Iron(3+) ion dipotassium 2-({2-[bis(carboxylatomethyl)amino]ethyl} (carboxylatomethyl)amino)acetate; hydrate

Endpoint summary

Description of key information

The environmental fate of EDTA-Fe(OH)K2 will be identical to that of EDTA-FeK. Only in highly concentrated solutions differences may occur. Because testing occurs normally in highly diluted solutions <1 g/L, it is considered justified to use the available fate data available for EDTA-FeK and EDTA-FeNa for read-across to EDTA-Fe(OH)K2.

For other EDTA-metal complexes there is more uncertainty also depending on the type of the test and this uncertainty can be compensated by e.g. an additional assessment factor.

Additional information

Information on the environmental fate of EDTA-Fe(OH)K2 is largely based on available information for EDTA and a number of its salts (e.g. EDTA-FeK, EDTA-Na4, EDTA-Na2H2, EDTA-CaNa2). A justification for the read-across between these substances and EDTA-Fe(OH)K2 is provided in a document attached to IUCLID section 13.

EDTA-Fe(OH)K2 is expected to be resistant to hydrolysis, neither strong acids nor alkalis cause any degradation. Several studies show that Fe(III)-EDTA is photodegraded in natural water. Due to its low log Kow, the substance does not significantly bioaccumulate in organisms. Based on the low log Kow together with the ionic structure of the substance under environmentally relevant conditions, no adsorption onto the organic fraction of sediments is expected and also found in a number of literature studies. A large number of degradation tests are available for EDTA and its salts. These tests show that EDTA is not readily biodegradable according to OECD criteria. In standard OECD 301D tests, EDTA complexes with a stability constant lower than 10E13 like EDTA-Na4, EDTA-CaNa2, EDTA-MgK2 etc. less than 60% biodegradation was observed after 28 days indicating that these substances should be not classified as readily biodegradable but in the same tests > 60% biodegradation was observed after 60 days in the prolonged (enhanced) tests indicating that these compexes, having stability constants < 10E13, are not persistent.

The EDTA-Fe(OH)K2 complex has a stability constant >10E12 and is therefore expected to be persistent according to OECD criteria, when tested in standard ready biodegradability tests. At lower environmentally more representative concentrations however significant biodegradation may occur. The level of the stability constant threshold dependents on the concentration balance between the starting complex and free metal ions (alkali and alkaline earth metals) in the matrix. The lower the starting concentration of the EDTA-metal complex the higher this stability constant threshold for biodegradation. EDTA-Iron complexes have a stability constant close to 10E23 and are expected to be persistent in standard ready biodegradability tests also at much lower test concentrations. As indicated EDTA-FeX complexes are very sensitive to photodegradation and at pH values above 7 free iron starts to precipitate as Iron hydroxide complexes liberating EDTA for biodegradation.

EDTA-H4 was found to be biodegradable in a modified SCAS test (according to OECD 302A; Ginkel, 1997) using slightly adapted conditions. Under standard STP conditions no significant removal in an activated sludge simulation test was observed. In soil using non-standard investigations 14% degradation was observed after 20 days under aerobic conditions.

 

Based on its low log Kow, EDTA-Fe(OH)K2 is not Bioaccumulative (not B).