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EC number: 205-381-9
CAS number: 139-89-9
toxicity of trisodium HEDTA to aquatic organisms was investigated in
studies on the substance itself, as well as on the structural analogues
disodium EDTA, tetrasodium EDTA, calcium disodium EDTA, manganese
disodium EDTA and EDTA. A justification for the read across can be found
in Section 13 of the IUCLID file.
HEDTA and EDTA are strong complexing agents. In the aquatic environment,
the ionised substances will rapidly form complexes with available metals
or trace nutrients. The complex stability constants with heavy metals
are several orders of magnitude higher than those of Ca or Mg complexes.
After addition of HEDTA or EDTA (as acid, Na-salt or Ca-salt) to water,
the concentration of uncomplexed trace metals present in the water
therefore decreases drastically. If enough HEDTA or EDTA is available,
Ca/Mg complexation will also then occur. Uncomplexed HEDTA or EDTA is
only found when it is present in over-stoichiometric concentrations (EU
Risk Assessment EDTA, 2004).
toxicity of the chelants HEDTA and EDTA to aquatic organisms is thought
to be based on their disturbance of metal metabolism. Due to the complex
nature of the EDTA-metal interactions, the impact may vary from one
environment to the other, depending on metal concentration, pH, nature
of the sediment, concentration of organics, etc. (EU Risk Assessment
EDTA, 2004). In laboratory settings, the ability of HEDTA or EDTA to
bind metals and nutrients in the test media causes nutrient deficiency
by reducing the essential concentration of different ions.
the acute toxicity of trisodium HEDTA and its structural analogues to
fish and Daphnia appear to be in the same order or magnitude, mainly
influenced in laboratory settings by water hardness and pH. The lowest
value, retained for risk assessment purposes, is a 21 d NOEC of 25.6
mg Na3-HEDTA from a study in Daphnia magna (recalculated
value from the original 21 d NOEC of 25 mg/L expressed as Trilon BD,
algae, toxicity could clearly be demonstrated to be secondary effects
linked to iron complexation in the medium. The EC50 values from studies
in algae were therefore not retained for risk assessment purposes.
toxicity of HEDTA on microorganisms is considered likely to be low based
on read-across to the structural analogue EDTA and one available study
of low quality on HEDTA. The toxicity of Na2-EDTA, a structural analogue
of the substance, on microorganisms in an activated sludge resulted in
an EC10 value after 30 minutes of >500 mg/L. Similar low toxicity was
observed in additional studies on activated sludge. Thus, inhibition of
degradation activity of activated sludge is not anticipated.
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