3-anilino-5-methyl-5-(4-phenoxyphenyl)-1,3-oxazolidine-2,4-dione;famoxadone (ISO)

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: ASTM Method E1415-91

Qualifier:

according to guideline

Guideline:

other: Pesticide Assessment Guidelines, Non-Target Aquatic Plant Studies, 122-2, 123-2

GLP compliance:

yes

Specific details on test material used for the study:

Purity: 97.8%
Batch: DPX-JE874-221

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

control and solvent control (acetone)

Details on test solutions:

A stock solution was prepared by dissolving the test substance in HPLC-grade acetone for a nominal concentration of 1010 mg famoxadone/L (1010 ppm). A 0.1 mL aliquot of this stock was diluted with filter-sterilized 20X AAP nutrient medium to make a second stock (= test rate) solution for a nominal concentration of 101 µg famoxadone/L (101 ppb). For the solvent control, 0.1 mL of HPLC grade acetone was added to 1 L of filter-sterilized 20X AAP nutrient medium. For the blank control, filter-sterilized 20X AAP nutrient medium was used. For the abiotic control, the nominal 101 µg/L test rate solution was used.

Test organisms (species):

Lemna gibba

Test type:

static

Water media type:

freshwater

Remarks:

20X AAP nutrient medium

Total exposure duration:

14 d

Test temperature:

24.8 to 25.4ºC

pH:

The pH measurements ranged from 7.49 to 7.62 on day 0 and from 8.42 to 9.52 on day 14

Nominal and measured concentrations:

Nominal: Blank control, solvent control, abiotic control, and 101 µg famoxadone/Liter
Mean Measured: 81 µg/L, which was 81% of the expected value

Details on test conditions:

The organisms were exposed for fourteen days without test medium renewal. A nominal concentration of 101 µg/L, an abiotic control, a solvent control, and blank (culture medium) control were arranged on a lighted shelf in an environmental chamber in a non-systematic design and re-positioned each working day. Each nominal 101 µg/L test rate, blank control, solvent control, and abiotic control was tested as three replicates. Frond counts were made on days 0, 2, 4, 7, 9, 11, and 14. Biomass was determined at the completion of the test combining all three replicates for each of the test rate, blank control, and solvent control.

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

> 101 µg/L

Nominal / measured:

nominal

Basis for effect:

biomass

frond number

Details on results:

The organisms were exposed for fourteen days without test medium renewal. The effects were expressed as inhibition in mean healthy frond count and biomass relative to the pooled blank and solvent controls on day 14 of the definitive test.

The results are as follows:
Healthy Frond Count -2.1% inhibition (95% C.L = -17.6 to 12.0)
Biomass 1.7% inhibition (95% C.L = -6.4 to 8.9)

The Welch's t-test indicated no significant inhibition at the nominal 101 µg/L rate for the definitive test.

Validity criteria fulfilled:

yes

Conclusions:

14-day EC50 (Lemna gibba) > 101 µg/L (based on healthy frond count and biomass)

Executive summary:

A study was conducted to determine the effect of famoxadone on the growth and reproduction of Lemna gibba G3 which is a freshwater, floating vascular plant; common name duckweed. The plants were exposed to a nominal concentration of 101 µg famoxadone/Liter of nutrient medium (101 ppb), which was determined to be the solubility limit in the nutrient medium. The organisms were exposed for fourteen days without test medium renewal. The effects were expressed as percent inhibition in mean healthy frond count and biomass (expressed as milligrams dry weight) relative to the pooled blank and solvent controls on day fourteen of the definitive test.

 

The results including the 95% confidence intervals (C.I.) are as follows:

Healthy Frond Count -2.1% inhibition (95% C.L = -17.6 to 12.0)

Biomass 1.7% inhibition (95% C.L = -6.4 to 8.9)

 

This study indicates that famoxadone has no significant inhibitory effect on the growth and reproduction of Lemna gibba G3 when exposed to a nominal test substance concentration of 101 g famoxadone/Liter of nutrient medium (101 ppb).

