GASIR1

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

9/2/2005-18/4/2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study according to international guidelines. Methods and results well presented.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

yes

Remarks:

The initial and final dissolved oxygen concentrations were below those recommend in the test guidelines. This had no adverse effect level.

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Details on test material:

- Name of test material (as cited in study report): GASIR1

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Details on test solutions:

Amounts of test material (160, 280, 500, 900 and 1600 mg) were each seperately dispersed in approximately 250 ml of dechlorinated laboratory tap water and subjected to ultrasonication for approximately 30 minutes. Synthetic sewage (16 ml), activated sewage sludge (200 ml) and water were added to a final volume of 500 ml to give the required concentrations.

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Preparation of inoculum for exposure: The activated sewage sludge sample was maintained on continuous eration in the laboratory at a temperature of 21°C and was used on the day of collection.

- Initial biomass concentration:4.1g/l

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Remarks on exposure duration:

After 30minutes an extra aliqout wa sampled

Post exposure observation period:

/

Test conditions

Hardness:

100mg/l CaCO3

Test temperature:

21°C (Temperature controlled room)

pH:

8.1-8.2

Dissolved oxygen:

/

Salinity:

/

Nominal and measured concentrations:

Initial range finding test: nominal test concentration: 100 and 1000mg/l
Range finding test: 180, 320, 1800 and 3200mg/l
Definitive test: 320, 560, 1000, 1800, 3200 mg/l

Details on test conditions:

TEST SYSTEM
- Test vessel:500 ml conical flask

- Aeration:0.5-1l/min

- Biomass loading rate:200ml

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:tap water dechlorinated by passage through an activate carbon filter and partly softened
- Total organic carbon:1.7 mg C/l
- Metals:
- Pesticides:<0.01μg/l
- Chlorine:0.221mg/l
- Alkalinity:113 mg HCO3/l
- Ca/mg ratio:6.375
- Conductivity:439.164μS/cm


OTHER TEST CONDITIONS
- Adjustment of pH:/
- Photoperiod:/
- Light intensity/:

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :/

TEST CONCENTRATIONS

- Range finding study: yes
- Test concentrations: Preliminary: 100-1000mg/l, Second test: 90, 160, 900, 1600mg
- Results used to determine the conditions for the definitive study:

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (Final concentration: 3.2 and 32 mg/l)

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 3 200 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Effect concentrations 2

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

560 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: 13% inhibition compared to control

Details on results:

- Effect concentrations exceeding solubility of substance in test medium:The water solubility of Gasir1 was < 1.0E-4 g/l . Given this extremely low value and that no significant effects on respiration was observed in the range-finding tests at 100, 180 and 320 mg/l, it was considered justifiable to conduct the definitive study at a nominal test concentration in excess of the water solubility of the test material.
- % inhibition at concentrations tested:
320 mg/l: 4%
560 mg/l: 13%
1000 mg/l: 20%
1800 mg/l: 27%
3200 mg/l: 29%

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: EC50 (30min) = 12mg/l; EC50 (3h) = 10mg/l

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The effect of the test material on the respiration of activated sludge micro-organisms gave a 3-hour EC50 of greater than 3200mg/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 560mg/l. No verification on the determination of this value was given. An EC10 value of 374 mg/l was calculated based on the presented data and a log-logistic model (TRAP 1.21).