1-bromobutane

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010

Reliability:

1 (reliable without restriction)

Guideline:

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

Guideline:

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

GLP compliance:

yes

Analytical monitoring:

yes

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temp. of appr. 21 deg. C, and was used on the day of collection. The pH of the sample was 7.9 measured using a WTW pH/Oxi 340i pH and dissolved oxygen meter. Determinationof the suspended solids level of the activated sewage sludge was carried out by filtering a sample (100 ml) of the activated sewage sludge by suction. The suspended solids concentrationwas equal to 3.9 g/l prior to use.

Test type:

static

Water media type:

freshwater

Total exposure duration:

5 min

Hardness:

140 mg/l as CaCO3

Test temperature:

21 deg C +-1 deg C

pH:

7.6

Dissolved oxygen:

In some instances, the initial and the final dissolved oxygen concentrations were below those recommended in the test guideline. This was considered to have had no adverse effect on the results of the study given that in all cases the oxygen consumption rate was determined over the linear portion of the oxygen consumption trace.

Reference substance (positive control):

yes

Remarks:

3.5-dichlorphenol

Duration:

5 min

Dose descriptor:

EC50

Effect conc.:

270 mg/L

Duration:

5 min

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Validity criteria fulfilled:

yes

Executive summary:

A study was performed to assess the effect of the test item on the respiration of activated sewage sludge. The method followed that described in the OECD guidlines for testing of chemicals (1984) No 209 "activated sludge, respiration inhibition test", method C.11 of commission regulation (EC) No. 440/2008 and US EPA draft ecological effects test guidelines OPPTS 850.6800.

Following prelinimary work and range-finding test, activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 100, 180, 320, 560 and 1000 mg/l for a period of 5 minutes in sealed vessels at a temperature of 21+- 1 degree celsius with the addition of a synthetic sewage as a respiratory substrate. Due to the volatile nature of the test item, the test duration was reduced from 3 hours, as specified in the test guidelines, to 5 minutes as it was considered likely that a longer test duration would result in significant losses of test item from the test system. In order to minimise any losses of test item from the test system, rathar than vigorous aeration of the test vessels, the test preparations were kept in suspension by stirring via magnetic stirrers and all vessels were sealed with film. The vapour pressure of the test item is 14.8 KPa at 20 degree celsius and the Henry's law constant for the test item was also calculated to be over 700 Pa.M3/mol which also confirms that the test item would be volatile under the normal conditions employed in an activated sludge, respiration inhibition test.

The rate of respiration was determined after 5 minutes contact time and compared to data for the control and a reference item 3,5-dichlorophenol

Results. The effect of the test item on the respiration of activated sewage sludge gave a 5 minute EC50 of 270 mg/l. The no observed effect concentration (NOEC) after 5 minutes exposure was 100 mg/l.

The reference item gave a 5 minute EC50 value 8.7 mg/l, 95% confidence limits 6.9-11 mg/l.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Read across to structural analogue.

Justification for type of information:

Please see attached justification for read across in Section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

5 min

Dose descriptor:

EC50

Effect conc.:

270 mg/L

Key result

Duration:

5 min

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Key value for chemical safety assessment

EC50 for microorganisms:

270 mg/L

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

The test item showed under the conditions of the study that it will have an inhibitory effect on sewage sludge respiration if released to a waste water treatment plant.

The effect of the test item on the respiration of activated sewage sludge gave a 5 minute EC50 of 270 mg/l. The no observed effect concentration (NOEC) after 5 minutes exposure was 100 mg/l.

However, due to the volatility of the substance under the test conditions, the EC50 value obtained after 5 minutes can only be based on a nominal substance loading value. Therefore, the EC50 value should be treated with some caution when considering hazard identification and risk characterization for the appropriate environmental compartment.