Tetrahydro-4-methyl-2H-pyran

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

Study period:

2017-04-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution of the test substance with a concentration of 5000 mg/L was prepared.

Test organisms (species):

activated sludge

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Activated sludge was obtained from Kurume central sewage treatment center (Kurume-shi, Fukuoka, Japan) that consists of an aeration reactor of a sewage treatment plant receiving predominantly domestic sewage.
- Method of cultivation: The activated sludge (2.5 L) was fed with synthetic sewage (125 mL) and cultivated for 18.5h at 20 ± 2°C under aerobic condition in order to acclimate the sludge to the test temperature.
- Initial biomass concentration: 3020 mg/L (concentration of suspended solid)

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

30 min

Remarks on exposure duration:

To reduce the loss of the test substance as it is volatile, exposure time was shorten to 30 minutes.

Test temperature:

20 +- 2°C

pH:

7.5 +- 0.5°C

Nominal and measured concentrations:

Nominal: 1000 mg/L
Measured: 540 mg/L (mean)

Details on test conditions:

TEST SYSTEM
- Test vessel: 300 mL glass vessel
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 250 mL
- Aeration: yes, airpump (controllable flow rate at 0.5 - 1 L/min)
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

OTHER TEST CONDITIONS
- Adjustment of pH: No

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

>= 540 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

- Results with reference substance valid?
- Relevant effect levels: Yes, the EC50 of 3,5-dichlorophenol as reference substance was 13 mg/L and met the criterion values between 2 and 25 mg/L.

Table 1: Oxygen consumption rate, percentage inhibition of respiration and measured concentration of the test substance after 30 minutes exposure.

Nominal loading concentration (mg/L)	Measured concentration (mg/L)	Oxygen consumption rate (mgO2/L_h)	Percentage inhibition of respiration (%)	Average percentage inhibition (%)
1000	570	33.9	18	14
1000	540	34.2	17
1000	520	39	6

Validity criteria fulfilled:

yes

Conclusions:

The EC50 was determined to be greater than 540 mg/L based on mean measured concentration.

Executive summary:

An activated sludge respiration inhibition test according to OECD 209 and in compliance with GLP was conducted to determine the inhibition potential of Tetrahydr-4 -methyl-2H-pyran on microorganisms. The activated sludge obtained from a sewage treatment plant was exposed to the test substance in a nominal concentration of 1000 mg/L, equivalent to 540 mg/L mean measured concentration, for 30 minutes. The concentration was analytically verified by GC-FID. As no inhibition of the respiration of the microorganisms was observed, the EC50 was determined to be greater than 540 mg/L based on mean measured concentration.

Description of key information

EC50 (30 min.) > 540 mg/L based on mean measured concentration

Key value for chemical safety assessment

EC50 for microorganisms:

540 mg/L

Additional information

An activated sludge respiration inhibition test according to OECD 209 and in compliance with GLP was conducted to determine the inhibition potential of Tetrahydr-4 -methyl-2H-pyran on microorganisms. The activated sludge obtained from a sewage treatment plant was exposed to the test substance in a nominal concentration of 1000 mg/L, equivalent to 540 mg/L mean measured concentration, for 30 minutes. The concentration was analytically verified by GC-FID. As no inhibition of the respiration of the microorganisms was observed, the EC50 was determined to be greater than 540 mg/L based on mean measured concentration.