Fenamiphos

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2005-08-03 to 2005-09-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

as revised in 1997

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Chemical name: Ethyl 3-methyl-4-(methylthio)phenyl (1-methylethyl)phosphoramidate

Analytical monitoring:

yes

Details on sampling:

Samples of test medium were analysed in suitably sized batches. No procedural recoveries were performed because the calibration line was prepared in Elendt M4 medium and as the samples were directly injected onto the chromatography system, the calibration standards were identical to the samples.

Vehicle:

no

Details on test solutions:

- Method: Under safelight conditions, the test substance (10 mg) was added directly to a volumetric flask containing Elendt M4 medium (700 mL). The contents of the flask were shaken vigorously and treated by ultrasound for 15 minutes, with periods of intermittent vigorous shaking every five minutes, before being made up to volume (1 L) and diluted to provide the test media.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Age at study initiation: juvenile, less than 24 hours old
- Method of breeding: Stock cultures of Daphnia magna were maintained in glass vessels containing approximately 0.8 litres of Elendt M4 culture medium in a temperature-controlled laboratory at nominally 20 ± 2 °C. A photoperiod of 16 hours light : 8 hours dark was maintained, with periods of subdued lighting at the beginning and end of each light phase. The culture medium was renewed at least twice each week. Cultures were fed daily with a suspension of the unicellular green alga, Chlorella vulgaris, to provide 0.1 to 0.2 mg carbon per daphnid, per day, except during the initial three days when a slightly lower ration was given. The applied culture conditions ensured that the stock animals reproduce by parthenogenesis.
- Source: laboratory culture, strain obtained from the Institute National de Recherche Chimique Appliqué (IRChA), France
- Feeding during test: no

ACCLIMATION
- Acclimation period: The day before the start of the study, all juvenile Daphnia were removed from the laboratory cultures. The following morning, juveniles produced by the gravid (egg-bearing) adult Daphnia were removed from the culture vessels and held in a separate holding vessel; these animals, which were less than 24 hours old, were used in the test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

none

Hardness:

246 mg /L CaCO3

Test temperature:

20.3 °C (mean)

pH:

7.7 (mean)

Dissolved oxygen:

101 % air saturation value

Salinity:

not applicable

Conductivity:

not specified

Nominal and measured concentrations:

Nominal: 0.427, 0.939, 2.07, 4.55 and 10 µg/L; Measured: 0.325, 0.659, 1.43, 3.34 and 7.02 µg/L (geom. mean measured)

Details on test conditions:

TEST SYSTEM
- Test vessel: glass dishes
- Volume of solution: 100 mL
- Aeration: no
- Renewal rate of test solution: 24 hours
- No. of organisms per vessel: 5
- No. of vessels per concentration: 4
- No. of vessels per control 4
- Biomass loading rate: 20 mL medium per organism

TEST MEDIUM: Elendt M4 Medium

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: darkness

EFFECT PARAMETERS MEASURED: immobility after 24 and 48 hours of exposure


RANGE-FINDING STUDY
A formulation trial and two range finding tests (the first of which was repeated because all of the Daphnia were immobile after 24 hours) were followed by the definitive test, which was conducted with five test concentrations plus a dilution medium control.
- Test concentrations: The range finding tests employed nominal concentrations of 0.1, 1 and 10 µg/l.
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.06 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95 % confidence interval: 0.943 - 1.43 mg/L

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.659 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Behavioural abnormalities: not reported
- Any other effects: not reported
- Effect concentrations exceeding solubility of substance in test medium: no

Results with reference substance (positive control):

The 48-hour EC50 to Daphnia magna was 0.7 mg/L: this was within the range typically obtained in the laboratory (0.3 to 0.8 mg/L).

Reported statistics and error estimates:

EC50 values were calculated using the SAFEStat LD50 application (SAS 8.2.). Logistic regression (Berkson, 1944) was performed using log mean measured concentrations and not assuming zero mortality in the control group. Confidence levels (95%) were calculated using the profile likelihood method (Williams, 1986). Also, each group was compared to control using one-tailed Fishers exact tests (Fisher, 1973).
The “no observed effect concentration” (NOEC) was derived by direct inspection of the data on the immobility of the animals. An incidence rate of more than 10 % is considered to be significant.

Validity criteria fulfilled:

yes

Conclusions:

In a semi-static test according to OECD TG 202 with Daphnia magna the 48-hour EC50 of the test item was determined to be 1.06 µg/L (geom. mean measured).

