a.i./L in a study based on OECD TG 201. Effects were evaluated based on cell density, yield, and growth rate usingmean measuredtest concentrations. The 72‑hour EC50, EyC50, and ErC50values were all estimated to be >99 mg a.i./L. The 72-hour NOEC was determined to 47 mg a.i./L.

Description of key information

In accordance with  OECD TG 201 following GLP conditions, the freshwater alga, Raphidocelis subcapitata, was exposed to a geometric series of five mean, measured concentrations of 2-(2-methoxyethoxy) ethyl methacrylateranging from 5.8 to 64 mg a.i./L in a study based on OECD TG 201. Effects were evaluated based on cell density, yield, and growth rate usingmean measuredtest concentrations. The 72‑hour EC50, EyC50, and ErC50values were all estimated to be >99 mg a.i./L. The 72-hour NOEC was determined to 47 mg a.i./L.

Key value for chemical safety assessment

EC50 for freshwater algae:
99 mg/L
EC50 for marine water algae:
99 mg/L
EC10 or NOEC for freshwater algae:
47 mg/L
EC10 or NOEC for marine water algae:
47 mg/L

Additional information