Acetic acid, oxo-, sodium salt, reaction products with ethylenediamine and hydroxybenzenesulfonic acid monosodium salt, iron sodium salts

Biodegradation in water: screening tests

Description of key information

Fe(Na)EDDHA: Biodegradation, OECD 301A: Not readily biodegradable (10 - 20 % degradation after 28 days)
Fe(3K)EDDHSA: Biodegradation, OECD 301B: Not readily biodegradable (39 % degradation after 28 days, fulfilling the 10-day window) 
The test substance is regarded as ultimately biodegradable. 

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

No experimental investigations concerning the biodegradability of Fe(3Na)EDDHSA are available. Therefore, read-across from the structurally related substances Fe(Na)EDDHA (CAS 84539-55-9) and Fe(3K)EDDHSA (EC 462 -492 -6) is performed.

The biodegradability of the read-across substance Fe(3K)EDDHSA was investigated according to OECD Guideline 301B in compliance with the principles of GLP (L´Haridon, 2001). A mixed population of activated sewage sludge micro-organisms collected from the aeration stage of the water treatment plant Emeraude (France), which treats predominantly domestic sewage was used as inoculum. Sodium acetate was used as reference substance. The test material plus the reference substance in inoculated culture medium to give a final concentration of 10 mg carbon/L to act as toxicity control. A blank (inoculated culture medium) was run in parallel. Each test vessel was inoculated with the prepared inoculum at a final concentration of 12 mg suspended solids (dry weight). The study was conducted under aerobic conditions by aeration at the rate of 30 - 100 mL/min during the test. The pH was measured before the beginning of the test in the mineral medium and at the end of the test in all test suspensions. Sodium acetate attained 67 % degradation after 14 days thereby confirming the suitability of the inoculum and test conditions. The toxicity control attained 39 % degradation (based on ThCO2) at day 14, confirming that the test material was not toxic to the sewage treatment microorganisms used in this experiment. The test material attained 39 % degradation after 28 days and therefore cannot be considered to be "readily biodegradable" under the strict terms and conditions of OECD Guideline 301B. The 10 -day window started at day 4 and at the end (Day 14) 32 % degradation has occurred. All validity criteria were fulfilled.

The DOC Die-Away Test is a batch test method to determine the ultimate aerobic biodegradability of the read-across substance Fe(Na)EDDHA in water. Mixtures of the test substance, a defined inorganic medium and a non pre-adapted inoculum (e.g. activated sludge or effluent from a municipal wastewater treatment plant) are incubated and aerated at a temperature of 22 +/- 2 °C for up to 28 days (Schwarz, 2010). Samples are taken at regular intervals to determine the Dissolved Organic Carbon concentration (DOC). The mean value of two test assays was used to determine the final biodegradation rate after the regular exposure time. Thereby the test substance attained 10 - 20 % degradation. Based on the co-incubation with the reference substance aniline, it could be demonstrated that the test concentration used (20 mg/L DOC) was not toxic (inhibitory effect) on the sewage treatment bacteria flora. Aniline attained 91 % degradation after 14 days, indicating that the test system was suitable. In this experiment, the test substance was poorly biodegradable and is therefore considered as "not readily biodegradable" according to OECD criteria.