Chlorhexidine dihydrochloride

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:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Sampling site: STP Marl-west (Germany)
- Preparation of inoculum for exposure: Activated sludge (approx. 10 L) was sampled and purified by settling and washing several times with drinking water.
After the last washing step 400 ml synthetic sewage were added and activated sludge was aerated and stirred overnight.
At the test day sludge was again allowed to settle and the supernatant was discarded. 400 ml synthetic sewage were added and sludge was then made up to 8 L with drinking water.
The supernatant were again rejected, and sludge was brought to a defined value of suspended solids.
- Initial biomass concentration: 3850 mg suspended solids/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

18 - 19° C

pH:

8.3 - 8.7

Dissolved oxygen:

3.91 - 9.43 mg/l

Nominal and measured concentrations:

6, 12, 40, 25, 50, 100 mg/L
The concentrations are based on the main product

Details on test conditions:

TEST SYSTEM
- Test vessel: 1000 mL Erlenmeyer flasks
- Type (delete if not applicable): open.Test substance is not volatile
- Aeration: Clean, oil-free air. Air flow: 0.5 to 1 L/min
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- No. of vessels per reference substance (replicates): 3
- Biomass loading rate: 1571 mg/L in the test batches
TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Synthetic sewage according to OECD 209
EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Respiration inhibition.
Oxygen consumption determined after 3 hours of incubation with test substance
- Measuring equipment: Microprocessor oximeter: WTW OXI 2000

Reference substance (positive control):

yes

Remarks:

3.5-Dichlorophenol

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

6 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

12 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: 95% CL 4.4 – 23 mg/L

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

23 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

Concentrations: 3, 7.5, 19 mg/L
EC50 = 11.2 mg/L

Reported statistics and error estimates:

Determination of ECx values by regression line according to Cavalli-Sforza

Validity criteria fulfilled:

yes

Conclusions:

Chlorhexidine dihydrochloride was harmful towards activated sludge microorganisms. The 3h-EC50 was determined to be 12 mg/L.

Description of key information

The inhibition of activated sludge respiration was studied in a GLP study according to the OECD209 guideline.

Chlorhexidine dihydrochloride was harmful towards activated sludge microorganisms. The 3h-EC50 was determined to be 12 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

12 mg/L