Dibutyl hydrogen phosphate

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study planned

Study period:

The study will be performed in 2022 or in the following years depending on ECHA decision.

Justification for type of information:

Non-Confidential Name of Substance
Dibutyl hydrogen phosphate

Considerations That The General Adaptation Possibilites Of Annex XI Of The Reach Regulation Are Not Adequate To Generate The Necessary Information
- Available GLP studies: There are no GLP studies available for this substance covering the endpoint of long-term toxicity toward invertebrates
- Available non-GLP studies: There is a non-GLP studies available for this substance covering the endpoint of long-term toxicity toward invertebrates (MITI, 1992). However, the study has major methodological deficiencies and furthermore is conducted according to OECD 202 (1984). Thus, 40 animals were exposed per concentration with 10 animals per vessel. The methodological deficiencies are listed below:
At the beginning already quite a number of animals had died, e.g at the lowest concentration, there is just one vessel in which no animal died before day 1. In the next highest concentration there is even no vessel starting with the full number of ten animals on day 1. Thus, it is possible the animals already have a physical problem which could influence the outcome of the experiment. Furthermore, the guideline (R.7b) demands the "number of offspring produced per female". This is not possible with the existing data, as the offspring cannot be accounted to one parent animal. The pH-value could also have influenced the outcome of the study as it was not adapted and was below 6 at 180 mg/L and higher concentrations (320, 560, 1000 mg/L).
Thus a new study is necessary to give a decent insight in the toxicity of the substance towards invertebrates and their reproduction.
- (Q)SAR: There is no valid (Q)SAR model available to address long-term toxicity towards invertebrats and which outcome would be reliable enough to suffice the information requirements under REACH Annex IX (ECHA Guidance on Information Requirements and Chemical Safety Assessment Chapter R 7a: Endpoint specific guidance)
- Weight of evidence: There is no data available which is sufficient for a weight of evidence approach for the endpoint of long-term toxicity towards invertebrates
- Grouping and read-across: there are no substances which apply for read-across addressing the endpoint of long-term toxicity towards invertebrates.


Considerations That The Specific Adaptation Possibilites Of Annex VI To X (And Column 2 Thereof) Of The Reach Regulation Are Not Adequate To Generate The Necessary Information
According to REACH Annex IX data on long-term toxicity towards aquatic invertebrates is a standard information requirement for substances produced or imported > 100 t/a.

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

pH was not adapted to >6, a number of daphnids died before start of testing, number of offspring cannot be accounted to one individual female

Qualifier:

according to guideline

Guideline:

other: OECD 202

Version / remarks:

1984

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

At first, in order to know the breeding status of Daphnia magna, they were bred in a control area and the number of births of 3 litters was observed.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Test temperature:

20 - 22 °C

Dissolved oxygen:

7.3 - 8.0

Nominal and measured concentrations:

2.1, 6.5, 21, 66 and 210 mg/L

Details on test conditions:

- Five concentration
- contral: Dilution water
- Feeding: cultured green algae
- total volume 400 mL
- Four tanks were prepared for each concentration group (including the control group), and 10 daphnia were placed in each
- semi-static: water is replaced every 48 h
- Temperature: 20-22 ° C (constant temperature bath)
- ambient light with 16 hours of light period and 8 hours of dark period
- feeding and measurement of larvae are performed daily
- pH and dissolved oxygen concentration are measured at the time of water conversion, the deviation of the pH from the value at the start of the test was 0.3 or less, and the dissolved oxygen concentration was 70% or more of the saturated dissolved oxygen concentration
- Duration: 21d

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

66 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Validity criteria fulfilled:

no

Remarks:

pH was not adapted to >6, a number of daphnids died before start of testing, number of offspring cannot be accounted to one individual female

Conclusions:

A 21d-NOEC of 66 mg/L was determined for Dibutylphosphat towards daphnids under exposure conditions.

Executive summary:

A study was conducted according to OECD 202 (1984) "Daphnia sp., Acute Immobilisation Test and Reproduction Test" to assess the toxicity of Dibutylphosphate towards daphnids after an exposure of 21 d..

A preliminary 24h test with five concentrations (0, 100, 180, 320, 560, 1000 mg/L) was conducted and the concentration for the main test was determined based on the results of the 24h-EC50.

The Daphnia were exposed to a range of concentrations, nominally 2.1, 6.5, 21, 66 and 210 mg/L of Dibutylphosphat dissolved in dilution water. 40 daphnids (10 per vessel) were exposed per concentratins and control. Breeding conditions are 20-22 ° C (in a constant temperature bath), ambient light with 16 hours of light period and 8 hours of dark period, feeding and measurement of larvae are performed daily, pH and dissolved oxygen concentration are measured at the time of water conversion, Was conducted for 21 days to examine the effects of the test chemicals. The deviation of the pH from the value at the start of the test was 0.3 or less, and the dissolved oxygen concentration was 70% or more of the saturated dissolved oxygen concentration.

Offspring was counted daily.

A 21d-NOEC of 66 mg/L was determined for Dibutylphosphat towards daphnids under exposure conditions.

Description of key information

The available data on long-term toxicity conducted by the National Institute of Technology and Evaluation, Japan are considered to be reliable, but they are not taken into account for assessment, based on methodological deficiencies. Therefore, a testing proposal as best mode of action is provided.

Additional information

Data on long-term toxicity of dibutyl hydrogen phosphate towards aquatic invertebrates was found for Daphnia magna. A 21d-NOEC of 66 mg/l conducted according OECD TG 202 Part II (1984) by the National Institute of Technology and Evaluation, Japan is reported.

This value is not taken into account for assessment, based on the following reason:

In the studies conducted by the National Institute of Technology and Evaluation, Japan show a high mortality of the daphnids in the control group at the beginning of the test. Reproduction cannot be assessed base on individual organisms but only as the mean based on 10 daphnids. It could be possible, that one individual produced a high number of offspring, whereas another has not reproduced at all. Therefore, the study has to be disregarded due to major deficiencies.