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Ecotoxicological information

Sediment toxicity

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Description of key information

EDG is readily biodegradable. Furthermore, EDG is expected not to accumulate relevantly in sediment, even when emitted directly to surface water. Therefore, EDG poses no hazard to sediment-dwelling organisms, and sediment-dwelling organisms will not be exposed to EDG, regardless of its use. In accordance with column 2 of REACH Annex X, testing does not need to be conducted.

Key value for chemical safety assessment

Additional information

In Annex X of Regulation (EC) No 1907/2006, it is stated that long-term toxicity to sediment 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 sediment organisms. Column 2 of Annex X states that studies do not need to be conducted if direct and indirect exposure of the sediment compartment is unlikely. There are no reliable ecotoxicity studies for sediment organisms relating to EDG and the requirement for sediment data is waived based on the low adsorption, low bioaccumulation potential, very low toxicity to aquatic organisms (extrapolated to sediment organisms), ready biodegradability and unlikely exposure to EDG in sediment, based on data for EDG and the structurally comparable Na3NTA (read across data).

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 Dunlap et al.,(1971) and Bolton 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 sediment. Indirect exposure of sediment 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 sediment organisms.

Exposure

There are no identified uses of the substance which involve direct application to sediment. 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 sediment 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 sediment organisms) and ready biodegradability, no tests on sediment organisms are required.