Naphthalene-2,6-dicarboxylic acid

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:

28 March 208 - 14 June 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Version / remarks:

July 22, 2010

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Batch No.of test material: 0012747069
- Expiration date of the lot/batch: January 24, 2019
- Purity test date: 99.96%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At ambient temperature
- Stability under test conditions: stable

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Flörsheim/Main, Germany
- Preparation of inoculum for exposure: The activated sludge was washed with reconstituted water. After that it was centrifuged, and the supernatant was decanted. The activated sludge pellet was re-suspended in washing medium. This treatment procedure was repeated twice.
- Pretreatment: Storing at ambient temperature
- Initial biomass concentration: The solids level in the microbial inoculum on testing day was 3.96 g/L.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20.8–21.3 °C

pH:

7.1–7.3

Nominal and measured concentrations:

Nominal: 10.0, 31.6, 100, 316 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 1000 mL glass beakers, fill volume 500 mL
- Type: open (test vessels covered with watch glasses)
- Aeration: 0.5–1 L of air per hour
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per positive control (replicates): 4
- Volume of microbial inoculum: 200 mL
- Nitrification inhibitor used (delete if not applicable): N-allylthiourea
TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The dilution water was based on deionized water containing mineral salts. It was prepared within one month before use.
EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Inhibition of respiration
TEST CONCENTRATIONS
- Spacing factor for test concentrations: Square root of 10
- Range finding study
- Test concentrations: 10, 100 and 1000 mg/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

N-Allylthiourea

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

90.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

615 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

- Results with reference substance valid?
- Relevant effect levels: The EC50 of the total respireation inhibition of 3,5-dichlorophenot was 5.99 mg/L which is within the accepted range of 2-25 mg/L. The results of the reference substance are therefore considered to be valid.

Validity criteria fulfilled:

yes

Conclusions:

The definitive test showed a concentration-response relationship with an inhibition of total respiration rate of up to 34.6% of control respiration at 1000 mg test item/L. Since even at the highest test concentration of 1000 mg/L the overall inhibition of total respiration was less than 50%, the EC50 is considered to be >1000 mg/L.

Description of key information

Since even at the highest test concentration of 1000 mg/L the overall inhibition of total respiration was less than 50%, the EC50 is considered to be > 1000 mg/L. The EC₁₀ of 90.2 mg/L is therefore used as the key value for the risk assessment.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

90.2 mg/L