Reference 2

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

January 22, 2014 - January 29, 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Version / remarks:

2006

Qualifier:

according to guideline

Guideline:

OCSPP 850.4400 (Aquatic Plant Toxicity Test Using Lemna spp.) (January 2012)

Version / remarks:

1996

GLP compliance:

yes

Specific details on test material used for the study:

Purity: 99.1%
Batch: DPX-JE874-427

Analytical monitoring:

yes

Details on sampling:

A primary stock solution of famoxadone was prepared on 09 December 2013 at a concentration of 3.46 mg a.s./mL by transferring 87.3 mg of famoxadone into a 25-mL volumetric flask, correcting for purity, and bringing to volume with acetonitrile. Dilutions of this solution were made in 50:50:0.04 HPLC water:acetonitrile:formic acid to prepare analytical standard and matrix spiking solutions. A dilution of this solution was made in acetonitrile to prepare analytical standard solutions.
All solutions were stored refrigerated.

The concentrations of the famoxadone were measured in all blank control, solvent control, and test substance treatments at Day 0, 1, 3, 4, 6, and 7 of the definitive test. Samples were taken from parent solutions at Day 0, 3, and 6, replicate B and C solutions at Day 1, 4, and 7. Famoxadone-fortified samples were also prepared for analysis at each sampling period.

Vehicle:

yes

Remarks:

control and solvent control (DMF)

Details on test solutions:

For the definitive study: A primary standard at a concentration of 1.01 mg a.s./mL was prepared on 22 January 2014, by adding 0.0102 g of famoxadone (0.0101 g adjusted for purity) to a 10 mL glass volumetric flask and bringing the flask to volume with dimethylformamide (DMF). Working standards were prepared by serially diluting the primary standard to volumes of 10 mL with DMF to prepare concentrations of 0.063, 0.13, 0.25, and 0.51 mg a.s./mL. The working standards were used to prepare test substance treatments by diluting a 0.100 mL aliquot of to a volume of 1.0 L in test medium for final test concentrations of 0.0063, 0.013, and 0.025 mg a.s./L. The working and primary standards were used to prepare test substance treatments by diluting a 0.200 mL aliquot of to a volume of 2.0 L in test medium for final test concentrations of 0.051, and 0.101 mg a.s./L. The solvent control was prepared by diluting 0.200 mL of DMF to a volume of 2.0 L in test medium. The blank controlconsisted of test medium only. At initiation and throughout the duration of the test, the blank control, solvent control, and all test substance treatment solutions were clear and colorless with no visible precipitate, surface film, or undissolved test substance.

Test organisms (species):

Lemna gibba

Details on test organisms:

The parent stock of Lemna gibba used in the definitive test was obtained from the USDA/ARS Beltsville Agricultural Research Center, Beltsville, Maryland, on November 27, 2002. The parent stock was identified by the supplier as Lemna gibba G3 clone. Periodically, new Lemna gibba cultures were cloned from an existing culture derived from the parent stock. The Lemna gibba cultures used to inoculate the range-finding and definitive test were transferred to fresh nutrient medium seven days prior to study initiation to acclimate the cultures to the testing conditions (i.e., temperature, growth medium, and light quality). The number of fronds in the cultures used to initiate the definitive test had increased approximately 8-fold in seven days.

Test type:

static

Water media type:

freshwater

Remarks:

20X AAP nutrient medium was prepared by the addition of appropriate reagent grade salts to autoclaved ABC reagent water. the medium was pH-adjusted to 7.5 ± 0.1

Total exposure duration:

7 d

Test temperature:

23.1 to 25.9ºC

pH:

The pH of the new test solutions on days 0 to 6 ranged from 7.5 to 7.7. The pH of the old test solutions on days 1 to 7 ranged from 8.3 to 8.9.

Nominal and measured concentrations:

Nominal: Blank control, solvent control, 0.0063, 0.013, 0.025, 0.051, and 0.101 mg/L
Measured: ND, ND, 0.00391, 0.00558, 0.00769, 0.0113, and 0.0159 mg/L

Details on test conditions:

Each test flask received three plants, for a total of 12 fronds, at test initiation. Aseptic addition of Lemna gibba was initiated and completed within one hour of test solution preparation. Growth was measured by determining the change in the number of total fronds during the exposure period. Every frond that visibly projected beyond the edge of the parent frond was counted as a separate frond. Any change in plant development, frond size, appearance, necrosis or chlorosis was noted if observed. Frond observations and counts were performed on days 2, 5, and 7 for all replicates of the blank control, solvent control, and each test substance treatment.

