cyproconazole (ISO); (2RS,3RS;2RS,3SR)-2-(4-chlorophenyl)-3-cyclopropyl-1-(1H-1,2,4-triazol-1-yl)butan-2-ol

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

28 Jul 2006 to 29 Aug 2006

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

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.4400 (Aquatic Plant Toxicity Test using Lemna spp. Tiers I & II))

Version / remarks:

1996

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

Lemna gibba

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Reference substance (positive control):

no

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

25 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

frond number

growth rate

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

> 200 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

12.5 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

dry weight

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

59 µg/L

95% CI:

>= 51 - <= 67

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

frond number

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

67 µg/L

95% CI:

>= 58 - <= 76

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

dry weight

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

97 µg/L

95% CI:

>= 46 - <= 150

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

The concentrations of the test item in freshly prepared test solutions were found to be in the range 88 -120 % of the nominal values and in the old test solutions at renewals were in the range 79 - 103 % of the nominal values, see Table 1. Nominal concentrations were used for the calculation and reporting of results.

 

The initial number of fronds in all test concentrations and the control was 11. After 7 days of exposure the mean frond number in the control was 109. The initial weight of 11 fronds on Day 0 was 1.1 mg. After 7 days of exposure the mean frond dry weight in the control was 15.9 mg. The results of Dunnett's test  showed that for increase in frond number and growth rate the three highest test item treatments are significantly different to the control. For area under the growth curve and increase in dry weight the four highest test item treatments are significantly different to the control. Results on effect concentration are shown in Table 2.

 

Visual observations at Days 3, 5 and 7 (which were not analyzed statistically), showed more than 30% of the test population exhibited visual symptoms of toxicity at the three highest concentrations (nominally 50, 100 and 200 μg/L). On Days 5 and 7 fronds appeared stunted, and some new fronds were also browned (on Day 7 only). Additionally, at Day 3, between 11 and 30% of the test population exhibited the same symptoms of toxicity at 100 μg/L, and at Day 7 the same symptoms were seen at 25 μg/L.

 

Table 1, Analytical Results

Nominal conc. (μg/L)	Measured % of nominal in fresh solutions		Measured % of nominal in old solutions
	0-d	4-d	4-d	7-d
0 (control)	<LOQ	<LOQ	<LOQ	<LOQ
6.25	88	98	87	97
12.5	102	93	82	79
25	120	95	91	81
50	100	93	83	89
100	111	89	87	83
200	113	97	103	90

<LOQ – less than the limit of quantification (0.05 μg/L)

 

Table 2, Effect of the test substance on Lemna gibba

	Cyproconazole μg/L
	EC50 value		NOEC	LOEC
	7-day value	95% confidence interval
Increased frond number	59	51-67	25	50
Growth rate	>200	-	25	50
Area under the growth curve	97	46-150	12.5	25
Increase in dry weight	67	58-76	12.5	25

 

Validity criteria

The validity criteria were met, with the frond numbers in the controls more than doubling within 2.5 days, resulting in a greater than 7-fold increase in frond number. The increase in frond number in all control replicates at 7 days was between 9- and 10-fold.

Validity criteria fulfilled:

yes

Remarks:

See validity criteria in 'Any other information on results incl. tables'

Conclusions:

In a aquatic plant growth inhibition test performed following OECD TG 221 and OPPTS 850.4400 guidelines the 7-day NOErC and ErC50 for Lemna gibba were determined to be 25 and > 200 µg/L, respectively.

Executive summary:

Growth inhibition caused by the test substance to the freshwater plant Lemna gibba was determined in a 7-day semi-static test according to OECD TG 221 and OPPTS 850.4400 guidelines. The study was compliant with GLP principles. Lemna plants were exposed to nominal test substance concentrations of 0 (control), 6.25, 12.5, 25, 50, 100 and 200 µg/L. The concentrations of the test item in freshly prepared test solutions were found to be in the range 88 -120 % of the nominal values and in the old test solutions at renewals were in the range 79 - 103 % of the nominal values. Nominal concentrations were used for the calculation and reporting of results. Test vessels were maintained under continuous illumination of 8530 - 9050 lux. Temperature was 23.1 to 25.4 ºC and pH ranged between 7.60 and 8.30.

The initial number of fronds in all test concentrations and the control was 11. After 7 days of exposure the mean frond number in the control was 109. The initial weight of 11 fronds on Day 0 was 1.1 mg. After 7 days of exposure the mean frond dry weight in the control was 15.9 mg. The results of Dunnett's test showed that for increase in frond number and growth rate the three highest test item treatments are significantly different to the control. For area under the growth curve and increase in dry weight the four highest test item treatments are significantly different to the control.Therefore, the 7-day NOErC was determined to be 25 µg/L based on nominal concentrations. The 7-day ErC50 was determined to be > 200 µg/L based on nominal concentrations.

Description of key information

One study on a freshwater higher plant was performed and included here as a supporting study.

Freshwater, 7-d NOErC = 25 µg/L (nominal concentrations), Lemna gibba, OECD TG 221, OPPTS 850.4400, Everett et al 2007

Freshwater, 7-d ErC50 = > 200 µg/L (nominal concentrations), Lemna gibba, OECD TG 221, OPPTS.4400, Everett et al 2007

Key value for chemical safety assessment

EC50 for freshwater plants:

200 µg/L

EC10 or NOEC for freshwater plants:

25 µg/L

Additional information

There is one standard guideline followed and GLP compliant study available for this endpoint, which is included here as supporting study for freshwater conditions. The supporting study was performed with the duckweed species Lemna gibba. Plants were exposed to nominal test substance concentrations of 0 (control), 6.25, 12.5, 25, 50, 100 and 200 µg/L. The concentrations of the test item in freshly prepared test solutions were found to be in the range 88 -120 % of the nominal values and in the old test solutions at renewals were in the range 79 - 103 % of the nominal values. Based on nominal concentrations, the 7-day NOErC and the 7-day ErC50 were determined to be 25 µg/L and > 200 µg/L, respectively (Everett et al 2007, OECD TG 221, Reliability 1).