Acute toxicology of sodium nitrilotriacetic acid (NTA) and NTA-containing detergents to marine organisms

Abstract

Static acute toxicity tests were conducted at 20°C and 20% salinity with (CH2COONa)3N-H2O (NTA) and two NTA-containing commercial household synthetic detergents (syndets), using adults or juveniles from eleven species of marine fishes and invertebrates. Concentrations of NTA in the medium allowing 50 per cent survival of individual test species in 168 h, = TL50 (168 h) values, ranged between 1800 mg 1−1 for grass shrimp, Palaemonetés vulgaris, and > 10,000 mg 1−1 for quahaug clam, Mercenaria mercenaria. Intermediate in sensitivity to NTA were hermit crab, Pagurus longicarpus (1875 mg 1−1); scup (fish), Stenotomus chrysops (2200 mg 1−1); common starfish, Asterias forbesi (3000 mg 1−1); American lobster, Homarus americanus (3150 mg 1−1); bay mussel, Mytilus edulis (3400 mg 1−1); eastern mud snail, Nassarius obsoletus (5100 mg 1−1); sandworm, Nereis virens (5500 mg 1−1); mummichog (fish), Fundulus heteroclitus (5500 mg 1−1); and striped bass, Roccus saxatilis (5500 mg 1−1). The two syndets tested were considerably more toxic than NTA to marine organisms under identical assay conditions. Fishes were the least resistant group of organisms tested to syndets; sptl50 (168 h) values for teleosts ranged between 4.6 and 36.0 mg 1−1 total packaged product.Histopathology was investigated for grass shrimp, hermit crab, quahaug clam, sandworm, scup, striped bass and mummichog that survived high concentrations of NTA or syndets for 168 h. Among invertebrates, pathological changes were confined to digestive diverticula and kidney of shrimp exposed to 1000 mg 1−1 of NTA. With fishes, pathology in striped bass and mummichog was observed in proximal kidney tubules at NTA levels > 3000 mg 1−1. However, significant intestinal lesions were noted in mummichog at NTA levels as low as 1 mg 1−1. No pathology was observed among fish and invertebrates subjected to syndets.The effect of biomass, water temperature and salinity on acute toxicity of NTA and syndets to mummichogs was also investigated. Increasing the biomass between 0.5 and 10.0 g 1−1 of test medium was associated with increasing survival at any given concentration of syndet during a 48 h period; the reverse was observed for NTA. Within the salinity range 5–35%, mummichogs were most sensitive to NTA at comparatively low salinities; but syndets were most toxic at higher salinities. Water temperatures of 5° and 20°C had negligible influence on NTA- or syndet-induced mortality patterns.Mixtures of NTA and salts of cadmium or mercury were evaluated for toxicity to mummichog. An observed decrease in biocidal properties of Cd2+ was observed with increasing levels of NTA; concentrations as low as 10 mg 1−1 NTA effected a measurable depression in Cd2+ lethality. Results of studies with NTA—Hg2+ mixtures were inconclusive. Tests with mixtures of syndet and Cd2+ or Hg2+ demonstrated that toxicity to mummichog of these mixtures could be expressed as a simple summation of the toxicity of individual components.It is concluded that NTA might be hazardous to marine fishes and macroinvertebrates when used as a partial replacement for sodium tripolyphosphate in household syndets.