Dimethyl ether

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1989

Report date:

1989

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

other: Robra toxicity test to bacteria

Deviations:

yes

Remarks:

some minor differences in methods

Principles of method if other than guideline:

Deviations compared to guidance: low temperature batch culture, no data on density of bacteria used, washing procedure cell suspension shorter but at higher centrifugation. No actual concentration of stock determined. No data on exposure/incubation duration (guideline specifies 30 min at 20°C).
No positive or negative control used.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Dimethyl ether

EC Number:

204-065-8

EC Name:

Dimethyl ether

Cas Number:

115-10-6

Molecular formula:

C2H6O

IUPAC Name:

dimethyl ether

Details on test material:

Sample received from AkzoChemicals bv, Weert, The Netherlands
Name: dimethyl ether (DME)
Molecular formula: CH3OCH3
Molecular weight: 46
Cas no: 115-10-6
Purity: aerosol grade
Satbility: stable at test conditions
Solubility in water: 7.8 g/L (18C)
Pressure: 4.2 bar
Storage: at ambient conditions in the dark
CRL code: T89-8-1.1

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Details on test solutions:

100 ml of demineralized water was put in a 120 ml erlenmeyer flask closed with a miniert valve. Then 270 ml of test substance gas was injected through the valve into the erlenmeyer resulting in a nominal 5 g/L stock solution.

Test organisms

Test organisms (species):

Pseudomonas putida

Details on inoculum:

The P. putida strain DSM 50026 was obtained from the Deutsche Sammlung fur Mikroorganismen (Braunschweig, Germany)

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Test conditions

Hardness:

BOD water contained per litre demineralized water:
8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.3 mg Na2HPO4, 1.7 mg NH4Cl, 22.5 mg MgSO4(H2O)7, 27.5 mg CaCl2 and 0.25 mg FeCl3(H2O)6

Test temperature:

20°C

pH:

pH of maintenance medium and wash buffer: 7.5 and 7.2 respectively

Dissolved oxygen:

Oxygen is result parameter

Salinity:

BOD water contained per litre demineralized water :
8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.3 mg Na2HPO4, 1.7 mg NH4Cl, 22.5 mg MgSO4(H2O)7, 27.5 mg CaCl2 and 0.25 mg FeCl3(H2O)6

Nominal and measured concentrations:

Nominal concentrations:
100, 200, 400, 800, and 1600 mg/L

Details on test conditions:

Oxygen uptake rates were determined in a Biological Oxygen Monitor (BOM) (Yellow Springs Instruments, Ohio, USA) at 20°C. The BOM consists of a thermostated vessel (5 mL) with a magnetic stirrer and a Clark type oxygen electrode. The vessel is air closed tightly by this electrode. The reaction mixture in the BOM contained 0.1 mL of the washed cell suspension, 0.1 mL of a glucose solution (2.5 M), x ml of the test substance stock solution and 4.8-x mL of BOD water. To prevent the evaporation of the test substance from the mixture the test substance stock solution was injected directly into the closed vessel of the BOM containing the other constituents of the mixture.

Reference substance (positive control):

no

Remarks:

neither positive or negative

Results and discussion

Effect concentrations

Dose descriptor:

EC10

Effect conc.:

> 1 600 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

Measurements were carried out twice, but for the 100 mg/L dose, 4 times. No dose response could be observed. Under the test conditions, the highest attainable dose did not show a reduction > 10% compared to the control, based on nominal concentrations. In the 800 mg/L dose, an outlier was found (increased respiration rate), which was not considered in results.

Any other information on results incl. tables

Concentration (mg/L)	% inhibition
Control
100	15
200	0
400	-3
800	-6
1600	9

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

Based on nominal concentrations and a 10% inhibition of oxygen uptake at the highest tested concentration (1600 mg/L), the EC10 was estimated to be > 1600 mg/L.

Executive summary:

In this toxicity test Pseudomonas putida cells were cultured under specified conditions. Subsequently the respiration rates of a washed cell suspension of these bacteria in the presence of various concentrations of the test substance were measured to determine the EC values. The toxicity test has been performed according to a modified ROBRA test guideline. The EC10 and the EC50 for Pseudomonas putida could not be determined due to the absence of oxygen respiration inhibition at the maximal attainable concentration tested (i.e. 1600 mg/litre). The EC10 can therefore be concluded > 1600 mg/L based on nominal concentration.