Methyl 2,3-dibromopropionate

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 2019-02-11 to 2019-10-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study performed to current OECD guidelines with no significant deviations and run in OECD GLP certified lab.

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

April 13, 2004

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Batch No.: 800327680
Purity: 98%

Analytical monitoring:

yes

Details on sampling:

- Concentrations: all test concentrations ( 0.010, 0.022, 0.046, 0.10 and 0.22 mg/L) and the control
- Sampling method: 2.0 mL from the approximate centre of the test vessels at the start of the test
- Sample storage conditions before analysis: Not applicable, samples were transferred to the analytical laboratory at the Test Facility and analysed on the day of sampling.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Preparation of test solutions started with the highest concentration of 100 mg/L in the first range-finder and 10 mg/L in the second range-finder and final test, applying an overnight period of magnetic stirring to accelerate dissolution of test item in test medium. In the first range-finder, a few particles of undissolved material were observed at the surface of the solution. Since the test item is a liquid, these solid particles are probably related to salts in the test medium. It was considered that these particles would cause no mechanical effects towards daphnids, since the number of particles that could be visually observed was negligible. No such particles were observed at the highest concentration prepared (i.e. 10 mg/L) in the second range-finder and final test. Therefore, the test item was considered to be completely dissolved and lower test concentrations were prepared by subsequent dilution of the highest concentration in test medium. All test solutions were clear and colorless at the end of the preparation procedure.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Age at study initiation (mean and range, SD): less than 24 hours old
- Method of breeding:
Start of each batch: Approximately 250 newborn daphnids, i.e. less than 3 days old, were placed into 5 litres of medium in an allglass culture vessel.
Maximum age of the cultures: 4 weeks
Renewal of the cultures: After 7 days of cultivation, half of the medium twice a week.
Temperature of medium: 18-22°C
Feeding: Daily, a suspension of fresh water algae.
Culture medium: M7, as prescribed by Dr. Elendt-Schneider (Elendt, B.-P., 1990: Selenium deficiency in Crustacea. An ultrastructural approach to antennal damage in Daphnia magna Straus. Protoplasma 154, 25-33).
- Source: In-house laboratory culture with a known history.
- Age of parental stock: more than two weeks old
- Feeding during test : No feeding

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

180 mg/L as CaCO3

Test temperature:

19 - 20°C

pH:

8.0 -8.1

Dissolved oxygen:

8.5-9.1 mg/L

Nominal and measured concentrations:

Nominal: 0.010, 0.022, 0.046, 0.10 and 0.22 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 60 mL, all-glass
- Volume of solution: 50 mL
- Aeration: no
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 5 per vessel containing 50 mL of test solution.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The following salts (analytical grade) were added to tap water purified by Reverse Osmosis (RO-water, GEON Waterbehandeling, Berkel-Enschot, The Netherlands):
CaCl2.2H2O: 211.5 mg/L; MgSO4.7H2O: 88.8 mg/L; NaHCO3: 46.7 mg/L; KCl: 4.2 mg/L

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: A daily photoperiod of 16 hours.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Immobility (including mortality): At 24 hours and at 48 hours.
- pH and dissolved oxygen: At the beginning and at the end of the test, for all concentrations and the control.
- Temperature of medium: Continuously in a temperature control vessel, beginning at the start of the test.

RANGE-FINDING STUDY
- First Range-Finding Test:
Ten daphnids per concentration (in duplicate, 5 per vessel) were exposed to a range of 0.10 to 100 mg/L increasing by a factor of 10 and to a blank control.
Complete immobility was observed at all test concentrations after 48 hours of exposure
- Second Range-Finding Test:
Ten daphnids per concentration (in duplicate, 5 per vessel) were exposed to a range of
0.00010 to 0.10 mg/L increasing by a factor of 10 and to a blank control.
The 48h-EC50 is expected to lay between 0.010 and 0.10 mg/L.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.076 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

0.11 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Immobility:
No immobility was observed in the control and at the three lowest test concentrations throughout the exposure period. After 24 hours of exposure, 25 and 100% immobility was found at nominally 0.10 and 0.22 mg/L, respectively. At the end of the test, 85 and 100% immobility was observed at similar concentrations.

- Measured Concentrations:
Since no test item was detected in any of the samples taken from comparable concentrations at commencement of the Freshwater Algal Growth Inhibition Test (OECD 201; Report No. 20176475), it was decided to not analyse the samples taken and no further sampling was considered in this study.
Although exposure concentrations are not analytically confirmed, the test item was completely soluble in test medium upon preparation of test solutions.