Executive summary:

The acute toxicity of the test item to Daphnia magna was assessed under static exposure Conditions in accordance with OECD TG 202. Information provided by the Sponsor indicated that the photolytic DT50 of Fenamiphos in water was 3.6 hours. Consequently, the test was conducted in darkness, with the preparation of the media and observation of the organisms under safelight. Groups of twenty Daphnia, less than 24 hours old, were exposed for 48 hours to a dilution of fenamiphos prepared at nominal concentrations of 0.427, 0.939, 2.07, 4.55 and 10 µg/l. The test media were prepared in Elendt M4 from a concentrated stock solution (10 mg/L), which was treated with ultrasound to aid dissolution. At the start of the test, the measured concentrations of the test item in samples of test media ranged from 74 to 86 % of their nominal values. After 48 hours, the measured concentrations were between 81 and 91 % of the initial values except at 2.07 µg/l, where the measured level was 65 % of its initial value. The overall measured levels (based on a geometric mean) were 0.325, 0.659, 1.43, 3.34 and 7.02 µg/L. All validity criteria of the guideline were fulfilled. Observations of the Daphnia in each control and test vessel were made after approximately 24 and 48 hours. After 48 hours, the lowest measured concentration resulting in 100% immobility was 3.34 µg/L and the highest concentration at which no immobilisation occurred was 0.659 µg/L. Based on these findings the following values have been determined: The 48-hour EC50 value was 1.06 µg/L, the  NOEC was 0.659 µg/L.

Description of key information

In a semi-static test according to OECD TG 202 with Daphnia magna the 48-hour EC50 of the test item was determined to be 1.06 µg/L (geom. mean measured).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

1.06 µg/L

Additional information

 

 

Key information

The acute toxicity of the test item to Daphnia magna was assessed under static exposure Conditions in accordance with OECD TG 202 (Taylor, 2005). Information provided by the Sponsor indicated that the photolytic DT50 of Fenamiphos in water was 3.6 hours. Consequently, the test was conducted in darkness, with the preparation of the media and observation of the organisms under safelight. Groups of twenty Daphnia, less than 24 hours old, were exposed for 48 hours to a dilution of fenamiphos prepared at nominal concentrations of 0.427, 0.939, 2.07, 4.55 and 10 µg/l. The test media were prepared in Elendt M4 from a concentrated stock solution (10 mg/L), which was treated with ultrasound to aid dissolution. At the start of the test, the measured concentrations of the test item in samples of test media ranged from 74 to 86 % of their nominal values. After 48 hours, the measured concentrations were between 81 and 91 % of the initial values except at 2.07 µg/l, where the measured level was 65 % of its initial value. The overall measured levels (based on a geometric mean) were 0.325, 0.659, 1.43, 3.34 and 7.02 µg/L. All validity criteria of the guideline were fulfilled. Observations of the Daphnia in each control and test vessel were made after approximately 24 and 48 hours. After 48 hours, the lowest measured concentration resulting in 100% immobility was 3.34 µg/L and the highest concentration at which no immobilisation occurred was 0.659 µg/L. Based on these findings the following values have been determined: The 48-hour EC50 value was 1.06 µg/L, the  NOEC was 0.659 µg/L.

 

Supporting information

Additionally, a supporting study of Surprenant (1988) on the acute toxicity of Fenamiphos towards aquatic invertebrates is available. The study followed the standard procedures presented in the EPA/OTS guidelines for testing the effects of chemicals on biotic systems and the US EPA 1985 standard evaluation procedures for acute toxicity test for freshwater invertebrates. The test was carried out in compliance with the GLP principles and no major deviations from the applied guidelines are reported. In the course of the study 20 organisms (10 per replicate) of Daphnia magna were exposed in a static test system for 48 h to fenamiphos concentrations of 1.0, 1.5, 2.4, 4.2 and 6.9 µg a.i./L (mean measured). The no-observed-effect-concentration (24 h) was 0.0024 mg as/L and the no-observed-effect-concentration (48 h) was < 0.0010, compared to the controls. The EC₅₀ (48 h) was determined to be 0.0019 mg as/L.

 

Conclusion

Based on the most current and reliable information (Taylor, 2005) the 48-hour EC50 of Fenamiphos towards Daphnia magna is determined to be 1.06 µg/L (geom. mean measured). This effect value is supported by data from a previous study of Surprenant (1988). In this study the EC50 (48 h) was 1.9 µg a.i./L (mean measured). Both effect values are in the same order of magnitude. Following worst case considerations, the most critical EC50 (1.05 µg/L) is considered for the hazard and risk assessment. This approach complies with the outcome of the Dossier ffor Fenamiphos according to Directive 91/414/EEC (April 2002) and the EU Renewal Dossier for Fenamiphos (December 2017).