Tetrahydro-4-methyl-2H-pyran

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-02-02 to 2010-02-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Algal Growth Inhibition Test stipulated in the "Testing Methods for New Chemical Substances"

Version / remarks:

2006

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Samples of all concentrations were taken at the start and at the end of exposure.

Vehicle:

no

Test organisms (species):

Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Freshwater green algae
- Strain: ATCC 22662
- Source (laboratory, culture collection): American Type Cultrue Collection
- Age of inoculum (at test initiation): 3 days
- Method of cultivation: Passage cultured under sterile conditions in the laboratory.

ACCLIMATION
- Acclimation period: Preculture was incubated under the same conditions as the test.
- Culturing media and conditions (same as test or not): Yes
- Any deformed or abnormal cells observed: No

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

23.8°C

pH:

at test start: 7.8 - 7.9
at test end: 9.5 - 10.3

Nominal and measured concentrations:

Nominal: 0 (control), 1.0, 3.2, 10, 32 and 100 mg/L
Measured: 0 (control), 1.0, 3.1, 9.4, 32, 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 mL Erlemneyer flask.
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: Glass
- Aeration: No.
- Initial cells density: 0.50 x 10^4 cells/mL
- No. of vessels per concentration (replicates): 3.
- No. of vessels per control (replicates): 6.

GROWTH MEDIUM
- Standard medium used: Yes (OECD medium)

TEST MEDIUM / WATER PARAMETERS: Not measured.

OTHER TEST CONDITIONS
- Sterile test conditions: Yes.
- Adjustment of pH: No.
- Photoperiod: 24-hours light
- Light intensity and quality: 90 µE x m^-2·x s^-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
Paiticle counter: Model COULTER Z1 (BeckmanCoulter, Inc.)
Microscope: Model BX41 (Olympus Corporation)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: v10
- Range finding study: Yes
- Test concentrations: 0 (control), 0.32, 1.0, 3.2, 10 and 100 mg/L
- Results used to determine the conditions for the definitive study: Yes

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

32 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50 (0-3d): 0.83 mg/L. This value was within the normal range in the laboratory (mean ± 2S.D.: 0.55 to 1.4 mg/L) [mean ± S.D.: 0.96 ± 0.21 mg/L (n=13)].

Table 1: pH of test solutions

Nominal concentrations (mg/L)	pH
	Start	End
Control	7.9	10.1
1	7.8	10.3
3.2	7.8	10.0
10	7.8	10.0
32	7.8	9.9
100	7.8	9.5

Table 2: Cell concentrations

Nominal concentration (mg/L)		Cell concentration (x10^4 cells/mL)
		0 hours	24 hours	48 hours	72 hours
Control	Mean	0.50	2.4	14	34
	SD	0	0.45	0.99	2.7
1.0	Mean	0.50	2.4	14	34
	SD	0	0.32	0.73	4.5
3.2	Mean	0.5	2.2	12	33
	SD	0	0.23	0.86	1.2
10	Mean	0.5	2.3	13	32
	SD	0	0.059	1.1	0.70
32	Mean	0.5	2.3	11	30
	SD	0	0.42	1.7	2.4
100	Mean	0.5	1.6	6.6	21
	SD	0	0.23	1.7	3.2

Table 3: Growth rate of the algae

Nominal concentration (mg/L)		Growth rate	Inhibition rate (%)
Control	Mean	1.4	-
	SD	0.027	-
1.0	Mean	1.4	0.1
	SD	0.046	3.2
3.2	Mean	1.4	0.96
	SD	0.013	0.91
10	Mean	1.4	1.1
	SD	0.0071	0.51
32	Mean	1.4	2.7
	SD	0.027	1.9
100	Mean	1.2	12
	SD	0.054	3.8

Validity criteria fulfilled:

yes

Conclusions:

The ErC50 was determined as > 100 mg/L, the respective NOEC was 32 mg/L, both values were based on nominal concentrations.

Executive summary:

The toxicity of the test item Tetrahydro-4-methyl-2H-pyran was examined in an algae test according to OECD 201 and under GLP conditions. Cells of Pseudokirchneriella subcapitata were exposed to MTHP in concentrations of 0 (control), 1, 3.2, 10, 32 and 100 mg/L, equivalent to 1, 3.1, 9.4, 32, 100 mg/L mean measured concentrations, for 72 hours. Concentrations were analytically verified via GC-FID. As no growth inhibition was observed in the highest concentration the ErC50 was determined as > 100 mg/L, the respective NOEC was 32 mg/L, both values were based on nominal concentrations.

Description of key information

ErC50 (72 -h) > 100 mg/L based on nominal concentration

NOEC (72 -h) = 32 mg/L based on nominal concentration

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

32 mg/L

Additional information

The toxicity of the test item Tetrahydro-4-methyl-2H-pyran was examined in an algae test according to OECD 201 and under GLP conditions. Cells of Pseudokirchneriella subcapitata were exposed to MTHP in concentrations of 0 (control), 1, 3.2, 10, 32 and 100 mg/L, equivalent to 1, 3.1, 9.4, 32, 100 mg/L mean measured concentrations, for 72 hours. Concentrations were analytically verified via GC-FID. As no growth inhibition was observed in the highest concentration the ErC50 was determined as > 100 mg/L, the respective NOEC was 32 mg/L, both values were  based on nominal concentrations.