[[(phosphonomethyl)imino]bis[ethylenenitrilobis(methylene)]]tetrakisphosphonic acid, ammonium salt

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to microorganisms, other

Remarks:

non-standard study for the effects of the tested substance on sewage gas production volume

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was well documented and meets generally accepted scientific principles, but was not conducted in compliance with GLP.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Non-quantitative study of effect of increasing concentration of test substance on the sewage treatment process

GLP compliance:

not specified

Vehicle:

no

Test organisms (species):

activated sludge

Test type:

not specified

Water media type:

not specified

Limit test:

no

Duration:

30 d

Dose descriptor:

NOEC

Effect conc.:

200 mg/L

Nominal / measured:

nominal

Conc. based on:

not specified

Basis for effect:

other: sewage gas production volume

Duration:

30 d

Dose descriptor:

LOEC

Effect conc.:

500 mg/L

Nominal / measured:

nominal

Conc. based on:

not specified

Basis for effect:

other: sewage gas volume reduced and fermentation delayed

Details on results:

At 50 mg/L Dequest 2000 showed no effects.
At 100 and 200 mg/L the start of fermentation was delayed, but constant gas volume was achieved in the same period as in the control.
At 500 mg/L Dequest 2000, the system was strongly disturbed, as indicated by a late beginning of fermentation, and greatly reduced sewage gas production volume.

Conclusions:

A non-standard study of effects on sewage treatment plant micro-organisms was conducted according to generally accepted scientific principles but lacks detail in the study report. The result of a lack of effects on respiration up to 200 mg/L provides reliable evidence.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to an appropriate OECD test guideline. It was not compliant with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

no

Analytical monitoring:

not specified

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Source: The aeration stage of Severn Trent Water PLC Sewage Treatment Plant, Belper, Derbyshire. The sample was maintained at 21 °C with continuous aeration and used on the day of collection. The pH 6.8 and the suspended solids level equal to 4.1 g/l prior to use.

Test type:

not specified

Water media type:

not specified

Limit test:

yes

Total exposure duration:

3 h

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

3.2 mg/l 1% inhibition
32 mg/l 79% inhibition

Concentration (mg/l)	O2consumption rate (mg O2/l/min)	% Inhibition respiration rate
Control (R1)	0.40	-
Control (R2)	0.37	-
Test substance 1000 (R1)	0.37	11
Test substance 1000 (R2)	0.37	11
Test substance 1000 (R3)	0.38	8
Reference 3.2	0.36	13
Reference 32	0.06	86

Validity criteria fulfilled:

yes

Conclusions:

An EC50 value of >1000mg/l was determined in a reliable study conducted according to an appropriate test protocol. Not conducted according to GLP.

Reference 3

Endpoint:

toxicity to microorganisms, other

Remarks:

non-standard study for the effects of the tested substance on the bioluminescence of the bacterium Photobacterium phosphoreum

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

4 (not assignable)

Principles of method if other than guideline:

Method: other

GLP compliance:

not specified

Analytical monitoring:

not specified

Test organisms (species):

Photobacterium phosphoreum

Total exposure duration:

30 min

Details on test conditions:

Type: aquatic

Duration:

30 min

Dose descriptor:

EC0

Effect conc.:

> 2 500 mg/L

Result expressed as nominal concentration. Properties of the
test substance and evidence from other studies (where
concentrations were measured) indicate that nominal and
measured concentrations are likely to be in good agreement.

Reference 4

Endpoint:

toxicity to microorganisms, other

Remarks:

non-standard study for the effects of the tested substance on sewage gas production volume

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was well documented and meets generally accepted scientific principles, but was not conducted in compliance with GLP.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Non-quantitative study of effect of increasing concentration of test substance on the sewage treatment process

GLP compliance:

not specified

Vehicle:

no

Test organisms (species):

activated sludge

Test type:

not specified

Water media type:

not specified

Limit test:

no

Duration:

30 d

Dose descriptor:

NOEC

Effect conc.:

200 mg/L

Nominal / measured:

nominal

Conc. based on:

not specified

Basis for effect:

other: sewage gas production volume

Duration:

30 d

Dose descriptor:

LOEC

Effect conc.:

500 mg/L

Nominal / measured:

nominal

Conc. based on:

not specified

Basis for effect:

other: sewage gas volume reduced and fermentation delayed

Details on results:

At 50 mg/L HEDP showed no effects.
At 100 and 200 mg/L the start of fermentation was delayed, but constant gas volume was achieved in the same period as in the control.
At 500 mg/L HEDP, the system was strongly disturbed, as indicated by a late beginning of fermentation, and greatly reduced sewage gas production volume.

