4-methylpyrazole

Toxicity to soil microorganisms

Administrative data

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Information published in peer reviewed literature, limitations in design and/or reporting but otherwise adequate for assessment

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1989

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Surface soil samples were treated with test substance and incubated, after which the percentage inhibition of nitrification was calculated.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

4-methylpyrazole

EC Number:

231-445-0

EC Name:

4-methylpyrazole

Cas Number:

7554-65-6

Molecular formula:

C4H6N2

IUPAC Name:

4-methyl-1H-pyrazole

Details on test material:

- Name of test material (as cited in study report): 4-Methylpyrazole

Sampling and analysis

Details on sampling:

Soil samples were placed in 25 x 200 mm test tubes and treated with 6 mL water containing 4 mg nitrogen as (NH4)2SO4 and 0, 0.01, 0.10, or
0.50 µmol test compound/g soil. The test tubes were then placed unsealed in an incubator maintained at 25 °C. The amount of water lost from
the soil samples during the incubation was measured gravimetrically at 5-day intervals and was replaced if it exceeded 1 mL. After 21 days, of test tubes were removed from the incubator, and their triplicate contents were analyzed for NH4+-N, NO2--N, and NO3--N as described by Bremner and Keeney (1966).

Test substrate

Vehicle:

no

Details on preparation and application of test substrate:

The soils used were surface (0-15 cm) samples of Iowa soils selected to obtain a range in pH (6.1-8.1), texture (9%-60% sand, 12%-49% silt, 28%-42% clay), organic-C content (1.2%-4.2%), and CaCO3 equivalent (0%-4,1%). Before use, each sample was air-dried and crushed to pass through a 2-mm screen.

Test organisms

Test organisms (inoculum):

soil

Study design

Total exposure duration:

21 d

Test conditions

Nominal and measured concentrations:

0.01; 0.1; 0.5 µmol/g

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

2 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Remarks on result:

other: based on visual interpolation of test data (Webster soil)

Effect concentrations 2

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

4 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Remarks on result:

other: based on visual interpolation of test data (Harps soil)

Reported statistics and error estimates:

The amount of (NO3- +NO2-)-N produced during the incubation was calculated from the results of analyses for (NO3- +NO2- )-N before and after the incubation, and the percentage inhibition of nitrification by the test compound was calculated from (C-T)/Cx 100, where T is the amount of (NO3-+NO2)-N produced in the soil sample treated with the test compound and C is the amount of (NO3 +NO2 )-N produced by the control sample (no test compound added). None of the incubated soil samples contained more than 1 µg NO 2-N per g of soil, and no NH4+N was detected after incubation for 21 days of the (NH4)2SO4-amended soil samples that had not been treated with a test compound.

Any other information on results incl. tables

Note from the reviewer: the article only provides inhibition of nitrification % per concentration. EC50 Effect values were interpolated via log normal interpolation and there after linear regression to establish the EC50