Disodium [[N,N'-ethylenebis[N-(carboxymethyl)glycinato]](4-)-N,N',O,O',ON,ON']cuprate(2-)

Biodegradation in soil

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in soil: simulation testing

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:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
See chapter 13 for read-across jusification

Reason / purpose for cross-reference:

read-across source

Qualifier:

no guideline followed

Principles of method if other than guideline:

Laboratory study on biodegradation of EDTA in different agricultural soils over an incubation time of 4 to 45 weeks.

GLP compliance:

no

Test type:

laboratory

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch number of test material: 4813

RADIOLABELLING INFORMATION (if applicable)
- Radiochemical purity: 99%
- Specific activity: 2.54 mCi/mM
- Locations of the label: 14C-carboxyl-EDTA

Radiolabelling:

yes

Oxygen conditions:

aerobic

Soil classification:

not specified

Year:

1977

Soil no.:

#1

Soil type:

other: Brookston loam

pH:

6.8

Soil no.:

#2

Soil type:

other: Conover sandy loam

pH:

6.7

Soil no.:

#3

Soil type:

other: Spinks loamy fine sand

pH:

6.4

Soil no.:

#4

Soil type:

other: Miami sandy loam

pH:

6

Details on soil characteristics:

SOIL COLLECTION AND STORAGE
All soil samples were collected and stored in sealed plastic bags at 2 °C. All samples were taken in Michigan and each were a composite of subsamples collected at three locations within a 10 m2 area.

Soil No.:

#1

Duration:

4 - 45 wk

Soil No.:

#2

Duration:

4 - 45 wk

Soil No.:

#3

Duration:

4 - 15 wk

Soil No.:

#4

Duration:

4 - 15 wk

Soil No.:

#1

Initial conc.:

2.5 - 4.5 mg/kg soil d.w.

Based on:

test mat.

Soil No.:

#2

Initial conc.:

2.5 - 4.5 mg/kg soil d.w.

Based on:

test mat.

Soil No.:

#3

Initial conc.:

2.5 - 4.5 mg/kg soil d.w.

Based on:

test mat.

Soil No.:

#4

Initial conc.:

2.5 - 4.5 mg/kg soil d.w.

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Details on experimental conditions:

25 g fresh weight of soil was added to 125 mL Erlenmeyer flasks that had been fitted with rubber stoppers which supported a 2 mL plastic beaker containing 1 mL of 1N NaOH. The soils were adjusted to ~ field capacity. Microdrops of neutralized 14C-EDTA solutions were randomly distributed over the soil surface using a 28-gage needle on a 100 µL syringe. All soils were sealed and incubated at room temperature (25-27 °C). All of the reported data are means from duplicate or triplicate.

Key result

Soil No.:

#1

% Degr.:

65

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

45 wk

Key result

Soil No.:

#2

% Degr.:

70.5

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

45 wk

Soil No.:

#1

% Degr.:

44.5

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

15 wk

Soil No.:

#2

% Degr.:

43.5

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

15 wk

Soil No.:

#3

% Degr.:

32

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

15 wk

Soil No.:

#4

% Degr.:

44.5

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

15 wk

Soil No.:

#1

% Degr.:

11

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

4 wk

Soil No.:

#2

% Degr.:

12.2

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

4 wk

Soil No.:

#3

% Degr.:

11.3

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

4 wk

Soil No.:

#4

% Degr.:

10

Parameter:

CO2 evolution

Remarks:

[14CO2]

Sampling time:

4 wk

Transformation products:

no

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

no

Details on results:

14C-EDTA was (slowly) biodegraded to 14CO2 by all soils (varying in pH and texture) tested from a major agricultural EDTA use area. No detectable quantities of intermediates accumulated under aerobic conditions.

Generally, the variation between duplicates/triplicates was < 8%.

Conclusions:

EDTA is (slowly) biodegradable in soils.

Description of key information

According to the EU RAR for EDTA (60-00-4), no adsorption onto the organic fraction of soil is expected due to the ionic structure under environmentally relevant pH conditions. Furthermore, the substance is ultimately biodegradable.

Key information was obtained from the EU RAR (2004), with the addition of the study by Wen et al (2009). EDTA will slowly be degraded in soil depending on complexation, soil type and pH. >= 65% degradation in 45 weeks (read across)

Key value for chemical safety assessment

Additional information

Since no studies are available investigating the biodegradability of Disodium copper ethylenediaminetetraacetate (CAS No. 14025-15-1) in soil, the assessment was based on studies conducted with subcategory 1 member edetic acid (CAS No. 60-00-4) in a read across approach. This is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Grouping of substance and read across approach. Further justification for suitability of read across between Subcategory 1 members is given within the category justification attached to chapter 13.

For the determination of biodegradation in soil non-standard investigations under various conditions show that EDTA can be biodegraded in soil under aerobic conditions. The rate of EDTA degradation was determined in different agricultural soils after 4 - 45 weeks of exposure. While degradation rate was 10-12% only after 4 weeks the degradation continued showing 32-45% degradation after 15 weeks and >= 65% after 45 weeks incubation time. This indicates that EDTA is (slowly and completely) biodegradable in soil. Micronutrients should be slowly released to allow efficient uptake by plants. The degradation of EDTA is limited by the slow release of the micronutrient.

Based on the suitability of the read across approach this conclusion can also considered to be true for Disodium copper ethylenediaminetetraacetate (CAS No. 14025-15-1).