Conclusions:

A non-standard study of effects on sewage treatment plant micro-organisms was conducted according to generally accepted scientific principles but lacks detail in the study report. The result of a lack of effects on respiration up to 200 mg/L provides reliable evidence.

Description of key information

No study of microbial inhibition is available for the DTPMP ammonium salt. The available data provide a general weight of evidence of a lack of inhibition of micro-organisms at concentrations up to ca. 200 mg/L. Furthermore a reliable ASRI study is available for an ammonium salt of a structurally analogous phosphonate (EC₅₀ >1000 mg/L).

Additional information

The assessment of the toxicity of the substance to microrganisms for the purposes of hazard classification is based on the available test result determined with the analogous substance ATMP-xNH₄ (CAS 34274-28-7).

 

DTPMP-xNH₄ will dissociate when it is released into aqueous environments to yield DTPMP and ammonia. DTPMP and ammonia are therefore be treated separately for the purposes of deriving PNEC_STP.

ATMP-xNH₄:

A 30-minute EC₅₀ value of >1000 mg/L has been obtained in an activated sludge respiration (ASRI) test with ATMP-xNH₄.

DTPMP:

A reliability 4 EC₅₀ value of >2500 mg/l has been determined for the effects of DTPMP acid on the bioluminescence of the bacterium Photobacterium phosphoreum (Grohmann and Horstmann 1989).

A non-standard study of effects on sewage treatment plant micro-organisms was conducted according to generally accepted scientific principles but lacks detail in the study report. The study reports a lack of effects on respiration for 30 days up to 200 mg/L with ATMP and HEDP.

The data can be directly read across to DTPMP-xNa because they are structural analogues and because the effects may be due acidic effects.

All these studies have been used as weight of evidence to determine the low toxicity of DTPMP-xNa to micro-organism toxicity. The data from ATMP and HEDP has been used to determine the PNEC being non-limit results.

Ammonia: Typical levels of free ammonia in municipal WWTPs range from ca. 12-50 mg/l in the WWTP collection system (Lehr, Jay; Keeley, Jack; Lehr, Janet Water Encyclopedia, Volumes 1-5. (section 1.4.49). John Wiley & Sons.). A NOEC of >50 mg/l, can therefore be predicted for ammonia toxicity to microorganisms.

DTPMP-xNH₄ will dissociate when it is released into aqueous environments to yield DTPMP and ammonia. DTPMP and ammonia are therefore treated separately for the purposes of deriving PNEC_STP. The PNEC_STP for ammonia has been derived from the data presented here and in section 7.6 of the CSR. The PNEC_STP for DTPMP has been determined using test data for DTPMP-H and read-across from structurally analogous substances. For hazard classification, DTPMP-xNH₄ has been assessed based on the available aquatic data for the whole substance (based on read-across data from the ammonium salt of ATMP, a structurally analogous substance).

The influence of the ammonium salt is discussed in IUCLID Section 6.0 Ecotoxicological Information and Section 7.0 of the CSR.

The acid and salts in the DTPMP category are freely soluble in water and, therefore, the DTPMP anion is fully dissociated from its cations when in solution. Under any given conditions, the degree of ionisation of the DTPMP species is determined by the pH of the solution. At a specific pH, the degree of ionisation is the same regardless of whether the starting material was DTPMP-H, DTPMP (1-3Na), DTPMP (5-7Na), DTPMP (4-8K), DTPMP (xNH₄) or another salt of DTPMP.

 

Therefore, when a salt of DTPMP is introduced into test media or the environment, the following is present (separately):

1. DTPMP is present as DTPMP-H or one of its ionised forms. The degree of ionisation depends upon the pH of the media and not whether DTPMP-H, DTPMP (1-3Na), DTPMP (5-7Na), DTPMP (4-8K), DTPMP (xNH₄), or another salt was used for testing.
2. Disassociated ammonium, potassium or sodium cations. The amount of ammonium, potassium or sodium present depends on which salt was added.
3. Divalent and trivalent cations have much higher stability constants for binding with DTPMP than the sodium, potassium or ammonium ions so would preferentially replace them. These ions include calcium (Ca²⁺), magnesium (Mg²⁺) and iron (Fe³⁺). Therefore, the presence of these in the environment or in biological fluids or from dietary sources would result in the formation of DTPMP-dication (e.g. DTPMP-Ca, DTPMP-Mg) and DTPMP-trication (e.g. DTPMP-Fe) complexes in solution, irrespective of the starting substance/test material.

In this context, for the purpose of this assessment, read-across of data within the DTPMP Category is considered to be valid.