4-(4-chlorophenyl)-2-phenyl-2-[(1H-1,2,4-triazol-1-yl)methyl]butanenitrile

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1994-03-10 to 1994-12-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 123-3 (Algal Toxicity, Tiers I and II)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

The measured concentration of the Fenbuconazole in test diluation water were determined from samples of each test level, control, and Fenbuconazole quality control samples collected at 0 abd 120 hours of the toxicity test.

Vehicle:

yes

Remarks:

Acetone

Details on test solutions:

A 40 mg/mL primary standard was prepared by adding 0.4082 g of RH-57.592 Technical to 10 mL of acetone. A 0.20 mL aliquot of the primary standard was added to 2000 mL of algal nutrient medium to prepare the 0.0040 mg/mL working standard (level 6). Test levels 1-5 were prepared by adding the following aliquots of the 4000 µg a.s./L test solution to 1.0 L volumetric flasks and diluting with algal nutrient medium: 2.5, 8.25, 27.5, 92.5, and 300 mL, respectively.

Test organisms (species):

Selenastrum sp.

Details on test organisms:

Selenastrum capricornutum Printz

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

120 h

Test temperature:

24 ± 2°C

pH:

7.5 to 8.5

Nominal and measured concentrations:

Nominal test concentrations were 10, 33, 110, 370, 1200, and 4000 µg/L

Details on test conditions:

The algal toxicity study was conducted in 250-mL Erlenmeyer flasks that were stoppered with a foam plug and sterilized in an autoclave. All test flasks were labeled with a felt marker as to compound code, concentration, replicate, and grid position. Following preparation of the test solutions, the test vessels were positioned in a random fashion and incubated for 120 hours at 24 ± 2°C under continuous cool-white fluorescent lighting and constant rotary agitation. Light intensity was maintained at 400 ± 10% footcandles (approximately 4300 lux) and the agitation rate was approximately 100 rpm.

Duration:

120 h

Dose descriptor:

NOEC

Effect conc.:

0.29 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.077 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.025 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

51 mg/L

Nominal / measured:

meas. (initial)

Basis for effect:

growth rate

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.42 mg/L

Nominal / measured:

meas. (initial)

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.33 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Reported statistics and error estimates:

ANOVA
A one-way analysis of Variance (ANOVA) (using PROC GLM in SAS) was conducted for each timepoint with a Dunnett's comparison to the vehicle blank. A one-tailed Dunnett's test was
conducted at the 0.05 level of significance with the alternate hypothesis being that the mean number of cells has been reduced in comparison to the vehicle blank mean. Prior to the Dunnett's test, a Levene's test was conducted to test for homogeneity of variance over treatments at each hour. If the p value from the Levene's test is greater than 0.01, indicating insignificant heterogeneity, then the analysis is performed on the cell counts divided by 10^4. If the p value is less than 0.01 for some hour(s), then the cell counts for each replicate are transformed using the square root of the cell count, the recommended transformation for count data.

EC Calculation and 95% Confidence Limits
The SAS nonlinear modeling procedure (PROC NUN) is used to estimate B and EC50.
The distribution of x hat method is used to estimate the 95 % confidence limits for EC25 and EC50.

Table 1:  Growth data (cells/mL)

Nominal concentration (mg/L)	0-Hour measured concentration (mg/L)	Cell count (10^4 cells/mL)
		24 Hours	48 Hours	72 Hours	96 Hours	120 Hours
Control	<MQL ^a	1.8	7.4	40	110	280
Solvent Control	<MQL ^a	1.3	7.9	38	100	190
0.010	0.079	0.89	7.6	37	110	300
0.033	0.025	1.3	7.6	40	110	300
0.11	0.077	1.1	6.7	29 *	110	180
0.37	0.29	0.93	6.4 *	21 *	80 *	180
1.2	0.76	0.82 *	4.0 *	12 *	14 *	20 *
4.0	2.9	0.56 *	2.1 *	1.8 *	0.48 *	0.0 *

 ^a   minimum quantifiable limit = 0.0029 mg a.s./L
*significantly different from control values (Dunnett’s test, p<=0.05)
Note:  0-hour control and solvent control cell counts were 0.33x10⁴ and 0.37x10⁴ cells/mL, respectively.

Validity criteria fulfilled:

yes

Conclusions:

The 72-hour EC50 value for fenbuconazole for the green alga Selenastrum capricornutum was 0.33 mg/L (0-hour measured). The 72-hour NOEC was 0.025 mg/L.

Executive summary:

Growth, measured as cells/mL, was significantly reduced at concentrations ≥0.077 mg a.s./L at 72-hours as compared to the vehicle control. At 96-hours growth was significantly reduced at concentrations ≥0.29 mg a.s./L and at 120-hours growth was significantly reduced at 0.76 and 2.9 mg a.s./L as compared to the vehicle control. The 72-, 96- and 120-hour EC50 values based on cell count were 0.33, 0.42, and 0.51 mg a.s./L, respectively. The 72-, 96-, and 120-hour NOEC values were 0.025, 0.077, and 0.29 mg a.s./L, respectively. Results for the growth parameters of area under the growth curve and growth rate were not calculated.

Description of key information

The 72-hour EC50 value for fenbuconazole for the green alga Selenastrum capricornutum was 0.33 mg/L (0-hour measured).

Key value for chemical safety assessment

EC50 for freshwater algae:

0.33 mg/L