Ethylenediamine tetraacetic acid (EDTA)

(endorsed 1996)

Guideline

Based on health considerations, the concentration of ethylenediamine tetraacetic acid in drinking water (as the free acid) should not exceed 0.25 mg/L.

General description

EDTA is a metal-complexing agent and may act to mobilise some heavy metals in the environment. It has occasionally been detected in drinking water supplies overseas at concentrations of up to 0.9 mg/L, but usually less than 0.1 mg/L.

EDTA is used widely in industry and agriculture. It is used in laundry detergents, water softening, electroplating, textile and paper production, as a food additive, and in cosmetics. Most of these uses will result in the release of EDTA to the aquatic environment. It is also used as a drug in chelation therapy, particularly in cases involving lead poisoning.

Typical values in Australian drinking water

EDTA has not been found in Australian drinking waters. It is included here to provide guidance in the unlikely event of contamination, and because it has been detected occasionally in drinking water supplies overseas.

Treatment of drinking water

There are no published reports on methods for the removal of EDTA from drinking water, although it may be oxidised by ozone.

Measurement

EDTA can be analysed by potentiometric stripping analysis (Fayyad et al. 1988). The limit of determination is 0.001 mg/L.

Health considerations

EDTA is poorly absorbed in the gut and does not form any significant metabolites. It does not accumulate in the body.

There is considerable clinical experience in the use of EDTA for the treatment of heavy metal poisoning.

Long-term feeding studies with rats and dogs reported no interference to mineral metabolism. Results from other studies have been affected by the formation of zinc complexes in the gastrointestinal tract, which prevents the zinc from being absorbed.

Derivation of guideline

The guideline value for EDTA (as the free acid) in drinking water was determined as follows:

$$\text{ 0.25 mg/L } = \dfrac{\text{ 1.9 mg/kg body weight per day x 13 kg x 0.1 }}{\text{ 1 L/day x 10 }}$$

where:

• 1.9 mg/kg body weight per day is the amount of EDTA that can be consumed from all sources per day without adverse effects (WHO 2003).

• 13 kg is the average weight of a child at 2 years of age (this value was used because of the possibility of complexation of zinc, an essential element for humans, and the need to protect the most sensitive group).

• 0.1 is the proportion of total daily intake attributable to the consumption of water.

• 1 L/day is the average amount of water consumed by a 2-year-old child.

• 10 is a safety factor to reflect the fact that the data for EDTA are relatively old (the World Health Organization assessment was dated 1974), and concern over zinc complexation.

The World Health Organization guideline value of 0.2 mg/L was based on a child body weight of 10 kg. The difference in guideline values is not significant.

References

Fayyad M, Tutunji M, Taha Z (1988). Indirect trace determination of EDTA in waters by potentiometric stripping analysis. Analytical Letters, 21:1425–1432.

WHO (World Health Organization) (2003). Edetic acid (EDTA) in drinking-water. Background document for preparation of WHO Guidelines for drinking-water quality. WHO, Geneva (WHO/SDE/WSH/03.04/58).