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Ecotoxicological information

Toxicity to aquatic plants other than algae

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Reference
Endpoint:
toxicity to aquatic plants other than algae
Type of information:
other: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
From July 30, 2014 to August 08, 2014
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
The test was conducted on a similar substance. The complete justification for the read across is attached at section 13.
Qualifier:
according to
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition Test)
Deviations:
no
Principles of method if other than guideline:
Guidelines followed
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
The test medium samples (100 mL) were stored deep-frozen (below -18 °C) until analysis
Vehicle:
no
Details on test solutions:
Due to low water solubility of the test item a saturated solution was prepared by weighing 100 mg FAT 36014/Z TE on a weighing scoop and transferring it to a volumetric flask. Test medium was added up to the bench mark (1 L). The solution was stirred for 48 hours in the dark. Afterwards the stock solution was withdrawn from the middle of the preparation vessel by suction without transferring undissolved test item (according to OECD SERIES ON TESTING AND ASSESSMENT No. 23). Aliquots of the withdrawn phase were diluted with test medium to receive the lower test item concentrations.
Test organisms (species):
Lemna gibba
Details on test organisms:
The test organism was the aquatic plant duckweed, Lemna gibba G3 (Alismatales: Araceae). The plants used in this study were taken as aseptic clones from the cultivation of the testing facility. They were primarily cultured by Dr. Janet Slovin, Horticulture Crops Quality Laboratory, U.S. Department of Agriculture. BARC-West, Bldg. 050 HH-4, Beltsville, MD 20705, U.S.A.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Remarks on exposure duration:
None
Post exposure observation period:
Not available
Hardness:
Not available
Test temperature:
Not available
pH:
Not available
Dissolved oxygen:
Not available
Salinity:
Not available
Nominal and measured concentrations:
see table below
Details on test conditions:
Test procedure:semi-static test
Duration:7 days
Temperature:22.9 – 25.1 °C
pH-value of fresh solution:7.37 – 8.55
Light intensity (mean): ~ 7000 lux
Light tubes:OSRAM light tubes (L 30 W77 and L 30 W25)
Exposure to light:continuously
Test vessels:250 mL glass beakers filled with 150 mL
Number of fronds:12 per test vessel
Reference substance (positive control):
no
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
0.051 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of frond number
Remarks on result:
other: 0.000217-0.183
Duration:
7 d
Dose descriptor:
EC20
Effect conc.:
0.156 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of frond number
Remarks on result:
other: 0.00605-0.444
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
0.846 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of frond number
Remarks on result:
other: 0.270-5.80
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
0.03 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of frond number
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
0.098 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of frond number
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
0.29 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of frond number
Remarks on result:
other: 0.163-0.437
Duration:
7 d
Dose descriptor:
EC20
Effect conc.:
0.812 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of frond number
Remarks on result:
other: 0.552-1.20
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
> 2 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of frond number
Remarks on result:
other: -
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
0.03 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of frond number
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
0.098 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of frond number
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
0.017 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of dry weight
Remarks on result:
other: -
Duration:
7 d
Dose descriptor:
EC20
Effect conc.:
0.105 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of dry weight
Remarks on result:
other: -
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
1.74 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of dry weight
Remarks on result:
other: -
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
0.098 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of dry weight
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
0.313 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield of dry weight
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
0.409 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of dry weight
Remarks on result:
other: -
Duration:
7 d
Dose descriptor:
EC20
Effect conc.:
> 2 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of dry weight
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
> 2 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of dry weight
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
0.313 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of dry weight
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
2 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate of dry weight
Details on results:
Not available
Results with reference substance (positive control):
Not available
Reported statistics and error estimates:
The statistical evaluation for day 7 was performed for yield of frond numbers, growth rate of frond numbers, growth rate dry weight and yield of dry weight. A test for normality of the data was performed by calculating the Shapiro-Wilk’s statistic, a test for homogeneity of the data was performed according to Levene. The NOEC and LOEC were determined by using a multiple comparison method (Dunnett`s t-test). The calculation of EC10 and EC20 values of all parameters was performed using probit analysis following normal and Gompertz procedure. The calculation of EC50 values for yield of frond numbers and yield of dry weight was done using probit analysis following normal procedure. For yield of dry weight the calculation was done without the lowest loading rate of 0.954 mg/L to cover only the area with a clear dose-response relation. The calculation of EC50-values for growth rate of frond numbers and dry weight were not indicated since inhibition was below 50 %. The evaluation of data was performed by SAS® (2002-2010).

Toxicological endpoints for test substance:

 

test item [mg/L loading rate]

Endpoint

EC10

95 % confidence limit

EC20

95 % confidence limit

EC50

95 % confidence limit

NOEC1)

LOEC1)

Yield of frond numbers

4.232)

-

10.42)

-

59.02)

-

3.05

9.77

Growth rate of frond numbers

22.63)

0.0201-56.3

52.33)

-

>100

-

3.05

9.77

Yield of dry weight

9.652)

-

20.02)

-

80.32)

-

9.77

31.3

Growth rate of dry weight

31.12)

-

>100

-

>100

-

31.3

100

1) following Dunnetts-t-test

2) probit following normal procedure

3) probit following Gompertz

- not applicable

Validity criteria fulfilled:
yes
Conclusions:
EC50(7d)> 2 mg/l.
Executive summary:

The aim of the study was to assess the effect of the test item on the growth of Lemna gibba according to OECD Guideline 221 and determine EC10, 20, 50 and NOEC/LOEC values.

