Nitrilotrimethylenetris(phosphonic acid)

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

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:

guideline study with acceptable restrictions

Remarks:

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

Total exposure duration:

30 d

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 the test material 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 the test material , 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:

guideline study with acceptable restrictions

Remarks:

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:

Results determined in Sapromat test, derived from comparison of biochemical oxygen demand

GLP compliance:

not specified

Analytical monitoring:

not specified

Vehicle:

no

Test organisms (species):

activated sludge

Details on inoculum:

Klaeranlage-Muenchen-Grosslappen

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

5 d

Remarks on exposure duration:

Whilst the exposure duration is not explicitly stated, BOD5 values are quoted and so it is deduced that the exposure period is at least 5 days duration.

Post exposure observation period:

Not reported

Hardness:

Not reported

Test temperature:

Not reported

pH:

Not reported

Dissolved oxygen:

Not reported

Salinity:

Not reported

Nominal and measured concentrations:

Not reported

Details on test conditions:

Test concentration series: 1, 5, 10, 50 and 100 mg/L

Reference substance (positive control):

no

Duration:

5 d

Dose descriptor:

EC0

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Validity criteria fulfilled:

not applicable

Conclusions:

A non-standard study of activated sludge respiration inhibition determined that the top concentration of 100 mg/L did not cause inhibition. The result is considered reliable.

Description of key information

EC0 200 mg/l activated sludge respiration inhibition (non-standard test) Henkel 1972

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

200 mg/L

Additional information

A number of non-standard studies are available giving evidence that ATMP has no inhibitory effect on micro-organisms at concentrations up to ca. 200 mg/L.

A study of seven Swiss WWTPs in 1996 shows a maximum concentration of ATMP in WWTP untreated influent of ca. 0.8 µmol/L, equivalent to ca. 0.26 mg/L.

The data set is further supported by the findings of an activated sludge respiration inhibition test conducted with an ammonium salt of ATMP (Worth and Mead, 1995). In this reliable study conducted in accordance with OECD Test Guideline 209, an EC50 >1000 mg/l was determined based on a 3-hour exposure period.

Read-across of microbial inhibition data between acid and salt forms in the ATMP Category

This substance is a member of a category of various ionised forms of the acid ATMP (CAS 6419-19-8).

The category hypothesis is that all the members are various ionised forms of the acid CAS 6419-19-8. In dilute aqueous conditions of defined pH, a salt will behave no differently to the parent acid, at identical concentration of the particular speciated form present, and will be fully dissociated. Hence some properties (measured or expressed in aqueous media, e.g. ecotoxicity) for a salt can be directly read across (with suitable mass correction, see Section 1.4 of the CSR) to the parent acid and vice versa. In the present context the effect of the sodium and potassium counter-ions will not be significant. The ammonium salt present a particular issue in respect of tests conducted at relatively high pH conditions where un-ionised ammonia is present, which drives the toxicity of ammonium salts under these conditions.

The behaviour of phosphonates in the environment will be profoundly affected by their concentration in water, the concentration and identities of metal ions, and the solids content per unit volume of water. From surface water through to soil a wide range of these parameters will be exhibited. Very few data concerning background concentrations of phosphonates in the environment are published, possibly due to the difficulties in detecting these substances at low concentrations in environmental media. Almost all natural waters contain more ions than the usual PEC values of the phosphonates.

In addition, in the environment the salt form is immaterial and speciation will occur in natural media. Similarly, all environmental related endpoints, use of buffered test media results often reflect a salt speciation relevant for ~pH7 only and it would be impossible to test specific salts associated with high and low pH. Detaching or attracting a proton does not change the chemical safety assessment of the molecule as long as no other part of the molecular skeleton is changed, because in studies or when there is exposure, the pH will control the identity of the form or forms present.

Therefore, it is considered appropriate to read-across between the ATMP category members and attribute the effects to the acid component of the phosphonate.

Please refer to the Chapter 5 Endpoint Summary, and CSR Section 1.4 and Chapter 7, for further information on read-across.