Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

EDTA is not found to be readily biodegradable according to OECD criteria. In standard OECD 301D ready biodegradability tests with natural river water as inoculum it was shown that EDTA complexes with a stability constant lower than 10E14 like EDTA-Na4, EDTA-CaNa2, EDTA-MgNa2 etc. less than 60% biodegradation was observed after 28 days indicating that these substances should indeed not be classified as readily biodegradable. In these same tests however > 60% biodegradation was observed when these tests are prolonged to day 60 (Ginkel, 2018) indicating that these compexes, having stability constants < 10E14, are ultimately biodegradable and should be classified as "not persistent". EDTA-CaNa2 has a stability constant < 10E14 and is therefore under the conditions applied considered to be inherently biodegradable fulfilling specific criteria.

Complexes with a stability constant >= 10E14 like EDTA-CuX complexes (where X stands for K2, Na2 or (NH4)2) should be considered "Completely and inherently biodegradable". The dissociation rates are however considered too low to allow classification as not persistent.

Additional information

EDTA is not readily biodegradable according to OECD criteria. It was shown that with natural river water as inoculum, in standard OECD 301D tests, EDTA complexes with a stability constant lower than 10E14 like EDTA-Na4, EDTA-CaNa2, EDTA-MnK2 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 < 10E14, are not persistent.

This stability constant threshold of 10E14 will be dependent on the concentration balance between the starting complex and free metal ions (alkali and alkaline earth metals). The lower the starting concentration of the EDTA-metal complex the higher this stability constant threshold for biodegradation. Complexes with a stability constant >= 10E14 like EDTA-CuX complexes (where X stands for K2, Na2 or (NH4)2) should be considered "Completely and inherently biodegradable". The dissociation rates are however considered too low to allow classification as not persistent.