Registration Dossier

Ecotoxicological information

Toxicity to microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
yes
Analytical monitoring:
no
Details on sampling:
not reported
Vehicle:
no
Details on test solutions:
no further information
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Inoculum source: Buckland sewage treatment works, Newton Abbot, Devon, UK (predominantly domestic sewage)
- Pretreatment: kept aerated and maintained at 20ºC
- Initial biomass concentration: suspended solids 5112 mg/L
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Post exposure observation period:
not reported
Hardness:
not reported
Test temperature:
20ºC
pH:
not reported
Dissolved oxygen:
not reported
Salinity:
not reported
Nominal and measured concentrations:
Nominal concentration: 100 mg/L as active acid.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: active acid
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
The % inhibition reported for this test substance after 3 h duration was 5.4%.
Results with reference substance (positive control):
- Result with reference substance was valid
- Relevant effect levels: EC50 19.5 mg reference substance/L
Reported statistics and error estimates:
not reported
Validity criteria fulfilled:
yes
Remarks:
The EC50 for the reference substance was in the expected range. The oxygen uptake in the blank control is not reported.
Conclusions:
The EC50 to WWTP micro-organisms was determined to be >100 mg/L as active acid, in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
HMDTMP is an example of the aminomethylenephosphonic acid class. In the context of the RAAF, read-across of environmental, ecotox human health and physicochemical data within the group of aminomethylenephosphonates is considered as Scenario 2.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The aminomethylenephosphonates are registered phosphonates which share a common chemistry incorporating alkyl backbones with one or more tertiary amine centres and multiple methylphosphonate groups present. HMDTMP acid (CAS 23605-74-5) has two aminobismethylphosphonate groups, connected by a hexyl chain. EDTMP acid (CAS 1429-50-1) has two aminobismethylphosphonate groups, connected by an ethyl chain. Typically, impurities include residual inorganic acids/salts and organic by-products from manufacturing.
As well as being structural analogues, both phosphonates have consistent chemical properties including high MW (492 and 436 respectively), very low log Kow (≤-4 for both substances) and are highly soluble in water. The substances generally possess similar physicochemical properties and are not readily biodegradable or bioaccumulative.
The sodium and potassium counterions of these phosphonates are not significant in respect of the properties under consideration and have been assessed in depth in the public literature. Additionally, the counterions are expected to dissociate when in contact with water, including atmospheric moisture.

3. ANALOGUE APPROACH JUSTIFICATION
The justification of the aminomethylenephosphonates as a group is primarily made on the grounds that the identified phosphonates share a common chemistry incorporating alkyl backbones with one or more tertiary amine centres and multiple methylphosphonate groups present. Both acid and certain salt forms of these phosphonates are substances for REACH registration.
In the present context the effect of the alkaline metal counter-ion (sodium or potassium) will not be significant. For ammonium salts, the role of ammonia is given due consideration.
In biological systems and the environment, polyvalent metal ions will be present, and the phosphonate ions show very strong affinity to them.
The aminomethylenephosphonates are consistent in their physicochemical properties. The acid and salt forms of all the phosphonates are all of relatively high solubility in water (in general, more than 100 g/l), very low octanol-water partition coefficient (<0). The relatively high proportions of the phosphonate groups relative to the number of carbon atoms confers something of an inorganic quality to the substances.
The aminomethylenephosphonates are susceptible to biodegradation but only small fractions are removed in standard tests. They undergo photodegradation and bind strongly and effectively irreversibly to substrates including soil and sediment. They show low bioconcentration in fish. 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.
The aminomethylenephosphonates are typically not of high ecotoxicity to fish and invertebrates under neutral conditions, probably due to low bioavailability. Effects caused in aquatic plants (algae) are due to complexation of minerals and is not relevant in the wider environment.

4. DATA MATRIX
A data matrix table of all the data available on the various aminomethylenephosphonates is available in Section 13 of the technical dossier.
Reason / purpose:
read-across source
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: active acid
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate

Description of key information

No study of toxicity to micro-organisms is available  for HMDTMP (4-7Na). A reliable study, performed with a Na/H salt of EDTMP, is available. The EC50 to WWTP micro-organisms was determined to be >100 mg/L as active acid, in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L

Additional information

5.4% inhibition was seen at 100 mg/L loading (in terms of active acid), thus the EC50 is >100 mg/L. No NOEC or EC5 was derived by the report authors, however in view of the low level of inhibition (approximately 5%) seen at a loading of 100 mg/l, it is considered acceptable to interpret this concentration as an approximation of the EC5 for the purpose of PNEC derivation.

The registration substance is part of an analogue group (aminomethylenephosphonates analogue group; see CSR for more details) which consists of several phosphonates that share a common chemistry incorporating alkyl backbones with one or more tertiary amine centres and multiple methylphosphonate groups present.

 

HMDTMP acid (CAS 23605-74-5) has two aminobismethylphosphonate groups, connected by a hexyl chain. EDTMP acid (CAS 1429-50-1) has two aminobismethylphosphonate groups, connected by an ethyl chain.

 

As well as being structural analogues, both phosphonates have consistent chemical properties including high MW (492 and 436 respectively), very low log Kow(≤-4 for both substances) and are highly soluble in water. The substances generally posses similar physico-chemical properties and are not readily biodegradable.

 

The sodium counterions of these phosphonates are not significant in respect of the properties under consideration and have been assessed in depth in the public literature.Additionally, the counterions are expected to dissociate when in contact with water, including atmospheric moisture.

 

Therefore, for the purpose of this assessment, read-across is considered valid. Further information on the analogue group and the validity of read-across are presented in the CSR Chapter 1.