1-[2-fluoro-6-(trifluoromethyl)benzyl]-5-iodo-6-methylpyrimidine-2,4(1H,3H)-dione

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27th August 2018 to 6th September 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: MEP, P.R. China, the Guidelines for the Testing of Chemicals, Effects on biotic systems (2nd Edition) No. 201 "Algal Growth Inhibition Test". (2013.8)

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: EC, DG Health and Consumer Protection: Residues: Guidance on analytical quality control & validation procedures for pesticide residue analysis in food & feed SANCO/1257/2013 19/11/13 rev 0

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

1-{[2-fluoro-6-(trifluoromethyl)phenyl]methyl}-5-iodo-6-methyl-1,2,3,4-tetrahydropyrimidine-2,4-dione

EC Number:

687-893-6

Cas Number:

1150560-54-5

Molecular formula:

C13H9F4IN2O2

IUPAC Name:

1-{[2-fluoro-6-(trifluoromethyl)phenyl]methyl}-5-iodo-6-methyl-1,2,3,4-tetrahydropyrimidine-2,4-dione

Test material form:

solid: particulate/powder

Sampling and analysis

Analytical monitoring:

yes

Remarks:

HPLC/UV

Details on sampling:

Analysis frequency: in 0-hour fresh solution and 72-hour old solution

Test solutions

Details on test solutions:

A weight of 0.1001g of test item was weighed into 1L of test medium to give a nominal concentration of 100mg/L. The solution was mixed using a magnetic stirrer using a stirring rate of 400 rpm for 24 hours. Solutions were filtrated with 0.45 μm membrane.

The stock solution was diluted to give concentrations of 50, 89.0, 158.0 and 281mL. These were diluted to 500ml with test medium to give 10.0, 17.8, 31.6, 56.2 and 100mg/L.

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Source: Institute of Hydrobiology, Chinese Academy of Sciences and cultured continuously in the facility.
Batch No.: 20180824
Initial Biomass Concentration: 5 x 10 3 cell/mL

Study design

Test type:

static

Water media type:

not specified

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

0, 24, 48 and 72 hours

Test conditions

Test temperature:

21 - 24 °C

pH:

pH 7.69 - 8.53

Nominal and measured concentrations:

The measured concentrations were 0.134, 0.242, 0.448, 0.759 and 1.342 mg/L of the fresh test solution. The measured concentrations were 0.144, 0.230, 0.433, 0.764 and 1.293mg/L of old solution. The overall mean concentrations were 0.139, 0.236, 0.441, 0.762 and 1.318mg/L respectively. 

Details on test conditions:

A weight of 0.1001g of test item was weighed into 1L of test medium to give a nominal concentration of 100mg/L. The solution was mixed using a magnetic stirrer using a stirring rate of 400 rpm for 24 hours. Solutions were filtrated with 0.45 μm membrane.

The stock solution was diluted to give concentrations of 50, 89.0, 158.0 and 281mL. These were diluted to 500ml with test medium to give 10.0, 17.8, 31.6, 56.2 and 100mg/L.

Each solution was divided into 3 replicates and the control was 100ml Algal Growth Medium for each replicate.

The biomass of the pre-cultured algae solution was counted. The mean concentration was 1.2 x 10 6 cell/mL. 0.418ml of pre-cultured algal solution was added to each replicate vessel, mixed well, resulting in an initial test biomass of 5 x 10 3 cell/mL. The test vessels were placed in an incubator.
The algal biomass was measured daily (24, 48 and 72 hours) during the test period. The biomass was measured by manual cell counting using a microscope four times. Any abnormal symptoms were recorded.

Reference substance (positive control):

yes

Remarks:

Potassium Dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.82 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Growth yield

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1.318 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.139 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Results with reference substance (positive control):

72 hour EyC50 with 95% Confidence Limit: 0.5mg/L (0.39 ~ 0.65 mg/L)
72 hour ErC50 with 95% Confidence Limit: 0.55mg/L (0.41 ~ 0.75 mg/L)

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Based on the results and measured concentration, the 72-hour median effective concentration of the test item to algal Desmodesmus subspicatus, the  ErC50 was greater than 1.318 mg/L the EyC50 was 0.850mg with 95% Confidence Limit of  0.666 - 1.01 mg/L.

The NOEC was 0.139mg/L for growth rate and growth yield.

Executive summary:

An algal growth inhibition study of Methyl iodouracil was conducted for a period of 72 hours.

The definitive test was carried out with five nominal concentrations of 10.0, 17.8, 31.6, 56.2 and 100mg/L. A concurrent blank control was treated in parallel. There were 3 replications for the test concentrations and control and 100ml for each replication. The algal species used was Desmodesmus subspicatus and the initial cell count was 5 x 10³ cell/mL. 

Algal growth medium recommended by MEP and OECD guidelines was used. The algal biomass in each flask was inspected daily (24, 48 and 72 hours) during the test period. 

During the 72 h exposure, the mean growth yield of control cultures was 4.0 x 10⁵ cell/mL. The cell density of control cultures increased by a factor of 80 in the control replicates. The co-efficient of variation for section by section specific growth rate in control cultures was 4.84%. The co-efficient of average specific growth rates during the whole test period in control replicates was 0.68%. The results met the requirements of test validity. 

During the 72 hours test period, there was no visible toxic signs observed in the control replicates or in test groups of 10.0, 17.8, 31.6, 56.2 and 100mg/L. There was no inhibition in concentrations of 10.0 and 17.8mg/L. Slight inhibition was observed in 31.6mg/L. Inhibition in 56.2 and 100mg/L was greater than 10%. There was no significant difference between control and 10mg/L group. There was significant difference between the control and 17.8, 31.6, 56.2 and 100mg/L groups.

During the test period, chemical analysis on test item concentrations in the test media by HPLC showed that for test media of 10.0, 17.8, 31.6, 56.2 and 100mg/L, the measured concentrations were 0.134, 0.242, 0.448, 0.759 and 1.342 mg/L of the fresh test solution. The measured concentrations were 0.144, 0.230, 0.433, 0.764 and 1.293mg/L of old solution. The overall mean concentrations were 0.139, 0.236, 0.441, 0.762 and 1.318mg/L respectively. 

Based on the results and measured concentration, the 72-hour median effective concentration of the test item to algal Desmodesmus subspicatus, the  E_rC₅₀ was greater than 1.318 mg/L the E_yC₅₀ was 0.850mg with 95% Confidence Limit of  0.666 - 1.01 mg/L.

The NOEC was 0.139mg/L for growth rate and growth yield.