1-o-tolylbiguanide

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:

48 hours

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

HPLC

Test organisms (species):

Daphnia magna

Details on test organisms:

Species: Daphnia magna
Variety: STRAUS
Strain: Berlin
Sex: Female
Age: Between 0 and 24 hours
Origin: Umweltbundesamt Berlin
Arrival of Strain: 27. Sep. 2007
Daphnia magna is bred in the LAUS GmbH throughout the year. The animals are kept for the use in toxicity tests. They multiply by parthenogenesis, thus being genetically identical. The husbandry is performed similar to the method described in EN ISO 6341, following SOP 115 002 01 (“Zucht und Hälterung von Daphnia magna STRAUS“), edition 11, adopted 15. Jan. 2013.

Vessels: Preserving glasses, nominal volume 2 l
Medium: M4-Medium (recipe of ELENDT), composition see annex
Food: Unicellular green algae (Desmodesmus subspicatus)
Medium renewal: Twice a week
Photo period: 16/8 hours, using neon tubes
Temperature: 20+/-2 °C

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Remarks on exposure duration:

After 24 and 48 hours, the immobilised daphnia were counted

Hardness:

2.502mmol/L

Test temperature:

20.3 – 21.2 °C

pH:

7.6 - 8.8

Dissolved oxygen:

The concentration of dissolved oxygen stayed above 8.7 mg/L throughout the test.

Nominal and measured concentrations:

The measured concentrations after 0 hours and 48 hours were in a range between 85 % and 109 % of the nominal concentration.
The recovery after 48 hours in all treatments was in a range between 105 % and 112 %

Details on test conditions:

Parameters of Instrument
Column: Reprosil 100 C18 5µm 150 x 4.6 mm
Mobile phase: 25 % Methanol / 75 % 20 mmolar KH2PO4-buffer
Flow rate: 1 mL/min.
Column temperature: 25 °C
Detection wavelength: 240 nm
Injection volume: 25 µL
Retention time: 4.1 – 4.4 min

Method Characterisation
Linear sector of method: 0.5 - 200 mg/L (see calibration curve, page 13)
r of calibration function: 0.999963554
Variation coefficient of method: 1.33 %
During validation, the following values were determined:
Recovery rate from the test medium: 103.6 % (1 mg/L); 100.9 % (100 mg/L)

Experimental Conditions
Test vessels: Glass beakers, nominal volume 50 mL, tall shape
Feeding: None
Lighting: None
Date of performance: 19. – 21. Feb. 2013
Treatments: 1.0 / 2.2 / 4.6 / 10 / 22 / 46 mg/L
Temperature: 20.3 – 21.2 °C
Duration: 48 hours
Observation times: 24 and 48 hours
Replicates: Four vessels, each containing 20 ± 5 mL test solution and five daphnia
Control: Four vessels, each containing 20 ± 5 mL dilution water and five daphnia

Reference substance (positive control):

yes

Remarks:

Potassium dichromate K2Cr2O7 (CAS No. 7778-50-9) was used as positive control in a current reference study (GLP study no. 201207R201). The value was determined as 1.5 mg/L, lying within the demanded range of 0.6 – 1.7 mg/L.

Duration:

24 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Duration:

24 h

Dose descriptor:

other: EC50i

Effect conc.:

21 mg/L

Duration:

48 h

Dose descriptor:

other: EC50i

Effect conc.:

15 mg/L

Duration:

24 h

Dose descriptor:

other: EC100i

Effect conc.:

46 mg/L

Duration:

48 h

Dose descriptor:

other: EC100i

Effect conc.:

22 mg/L

Details on results:

•The 24h-EC50i of K2Cr2O7 should lie between 0.6 and 1.7 mg/L. The 24h-EC50i of K2Cr2O7 was determined as 1.6 mg/L in a separate GLP study (201301R201).
•Immobilisation in the controls may not exceed 10 %. Immobilisation in the controls was 0 %.
•The concentration of dissolved oxygen at the end of the test must be at least 3 mg/L. The lowest concentration of dissolved oxygen at the end of the test was 8.7 mg/L.
•The pH-value in the test solutions should not vary more than 1 unit during the test.
The highest variation was 1.1 units. As pH values were in a range which causes no negative effect onto Daphnia magna (7.7 – 8.8), this was stated as uncritical for the outcome of the study.

The following deviation from the study plan was documented:

The pH deviation in the main study was slightly higher than demanded in teh study plans. As pH values were in a range which causes no negative effect on   Daphnia magna(7.7 – 8.8), this was stated as uncritical for the outcome of the study.

The deviation was signed and assessed by the study director on 26. Feb. 2013.

Validity criteria fulfilled:

yes

Conclusions:

All validity criteria but deviation of the pH values were met. For the estimation of the EC50s of test item and positive control, the fits showed sufficient statistical correspond-ence of the data with the dose-response-equation.

The concentration-response curve after 48 hours was extremely steep, showing a 0 % to 100 % rise in immobilisation between two successive treatments. No immobilisation oc-curred in the control.
At the start and at the end of the test, the content of the active ingredient of the test item in the test solutions was determined using HPLC. The measured concentrations showed good correlation with the nominal concentrations with the exception of treatment 1.0 mg/L. For the other treatments, the measured concentrations after 0 hours and 48 hours were in a range between 85 % and 109 % of the nominal concentration. The recovery after 48 hours in all treatments was in a range between 105 % and 112 %. As the nominal treatment of 1.0 mg/L was not used for determination of the biological results, because in the four lowest treatments no immobility was observed, the nominal concentrations were used for the determination of the results.
No observations were made which might cause doubts concerning the validity of the study outcome.
The result of the test is considered valid.

Description of key information

Based on key study

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

15 mg/L