The blank control, solvent control, and test substance treatments were renewed daily. Beginning with the blank control, plants were aseptically transferred, without harming roots or fronds, from spent test solutions to fresh test solutions. Biomass (Dry weight) measurements of each blank control, solvent control, and test substance treatment replicate were performed on day 7 (test termination), after frond observations had been conducted, as well as on four representative samples at test initiation. Each representative sample at test initiation was comprised of three plants, for a total of 12 fronds per sample. The dry weight of each replicate was determined by transferring all plants (fronds and roots) from each replicate to individually labeled and pre-weighed aluminum pans. All appropriately labeled pans containing Lemna gibba were allowed to dry at approximately 60°C for at least three days and then allowed to cool at ambient temperature. The aluminum pans were then reweighed to measure total dry weight.

Duration:

7 d

Dose descriptor:

IC50

Effect conc.:

> 0.016 mg/L

Nominal / measured:

meas. (geom. mean)

Basis for effect:

biomass

dry weight

frond number

growth rate

yield

Duration:

7 d

Dose descriptor:

LOEC

Effect conc.:

> 0.016 mg/L

Nominal / measured:

meas. (geom. mean)

Basis for effect:

biomass

dry weight

frond number

growth rate

yield

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

0.016 mg/L

Nominal / measured:

meas. (geom. mean)

Basis for effect:

biomass

dry weight

frond number

growth rate

yield

Details on results:

The doubling time of total frond number in the control was 1.5 days, corresponding to approximately a 19-fold increase in seven days, which met the doubling time requirement established by the OECD 221 test guideline (i.e., <2.5 days, corresponding to approximately a seven-fold increase in seven days). The control average specific growth rate for total number of fronds on day 0 to 7 was 0.422 day -1, exceeding the 0.275 day -1 minimum required by the OECD 221 test guideline. The coefficient of variation for the control average specific growth rate from day 0 to day 7, calculated as the standard deviation divided by the mean times 100, was 4%. The frond growth in the control over the 7-day test period and the low variability in average specific growth rate between control replicates demonstrated the acceptability of the test.

The percent inhibition of frond average specific growth rate as compared to the solvent control was 0, -1, -3, 2, and -1% for the 0.00391, 0.00558, 0.00769, 0.0113, and 0.0159 mg a.s./L test substance treatments,
respectively. The NOEC value on day 7 was 0.0159 mg a.s./L (geomean measured concentration), based on the lack of a statistically significant reduction in the average specific growth rate at this and lower test substance treatments. The LOEC value on day 7 was >0.0159 mg a.s./L, the highest treatment level tested. Based on the average specific growth rate, the estimated IrC50 value on day 7 was >0.0159 mg a.s./L, the highest treatment level tested.

The percent inhibition of frond yield as compared to the solvent control was 1, -5, -9, 6, and -3% for the 0.00391, 0.00558, 0.00769, 0.0113, and 0.0159 mg a.s./L test substance treatments, respectively. The NOEC values on day 7 were 0.0159 mg a.s./L (mean measured concentration), based on the lack of a statistically significant reduction in yield at this and lower test substance treatments. The LOEC values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested. Based on yield, the estimated IyC50 values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested.

The percent inhibition of biomass (dry weight), as compared to the solvent control, was 2, 0, -3, 4, and 10% for the 0.00391, 0.00558, 0.00769, 0.0113, and 0.0159 mg a.s./L test substance treatments, respectively. The percent inhibition of biomass yield (dry weight), as compared to the solvent control, was 2, -1, -3, 4, and 11% for the 0.00391, 0.00558, 0.00769, 0.0113, and 0.0159 mg a.s./L test substance treatments, respectively. The NOEC values on day 7 were 0.0159 mg a.s./L (geomean measured concentrations), based on the lack of a statistically significant reduction in biomass yield at this and lower test substance treatments. The LOEC values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested. Based on biomass yield, the estimated IyC50 values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested.

