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Short-term toxicity to aquatic invertebrates

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Description of key information

48h-EC50 Daphnia magna: 1.1 mg/L (OECD 202/EU C.2, GLP, read-across from structural analogue)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
1.1 mg/L

Additional information

The read-across hypothesis is based on the assumption that source substances and target do have comparable aquatic toxicity. Source substances and target are all alkyltriphenylphosphonium halogen salts. Source substance 1 and target do have as identical organic moiety the n-Butyltriphenylphosphonium ion, whereas source substance 2 has the Ethyltriphenylphosphonium ion. Source substance 2 and target do have bromide as counterion, whereas source substance 1 has chloride as counterion.

However, all substances are soluble in water. When dissolved, the organic moieties and the counterions act individually. The Daphnia magna 48h-EC50 values for n-Butyltriphenylphosphonium chloride and Ethyltriphenylfosfonium bromide are almost identical, 1.1 and 1.4 mg/L respectively, demonstrating that neither the kind of counterion - chloride instead of bromide - nor the minor variation in the length of the saturated alkyl chain - n-butyl instead of ethyl - significantly change the acute toxicity to aquatic invertebrates. Thus, read-across to a substance which is also an alkyltriphenylphosphonium halogen salt and is identical either in the organic moiety or in the halogen acting as counterion is justified.

The acute toxicity of test items n-Butyltriphenylphosphonium chloride and Ethyltriphenylphosphonium iodide to Daphnia magna was studied under static conditions according to OECD Guideline 202 (1984) and EU method C.2 (1992).

n-Butyltriphenylphosphonium chloride:

- 24h-EC50: 3.0 mg/L (95% confidence interval 2.6 and 3.7 mg/L).

- 48h-EC50: 1.1 mg/L (regression line: log10(conc.)=0.00+(probit-3.44)/33.51).

- n-Butyltriphenylphosphonium chloride did not induce immobilisation of Daphnia magna at 1.0 mg/L after 48 hours of exposure (NOEC).

These values are read across as key information to n-Butyltriphenylphosphonium bromide without molecular correction.

Ethyltriphenylfosfonium bromide

- 24h-EC50: 3.7 mg/L (95% confidence interval 2.9 and 6.9 mg/L).

- 48h-EC50: 1.4 mg/L (95% 1.1 and 1.6 mg/L)

- A NOEC value could not be determined, but based on the results of the range-finding test and the final test, the NOEC was expected to be on the upper site of a range between 0.1 and 1.0 mg/L.

These values are read across as supporting information to n-Butyltriphenylphosphonium bromide without molecular correction.