L-Aspartic acid, N,N'-1,2-ethanediylbis-

Toxicity to microorganisms

Description of key information

No activated sludge respiration tests were identified for EDDS acid (or its trisodium salt). However, in a test for biodegradability in sludge, 85% of trisodium EDDS was degraded after 28 days, demonstrating that the test substance did not significantly inhibit the activity of the sludge microflora (Lisec, 1993).
A 22-h NOEC and EC50 of 0.125 and 0.23 mg/L, respectively, were calculated for EDDS acid in the Microtox test (which measures the ability of a substance to inhibit the metabolic conversion of chemical energy to bioluminescence) in the marine bacterium Vibrio fischeri (Radix et al. 1999). [The bacterium used requires a saline environment, and therefore the results are only of limited relevance for assessing the potential toxicity to microorganisms residing in sewage treatment plants.]
However, in a test conducted according to OECD Guideline 209, no significant inhibition of the respiration rate was detected in an activated domestic sewage sludge treated with disodium EDTA at up to 500 mg/L ("referred as H4EDTA") after 30 minutes. Equimolar amounts of CaCl2 were added, thus calcium EDTA was formed in the stock solutions. Both the EC10 and NOEC values were concluded to be above 500 mg/L (van Ginkel and Stroo, 2000). The EU RAR (2004a,b) considers the EC10 of 500 mg/L determined in this study as the most relevant to use for deriving a PNEC.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

500 mg/L

Additional information

No activated sludge respiration tests were identified for EDDS acid (or its trisodium salt). However, in a test for biodegradability in sludge, 85% of trisodium EDDS was degraded after 28 days, demonstrating that the test substance did not significantly inhibit the activity of the sludge microflora (Lisec, 1993). However, relevant data on related compounds were identified in the literature.

In an agar inhibition test, with the fungi Aspergillus niger and Pycnoporus sanguineus and the bacterium Staphylococcus aureus, no growth inhibition was noted with 100 mM EDDS complexes with Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ or Pb²⁺. EDDS complexed with Hg²⁺at 10 mM slightly inhibited the growth of A. niger and S. aureus, but the zone of inhibition was equal to that of the free metal ion alone. Similarly, comparable zones of inhibition were seen with Cd²⁺-EDDS and Cd²⁺ when tested with P. sanguineus at 100 mM, although this chelate was slightly more toxic to A. niger than the free metal ion (presumably by facilitating the delivery of the toxic metal into the fungus). These results demonstrate that metal chelates of EDDS do not add to the toxicity of the free metal ions (Costa et al. 2008).

EDDS acid was tested for its potential toxicity (decrease in the ability of the bacteria to produce luminescence) in the bacterium Vibrio fischeri. Using a Microtox chronic test kit, which supplied all the reagents and the freeze-dried bacterium, the reconstituted bacterial cells were incubated for 22 h at 27oC with five unspecified concentrations of the test substance in a saline culture medium; each test was prepared in quadruplicate. Inhibition of luminescence (which is a combined function of cell division, metabolism, growth and luciferase induction) was measured photometrically. Full details of method not given. The 22-h EC10, EC20, EC50 and NOEC were 0.15, 0.17, 0.23 and 0.125 mg/L (Radix et al. 1999). [The bacterium used requires a saline environment, and therefore the results are only of limited relevance for assessing the potential toxicity to microorganisms residing in sewage treatment plants].

In a test conducted according to OECD Guideline 209, no significant inhibition of the respiration rate was detected in an activated domestic sewage sludge. Disodium EDTA was tested for 30 minutes in concentrations up to 500 mg/L ("referred as H₄EDTA"), however equimolar amounts of CaCl2 were added, thus CaEDTA was formed in the stock solutions. Thus, both the EC10 and NOEC values were concluded to be above 500 mg/L (van Ginkel and Stroo, 2000). The EU RAR (2004a,b) considers the EC10 of 500 mg/L determined in this study as the most relevant to use for deriving a PNEC.

In a bacterial oxygen consumption test conducted according to the method of Robra with disodium EDTA, the 30-minute EC10 was 55 mg/L (i.e. 48 mg/L EDTA) (BASF, 1990). A test on the growth inhibition of Pseudomonas putida with tetrasodium EDTA gave a 16-h toxic effect concentration (EC3) of 105 mg/L (i.e. 81 mg/L EDTA) (Bringmann and Kühn, 1976). [According to the citing source (EU, 2004a,b) no data on the test conditions were available for either test.]

