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Long-term toxicity to fish

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Reaction mass of bis(2-hydroxyethanaminium) sulfite and 2-(methylamino)ethanol - oxosulfane oxide (1:1)is soluble in water and dissociates to 2 -(methylamino)ethanol, (2- hydroxyethyl)ammonium and sulphite ions.

Since no studies on the aquatic toxicity of the substance are available, study reports and published literature about the toxic effects of 2-aminoethanol, 2 -(methylamino)ethanol and substances of the sulphite category have been consulted alternatively.

The most sensitive NOEC (1.2 mg/L) was derived after a 30-day exposure period of 2-aminoethanol (CAS 141-43-5) to the species Oryazis latipes [NITE, 1996]. The 100 day NOEC for reproduction, percent hatch and percent viability of Salvelinus fontinalis was determined to be 1.77 mg/L. The 100 day NOEC for survival, length and weight of this species was determined to be > 20 mg/L [Mayer et al., 1986].

The hazard assessment of 2 -(methylamino)ethanol (CAS 109-83-1) reveals neither a need to classify the substance as dangerous to the environment, nor is it a PBT or vPvB substance, nor are there any further indications that the substance may be hazardous to the envrionment. Therefore, a long-term toxicity testing in fish is not provided.

Reliable chronic toxicity data were reported in an early life stage study according to OECD guideline 210 using sodium sulphite (CAS 7757-83-7) as test substance [ECT, 2010]. Results show no adverse effects on hatching, post-hatch mortality, health, length and dry weight of surviving fish (Danio rerio). Consequently, a NOEC of ≥ 200.5 mg/L SO32- is proposed for this endpoint.

It should be noted, however, that the calculated NOEC for fish is almost a factor of 2 higher than the acute value of 149.6 mg SO32-/L. This is due to the fact that oxygen depletion caused acute toxicity, whereas the test design of the ELS test (aerated test media) prevents mortality of exposed fish due to oxygen depletion. A more realistic long-term NOEC is therefore an acute exposure concentration that:

-      does not reduce the pH of the test media below a level causing adverse effects

-      that does not reduce oxygen levels below unsafe levels at any point during the test.

An acute concentration of 84.1 mg SO32-/L did not cause a pH-drop in the test medium (pH range 6.1 - 6.8). Evaluating the oxygen levels in the acute tests that were conducted with sulphite compounds, significant O2 -depletion upon addition of the test substance only occured at concentration levels higher than 50 mg SO32-/L (test with K2SO3). Based on these findings, a more realistic long-term NOEC of 50 mg SO32-/L is put forward for the environmental classification and effects assessment of sulphite compouds.