Diisobutyl hydrogen phosphate

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:

2020

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)

Analytical monitoring:

yes

Details on sampling:

Sampling schedule:
Control : at 48 hours (on 2020-11-05)

Test concentration/s : 25, 50 and 100 mg/L in the freshly prepared media (on 2020-11-03 and 2020-11-04) and in the media after 24 h of exposure (on 2020-11-04 and
2020-11-05) according to the semi-static

Pre-treatment of test item and preparation of test item concentrations
A stock solution was prepared to give the desired series of test concentrations. To achieve this 100.5 mg of the test item on 2020-11-02 and 101.0 mg on 2018-11-03 were added to 1 litre of dilution water, treated for 60 seconds at 8000 rpm with an ultra turrax and stirred for 24 h on a magnetic stirrer. Undissolved particles of the test item were removed by filtration using a folded filter with a pore size of 7 - 12. The pH was measured to be 7.4 on 2020-11-03 and to be 7.5 on 2020-11-04.
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 exposure concentration and for the control exposure 4 replicates were prepared. After 24 hours of exposure, all media were renewed, and the neonates were transferred into the fresh media using a small sieve.

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

Test species
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 +/- 2 °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. The neonates were separated from their parent Daphnia by filtration prior to the acute test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 d

Hardness:

14.4 °dH (= 257 mg/L CaCO3)

Test temperature:

18 - 22 °C

pH:

7.4 - 7.5

Nominal and measured concentrations:

25, 50 and 100 mg/L (nominal)

Reference substance (positive control):

yes

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks:

alteration of the normal mobility behaviour and the loss of locomotory actions of the neonates

Validity criteria fulfilled:

yes

Conclusions:

No toxic effects against Daphnia were observed at a limit test concentration of 100 mg/L under exposure conditions.

Executive summary:

A study was performed to assess the acute toxicity of Diisobutyl phosphate to Daphnia magna STRAUS under semi-static conditions in a closed bottle system.

 

The study was conducted in accordance with the Council Regulation (EC) No　440/2008, Method C.2 ‘Acute toxicity for Daphnia’ (2008) which is equivalent to OECD Guideline for Testing of Chemicals No. 202 'Daphnia sp., Acute Immobilisation Test' (adopted April 13, 2004).

 

The Daphnia were exposed to a range of concentrations, nominally 25, 50 and

100 mg/L of Diisobutyl phosphate dissolved in dilution water.

 

Observations were made on the swimming ability and the percentage immobilised, respectively, after 24 and 48 hours of exposure. The following values were determined:

 

　

Time EC　50
[h] [mg/L]

 

24 > 100

48 > 100

 

　

No toxic effects against Daphnia were observed at a limit test concentration of 100　mg/L under exposure conditions.

 

The results are expressed in terms of nominal concentrations. Measured test item exposure concentrations ranged from 92 % to 97　% of their nominal target values in the freshly prepared media and from 82　% to 103　% in the media after 24 hours of exposure.

 

Description of key information

No toxic effects against Daphnia were observed at a limit test concentration of 100　mg/L under exposure conditions.

 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

> 100 mg/L