1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole

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:

20 Jul 1981 to 03 Aug 1981

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

no guideline followed

Principles of method if other than guideline:

The vascular freshwater plant duckweed was exposed to the test item for 14 days. The increase or decrease of frond production was determined at various time intervals.

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

Acetone

Test organisms (species):

Lemna gibba

Test type:

static

Water media type:

freshwater

Limit test:

no

Reference substance (positive control):

no

Duration:

14 d

Dose descriptor:

EC10

Effect conc.:

2.94 mg/L

95% CI:

> 1.26 - <= 2.03

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Basis for effect:

frond number

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

9.02 mg/L

95% CI:

>= 4.88 - <= 13.18

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Basis for effect:

frond number

Duration:

14 d

Dose descriptor:

EC90

Effect conc.:

21.87 mg/L

95% CI:

>= 11.72 - <= 40.8

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Basis for effect:

frond number

Analytical results: Measured concentrations in the samples taken at the start of exposure were ND, ND, 2.54, 6.50, 12.9, 23.4 and 46.9 mg/L at nominal test concentrations of 0 (blank control), 0 (solvent control), 3, 6, 12, 25 and 50 mg/L, respectively. Measured levels ranged from 85 % to 108 % of the nominal levels.

Biological results: Measured concentrations of ≥ 6.50 mg/L significantly affected growth of Lemna gibba after 14 days of exposure. Inhibition of frond production was from 4 % in cultures exposed to 2.54 mg/L to 93 % in cultures exposed to 46.9 mg/L. Flowering was not observed among any of the control plants or plants exposed to the test material during the 14 day exposure period. The 14-day EC10 and EC50 and their 95 % confidence limits were calculated by a probit analysis.

Validity criteria fulfilled:

not applicable

Conclusions:

In a toxicity study on the freshwater duckweed species Lemna gibba, performed without a standard guideline, the 14d-EC10 and EC50 values for frond production were calculated to be 2.94 mg/L and 9.02 mg/L, respectively, based on initial measured concentrations.

Executive summary:

The toxicity of the test substance to the freshwater duckweed species Lemna gibba, was tested without a standard guideline but in compliance with GLP criteria. Triplicate 7-day-old cultures were employed for each test concentration and the controls. The test duckweed were exposed to the test substance in a static system for 14 days. The range of nominal concentrations tested was 0 (blank control), 0 (solvent control), 3, 6, 12, 25 and 50 mg/L. Cultures were incubated at 24 °C under approximately 10,300 lux illumination. Measured concentrations in the samples taken at the start of exposure were ND, ND, 2.54, 6.50, 12.9, 23.4 and 46.9 mg/L at nominal test concentrations of 0 (blank control), 0 (solvent control), 3, 6, 12, 25 and 50 mg/L, respectively. Measured concentrations ≥ 6.50 mg/L significantly affected the growth of Lemna gibba after 14 days of exposure. Inhibition of frond production was from 4 % in cultures exposed to 2.54 mg/L to 93 % in cultures exposed to 46.9 mg/L. Given these results, the 14d-EC10 for frond production was calculated to be 2.94 mg/L with a 95% confidence interval of 1.26 to 2.03 mg/L, and the 14d-EC50 for frond production was calculated to be 9.02 mg/L with a 95% confidence interval of 4.88 to 13.18 mg/L. Effects were based on initial measured concentrations.

Description of key information

14-d EC10 = 2.94 mg/L (mean measured concentration) and 14-d EC50 = 9.02 mg/L (mean measured concentration); frond number; Lemma gibba; freshwater species; no guideline followed; Hollister 1981 

Key value for chemical safety assessment

EC50 for freshwater plants:

9.02 mg/L

EC10 or NOEC for freshwater plants:

2.94 mg/L

Additional information

One GLP study is available for this endpoint and included as a supporting study. Triplicate 7-day-old freshwater duckweed Lemna gibba was employed for each test concentration and the controls. The test duckweed was exposed to the test substance in a static system for 14 days. The range of nominal concentrations tested was 0 (blank control), 0 (solvent control), 3, 6, 12, 25 and 50 mg/L (initial measured concentrations ND, ND, 2.54, 6.50, 12.9, 23.4 and 46.9 mg/L, respectively). Cultures were incubated at 24 °C under approximately 10,300 lux illumination. The 14d-EC10 for frond production was calculated to be 2.94 mg/L and EC50 for frond production was calculated to be 9.02 mg/L, based on initial measured concentrations (Hollister 1981, no standard guideline followed, Reliability 2).