Trisodium 2-(carboxylatomethyl(2-hydroxyethyl)amino)ethyliminodi(acetate)

Endpoint summary

Description of key information

It is considered likely that HEDTA will behave similarly to EDTA. It is expected to poorly absorb across the gastrointestinal tract and will be excreted rapidly and largely unchanged. Dermal absorption is expected to be minimal.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

10

Absorption rate - dermal (%):

0.1

Additional information

There is limited information available on the toxicokinetics of HEDTA. The mode of action of this type of substance is thought to be due to its chelating capabilities. A higher chelating potential (and a large size) will reduce the potential for the substance to move across membranes and therefore reduce absorption and bioavailability. A review of the binding and ionisation potential of HEDTA and its structural analogue, EDTA, indicates that the behaviour of both is similar (Dwibedyet al., 1999). The rate constants for the reaction of both chemicals with OH radicals indicate an increase with increase in pH, with an opposite trend observed in a small mid-region of pH (between 1 and 3).

There are no studies on the absorption, metabolism, distribution or elimination (ADME) of HEDTA. Toxicokinetic studies in humans and rats indicate that the structural analogue, EDTA, is poorly absorbed across the gastrointestinal tract. The absorbed EDTA did not undergo any biotransformation and was rapidly excreted unchanged in urine. However it was noted that there as an increase in excretion of necessary ions such as Zn, Mn or Ca. It is considered likely that HEDTA will behave similarly to EDTA and on this basis it is expected to poorly absorb across the gastrointestinal tract and will be excreted rapidly and largely unchanged.

In a study on young, healthy, male volunteers, Foremanet al.(1954) investigated the dermal absorption of CaNa2-EDTA. 3 mg of a mixture of 14C labelled and unlabelled substance was prepared in a water soluble base which was applied over an area of 100 cm2 for 24 hours under occlusive conditions. The maximum activity in the urine was 0.001% of the administered dose.