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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

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Diss Factsheets

Ecotoxicological information

Ecotoxicological Summary

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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 aquatic toxicity of potassium thiosulfate are not available and thus, read-across to sulfite/disulfite and thiosulfate substances is applied.Upon contact with water, salts of sulfur oxyacids including potassium thiosulfate dissociate into sulfur oxyacid anions and the respective counterions. Only the properties of the thiosulfate anion are considered a relevant determinant of environmental toxicity since potassium cations are essential and have a very low potential for toxicity to freshwater and saltwater organisms.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 potassium thiosulfate is an inorganic substance, biodegradation is not relevant.

For the classification of potassium thiosulfate, the acute and long-term ecotoxicity reference values of 124.2 and 28 mg sulfite/L are converted to mg K2S2O3/L, resulting in 295.3 mg/L and 66.6 mg/L potassium thiosulfate, respectively. Based on the acute ecotoxicity reference value and classification criteria of Regulation (EC) No 1272/2008, Table 4.1.0 (a), potassium 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, potassium 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)).