Reaction mass of dimethyl phosphonate and methyl hydrogenphosphonate and phosphonic acid

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

4 (not assignable)

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Test organisms (species):

Daphnia magna

Executive summary:

The 48-hour NOEC was  at least 1000 mg test item/L (nominal) and the 48‑hour LOEC as well as the 48-hour EC50 were > 1000 mg test item/L (nominal) .

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

other information

Study period:

2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP - guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

cited as Directive 92/69/EEC, C.2; in most parts equivalent to the OECD TG 202

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- samples were taken at the start (0 hrs) and end (48 hrs) of the experiment
- samples from control and test concentrations were analysed

Vehicle:

no

Details on test solutions:

- stock solution: 120 mg of test substance were added to 1 litre of dilution water (M4 medium) and treated for 30 min. on a magnetic stirrer

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Strain: STRAUS
- parthenogenetic females
- Source: Bundesgesundheitsamt, Berlin
- Age at study initiation (mean and range, SD): 0 - 24 hrs (neonates)
- feeding during test: no

METHOD OF BREEDING AND ACCLIMATISATION:
A population of parthenogenetic females of synchronized age structure is maintained since more than 15 years in the test facility under constant temperature conditions (20 +/ 1 °C) at a 16 : 8 light-dark photoperiod (illumination < 1000 lux). The culture water ('M4 medium') is partly renewed once a week. The daphnia are exclusively fed with unicellular green algae (Desmodesmus subspicatus) 'ad libitum'. Mortalities of parent daphnia during the culture period are recorded daily in a semi-quantitaive way. The neonates are separated from their parent daphnia by filtration prior the acute test.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

264.2 mg/l CaCO3 (measured at test start)

Test temperature:

during test: 18-22°C ± 1°C
measured at the end of the test (48 h): 21.1-21.4°C

pH:

measured at the end of the test (48 h): 7.2-7.9

Dissolved oxygen:

measured at the end of the test (48 h):
=> 7.9-8.4 mg/l
=> 89-96 % saturation

Nominal and measured concentrations:

=> 5 test concentrations (nominal): 6.25, 12.5, 25, 50 and 100 mg/l
=> 1 control

Details on test conditions:

TEST SYSTEM
- Test vessel: 50 ml glass beakers with 20 ml of test medium
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- Aeration: none

TEST MEDIUM
- M4 medium (originally described in Water Research 24 (9): 1157-1167)
- M4 medium was used for both, the breeding of the test animals and the preparation of stock and test solutions

OTHER TEST CONDITIONS
- Photoperiod: 16 h light : 8 h dark

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- mobility

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EC0

Effect conc.:

12.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

41.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% CL: 32.7-53.0

Duration:

24 h

Dose descriptor:

EC100

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

12.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

24.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% CL: 20.8-29.6

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Reported statistics and error estimates:

- probit analysis

Immobilisation for Daphnia magna (initial population: 20) - raw data:

	control		6.25 mg/l		12.5 mg/l		25 mg/l		50 mg/l		100 mg/l
	0 h	48 h	0 h	48 h	0 h	48 h	0 h	48 h	0 h	48 h	0 h	48 h
Absolute	0	0	0	0	0	0	7	6	12	6	17	3
Cumulative	0	0	0	0	0	0	7	13	12	18	17	20
Cumulative [%]	0	0	0	0	0	0	35	65	60	90	85	100

Chemical analysis:

The results of the two different analytical methods (HPLC and DOC-determination) clearly demonstrate that Dimethylphosphit hydrolysed within a few hours and that the overall concentration of organic carbon (measured by DOC) was stable throughout the complete exposure period. Therefore the results were expected based on nominal concentrations.

control

6.25 mg/l

12.5 mg/l

25 mg/l

50 mg/l

100 mg/l

0 h

48 h

0 h

48 h

0 h

48 h

0 h

48 h

0 h

48 h

0 h

48 h

DOC replicates [mg/l]

<5 /<5

<5 /<5

<5/<5

<5/<5

<5/<5

<5/<5

7 / 6

6 / 6

13 / 12

10 / 11

23 / 22

20 / 20

DOC mean value [mg/l]

< 5

< 5

< 5

< 5

< 5

< 5

6.5

6

12.5

10.5

22.5

20

HPLC replicates Dimethylphosphit [mg/l]

<0.375

<0.375

<0.375

<0.375

1.64

<0.375

5.10

<0.375

10.25

<0.375

48.11

<0.375

HPLC replicates Monomethylphosphit [mg/l]

< 0.375

< 0.375

2.20*

1.83*

4.32*

3.90*

8.18*

7.89*

15.27*

14.49*

22.22*

26.22*

 * Values calculated as dimethylphosphit.

Validity criteria fulfilled:

yes

Executive summary:

In a GLP study according to Directive 92/69/EEC, C.2, with analytical monitoring (DOC and HPLC), the EC50 of Daphnia magna was 24.8 mg/l (nominal) after 48 h (Bayer AG, 2003). Due to rapid hydrolysis of DMP to MMP, and the slow hydrolysis of MMP to phosphonic acid, there were significant concentrations of MMP at any DMP concentration (22 - 35 % w/w of initial DMP). At the nominal DMP concentration of 25 mg/l, the geometric mean of the measured MMP concentrations was 8.0 mg/l during this test. DOC measurements confirmed the presence of virtually all organic carbon of the initial carbon content of DMP.

Description of key information

For phosphonic ester residue, there is no short term toxicity study on invertebrates available. However, for two components, dimethyl phosphonate (CAS 868-85-9, DMP) and phosphonic acid (13598-36-2, PA) such studies are available. In the study with DMP, DMP was rapidly hydrolysed to monomethyl phosphonate (CAS 13590-71-1, MMP), which slowly hydrolyed to PA.  Thus, it is plausible to assume that the study with DMP considers also potential effects of MMP, the third component of the registered substance.

In the study with DMP, the EC50 of Daphnia magna was 24.8 mg/L (nominal) after 48 h. 

In the study with PA, the 48-hour NOEC was at least 1000 mg/L (nominal).

As worst case approach, the lowest 48 h-NOEC of 24.8 mg/L (nominal) is considered for phosphonic ester residue.