A saturated stock solution was prepared by stirring 100 mg of substance in 1000 mL test medium for 48 hours in the dark. The stock solution was withdrawn from the middle of the preparation vessel. Aliquots of the withdrawn phase were diluted to receive the lower test item concentrations.

A semi-static test with the following loading rates was performed: undiluted solution (corresponding to 100 mg/L loading rate), 3.2-fold diluted solution (corresponding to 31.3 mg/L loading rate), 10.2-fold diluted solution (corresponding to 9.77 mg/L loading rate), 32.8-fold diluted solution (corresponding to 3.05 mg/L loading rate), 104.9-fold diluted solution (corresponding to 0.954 mg/L loading rate) and control.

Vegetative growth was observed for a test period of 7 days by measuring the increase of frond numbers and dry weight. The following endpoints (NOEC/LOEC, EC10, 20, 50) were determined:

- frond numbers and dry weight

- growth rates of frond numbers and dry weight

- yield of frond numbers and dry weight

- doubling times of frond numbers

Toxicological endpoints:

 

test substance

 [mg/L loading rate]

Endpoint

EC10

EC20

EC50

NOEC1)

LOEC1)

Yield of frond numbers

4.232)

10.42)

59.02)

3.05

9.77

Growth rate of frond numbers

22.63)

52.33)

>100

3.05

9.77

Yield of dry weight

9.652)

20.02)

80.32)

9.77

31.3

Growth rate of dry weight

31.12)

>100

>100

31.3

100

 

test substance

 [mg/L] actual4)

Endpoint

EC10

EC20

EC50

NOEC1)

LOEC1)

Yield of frond numbers

0.05083)

0.1563)

0.8463)

0.0305

0.0977

Growth rate of frond numbers

0.2903)

0.8123)

>2.00

0.0305

0.0977

Yield of dry weight

0.01653)

0.1053)

1.743)

0.0977

0.313

Growth rate of dry weight

0.4092)

>2.00

>2.00

0.313

2.00

1) following Dunnetts-t-test

2) probit following normal procedure

3) probit following Gompertz

4)based on geometric mean of each concentration level

Significant inhibitory effects were determined for yield and growth rate of frond numbers at 9.77, 31.3 and 100 mg/L loading rate and 0.0977, 0.313 and 2.00 mg/L (actual), for yield of dry weight at 31.3 and 100 mg/L loading rate and 0.313 and 2.00 mg/L (actual) and for growth rate of dry weight at 100 mg/L loading rate and 2.00 mg/L (actual).

The overall LOEC was based on the most sensitive parameter and was determined to be 9.77 mg/L loading rate and 0.0977 mg/L (actual). The corresponding NOEC was determined at 3.05 mg/L loading rate and 0.0305 mg/L (actual).

The nominal EC10-value for yield of frond numbers is 4.23 mg/L loading rate, 9.65 mg/L loading rate for yield of dry weight, 22.6 mg/L loading rate for growth rate of frond numbers and 31.1 mg/L loading rate for growth rate of dry weight.

Based on the geometric mean of the analysed concentration levels, the EC10-value for yield of frond numbers is 0.0508 mg/L, 0.0165 mg/L for yield of dry weight and 0.409 mg/L for growth rate of dry weight. The actual EC10-value for growth rate of frond numbers is 0.290 mg/L.

The nominal EC20-value for yield of frond numbers is 10.4 mg/L loading rate, 20.0 mg/L loading rate for yield of dry weight, 52.3 mg/L loading rate for growth rate of frond numbers and >100 mg/L loading rate for growth rate of dry weight.

Based on the geometric mean of the analysed concentration levels, the EC20-value for yield of frond numbers is 0.156 mg/L, 0.105 mg/L for yield of dry weight and > 2.00 mg/L for growth rate of dry weight. The actual EC20-value for growth rate of frond numbers is 0.812 mg/L.

The nominal EC50-value for yield of frond numbers is 59.0 mg/L loading rate and 80.3 mg/L loading rate for yield of dry weight. The nominal EC50-value for growth rate of frond numbers and dry weight is >100 mg/L loading rate.

Based on the geometric mean of the analysed concentration levels, the EC50-value for yield of frond numbers is 0.846 mg/L and 1.74 mg/L for yield of dry weight and > 2.00 mg/L for growth rate of dry weight. The actual EC50-value for growth rate of frond numbers and dry weight is > 2.00 mg/L.

The test is valid as the doubling time of control frond numbers was calculated to be 33.2 h, corresponding to 1.385 days at day 7. This is less than the maximum allowable doubling time set in OECD guideline 221 (60 h, 2.5 days).

Conclusion:

Significant inhibitory effects were determined for yield and growth rate of frond numbers at 9.77, 31.3 and 100 mg/L loading rate and 0.0977, 0.313 and 2.00 mg/L (actual), for yield of dry weight at 31.3 and 100 mg/L loading rate and 0.313 and 2.00 mg/L (actual) and for growth rate of dry weight at 100 mg/L loading rate and 2.00 mg/L (actual).

Description of key information

Key value for chemical safety assessment

EC50 for freshwater plants:
2 mg/L
EC10 or NOEC for freshwater plants:
0.313 mg/L

Additional information