Disodium 2-hydroxyethyliminodi(acetate)

Toxicity to soil macroorganisms except arthropods

Description of key information

In accordance with column 2 of REACH Annex X, the long term toxicity testing on invertebrates study does not need to be conducted as direct and indirect exposure of the soil compartment is unlikely.  The substance shows a low adsorptive (worst case log Koc = 1) as well as a bioaccumulative (log Kow = -8.27) potential. Hence, a relevant distribution into soil and a considerable exposure of soil macroorganisms is not expected.

Additional information

In Annex X of Regulation (EC) No 1907/2006, it is stated that long-term toxicity to terrestrial organisms shall be proposed by the registrant if the chemical safety assessment indicates the need to investigate further the effects of the substance and/or relevant degradation products on terrestrial organisms. Column 2 of Annex X states that studies do not need to be conducted if direct and indirect exposure of the soil compartment is unlikely. There are no ecotoxicity studies for terrestrial organisms relating to EDG and the requirement for terrestrial data is waived based on the low adsorption, low bioaccumulation potential, very low toxicity to aquatic organisms (extrapolated to terrestrial organisms), ready biodegradability and unlikely exposure to EDG in soil.

 

Adsorption

It is not expected that EDG will adsorb onto the organic fraction of soils, sediments or suspended solids due to the ionic structure of the substance. The worst-case calculated log Koc for this substance is 1 (see IUCLID section 5.4.1, Mensink, 2013). However, interaction with the mineral phase may be possible. This assumption is supported by the studies with the structurally comparable NTA conducted by Dunlapet al.,(1971) andBolton et al.,(1993) who demonstrated that Na₃NTA is neither strongly adsorbed by loam, clay-loam and sandy soils or marine surface sediments (Kp sediment-water = 1.6 L/kg). In addition, EDG and Na3NTA are highly water-soluble organic substances.

Bioaccumulation

The partitioning behaviour of EDG was estimated using the EPIWIN4.1 model (see IUCLID section 4.7, Mensink 2013). The log Kow was calculated to be -8.27, indicating limited potential for bioaccumulation.

In addition, it was determined that the partitioning behaviour of the structurally comparable Na₃NTA is pH-dependent and the estimated Log Kow for the different NTA species is highest at pH 1.4, with a value of -4.14; at pH 7, the log Kow reduces to -13.2. At pH 14, the estimated log Kow is -31.2. The substance’s high hydrophilicity is demonstrated by the very low log octanol-water partition coefficient (Log Kow) of -13.2 at a neutral pH. These low distribution coefficients and Log Kow indicate these substances have a low adsorptive and bioaccumulative potential.

Biodegradability

The substance is regarded as readily biodegradable (see IUCLID section 5.2). 

In addition, the Canadian Ministry of the Environment (CCME, 2010) provides additional evidence of the rapid degradation of NTA and products where it was reported that NTA is readily biodegraded in all environmental compartments even at low environmental temperatures. Therefore, biodegradation can be considered to be an important removal process in soil, sediment, surface water, and water treatment plants.

There are no identified uses of the substance which involve direct application to soil. Indirect exposure of soil organisms, for example via sewage sludge disposal to land or release of residual quantities of dilute EDG to sediment, is unlikely as the substance is readily biodegradable and has a very low sorption potential.

Toxicity

Furthermore, it is reasonable to assume that trends seen in aquatic toxicity are likely to be observed in terrestrial organisms. Reliable toxicity data are available for freshwater species representing fish, invertebrates, algae and a mollusc. Short-term (acute) exposures of EDG and Na₃NTA showed values generally > 100 mg/L. All trophic levels of aquatic organisms revealed similar sensitivities to EDG and Na₃NTA. Long-term exposures to invertebrates and fish revealed NOECs of 7.5 and >43 mg/L, respectively based on the values from Na3NTA. For EDG a NOEC for algae was concluded at 12 mg/L. These short- and long-term data, when considered with bioaccumulative and degradation information, result in EDG being non-classified and considered to be practically non-toxic to aquatic organisms. It is reasonable to assume that EDG will also be non-toxic to soil organisms.

Exposure

There are no identified uses of the substance which involve direct application to soil. Moreover, due to the high solubility, ready biodegradability and low octanol-water partition coefficient of EDG, this substance will not sorb to or persist in aerobic soil when used as directed under environmental conditions. 

In summary, based on the evidence of low adsorption, low bioaccumulative potential, very low toxicity to aquatic organisms (extrapolated to soil organisms) and ready biodegradability, the requirement for terrestrial data is waived.