4,6-Dichloro-5-fluoropyrimidine

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 May to 20 May 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Commission Directive 88/302/EEC; Official Journal of the EG L133 Part C (1988)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Direct weighing into test flasks
- Controls: Yes, blank control
- Test concentration separation factor: 1.8

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Laboratory culture: mixed population of aquatic microorganisms(activated sludge)
- Name and location of sewage treatment plant where inoculum was collected: aeration tank of a domestic sewage treatment plant(Wupper area water authority)
- Method of cultivation: Stirring period of test item before start of incubation time: 16 h.
- Initial biomass concentration: 480 mg/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 +/- 2 °C

Nominal and measured concentrations:

10, 18, 32, 56, 100 mg/L as nominal concentrations of the test item.

Details on test conditions:

TEST SYSTEM
- Test vessel: Flask
- Aeration: Permanent aeration
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2 controls
- Sludge concentration (weight of dry solids per volume): 480 mg/L suspended solids
- Nutrients provided for bacteria: Daily feed with synthetic medium

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : respiration inhibition at 3 h.
TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.8

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

44 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

- Effect concentrations exceeding solubility of substance in test medium: The solubility was not exceeded.
- Blank controls oxygen uptake rate: 34 mg/L

Results with reference substance (positive control):

- Results with reference substance valid? Yes, all validity criteria are fulfilled.
- Relevant effect levels: 0 % inhibition at 2.5 mg/L, 82.4 % inhibition at 40 mg/L.

Validity criteria for the measurement of the toxicity to microorganisms:

Target condition according to guideline:	Actual condition according to the study:	Validity criteria met:
In a 2004 international ring test organized by ISO using activated sludge derived from domestic sewage, the EC50 of 3,5-dichlorphenol was found to lie in the range 2 mg/L to 25 mg/L for total respiration, 5 mg/L to 40 mg/L for heterotrophic respiration and 0.1 mg/L to 10 mg/L for nitrification respiration. If the EC50 of 3,5-DCP does not lie in the expected range, the test should be repeated with activated sludge from another source.	The EC 50 of the reference substance 3.5-dichlorophenol is in the range 5 - 30 mg/L, which is 5 mg/L above the range specified in the guideline. Considering the small deviation, this criterion is considered to be met.	Yes
The test should be performed at a temperature within the range 20 ± 2°C.	The test temperature was 20 ± 2°C.	Yes
The EC50 and, if possible, 95 % confidence limits, possibly EC20, EC80; possibly NOEC and the used statistical methods, if the EC50 cannot be determined shall be reported.	The EC50 including the 95% confidence limits are stated. The EC values were determined by probit analysis.	Yes

 

Validity criteria fulfilled:

yes

Remarks:

See 'Any other information on results incl. tables'.

Conclusions:

EC50 (3 h): 44 mg/L

Executive summary:

The test item showed 100 % respiration inhibition of activated sludge at a test item concentration of 10000 mg/L. The EC50 was determined to be 44 mg/L.

Description of key information

The test item showed 100 % respiration inhibition of activated sludge at a test item concentration of 10000 mg/L. The EC50 was determined to be 44 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

44 mg/L