Ditolyl ether

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Examined by chemical analysis (GC) in the freshly prepared media and in the media after 24 hours of exposure according to the semi static test conditions.
- Sampling schedule:
Stock solution : at 0 hours (on 2014-04-23)
Control: at 24 hours (on 2014-04-23)
Test concentration/s: 0.019, 0.094 and 1.0 mg/L in the freshly prepared media (on 2014-04-22 and 2014-04-23) and in the media after 24 h of exposure (on 2014-04-23 and 2012-04-24) according to the semi static conditions.
- Storage: Routinely, the samples were analysed immediately. Only in exceptional cases, they were stored overnight deep frozen and protected from light.
- Standard Solutions used for Calibration: 50.0 mg of the test item were dissolved in methanol and made up to the mark in a 100 mL volumetric flask to prepare a stock solution of 500 mg/L. Using this stock solution and a 1:10-dilution thereof, standard solutions were prepared by adding different volumes of standard to a certain volume of water. Concentrations in the range of 0.01 to 2.00 mg/L were thus obtained and further processed like samples. The concentration of the lowest used calibration solution was employed as the limit of quantification.

Vehicle:

no

Details on test solutions:

Pre-treatment of test item and preparation of test item concentrations:
To achieve this 1.9 mg of the test item were weighed out on 2014-04-22 and 2.1 mg/L on 2014-04-23 and were added each to 1 litre of dilution water and treated for 60 seconds at 8000 rpm with an ultra turrax and afterwards stirred for 2 hours on a magnetic stirrer.
The pH was measured to be 7.7 on 2014-04-22 and 8.0 on 2013-11-23.

To produce the different test item concentrations appropriate amounts of the stock solution were diluted with dilution water to a volume of 500 mL. 50 mL of the prepared solutions were taken per replicate and 0.5 mL of dilution water containing 5 daphnids was given to all replicates resulting in the final nominal concentrations. For each test item concentration and the control 4 replicates were prepared.

Test organisms (species):

Daphnia magna

Details on test organisms:

- Name: Daphnia magna STRAUS, parthenogenetic females
- Source: Strain of Bundesgesundheitsamt Berlin
- Maintenance and Acclimatisation: A population of parthenogenetic females of synchronized age structure has been maintained for more than 20 years in the test facility under constant temperature conditions (20 +/- 1 °C) at a 16 : 8 hour light-dark photoperiod (light intensity: < 20 µE x m-2 x s-1). The culture water (so-called 'M4 medium') was partly renewed once a week. The Daphnia were exclusively fed unicellular green algae (Desmodesmus subspicatus) 'ad libitum'. Mortalities of parent Daphnia during the culture period were recorded daily in a semi-quantitative way. The neonates were separated from their parent Daphnia by filtration prior to the acute test.
- Culture and dilution water: Reconstituted water (so-called 'M4 medium' according to OECD 202, annex 1) was used for the maintenance of the test animals and the preparation of stock and test solutions of the test item

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

15.5 °dH (= 276.7 mg/L CaCO3)

Test temperature:

20.3-21.1°C (New medium (0 h) 2014-04-22)
19.5-20.3°C (Old medium (24 h) 2014-04-23)

pH:

7.8 - 9.1 (New medium (0 h) 2014-04-22)
7.9 - 8.1 (Old medium (24 h) 2014-04-23)

Dissolved oxygen:

8.1 - 8.5 mg/L (New medium (0 h) 2014-04-22)
8.6 - 8.9 mg/L (Old medium (24 h) 2014-04-23)

Salinity:

no data

Nominal and measured concentrations:

0.019, 0.43, 0.094, 0.21, 0.45 and 1.0 mg/L

Details on test conditions:

- Test vessels: 100 mL glass beakers covered with watch glasses holding 5 neonates in 50 mL of test medium
- Experimental design: 6 concentrations plus 1 control, 5 neonates per vessel, 4 replicates per concentration/control, no feeding during the exposure period
- semi static system with daily renewal of test medium
- Method of initiation: neonates were placed in prepared media
- Photoperiod: 16 h light : 8 h dark
- Temperature of incubation unit: 19.5 to 20.3 °C
- Aeration: none
- Method of administration: stock solution (2 mg/L)
- Medium renewal: daily

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

0.18 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.156 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Validity criteria fulfilled:

yes

Remarks:

Immobilisation and other abnormalities in the controls did not exceed 10 % by the end of the test. Dissolved oxygen concentration remained above 3 mg/L throughout the exposure period

Conclusions:

An analysis of the immobilisation rates (by probit analysis) gave the following results: EC50 (24 h) = 0.1791 mg(L, EC50 (48 H) = 0.1564 mg/L.

Executive summary:

An analysis of the immobilisation rates (by probit analysis) gave the following results: EC50 (24 h) = 0.1797 mg(L, EC50 (48 H) = 0.1564 mg/L. The results are expressed in terms of geometric mean measured concentrations. Effective concentrations ranged from 16.8 % to 36.6 % in the freshly prepared media and from 14.7 % to 18.4 % in the media after 24 hours of exposure.

The Daphnia were exposed to a range of concentrations, (nominally 0.019, 0.043, 0.094, 0.21, 0.45 and 1.0 mg/L) of Ditolylether dissolved in dilution water for a period of 48 hours. Auxiliaries used to prepare the test media were an ultra turrax and a magnetic stirrer.

Defined concentrations of the test item led to a certain percentage proportion of immobilised Daphnia at the end of the 48 hour study period. Immobilisation rates were recorded at 24-hour intervals. The EC 50 was calculated by probit analysis using the statistics programme ToxRatPro Version 2.10 (released 2010-09-10). Additionally any abnormal behaviour or appearance of the Daphnia was reported. The test was conducted as a semi static test with daily renewal of test medium. During the test a temperature range of 18 - 22 °C was maintained in the test vessels, with a maximum temperature fluctuation of +/- 1 °C in each individual test. The temperature, the pH and the oxygen values were measured every day in the freshly prepared media and in the media after 24 hours of exposure. The criterion of adverse effects used in this study was the item-induced alteration of the normal mobility behaviour and the loss of locomotory actions of the neonates, observed at 24 and 48 hours. This study is classified as acceptable and satisfies the guideline requirements to assess the influence of the substance to acute toxicity on invertebrates.

Description of key information

An analysis of the immobilisation rates (by probit analysis) gave the following results: EC50 (24 h) = 0.18 mg(L, EC50 (48 H) = 0.16 mg/L. 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

0.16 mg/L