The percent inhibition of biomass (dry weight) average specific growth rate as compared to the solvent control was 1, 0, -1, 1, and 4% for the 0.00391, 0.00558, 0.00769, 0.0113, and 0.0159 mg a.s./L test substance treatments, respectively. The NOEC value on day 7 was 0.0159 mg a.s./L (geomean measured concentrations), based on the lack of a statistically significant reduction in biomass growth rate at this and lower test substance treatments. The LOEC values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested. Based on biomass growth rate, the estimated IrC50 values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested.

Validity criteria fulfilled:

yes

Conclusions:

Based on the average specific growth rate, the estimated IrC50 value on day 7 was >0.0159 mg a.s./L, the highest treatment level tested. Based on yield, the estimated IyC50 values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested. Based on biomass yield, the estimated IyC50 values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested. Based on biomass growth rate, the estimated IrC50 values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested. The LOEC value on day 7 was >0.0159 mg a.s./L, the highest treatment level tested for average specific growth rate, yield, biomass yield, and biomass growth rate. The biomass, yield, and growth rate, all based on frond count or dry weight, indicated no concentration-dependent response for exposure to the test substance, famoxadone.

Executive summary:

The acute toxicity of famoxadone to the freshwater aquatic plant, duckweed, Lemna gibba, was determined in a 7-day growth inhibition test. The test was conducted in accordance with Organization for Economic Cooperation and Development (OECD) Guidelines for Testing of Chemicals, Guideline No. 221 and U.S. EPA Ecological Effects Test Guidelines, OCSPP 850.4400. The study was conducted with a blank control, solvent control, and 5 concentrations of famoxadone at a temperature range of 23.1 to 25.9ºC. Twenty-strength synthetic algal-assay-procedure (20X AAP) nutrient medium was used as the test diluent and blank (culture medium) control. Test solutions were renewed daily. Four replicates were initiated per test concentration, solvent control, and blank control. Frond counts were conducted every 2 or 3 days, and biomass, yield, and growth rate were determined after 7 days based on both frond count and dry weight.

 

Nominal concentrations tested included a blank control, a solvent control, and 0.0063, 0.013, 0.025, 0.051, and 0.101 mg/L. Measured concentrations were not detected, not detected, 0.00391, 0.00558, 0.00769, 0.0113, and 0.0159 mg/L, respectively. The geomean measured concentrations of famoxadone active substance (a.s.) in the test concentration solutions ranged from 16 to 62% of nominal famoxadone concentrations. The measured concentrations of freshly prepared test solutions ranged from78 – 93% of nominal. The measured concentrations of old test solutions were below the limit of quantitation (LOQ = 0.00561 mg a.s./L). Frond counts increased in the blank control by at least a factor of 7 in 7 days and the doubling time in the blank control based on frond count was 1.5 days, thereby satisfying the appropriate test acceptance criteria.

 

Based on the average specific growth rate, the estimated IrC50 value on day 7 was >0.0159 mg a.s./L, the highest treatment level tested. Based on yield, the estimated IyC50 values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested. Based on biomass yield, the estimated IyC50 values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested. Based on biomass growth rate, the estimated IrC50 values on day 7 were >0.0159 mg a.s./L, the highest treatment level tested. The LOEC value on day 7 was >0.0159 mg a.s./L, the highest treatment level tested for average specific growth rate, yield, biomass yield, and biomass growth rate. The biomass, yield, and growth rate, all based on frond count or dry weight, indicated no concentration-dependent response for exposure to the test substance, famoxadone.

Description of key information

7-day IC50 (Lemna gibba) > 0.0159 mg/L; 7-day NOEC = 0.0159 mg/L, OECD 221 and OPPTS 850.4400, Reliability = 1

14-day EC50 (Lemna gibba) > 101 μg/L, OPP 122-2, 123-2, ASTM Method E1415-91, Reliability = 1

Key value for chemical safety assessment

EC50 for freshwater plants:

0.016 mg/L

EC10 or NOEC for freshwater plants:

0.016 mg/L

Additional information

Famoxadone was tested in two different studies in Lemna gibba with a result 7-day IC50 > 0.0159 mg/L and 14-day EC50 > 101 μg/L.