Hydroxyl-2-pyridone

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1994-06-08 to 1994-06-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: EC Directive 87/302 'Biodegradation - activated Sludge Respiration Inhibition test'

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Hydroxyl-2-pyridone

EC Number:

212-506-0

EC Name:

Hydroxyl-2-pyridone

Cas Number:

822-89-9

Molecular formula:

C5H5NO2

IUPAC Name:

1-hydroxy-1,2-dihydropyridin-2-one

Test material form:

solid: particulate/powder

Details on test material:

- Name of test material (as cited in study reports): Oxy PYRION
- Physical state: solid (powder)
- Appearance: white speckled gold powder

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: batch number 93100020

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: at ambient temperature in the original container

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test concentrations of Oxypyrion were prepared from aqueous stock solutions (1 and 2 g/L) whose pH had been adjusted to approximate neutrality with sodium hydroxide (5N). Test concentrations up to and including 560 mg/L were prepared from the 1 g/L stock and at 1000 mg/L from the 2 g/L stock.
- Differential loading: Two tests were conducted; the first with nominal test concentrations of 1, 10 and 100 mg/L, and the seconde with 56, 100, 320, 560 and 1000 mg/L.
- Controls: yes

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: A sample of activated sludge was obtained from Oakley sewage treatment works, a sewage plant treating predominantly domestic waste
- Preparation of inoculum for exposure:The concentration of suspended solids in a homogenised sample was determined on the day of collection and immediately before the start of the test. Aliquots (25 mL) of the activated sludge were filtered through dried and preweighed Whatman's GFC filter papers which were then dried again at 105°C for at least one hour, allowed to cool in a dessicator and reweighed. The mixed liquor suspended solids (MLSS) content of the activated sludge was then calculated and adjusted where necessary to fall in the range 2 to 4 g/L by the addition of dechlorianted tap water. Synthetic sewage (50 mL/L) was added when necessary and the mixture aerated overnight.
- Initial biomass concentration: 1.6 g SS/L

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

After 3h of exposure, a well-mixed sample of each mixture was transferred to a biochemical oxygen demand (BOD) bottle and its rate of oxygen consumption was measured over a period of ~10 minutes using a Yellow Springs Instruments (YSI) dissolved oxygen meter.

Test conditions

Test temperature:

- Preliminary test:
* initial: 19.1 - 20.5
* Final: 18.4 - 19.2
- Final test:
* Initial: 19.8 - 20.5
* Final: 19.6 - 20.7

pH:

- Preliminary test:
* initial: 7.8-8.1
* Final: 7.9-8.6
- Final test:
* Initial: 7.5-7.8
* Final: 8.3-8.5

Dissolved oxygen:

not specified

Salinity:

not applicable

Nominal and measured concentrations:

Loading rates for the test substance:
- Preliminary test: 1, 10 and 100 mg/L
- Final test: 56, 100, 320, 560 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: no data
- Material, size, headspace, fill volume: no data
- Aeration: the mixture was aerated overnight
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Sludge concentration (weight of dry solids per volume): 2 to 4 g SS/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: ultrapure water

OTHER TEST CONDITIONS
- Adjustment of pH: pH had been adjusted to approximate neutrality with sodium hydroxide (5N)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
TEST CONCENTRATIONS
- Range finding study yes
- Test concentrations: 1, 10 and 100 mg/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

320.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: 95% CL: 261.5 - 391.4 mg/L

Effect concentrations 2

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

115 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

- Blank controls oxygen uptake rate: The specific respiration rates of the control cultures established at the end of the 2 tests series were 99% and 108% of the rate of those established at the start.
- At 1000 mg/L 77% inhibition was observed

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: The EC50 for 3,5-DCP in the preliminary test was calculated to be 7.9 mg/L and in the final test 9.1 mg/L. This is within the recommended range of 2-25 mg/L confirming suitability of the activated sludge used.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

An activated sludge inhibition test (according OECD guideline 209) with activated sludge from a predominantly domestic sewage treatment plant resulted in a 3-h EC50 of 320.8 mg Oxypyrion/L. The results of the study can be considered reliable without restriction.