Bronopol

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:

other: Guideline study conducted in accordance with GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

- Stock solutions were prepared immediately before use (ca. 30 min before dosing the activated sludge) by making up 1 g of Bronopol to 1 litre with water.
- Tap water was used as the diluent.
- The dilution water used was aerated tap water held at ca. 21 +/- 2°C for at least 24 hours before use.

Test organisms (species):

activated sludge

Details on inoculum:

- Inoculum: activated sludge freshly collected on day of test from Beford Sewage Treatment Works, Meadow Lane, Bedford
- Treatment: sludge was centrifuged and washed with aerated tap water three times before use. The pellet was re-suspended in tap water to give a dry weight level of 4 g/L in the final inoculum.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

150 min

Test temperature:

20 - 23 °C

pH:

7.75 - 8.40

Nominal and measured concentrations:

- Concentrations tested (nominal): 0, 2, 6.3, 20, 63 and 200 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessels: glass BOD bottles with ground glass stoppers (300 ml volume nominal)
- Concentration of inoculum: 10 ml of the final inoculum were added to each test vessel giving a final concentration of 0.14 g/L dry weight, which was equivalent to 2.3 g/L wet weight in each test vessel

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

150 min

Dose descriptor:

other: EC20

Effect conc.:

2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

150 min

Dose descriptor:

EC50

Effect conc.:

43 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

150 min EC50 = 43 mg/L (nominal)
150 min EC80 = 887 mg/L (nominal)

Results with reference substance (positive control):

EC50 = 12 mg/L

Description of key information

Depending on local conditions and existing concentrations, disturbances in the biodegradation process of activated sludge are possible.

Key value for chemical safety assessment

EC50 for microorganisms:

43 mg/L

Additional information

The effects of bronopol to aquatic microorganisms were investigated in a GLP guideline study according to OECD 209 with activated sludge [Knoll MicroCheck 1996]. At test termination after 2.5 h an EC20 of 2 mg/L (nominal) was determined.

Additionally, another GLP guideline study according to OECD 209 with activated sludge as inoculum was conducted [BASF SE 2002]. After the test duration of 30 min an EC20 of ca. 20 mg/L (nominal) was determined and inhibition of respiration in activated sludge ranged from 14 to 67 %. In a third study, the effect of Bronopol on the growth of Pseudomonas putida was examined according to ISO guideline 10712 [Knoll MicroCheck 1996]. After 16 h of incubation an EC10 of 0.5 mg/L (nominal) was determined.

The effect concentrations obtained from the latter two studies were comparable to the ones retrieved from the key study and can therefore be used as supporting evidence of the acute toxicity of bronopol to aquatic microorganisms.