Phosphonic acid, monoethyl ester, sodium salt (1:1)

Endpoint summary

Additional information

The aquatic toxicity of Fosetyl-sodium is evaluated on the basis of short-term and long-term tests with species of three different trophic levels (algae, aquatic invertebrates, fish).

The acute aquatic studies, except for the acute fish study on Gobiocypris rarus, were conducted with Fosetyl-Sodium, technical grade with a content of 22.1% in the aqueous solution. The content of 22.1% in the technical concentrate was taken into account in the calculation of the ecotoxicological endpoints. All aquatic studies were conducted under accepted guidelines and GLP conditions.

Acute studies

Fish acute toxicity tests according to OECD guideline 203 were performed with the freshwater species rainbow trout (Oncorhynchus mykiss), and rare minnow (Gobiocypris rarus) in a static system for 96 hours. The study on rainbow trout tested five concentrations and a negative control, while the study on the rare minnow was conducted as a limit test with a nominal concentration of 100 mg/L. In both studies the measured concentrations of the test substance in test solutions was within +/- 20% of nominal concentrations. Therefore, results were based on nominal values. No mortality was observed in any of the tested concentrations and species, resulting in LC50 (96 h) values of > 100 mg/L (nominal; Oncorhynchus mykiss; equivalent to > 452 mgFosetyl-Sodium technical concentrate 22.1%/L), and > 100 mg/L (nominal; Gobiocypris rarus).

A short-term toxicity study on aquatic invertebrates according to OECD guideline 202 was performed on Daphnia magna in a static system for 48 hours. Five concentrations and a negative control were tested. The measured concentrations of the test substance in test solutions was within +/- 20% of nominal concentrations. Therefore, the result was based on nominal values. No immobility was observed in any of the tested concentrations, resulting in an EC50 (48 h) of > 121.6 mg/L (nominal; equivalent to > 550 mg Fosetyl-Sodium technical concentrate 22.1%/L).

The toxicity to aquatic algae was tested according OECD guideline 201 on the green freshwater algae Pseudokirchneriella subcapitata in a static system for 96 hours. Five concentrations and a negative control were tested. The measured concentrations of the test substance in test solutions was within +/- 20% of nominal concentrations. Therefore, the result was based on nominal values. No significant effect on the growth rate of the algae was observed in any tested concentration. Therefore, the 72 -hour ErC50 was > 100 mg/L (nominal; equivalent to > 452 mg Fosetyl-Sodium technical concentrate 22.1%/L).

Chronic studies

A long-term toxicity study on fish was conducted with Fosetyl-Sodium according to OECD guideline 215, which tested the effect of the test substance on the juvenile growth of the rare minnow (Gobiocypris rarus) in a semi-static system for 28 days. The fish were exposed to five concentrations and a negative control. The measured concentrations of the test substance in fresh and aged test solutions was within +/- 20% of nominal concentrations. Therefore, the result was based on nominal values. No mortality, abnormal behaviour, and effects on the growth were observed during the exposure period. Thus, the 28-day LOEC and NOEC values were > 100 mg/L and ≥ 100 mg/L, nominal, respectively.

A long-term toxicity study on aquatic invertebrates was performed according to OECD guideline 211, that tested the effects of Fosetyl-Sodium on reproduction and immobility of Daphnia magna in a semi-static system for 21 days. The daphnids were exposed to a limit concentration of 10 mg/L and a negative control. The measured concentrations of the test substance in fresh and aged test solutions was within +/- 20% of nominal concentrations. Therefore, the result was based on nominal values. No significant effects on reproduction and immobility were observed during the 21 day exposure period in Daphnia magna. Therefore, the 21-day NOEC value was ≥ 10 mg/L, nominal.

In the toxicity study on aquatic algae, conducted according to OECD guideline 201 on the green freshwater algae Pseudokirchneriella subcapitata in a static system for 96 hours, the 72-hour NOEC was ≥ 100 mg/L, nominal, based on growth rate inhibition.

The results of these tests are summarised in the table below:

Table 1. Results of acute and chronic aquatic studies on Fosetyl-Sodium

Species	Test system	Test duration (h)	Endpoint	Results (mg/L)	Purity of test substance
Oncorhynchus mykiss	static	96	LC50	> 100	22.1% (w/w), equivalent to 452 mg Fosetyl-Sodium technical concentrate (22.1%/L)
Gobiocypris rarus	static	96	LC50	> 100	97.6%
Daphnia magna	static	48	EC50	> 121.6	22.1% (w/w), equivalent to 550 mg Fosetyl-Sodium technical concentrate (22.1%/L)
Pseudokirchneriella subcapitata	static	96	ErC50	> 100	22.1% (w/w), equivalent to 452 mg Fosetyl-Sodium technical concentrate (22.1%/L)
Gobiocypris rarus	semi-static	28 (d)	NOEC	≥ 100	97.6%
Daphnia magna	semi-static	21 (d)	NOEC	≥ 10	97.6%
Pseudokirchneriella subcapitata	static	96	NOErC	≥ 100	22.1% (w/w), equivalent to 452 mg Fosetyl-Sodium technical concentrate (22.1%/L)

Furthermore, the effects of Fosetyl-Sodium on the respiration rate of aquatic microorganism in activated sludge were assessed in a study conducted according to OECD guideline 209.

No effects on respiration rate were observed after 3 h (EC50 > 1000 mg/L, nominal, equivalent to > 4524 mg Fosetyl-Sodium technical concentrate (22.1%/L)) in the study. As no toxicological effects on microorganisms are expected up to the water solubility for Fosetyl-Sodium, a disturbance in the biodegradation process of a sewage treatment plant is not anticipated.