EDTA—Ethylenediaminetetraacetic Acid

Summary

EDTA is used at low levels in some fabric washing powders as a bleach stabiliser. It is also used in soaps as a stabiliser and in some liquid products to enhance the action of preservatives. EDTA has, however, many other industrial applications and its use in detergents accounts for only approximately 20% of the total use. Calculations based on the worst case estimates of sewage flows suggest that the concentrations in European sewage effluents of EDTA arising from detergents use should be in the range of 100–300 μg L^-1 and in receiving waters 10–30 μL^-1. Where industrial discharges are also present, total concentrations of EDTA could of course be considerably higher. In many cases however, the concentrations of EDTA actually found in European rivers (0–60/μL^-1) are well below the range predicted from the combined industrial and detergent uses.

Since EDTA has been shown to be subject to biodegradation under some conditions and the Fe III chelate also undergoes photodegradation, it should not persist indefinitely in receiving waters and soil. However, the rate of biodegradation seems to be too slow to ensure efficient removal in the normal two-stage sewage treatment processes. EDTA has a low toxicity to aquatic organisms and, in the concentration ranges found, should have no adverse effect on sewage treatment processes or aquatic life. It also has no potential for bioaccumulation. As a powerful seéquestrant, EDTA has the potential to mobilise heavy metals and to keep them in aqueous solution. This is, however, unlikely to be significant at realistic concentrations on stoichiometric grounds alone. Natural variations in pH and the concentrations of competing ligands and precipitating anions are likely to have a more significant impact on aqueous concentrations of heavy metals in the practical situation.

EDTA has a low toxicity to mammals and is a permitted additive for foodstuffs in a number of countries. The WHO recommends that the acceptable daily intake of EDTA for man is 2.5 mg kg^-1. Even assuming up to 25/μL^-1 EDTA in drinking water, the daily intake from drinking 2 liters of this water would be well below this limit and a large margin of safety exists. There is therefore no risk to human health.