EDTA

ethylenediaminetetraacetic acid (EDTA)

EDTA acid was patented in Germany in 1935 by F. Munz. The molecule is a substituted diamine usually marketed as its sodium salts. At room temperature it occurs as a white powder. It is a powerful complexing agent of metals and a highly stable molecule, offering a considerable versatility in industrial and household uses2. Since it is applied predominantly in aqueous medium, it is released into the environment through wastewaters.

Notes

EDTA is mainly used in detergents and in the pulp and paper industry. Its use in Europe has increased in recent years from 26.000 tons in 1992 to 32.550 tons in 1997. Yearly 266 tonnes end of in river waste waters.

In natural environments EDTA occurs as metal–EDTA complexes. It is very stable molecule, which is not very biodegradable. In fact in surface waters, the only significant process of removal of EDTA is the possibility of photolysis by sunlight. In water it has a high solubility of 500 g/l and is expected not to adsorb to particles or sediments. It doesn't bioaccumulate in any organism. EDTA however does bind metals and forms complexes with them. By doing so it enhances their mobility and bioavailability. EDTA can avoid the precipitation of heavy metals in solution and it can even cause heavy metals adsorbed in sediments to dissolve. The metal-EDTA complexes are assumed to be less toxic than the free metals themselves, except for Cadmium and Copper which might be more toxic when bound to EDTA.

Dufková19 studied the interaction of EDTA with photosynthetic organisms and found that EDTA is toxic, since it inhibits cellular division, chlorophyll synthesis and algal biomass production

Paradoxically, even though literature provides evidence of the persistence and low natural degradability of the chelate, the study of its toxicity is basically documented for acute toxicity bioassays and there is not sufficient information for the evaluation of chronic toxicity.