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Environmental fate & pathways

Phototransformation in water

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Endpoint:
phototransformation in water
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
supporting study
Justification for type of information:
READ-ACROSS CATEGORY APPROACH
The complete Read-across justification text is attached in chapter 13 "Read-across Justification_2016" (two documents attached).
Read-across justification EDTA-DTPA-HEDTA aminocarboxylic acid-based metal chelants (2016). Category approach according to REACH Practical guide 6: How to report read-across and categories; REACH TGD, Chapter R.6: QSARs and grouping of chemicals.
Part 1: Physical Chemistry & Toxicology
Part 2: Environmental Fate & Ecotoxicology
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across source
Key result
% Degr.:
100
Sampling time:
24 h
Test condition:
Direct Photolysis
Remarks on result:
other: CAS 139-33-3
Key result
% Degr.:
74
Sampling time:
50 d
Test condition:
Exposure to sunlight
Remarks on result:
other: CAS 139-33-3
Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
supporting 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:
To investigate the photodegradation pathway of Fe-EDTA, an aqueous solution of the substance was irradiated with a xenon arc lamp.
The reaction mixture was sampled over a period of 4 days.
GLP compliance:
no
Radiolabelling:
yes
Light source:
Xenon lamp
Details on light source:
Wide spectrum 5500-W Xenon lamp
Details on test conditions:
To determine the extent of ferric EDTA removal from the environment by interaction with sunlight - i.e. photodegradation - the behaviour of aqueous solutions of ferric-1-14C-EDTA at pH 4.5, 6.9, and 8.5 under irradiation from a xenon lamp has been studied. 
Initial conc. measured:
0.002 mol/L
Key result
% Degr.:
100
Sampling time:
24 h
Test condition:
Direct photolysis
Details on results:
Carbon dioxide, formaldahyde, N-carboxy-methyl-N,N'-ethylenediglycine  (ED3A), N,N'ethylenediglycine (EDDA-N,N'), iminodiacetic acid (IMDA),  N-carboxymethyl-N-aminoethyleneglycine (EDDA-N,N), N-aminoethyleneglycine  (EDMA), and glycine have been identified as the major photodegradation products. No nitrilotriacetic acid (NTA) was detected during photodegradation.
The rate of photodegradation was pH dependent, being most rapid at pH 4.5. At a light intensity of 4000-ft candles and an initial concentration of 0.0016 M Fe(III)-EDTA removal was complete after 24 h of irradiation at either pH 4.5 or pH 6.9 and after 32 h at pH 8.5.
Endpoint:
phototransformation in water
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Study type:
not specified
Principles of method if other than guideline:
EDTA was disolved in natural lake water and photodegradation over a period of time was determined.
GLP compliance:
not specified
Radiolabelling:
not specified
Analytical method:
high-performance liquid chromatography
Details on sampling:
Exposure to Sunlight: Sampling volume was 10 mL and samples were taken first at the beginning, second after two weeks and thereafter samples were taken once a week.

Laboratory conditions: Sampling volume was 7 mL, further data are not available.
Buffers:
no data availble
Light source:
Xenon lamp
Light spectrum: wavelength in nm:
> 315 - < 400
Details on light source:
laboratory condition: two black lamps (Sylvania F40W/BL, black light 350), yileding 4.8 mW/cm2 at a distance of 100mm.

direct sunlight: The average intensity of solar radiation at the range 290-385 was 0.9 mW/cm2 in June, 0.92 mW/cm2 in July, 0.55 mW/cm2 in August and 0.30 mW/cm2 in September.
Details on test conditions:
laboratory conditions: Test solutionsin 500 mL glass bowls were placed on magnetic stirrers for mixing. Starting concnetration of EDTA was 0.13 mM in destilled and in lake water. The complexation by FeCl3 reduced pH from 6.5 to 3.1 in both media. Therefore one set was carried out where the pH was adjusted to 6.5 using NaOH

Exposure to sunlight: Four 100 L aquariums were used and each held 64 L of the test solution (destilled water in the dark, destilled water in the sunlight, lake water in the dark, lake water in the sunlight). Concentration of EDTA was 0.13 mM. Experiment lasted from June to September.
Duration:
14 wk
Initial conc. measured:
0.13 mmol/L
Reference substance:
not specified
Dark controls:
yes
Computational methods:
The rate of photodegradation of Fe(III)-EDTA seemed to follow first-order kinetics.
Preliminary study:
no data available
% Degr.:
50
Sampling time:
56.8 d
Test condition:
laboratory (lake water)
% Degr.:
50
Sampling time:
45 d
Test condition:
laboratory (destilled water)
Key result
% Degr.:
74
Sampling time:
50 d
Test condition:
Eposure to sunlight
Predicted environmental photolytic half-life:
< 50 d without pH adjustment, exposed to direct sunlight.
Transformation products:
not specified
Details on results:
The rate of photodegradation of EDTA was analysed in humic lake water and distilled water using exposure to sunlight, and in the laboratory using lamps emitting UV radiation in the range 315 -400 nm. Degradation was studied using Fe(III) complexes and sodium salts of chelates. Fe(III) complexes were illuminated at pH 3.1 and 6.5.
The result demonstrated that the rate of photodegradation of Fe(III) EDTA complexes seems to be pH dependent. In the laboratory experiments degradation occured much faster when the original pH was 3.1 rather than 6.5. The results indicated that in natural waters photodegradation of EDTA is dependent on its existence as Fe(III)-EDTA species. 0.13 mM Na2-EDTA did entirely disappear during 50 days from destilled water, wheras 74 % of NA2-EDTA degraded in lake water during this period of time.

Description of key information

Key value for chemical safety assessment

Additional information

As phototransformation in water is not a standard information requirement according to Regulation (EC) No. 1907/2006 and there is no indication from the Chemical Safety Assessment according to Annex I on the need to investigate further the fate and behavior of the substance (Annex X requirement), no further testing is considered necessary. Available supporting data for subcategory 1members indicate that some EDTA species, especially iron complexes, are to a certain degree photolysable.