Disodium 2-hydroxyethyliminodi(acetate)

Endpoint summary

Additional information

Discussion

A review of the limited reliable toxicity test results for exposure of aquatic organisms resulted in data from studies that included freshwater species representing fish, invertebrates, algae, and a snail. No reliable marine data were available.

Fish

Acute exposure: Rainbow trout (EDG) as well as fathead minnow and bluegill sunfish (both Na3NTA) have been tested. The LC50 values were > 101 mg/L and >= 103 respectively. Soft waters showed higher toxicity compared to hard water.

Chronic exposure: A 32 week NOEC result of >54 mg/L for NTA for survival and reproduction for the fathead minnow was concluded. This 32 week NOEC would correspond to > 43.4 mg/L EDG. Birge et al. (1979) exposed rainbow trout embryos. The 27d LC50 for 50 mg/L hardness test = 90.5 mg/L and, for 200 mg/L hardness test the LC50 = 114 mg/L.

Invertebrates

Acute exposure: The guideline study with Daphnia magna with EDG showed a measured EC50 value of > 105 mg/L. In addition, comparable LC50 results of 80 and 115 mg/L Na3NTA were obtained for the amphipod, Gammarus pseudolimnaeus, in soft water.

Adult snails in soft and hard dilution waters showed 96hr TLm of 400 ppm for soft water and 560 ppm for hard water.

Chronic exposure: 21 week NOEC results of 9.3 mg/L Na3NTA for survival for the amphipod, Gammarus pseudolimnaeus. This 21 week NOEC (survival) would correspond to 7.5 mg/L EDG. In addition, exposed snails (Helisoma trivolvis) for 120 days showed a NOEC of 12.5 mg/L Na3NTA.

Algae

Toxicity data for algae of substances with chelating properties should always be considered with care. Direct toxicity or indirect toxicity via (micro)nutrient deprivation might not always be clearly demonstrated in algal studies. From the available information - incl structural analogue Na3NTA- it can be concluded that EDG is not acutely nor chronically toxic to algae (chronic endpoint > 10 mg/L). However, it was shown that both hardness (Weaver, 1967) as well as the nutrient composition of the test medium (Millington, 1988) can affect the outcome; soft water showing higher toxicity, ISO/BBM medium showing less toxicity compared to OECD or EPA medium composition.

Microorganisms

Swisher et al. (1967) presented results from continuous and semicontinuous biodegradation study for NTA and is considered the Key Study as the other available studies have to be indicated as unreliable. Results indicated a NOEC of > 270 mg/L Na3NTA (corresponding to > 232 mg/L EDG).

Reliable toxicity data are available for freshwater species representing fish, invertebrates, algae, microorganisms and a mollusc. Short-term (acute) exposures of EDG and Na₃NTA showed toxicity values generally > 100 mg/L. All trophic levels of aquatic organisms revealed similar sensitivities to EDG and Na₃NTA. Long-term exposures to invertebrates and fish revealed NOECs of 7.5 and >43 mg/L, respectively, based on the values from Na3NTA. For EDG a NOEC for algae was concluded at 12 mg/L.

These short- and long-term data, when considered with bioaccumulative and degradation information, result in EDG being non-classified and considered to be practically non-toxic to aquatic organisms.