nickel(2+) disodium 2,2',2'',2'''-(ethane-1,2-diyldinitrilo)tetraacetate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

EDTA degrading strain (DSM 9103) was isolated and incubated to EDTA and EDTA complexes with Mg, Ca, Mn, Zn, Co, Cu and Pb.

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

not specified

Duration of test (contact time):

>= 24 - <= 48 h

Initial conc.:

1 mmol/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

The ability of strain DSM 9103 to degrade uncomplexed EDTA or EDTA complexes with Mg2+, Ca2+, Mn2+, Zn2+, Co2+, Pb2+, Cu2+, Cd2+, and Fe3+ was investigated by incubating resting cells with the appropriate EDTA species.

Key result

Parameter:

% degradation (test mat. analysis)

Value:

100

Sampling time:

10 h

Uncomplexed EDTA and its metal complexes with comparably low stability constants (below 10E16) were consumed at a constant rate down to very low concentrations. MgEDTA, CaEDTA, uncomplexed EDTA and MnEDTA was degraded to completion within less than 10 h.

Other EDTA (CuEDTA, CoEDTA, ZnEDTA, and PbEDTA) complexes were degraded only partly within 48 h (EDTA-Co complexes are more stable, stability constant K = 10E18.1).

In all cases a significant degradation of the chelating agent was observed only within the first 5-10 h, and then the rate of degradation slowed considerably or even ceased before the compound was exhausted. Within 48 h only 30% of the initially present CuEDTA had disappeared. In contrast, the extent of CoEDTA, ZnEDTA, and PbEDTA degradation was in the range of 55-85%.

Fe(III)EDTA and CdEDTA were not utilized by resting cells of strain DSM 9103 within 48 h of incubation, at least not at a detectable rate.

Interpretation of results:

inherently biodegradable

Conclusions:

EDTA-degrading bacterial strains degraded EDTA and EDTA complexes with Mg, Ca, Mn and Zn at a concentration of 1mM within 24 h. 1mM EDTA complexes of Cu, Zn, Co and Pb degraded in a range of 30 to 85 % within 48 h.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

This publication evaluates the biodegradability of uncomplexed EDTA and a wide range of EDTA metal complexes including heavy metal atoms. It is well documented and thus reliable for the assessment of the biodegradability.

Reason / purpose for cross-reference:

read-across source

Principles of method if other than guideline:

EDTA degrading strain (DSM 9103) was isolated and incubated to EDTA and EDTA complexes with Mg, Ca, Mn, Zn, Co, Cu and Pb.

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

not specified

Duration of test (contact time):

>= 24 - <= 48 h

Initial conc.:

1 mmol/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

The ability of strain DSM 9103 to degrade uncomplexed EDTA or EDTA complexes with Mg2+, Ca2+, Mn2+, Zn2+, Co2+, Pb2+, Cu2+, Cd2+, and Fe3+ was investigated by incubating resting cells with the appropriate EDTA species.

Key result

Parameter:

% degradation (test mat. analysis)

Value:

100

Sampling time:

10 h

Uncomplexed EDTA and its metal complexes with comparably low stability constants (below 10E16) were consumed at a constant rate down to very low concentrations. MgEDTA, CaEDTA, uncomplexed EDTA and MnEDTA were fully degraded within less than 10 h.

Other EDTA (CuEDTA, CoEDTA, ZnEDTA, and PbEDTA) complexes were degraded only partly within 48h

(EDTA-Co complexes are more stable, stability constant K= 10E18.1).

In all cases a significant degradation of the chelating agent was observed only within the first 5-10 h, and then the rate of degradation slowed considerably or even ceased before the compound was exhausted. Within 48 h 30% of the initially present CuEDTA for example had disappeared. In contrast, the degradation of CoEDTA, ZnEDTA, and PbEDTA was in the range of 55-85%.

In a further test described by the publication it was proved that free metal ions don't significnatly influence or lower the degradation rate.

Most of the EDTA metal complexes were degradated between 30% and 85% within 2 days. Thus an almost complete degradation after 28 days can be stated.

Validity criteria fulfilled:

not specified

Interpretation of results:

readily biodegradable

Conclusions:

This study shows that EDTA is inherently biodegradable and includes information about the degradation and stability of EDTA-metal complexes.
Most of the EDTA metal complexes were degradated between 30% and 85% within 2 days. Thus an almost complete degradation after 28 days can be stated.

Description of key information

For the assessment of the toxicity and environmental toxicity of the EDTA-NiNa2 complex it is important to identify how stable the complex is and how good its components can be degraded. As the Na+ ions are known to be non-toxic only the EDTA-Ni complex must be regarded.

It could be shown that EDTA metal complexes were degradated between 30% and 85% within 2 days. Thus an almost complete degradation after 28 days can be stated and EDTA.NiNa2 can be stated as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater