1,6-Hexanolide

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:

72 hours, 4 to 7 March 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline and GLP-compliant study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Caprolactone Consortium (BASF, Daizel, Dow and Solvay)/ Batch number: U 05175
- Purity test date: 99.95 %

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: at room temperature
- Stability: unlimited. Stability of the test substance under storage conditions over exposure period was guaranteed by the sponsor and the sponsor holds this responsability
- Aggregate state/appearance: liquid /clear, colourless
- Water-solubility: soluble
- Homogeneity: homogeneous (sponsor data)

Analytical monitoring:

yes

Details on sampling:

Samples were taken at 0 hours (fresh media) and 72 hours (expired media).

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test substance was stirred in deionised water for about 10 minutes at approximately 20 ± 2 °C.
- The nominal concentration of the stock solution was 5000.2 mg/I . By diluting this stock solution the following nominal concentrations (mg/I) were prepared: control, 4000, 1600, 640, 256 and 102 mg/l
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): The stock solution appears clear and colourless

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name:
- Strain: CHODAT SAG 86.81
- Source (laboratory, culture collection): SAG (Collection of algal cultures in Göttingen)

Pre-culture techniques
- Seed-culture: a seed culture was incubated for 4 days at 23 °C ± 2 °C. Final cell density: 89 x 10-4 cells/ml
- Pre-culture: seed-culture was taken to inoculate pre-culture (initial cell density: 1 x 10-4 cells/ml}. The pre-culture was incubated for 3 days at 23 °C ± 2 °C. Final cell density: 126 x 104 cells/ml.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Remarks on exposure duration:

none

Post exposure observation period:

not applicable

Hardness:

Not applicable

Test temperature:

23 ± 2 °C

pH:

6.9 - 8.2

Dissolved oxygen:

Not applicable

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal: 102, 256, 640, 1600, 4000 mg/L
Measured (mean of 2): 93, 260, 664, 1693, 4204 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks (nominal volume 250 ml) plugged with gas permeable siliconsponge caps
- Test volume: 100 ml
- Initial cells density: 1 x 104
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Intervals of water quality measurement:
- Measurement of temperature: continuously during the whole test period in the climate chamber
- Measurement of pH-values: after 0 h and 72 h in an additional uninoculated replicate and after 72h in the inoculated replicate

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Light intensity and quality: about 60 - 120 uE/(m2s) at a wave length of 400 - 700 nm. Artificial light, type universal white (OSRAM L 25), permanent illumination.


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: after 72 h in a counting chamber (Neubauer improved) from a control vessel
- Chlorophyll measurement: in vivo chlorophyll-a-fluorescence (pulsed excitation with light flashes having a wavelength of 435 nm)

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1 217 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2 616 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

256 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: biomass and growth rate

Details on results:

none

Reported statistics and error estimates:

Calculation of the integral of biomass growth over the total duration of the test for each concentration level and comparison of values of treated samples in relation to untreated samples.
Calculation of the growth rate over the total duration of the study for each concentration level and comparison of values of treated samples in relation to untreated samples.
The EC values were calculated (linear regression analysis) from the concentration-response relationship.
The LOEC was determined by comparing the means of the calculated biomass or growth rate of the various concentration levels with the control. The Dunnett's One-tailed T test was carried out at a 95% significance level.
The NOEC is the tested concentration immediately below the LOEC.

Results of the definitive test are compiled below:

Measured fluorescence (relative units)

Time (h)	Flask number	Concentration (mg/L)
		0 (control)	4000	1600	640	256	102
0	1	30	31	31	32	31	33
	2	31	32	34	33	31	35
	3	30	32	32	31	31	34
	no	0	0	0	0	0	0
24	1	130	98	130	130	150	130
	2	130	95	130	140	140	140
	3	130	95	130	140	150	140
	no	0	0	0	0	0	0
48	1	660	180	440	630	730	660
	2	700	190	420	670	750	680
	3	680	190	430	660	780	680
	no	0	0	0	0	0	0
72	1	3450	170	930	2720	3330	3380
	2	3500	150	780	2450	3800	3590
	3	3180	150	730	2350	3970	3630
	no	0	0	0	0	0	0

no = not inoculated

Cell density after 0 h, 24 h, 4$ h and 72 h

Time (h)	Flask number	Concentration (mg/L)
		0 (control)	4000	1600	640	256	102
0	1	1.5	1.6	1.6	1.6	1.6	1.7
	2	1.6	1.6	1.7	1.7	1.6	1.8
	3	1.5	1.6	1.6	1.6	1.6	1.7
	mean	1.5	1.6	1.6	1.6	1.6	1.7
24	1	6.6	5.0	6.6	6.6	7.6	6.6
	2	6.6	4.7	6.6	7.1	7.1	7.1
	3	6.6	4.8	6.6	7.1	7.6	7.1
	mean	6.6	4.9	6.6	7.0	7.5	7.0
48	1	33.6	6.2	22.4	32.1	37.2	33.6
	2	35.7	9.7	21.4	34.2	38.2	34.7
	3	34.7	9.7	21.9	33.6	39.8	34.7
	mean	34.7	9.5	21.9	33.3	38.4	34.3
72	1	175.9	8.7	47.4	138.7	169.8	172.3
	2	178.4	7.6	39.8	124.9	193.7	183.0
	3	162.1	7.6	38.7	119.8	202.4	185.1
	mean	172.1	8.0	42.0	127.8	118.6	180.1

Calculation of biomass and inhibition of biomass after 72h

Parameter	Flask number	Concentration (mg/L)
		0 (control)	4000	1600	640	256	102
Biomass (rel)	1	124	15	49	104	126	122
	2	128	14	44	100	138	129
	3	119	14	44	97	145	130
	mean	120	14	45	100	136	127
Inhibition (%)		0.0	88.4	63.2	19.0	-10.3	-2.9

 

Calculation of growth rate and inhibition of growth rate after 72h

Parameter	Flask number	Concentration (mg/L)
		0 (control)	4000	1600	640	256	102
Growth rate (rel)	1	0.066	0.024	0.047	0..062	0.065	0.064
	2	0.066	0.021	0.044	0.060	0.067	0.064
	3	0.065	0.021	0.044	0.060	0.067	0.065
	mean	0.065	0.022	0.045	0.061	0.066	0.064
Inhibition (%)		0.0	66.1	31.4	7.5	-1.4	1.4

 

Validity criteria fulfilled:

yes

Conclusions:

The 72-hour ErC50 (growth rate), EbC50 (integrated biomass) for D. subspicatus exposed to the test material under static conditions were 2616 and 1217 mg/L, respectively. The NOEC for biomass and growth rate was 256 mg/l.

Executive summary:

Desmodesmus subspicatus was exposed to test material at nominal concentrations of 102, 256, 640, 1600 and 4000 mg/L in a static 72 -hour toxicity test carried out according to OECD 201 guidelines. The study was reliable (Klimish 1) and conducted by GLP standards. The test design included an untreated control comprising untreated algal growth medium only. Analytical concentrations were verified at test initiation and termination (72h) and measured concentrations were 91 - 106% of nominal. The 72 -hour ErC50 and EbC50 endpoints determined were 2616 and 1217 mg/L, respectively. The corresponding 72hr NOEC, based on inhibition of specific growth rate or inhibition of biomass was 256 mg/L.

Description of key information

The 72-hour ErC50 (growth rate), EbC50 (integrated biomass) for D. subspicatus exposed to the test material under static conditions were 2616 and 1217 mg/L, respectively. NOEC for biomass and growth rate was 256 mg/l.

Key value for chemical safety assessment

EC50 for freshwater algae:

1 217 mg/L

EC10 or NOEC for freshwater algae:

256 mg/L

Additional information

Desmodesmus subspicatuswas exposed to test material at nominal concentrations of 102, 256, 640, 1600 and 4000 mg/L in a static 72 -hour toxicity test was carried out according to OECD 201 guidelines. The study was reliable (Klimish 1) and conducted by GLP standards. The test design included an untreated control comprising untreated algal growth medium only. Analytical concentrations were verified at test initiation and termination (72h) and measured concentrations were 91 - 106% of nominal. The 72 -hour ErC50 and EbC50 endpoints determined were 2616 and 1217 mg/L, respectively. The corresponding 72hr NOEC, based on inhibition of specific growth rate or inhibition of biomass, was 256 mg/L.