(1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

From 14th to 28th November 1991.

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

(1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide

EC Number:

259-467-6

EC Name:

(1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide

Cas Number:

55067-10-2

Molecular formula:

C5H4N4O2

IUPAC Name:

(1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide

Test material form:

solid: particulate/powder

Details on test material:

Test material: CYDI ((1,4,5,6-Tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide)
Description: Off-white powder
Storage: In original container at room temperature
Molecular formula: C5H4N4O2

Specific details on test material used for the study:

Test material: CYDI ((1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide).
Description: Off-white powder.
Storage: In original container at room temperature.
Molecular formula: C5H4N4O2.

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Vehicle:

no

Details on test solutions:

Direct dispersion in water.

Test organisms

Test organisms (species):

activated sludge

Details on inoculum:

A mixed population of activated sewage sludge microorganisms.
Souce: The aeration Stage of Severn Trent PLC Sewage Treatment Plant, Belper, Derbyshire.

Study design

Test type:

not specified

Water media type:

not specified

Limit test:

no

Total exposure duration:

3 h

Test conditions

Hardness:

Not specified.

Test temperature:

21°C.

pH:

6.5

Dissolved oxygen:

Not specified.

Salinity:

Not specified.

Conductivity:

Not specified.

Nominal and measured concentrations:

Nominal concentrations: 1, 10, 100 and 1000 mg/L in a range-finding study.
3 replicates of 100 mg/L in the final study.

Details on test conditions:

The sample was maintained at 21 " C wi th continuous aeration and used on the day of collection. The pH was buffered to pH 6.5 with sodium hydroxide solution and the suspended solids level adiusted to 3.6 g/l prior to use.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Results and discussion

Effect concentrations

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

EC50 (3-hour contact time) = 8.8 mg/L.

Any other information on results incl. tables

Table 1: Range-finding study

Concentration (mg/l)	O2 consumption rates mgO2/l/min 3-hour contact time	% Inhibition
Control 1	0.52	-
Control 2	0.50	-
1.0	0.52	<2>
10	0.51	0
100	0.50	2
1000	0.01	98
Reference 3.2 mg/L	0.43	16
Reference 32 mg/L	0.10	80

Table 2: 100 mg/L test substance replicates

Concentration (mg/1)	O2 consumption rates mgO2/l/min 3-hour contact time	% Inhibition
Control 1	0.44	-
Control 2	0.45	-
100, Replicate 1	0.43	3
100, Replicate 2	0.44	1
100, Replicate 3	0.41	8
Reference 3.2 mg/L	0.35	21
Reference 32 mg/L	0.06	87

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

The oxygen consumption rate of activated sludge decreases by an average of 4% in the presence of 100 mg/L of (1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide.

The EC50 after 3 hours of exposure was therefore determined to be > 100 mg/L.

Executive summary:

Respiration inhibition of (1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide on activated sludge has been studied. The activated sludge was subjected to various concentrations of test substance for 3 consecutive hours.

A preliminary study has been carried out with test substance concentrations of 1, 10, 100 and 1000 mg/L.

Based on the results obtained in this preliminary test, it was decided to make new measurements on 100 mg/L replicates.

The average respiration inhibition based on the 100 mg/L replicates was found to be 4%.

The EC50 for respiration inhibition of activated sludge by (1,4,5,6-tetrahydro-4,6-dioxopyrimidin-2-yl)cyanamide after 3 hours of exposure was therefore determined to be > 100 mg/L.