Reaction product of 2-hydroxybenzoic acid, styrene and oxozinc

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.6800 (Modified Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals)

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge, domestic

Details on inoculum:

Test System
Species: Activated sludge, microorganisms from a domestic waste water treatment plant.
Origin: The (controlled) activated sludge was supplied by the sewage plant for domestic sewage in Balatonfüred, Hungary on 10 July 2012 (One day before the main test.).
Preparation of Activated Sludge
Inoculum:
The coarse particles were removed by settling for 10 minutes, and the upper layer of finer solids was decanted. The activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in isotonic saline solution with shaking and again centrifuged. This procedure was repeated twice. An aliquot of the final sludge suspension
was weighed, dried and the ratio of wet sludge to dry weight determined. Based on this ratio, calculated amount of wet sludge was suspended in isotonic saline solution to yield a concentration equivalent to 3 g per litre (on dry weight basis). The activated sludge was not used on the day of the collection but continuously aerated (2L/minute) at the test temperature for about 24 hours (1 day) and was fed once with
50 mL synthetic sewage/L activated sludge. The pH of the activated sludge inoculum was checked after
preparation and before use. The pH of the activated sludge inoculum after preparation was 7.94, before use: 7.88. The pH adjustment before use was considered as not necessary. Foaming: Difficulties can arise if foaming occurs during the incubation to the extent that the foam and the sludge solids carried on it,
are expelled from the aeration vessels. In this test the occurring foaming was not significant, thus controlling was not necessary during the incubation.

Test type:

not specified

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

2.2-4.4℃

pH:

7.53

Nominal and measured concentrations:

nominal 1000 mg test item/L

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

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

Details on results:

The observed oxygen consumption rates consequently the specific respiration rates were in the range of the blank controls, no inhibitory effect (the observed slight 0.17 % “inhibition” was within the biological variability of the applied test system) of the test item was observed.
The specific respiration rates were compared with the blank control values using 2 Sample t-Test (α=0.01). No statistical significant differences were observed in the comparison with the blank control values, consequently based on the results of this study the NOEC can be statistically determined as ≥1000 mg/L.

Based on measured oxygen consumption values and calculated specific respiration rates it can be stated that the 3-hour EC10 and EC50 values of the test item are higher than 1000 mg/L.The EC50 value was determined as: EC50 > 1000 mg/L.

Results with reference substance (positive control):

The following concentrations of the positive reference control 3,5-Dichlorophenol were tested on the same
activated sludge and under identical conditions as the test item: 2, 7 and 24.5 mg/L. Each concentration of the 3,5-Dichlorophenol reference item was tested in three parallels. In comparison to the blank controls the specific respiration rate of the activated sludge was inhibited by 3.70 % at the lowest concentration of 2 mg/L, at the nominal concentrations of 7 and 24.5 mg/L, the respiration rate was inhibited by 8.81 % and 69.0 %, respectively.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the performed Activated Sludge Respiration Inhibition Test, the
EC10 and EC50 values of test item was determined as higher than 1000 mg/L. Based on the
statistical evaluation in this test the NOEC was ≥1000 mg/L.

Executive summary:

In an 3-hour OECD 209 study under GLP compliance, the influence of the test item Reaction product of 2-hydroxybenzoic acid,
styrene and oxozinc on the activity of the activated sludge was evaluated by measuring the respiration rate under defined conditions.The respiration rates (total, heterotrophic and nitrification oxygen uptake rates) of samples of activated sludge fed with synthetic sewage were measured in an enclosed cell containing an oxygen electrode after a contact time of 3 hours.Based on the preliminary information (the test item caused no effect on the activated sludge inoculum), the test item Reaction
product of 2-hydroxybenzoic acid, styrene and oxozinc was investigated at the concentration of 1000 mg/L as a limit
concentration, only.The test item was investigated at one (limit) concentration level of 1000 mg/L. The observed oxygen consumption rates consequently the specific respiration rates were in the range of the blank controls, no inhibitory effect of the test item was observed.Based on measured oxygen consumption values and calculated specific respiration rates it can be stated that the 3-hour EC10 and EC50 values of the test item are higher than 1000 mg/L. The EC50 value was determined as: EC50 > 1000 mg/L. All validity criteria of the study were met.

Description of key information

Activated Sludge Respiration Inhibition Test：EC50 > 1000 mg/L（OECD209，GLP）

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

In an 3-hour OECD 209 study under GLP compliance, the influence of the test item Reaction product of 2-hydroxybenzoic acid,
styrene and oxozinc on the activity of the activated sludge was evaluated by measuring the respiration rate under defined conditions.The respiration rates (total, heterotrophic and nitrification oxygen uptake rates) of samples of activated sludge fed with synthetic sewage were measured in an enclosed cell containing an oxygen electrode after a contact time of 3 hours.Based on the preliminary information (the test item caused no effect on the activated sludge inoculum), the test item Reaction
product of 2-hydroxybenzoic acid, styrene and oxozinc was investigated at the concentration of 1000 mg/L as a limit
concentration, only.The test item was investigated at one (limit) concentration level of 1000 mg/L. The observed oxygen consumption rates consequently the specific respiration rates were in the range of the blank controls, no inhibitory effect of the test item was observed.Based on measured oxygen consumption values and calculated specific respiration rates it can be stated that the 3-hour EC10 and EC50 values of the test item are higher than 1000 mg/L. The EC50 value was determined as: EC50 > 1000 mg/L. All validity criteria of the study were met.