Methyl 2-benzoylbenzoate

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:

November-December 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identification: RCX 14-672
Chemical name: methyl-2-benzoylbenzoate
Batch no.: N14003
CAS no.: 606-28-0
EC no.: 210-112-3
Molecular formula: C15H12O3
Molecular mass: 240.3 g/mol
Description: white to light yellowish powder
Purity: >99% (gas chromatography)
Water solubility: 117.7 mg/l
Test item storage: at room temperature, protected from light
Stability: stable under storage conditions
Expiry date: 30 November 2015

Analytical monitoring:

yes

Details on sampling:

HPLC analyses were performed in the water soluble fractions (WSF) at the beginning of the exposure and in the individual test vessels after 24 and 48 h of exposure, respectively.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Based on the effects observed in the preliminary test, the definitive test with RCX 14-672 was performed at the following loading rates (spacing factor 1.6): 15.3, 24.4, 39.1, 62.5 and 100 mg/l. The test concentrations used for the test were saturated solutions prepared by direct addition. To this end, the test item was directly weighed into empty glass vessels and then Daphnia medium was added, moderately stirred for a minimum of 24 h, followed by filtration (MILLIPORE AP15 glass fiber filter).

Test organisms (species):

Daphnia magna

Details on test organisms:

Test organism Daphnia magna (Straus, 1820)
Breeding Parental and young Daphnia held in 4 l glass aquaria (3 l medium) at 20 ± 2 °C
Illumination 16 h per day
Medium Continuously aerated Elendt M4 medium (Tables 1 and 2); prepared with deionised water (conductivity <1.5 µS/cm)
Feed Suspension of Desmodesmus subspicatus in Elendt M4 medium with an optical density OD680 of about 15 units
Frequency of feeding 400 μl per Daphnia per day, except on weekends
Control of sensitivity Acute reference test with potassium dichromate conducted twice a year

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

No post-exposure observation period.

Hardness:

Analyses of the Elendt M4 Daphnia medium by BMG Engineering Ltd, 2 – 3 July 2012 (mean values of three independent medium batches): total hardness (as sum of Ca and Mg): 2.52 mmol/l; carbonate hardness: 0.32 mmol/l; alkalinity (p-value/m-value): -0.08/0.70 mmol/l; Ca/Mg ratio: 4.11; Na/K ratio: 9.13.

Test temperature:

Determined in an additional flask without Daphnia at the start and at the end of the exposure. The temperature during the whole test period remained constant at 22.0°C (target: 20 ± 2°C).

pH:

Determined in the combined replicate solutions at the beginning and at the end of the exposure

Dissolved oxygen:

Determined in the combined replicate solutions at the beginning and at the end of the exposure

Salinity:

No data

Nominal and measured concentrations:

Nominal concentrations: 100-62.5-39.1-24.4 aand 15.3 mg/l.

HPLC analyses were performed in the water soluble fractions (WSF) at the beginning of the exposure and in the individual test vessels after 24 and 48 h of exposure, respectively. The analyses revealed that only part of the test item was dissolved; but that these concentrations could satisfactorily be maintained until the end of the exposure period. The geometric mean of the measured concentrations (GM0-24 h, GM0-48 h) corresponded to 84, 94, 88, 93 and 102% of the initial values after 24 h and 86, 93, 81, 80 and 101% of the initial values after 48 h at 100, 62.5, 39.1, 24.4 and 15.3 mg/l loading rates, respectively.

Details on test conditions:

Test vessel: 100 ml flasks, all-glass, with 50 ml of test medium
Test medium: continously areated Elendt M4 medium; prepared with deionised water (conductivity <1.5 µS/cm)
Number of Daphnia: 40 individuals per test concentration, 20 per vessel. Blank control, containing test medium, three replicate samples with 20 Daphnia each.
Age: Less than 24 h
Light: 16 h photoperiod a day, supplied by overhead white fluorescent tubes
Temperature (target): 20 ± 2 °C (temperature-controlled room)
Test type: Static exposure conditions
Test duration: 48 h

OTHER TEST CONDITIONS
- Photoperiod: 16 h photoperiod a day, supplied by overhead white fluorescent tubes

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.6
- Range finding study: yes
- Test concentrations: 0 - 10 - 33 - 100
- Results used to determine the conditions for the definitive study: 40% immobility at 100 mg/l

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EC10

Effect conc.:

19.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 12.6-23.7

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

44.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 38.8-54.8

Duration:

24 h

Dose descriptor:

NOEC

Effect conc.:

15.5 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC10

Effect conc.:

13.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 2.52-19.5

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

26.8 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 16.4-34.1

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

6.93 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

The actual concentrations of RCX 14-672 were measured by HPLC. The effective concentrations ECx and the no-observed-effect concentrations NOEC were then assessed based on the geometric mean (GM0–48h) of the measured concentrations.

After 24 h of exposure, the EC50 for RCX 14-672 was calculated to be 44.4 mg/l (95% confidence limits: 38.8–54.8 mg/l). The low effect concentrations (EC10, EC20) were calculated to be 19.3 mg/l (95% confidence limits: 12.6–23.7 mg/l) and 26.9 mg/l (95% confidence limits: 21.1–31.0 mg/l), respectively. The no-observed-effect concentration NOEC after 24 h was shown to be 15.5 mg/l.

After 48 h of exposure, the EC50 for RCX 14-672 was calculated to be 26.8 mg/l (95% confidence limits: 16.4–34.1 mg/l). The low effect concentrations (EC10, EC20) were calculated to be 13.1 mg/l (95% confidence limits: 2.52–19.5 mg/l) and 17.4 mg/l (95% confidence limits: 5.47–23.7 mg/l), respectively. The no-observed-effect concentration NOEC after 48 h was shown to be 6.93 mg/l.

Results with reference substance (positive control):

The EC50 for the control of sensitivity for 24 h of exposure with potassium dichromate was estimated to be 1.3 mg/l (data from 1 October 2014). The resulting EC50 value of the reference item was within the recommended range of 0.6 - 2.1 mg/L according to OECD Guideline 202.

Validity criteria fulfilled:

yes

Executive summary:

The effective concentrations (EC_10,EC_20,EC₅₀) of RCX 14-672 to Daphnia magna were investigated under static exposure conditions over a period of 48 hours. .Forty individual Daphnia divided into 2 test vessels were exposed to the test item. The applied loading rates were100, 62.5, 39.1, 24.4 and 15.3 mg/l (spacing factor: 1.6). The test solutions were prepared by direct addition of the test item to the medium, stirring for 24 h followed by filtration. HPLC analyses were performed in the water soluble fractions (WSF) at the beginning of the exposure and in the individual test vessels after 24 and 48 h of exposure, respectively. These analyses revealed that only part of the test item was dissolved; but that these concentrations could satisfactorily be maintained until the end of the exposure period. The geometric mean of the measured concentrations (GM_{0-24 h}, GM_{0-48 h}) corresponded to 84, 94, 88, 93 and 102% of the initial values after 24 h and 86, 93, 81, 80 and 101% of the initial values after 48 h at100, 62.5, 39.1, 24.4 and 15.3 mg/l loading rates, respectively. Therefore,the effective concentrations EC_xand the no-observed-effect concentrations NOEC of RCX 14-672 were assessed based onthe geometric mean of the measured concentrations (GM_{0-24 h}, GM_{0-48 h}).

Description of key information

The 48-hour EC50 for freshwater invertebrates (Daphnia magna) was 26.8 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

26.8 mg/L