The inhibition of cell multiplication with different protozoa was assessed in several studies, but apparently under identical experimental conditions. Stock and preliminary cultures of the test protozoa were fed with viable bacteria, whereas the test cultures were fed with inactivated bacteria. Tetrasodium EDTA was used as the test substance. The test medium (pH 6.9) contained 290 mg/L Ca(NO₃)₂.4 H2O and 70 mg/L Mg(NO₃)₂.6 H2O, therefore the EDTA was completely complexed with Ca and Mg. At the end of the test period, the cells were counted, and the toxic effect concentration (i.e. EC5) was determined as EDTA equivalents. The toxic effect concentrations were: 13 mg/L (20 h), 510 mg/L (48 h) and 28 mg/L (72 h) for Uronema parduczi, Chilomonas paramaecium and Entosiphon sulcatum, respectively (Bringmann, 1978; Bringmann et al. 1980; Bringmann and Kühn, 1980). The citing source (EU, 2004a,b) considered these studies were not well documented and felt that nutrient deficiency could not be excluded as the cause of these results.

[Due to their structural similarity, data on EDTA (and its simple salts) are considered relevant to use for understanding the effects of EDDS acid on the inhibition of microbial respiration rate, and is acceptable for using as read-across information].

References (for which no ESR has been created; need to move to reference list in CSR)

BASF (1990a). Sauerstoffkonsumptionstest nach Robra, Titriplex III (cited in EU, 2004a,b).

Bringmann G (1978). Bestimmung der biologischen Schadwirkung wassergefährdender Stoffe gegen Protozoen. Z. Wasser Abwasser Forsch. 11, 210-15 (cited in EU, 2004a,b).

Bringmann G and Kühn R (1976). Vergleichende Befunde der Schadwirkung wassergefährdender Stoffe gegen Bakterien (Pseudomonas putida) und Blaualgen (Microcystis aeruginosa). Gwf-wasser/abwasser 117, 410-413 (cited in EU, 2004a,b).

Bringmann G and Kühn R (1980). Bestimmung der biologischen Schadwirkung wassergefährdender Stoffe gegen Protozoen, II. Bakterienfressende Cilliaten. Z. Wasser Abwasser Forsch. Nr. 1, 26-31 (cited in EU, 2004a,b).

Bringmann G, Kühn R and Winter A (1980). Bestimmung der biologischen Schadwirkung wassergefährdender Stoffe gegen Protozoen. III. Saprozoische Flagellaten. Z. Wasser Abwasser Forsch. 13, 170-173 (cited in EU, 2004a,b).

Costa NSJ et al. (2008). Antimicrobial activity of ethylenediaminedisuccinate metal complexes. Short cummunication. Chemistry and Diversity 5, 2156 -2159.

EU (2004a). European Union Risk Assessment Report (RAR); edetic acid (EDTA). Vol. 49. European Chemicals Bureau (ECB). Final report available at http://ecb.jrc.ec.europa.eu/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/REPORT/edtareport061.pdf.

EU (2004b). European Union Risk Assessment Report (RAR); tetrasodium ethylenediaminetetraacetate (Na4EDTA). Vol. 51. European Chemicals Bureau (ECB). Final report available at http://ecb.jrc.ec.europa.eu/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/REPORT/na4edtareport062.pdf.

Lisec (1993) Adsorption/Desorption of E-4591.01 to Activated Sludge with 14C Analysis. Study No. WG-03- 002, LISEC Genk, Belgium (Unpublished report submitted by Procter and Gamble Manufacturing Pty Ltd) (cited in NICNAS, 2003).

NICNAS (2003). Full public report on trisodium ethylene diamine disuccinate. STD/1044. Available at http://www.nicnas.gov.au/publications/CAR/new/std/stdFULLR/std1000FR/std1044FR.pdf.

van Ginkel and Stroo (2000). Toxicity of EDTA to Activated Sludge. Final Research Report August 9, 2000 (cited in EU, 2004a,b).