- Analytical Trial:
The measured concentrations at the start of the analytical trial were 0.048 and 0.75 mg/L (being the means of duplicate analysis) in QC samples prepared at 0.10 and 1.0 mg/L, respectively. The concentrations were approximately 20 and 60 times lower after 3 hours of incubation relative to the initial values, respectively. These concentrations were below the lowest calibration point, and therefore, could not be quantified reliably. All test item responses detected at both QC concentrations were at carry-over level after 6, 16 and 24 hours of incubation. Therefore, it was assumed that the test item had completely degraded during the first 6 hours.
Based on the obtained results, no exact half-life times could be calculated as no test item concentrations could be quantified in any of the samples analysed after test commencement. However, when assuming that the concentrations analysed after three hours of incubation were 20 and 60 times lower than the initial values (i.e. 0.0024 and 0.013 mg/L, respectively), the DT50 was determined to be shorter than 1 hour at both QC levels.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- ECx:
The 24h-EC50 was 0.52 mg/L with a 95% confidence interval between 0.45 and 0.58 mg/L.
The 48h-EC50 was 0.33 mg/L with a 95% confidence interval between 0.27 and 0.38 mg/L

Reported statistics and error estimates:

The 24h-EC50 was calculated from the logits of the percentages of affected daphnids and the logarithms of the corresponding test item concentrations using the maximum likelihood estimation method.
The 48h-EC50 could not be determined using a regression method. Instead, the 48h-EC50 was calculated by applying the Spearman-Karber procedure (non-linear; without trimming) on the percentages of affected daphnids and the logarithms of the corresponding test item concentrations.
ToxRat Professional v 3.2.1 (ToxRat Solutions® GmbH, Germany) was used to perform the analysis.

Although no actual exposure concentrations could be analysed in this study, the exposure phase was performed in accordance with the recommendations for degrading test chemicals as put down in the OECD Guidance Document No. 23. The DT50 for Methyl 2,3-dibromopropionate in test medium was determined to be <1 hour using the results obtained in the analytical trial. According to the OECD guidance, acute toxicity testing with highly instable test items (i.e. DT50 <1 hour) has to be performed by exposing daphnids to the degradation product(s). In addition, effect parameters should be expressed in terms of measured concentrations of the product(s). At this point, it is unknown what processes are responsible for the decay and the degradation product(s) could not be identified within the scope of this project.

Based on the calculated DT50 in combination with the prolonged stirring applied during preparation of test solutions, it can be stated that all parent test item degraded prior to the start of the exposure phase. The obtained results therefore represent the toxicity of the degradation product(s), which is considered to be the most environmentally relevant scenario.

Analytical confirmation of exposure concentrations is obligatory for classification of chemicals and in risk assessment. In this study, effect parameters were expressed in terms of nominal concentrations as actual exposure concentrations could not be confirmed with the available analytical method, which was developed specifically for quantification of the parent substance. Based on the current results, the test item will be classified as Acutely Toxic Category 1 of the GHS2, being the most severe category that includes test items with EC50-values below 1.0 mg/L. From the perspective of a mass balance, in theory, the nominal concentrations should be equivalent to the concentration(s) of the product(s) in case there are no other losses than transformation. Hence, it is unlikely that the test item will be classified in a less severe category (i.e. EC50 >1.0 mg/L) when effect parameters would be expressed in terms of the product(s). The lack of analytical confirmation of exposure concentrations would therefore have no consequences for classification purposes.

Validity criteria fulfilled:

yes

Conclusions:

The 48h-EC50 for Daphnia magna exposed to the test item was less than 0.076 mg/L with a 95%-confidence interval of 0.067-0.086 mg/L based on the nominal concentration.

Executive summary:

The objective of the study was to evaluate the test item for its ability to generate acute toxic effects on the mobility of Daphnia magna during an exposure period of 48 hours and, if possible, to determine the EC50 at 24 and 48 hours of exposure.

The study procedures described in this report were based on the OECD guideline No. 202, 2004. In addition, procedures were based on the test methods described in the OECD series on testing and assessment number 23, 2019.

Twenty daphnids per group (5 per replicate, quadruplicate) were exposed to an untreated control and to nominal concentrations of 0.010, 0.022, 0.046, 0.10 and 0.22 mg/L. The total exposure period was 48 hours.

No immobility was observed in the control and at the three lowest test concentrations throughout the exposure period. After 24 hours of exposure, 25 and 100% immobility was found at nominally 0.10 and 0.22 mg/L, respectively. At the end of the test, 85 and 100% immobility was observed at these concentrations.

In conclusion, the 48h-EC50 for Daphnia magna exposed to test item was 0.076 mg/L (95% confidence interval between 0.067 and 0.086 mg/L) based on nominal test item concentrations.

It should be noted that the test item degraded completely prior to the start of the exposure and that concentrations of possible degradation products could not be quantified during this project due to the absence of an appropriate analytical method.

Description of key information

The ability to generate acute toxic effects on the mobility of Daphnia magna during an exposure period of 48 hours was evaluated based on the OECD guideline No. 202 and 23.

The 48h-EC50 for Daphnia magna exposed to test item was 0.076 mg/L (95% confidence interval between 0.067 and 0.086 mg/L) based on nominal test item concentrations.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.076 mg/L