α-n-butyl-α-(4-chlorophenyl)-1H-1,2,4-triazole-1-propanenitrile

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-17-07 to 2012-21-07

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

acetone

Details on test solutions:

100 mg/mL primary stock solution was prepared by placing 1.0672 g of the test substance in a 10-mL volumetric flask and bringing it to volume with acetone. The resulting stock solution was mixed by shaking and inversion of the volumetric flask and was observed to be clear and colorless with no visible undissolved test substance following preparation.

Additional untreated AAP medium was used for the control. A solvent control solution was prepared by adding 0.10 mL of acetone to a 1000-mL volumetric flask and bringing it to volume with AAP medium. All test solutions were observed to be clear and colorless with no visible undissolved test substance following overnight mixing using a magnetic stir plate.

An inoculum of 0.47 mL of Pseudokirchneriella subcapitata cells was added to each of the exposure flasks (100 mL/flask) at a density of 214 x 10^4 cells/mL. At each subsequent 24-hour interval, a single cell count was conducted on each replicate solution of the treatment levels and the controls using a hemacytometer (Neubauer Improved) and a compound microscope with the exception of the solvent control. One sample was removed from each flask for counting. One or more hemacytometer fields, each 0.10 x 0.10 cm in surface area and 0.010-cm deep and containing 0.00010 mL of culture, were examined for each sample until at least 400 algal cells or four fields were counted. Observations of the health of the algal cells were also made at each 24-hour interval.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

Source - Smithers Viscient (Wareham) culture

Test type:

static

Water media type:

other: Algal Assay Procedure (AAP) medium

Total exposure duration:

72 h

Test temperature:

22 to 23 ºC

pH:

6.9 to 7.6

Conductivity:

100 to 110 µS/cm

Nominal and measured concentrations:

Nominal concentrations: 0.10, 0.26, 0.64, 1.6, 4.0 and 10 mg/L,
Means measured concentrations: 0.093, 0.26, 0.64, 1.5, 3.8 and 9.7 mg/L

Details on test conditions:

72-hour duration, temperature range of 22 to 23ºC, continuous illumination at a range of 440 to 550 footcandles (4800 to 5900 lux), shaking rate of 100 rpm

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.54 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

yield

Key result

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

0.085 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

yield

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.042 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

yield

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.26 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

yield

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.26 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2.5 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

0.65 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.37 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Validity criteria fulfilled:

yes

Conclusions:

In an algal growth inhibition test with myclobutanil, the 72-h EC50 values for yield and growth rate were determined to be 0.54 and 2.5 mg a.s./L, respectively. The 72-hour NOEC for yield and average growth rate was determined to be 0.26 mg a.s./L.

Executive summary:

The purpose of this study was to determine the effect of myclobutanil on the growth of the freshwater green alga Pseudokirchneriella subcapitata over 72 hours according to OECD 201. based on the measured concentration the 72 hour EC₅₀ for yield and growth rate were determined to be 0.54 and 2.5 mg/L, respectively. The 72-hour NOEC for yield and average growth rate was 0.26 mg/L.

Description of key information

In an algal growth inhibition test performed according to GLP and OECD TG 201 with myclobutanil, the 72 hour EC₅₀-values for yield and average growth rate were calculated to be 0.54 and 2.5 mg/L, respectively. The 72-hour NOEC for yield and average growth rate was 0.26 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

2.5 mg/L

EC10 or NOEC for freshwater algae:

0.26 mg/L