Registration Dossier
Registration Dossier
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EC number: 231-982-0 | CAS number: 7783-18-8
Ecotoxicological Summary
Administrative data
Hazard for aquatic organisms
Freshwater
- Hazard assessment conclusion:
- no hazard identified
Marine water
- Hazard assessment conclusion:
- no hazard identified
STP
- Hazard assessment conclusion:
- no hazard identified
Sediment (freshwater)
- Hazard assessment conclusion:
- no hazard identified
Sediment (marine water)
- Hazard assessment conclusion:
- no hazard identified
Hazard for air
Air
- Hazard assessment conclusion:
- no hazard identified
Hazard for terrestrial organisms
Soil
- Hazard assessment conclusion:
- no hazard identified
Hazard for predators
Secondary poisoning
- Hazard assessment conclusion:
- no potential for bioaccumulation
Additional information
Conclusion on classification
Studies on the acute aquatic toxicity of ammonium thiosulfate are available for three trophic levels (algae, invertebrates, fish), whereas studies on the chronic aquatic toxicity of ammonium thiosulfate are only available for algae. Thus, additionally read-across to thiosulfate and sulfite/disulfite substances and ammonium cations is applied.Upon contact with water, salts of sulfur oxyacids including ammonium thiosulfate dissociate into sulfur oxyacid anions and the respective counterions.
Ammonium is a natural component of the environment and found in soil, air, and water.Ammonium is essential for many biological processes, serves as a precursor for amino acid and nucleotide synthesis and provides e.g. a source of nitrogen for plants. Ammonium is produced by bacteria in water and soil from decomposition of organic matter, including plants, animals and animal wastes. Ammonium goes through biochemical transformations in soil and water as part of the nitrogen cycle, is rapidly degraded, i.e. mineralized by numerous species of bacteria, and therefore not expected to accumulate in the environment. Based on acute and chronic effect concentrations, fish, aquatic invertebrates and algae do not appear to be sensitive at concentrations around short- and long-term aquatic hazard classification criteria of Regulation (EC) No 1272/2008.
Thiosulfate anions are unstable under environmentally relevant conditions and will disproportionate to sulfite. Acute and long-term toxicity data for thiosulfate and sulfite/disulfite substances are available for three trophic levels. The lowest LC/EC50 for fish, crustacean or algae is a 72-h ErC50 of 36.8 mg SO32-/L (based on sulfite), observed for the effect of disodium sulfite on the growth rate of Desmodesmus subspicatus in a guideline test (BASF, 1989). However, a pH decrease was observed at the level of the derived EC50 so that it cannot be excluded that observed toxicity was caused by it. The lowest LC/EC50 of acute toxicity tests with controlled pH and oxygen concentrations is the 48-h EC50 of 124.2 mg SO32-/L derived for the immobilization of Daphnia magna by ammonium thiosulfate in a guideline test (Springborn Binomics Inc, 1986), and this EC50 is selected as acute ecotoxicity reference value for classification.
The lowest chronic NOEC/EC10 for freshwater fish, invertebrates or algae from a standard test is the 72-h EC10 of 28 mg SO32-/L for the effect of disodium sulfite on the growth rate of Desmodesmus subspicatus (BASF, 1989), and this value was selected as chronic reference value for classification.
Since ammonium thiosulfate is an inorganic substance, biodegradation is not relevant.
For the classification of ammonium thiosulfate, the acute and long-term ecotoxicity reference values of 124.2 and 28 mg sulfite/L are converted to mg (NH4)2S2O3/L, resulting in 229.9 mg/L and 51.8 mg/L ammonium thiosulfate, respectively. Based on the acute ecotoxicity reference value and classification criteria of Regulation (EC) No 1272/2008, Table 4.1.0 (a), ammonium thiosulfate does not meet classification criteria of Acute (short-term) aquatic hazard (acute reference value > 1 mg/L). Taking into account the chronic ecotoxicity reference value, ammonium thiosulfate does also not meet classification criteria of Chronic (long-term) aquatic hazard (chronic reference value > 1 mg/L) in accordance with Table 4.1.0 (b(i)).
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