The implications of trace metal-nitrilotriacetetic acid speciation on its environmental impact and toxicology.

Substitution of nitrilotriacetic acid (NTA) for polyphosphates in detergents has brought questions concerning its potential toxicity and impact on trace metal distribution in the environment. A calculation based upon metal ligand equilibria, known environmental concentrations of NTA following extensive detergent usage, and the presence of competitive metal-binding ligands and trace elements demonstrates that NTA will be present almost completely as the calcium and magnesium chelates. An analogous estimate of the speciation of NTA in various toxicity studies demonstrates that the onset of chronic toxicity in feeding studies is coincident with the presence of significant concentrations of "free" NTA in the gastrointestinal tract. Massive doses of NTA over long periods of time cause reproducible renal tumors in rats, but dosages of 7500 ppm administered indefinitely are without measurable effect.