Trisodium hydrogen ethylenediaminetetraacetate

Endpoint summary

Additional information

Edetic acid (EDTA) is mainly produced industrially and used as acid (H4-EDTA) and different sodium salts (mainly Na4-EDTA but also Na2- and Na3-EDTA). Other salts or metal complexes are produced in lower amounts (European Union, 2004 and 2004a). Each substance has the identical backbone structure which is substituted with four carboxylic groups resulting in a similar chemical reactivity. If edetic acid as well as the different salts are released to the environment the same ionic species are formed. The anionic form of EDTA is strongly capable to complex metal cations present in the environment to form stable chelate complexes (e.g. Fe3+, Co2+, Ni2+).

Based on the comparable chemistry of EDTA and its different salts the different substances are highly likely to share the same environmental behavior and toxicity. The cations of the salts (e.g. Na+, Ca2+) are not expected to contribute to the overall toxicity profile. Thus, a read-across from edetic acid as well as different salts to predict the hazard of Na3-EDTA is considered justified. This approach is in line with the EU Risk Assessment report for EDTA and Na4-EDTA (European Union, 2004 and 2004a). A detailed justification on read-across is attached in IUCLID Section 13.

For the hazard assessment of trisodium hydrogen EDTA (CAS 150-38-9) several studies performed with EDTA, Na4-EDTA, Na2H2-EDTA are available. All experimental data indicate low toxicity to aquatic organisms. The observed effects are mainly related to reduced pH in the test medium at very high concentrations and/or complexation of micronutrients which are essential for health of test species. Complexation of nutrients is especially problematic in algae tests since the demand of nutrients by the algae is very high during exponential growth.

The acute toxicity of EDTA to fish highly depends on water hardness, pH and metal speciation (European Union, 2004 and 2004a). The toxicity of EDTA complexes to bluegill sunfish was determined in a key study performed by Batchelder et al. (1980), taking into account water hardness and pH. The revealed LC50 values are in a range of 41 mg/L to 1592 mg/L. Consequently, and in line with the EU Risk Assessment (2004), the LC50 of EDTA is estimated to be higher than 100 mg/L, due to the fact that this predicted value represents the lowest LC50 at acceptable pH in a study performed in natural non-synthetic water.
Tests on the acute toxicity with Daphnia magna resulted in an EC50 (48 h) of 140 mg/L detected in a non-GLP study according to DIN 38412 with Na2H2-EDTA.
The results of four studies on freshwater green algae indicate that the predicted EC50 (72 h) for EDTA (acid form) and its salts are > 60 mg/L (measured) and can be estimated to be higher than 300 mg/L in studies where the complexation of nutrients was limited to a minimum.

The long-term toxicity of Na2H2-EDTA on Daphnia magna was measured in a reproduction test according to OECD 211 (GLP). After 21 days of exposure a NOEC of 25 mg/L based on reproduction was observed.

The toxicity of Na2H2-EDTA on microorganisms was tested in an activated sludge respiration inhibition test according to OECD guideline 209 (van Ginkel & Stroo, 2000). The EC50 (30 min) was measured to be > 500 mg/L. For Na4-EDTA a similar low toxicity on activated sludge was measured in a respiration inhibition test according to ISO 8192. A test concentration of 1000 mg/L caused no effects on the respiration rate of microorganisms resulting in an EC10 (30 min) > 1000 mg/L.

In conclusion the ionic species of EDTA are of low toxicity to aquatic species.