Octane-1,2-diol

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Fully adequate for assessment: According to international guideline(s); GLP-compliant with the exception of the analytical measurements; performed in recognized contract research organization; deemed scientifically acceptable based on results.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

; 2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)

Version / remarks:

; 2004

Deviations:

no

GLP compliance:

yes

Remarks:

except TOC analyses

Analytical monitoring:

yes

Details on sampling:

- Concentrations: test start: stock solution (250 mg/L); test end: 200, 100 and 50 mg/L (without algae)
- Sample storage conditions before analysis: samples were stored frozen.

Details on test solutions:

A stock solution of 250 mg/L was prepared in test medium. The stock solution was stirred at approx. 35°C for 2 hours. The stock solution was used for preparing a dilution series of the test material in the test medium.
Increased temperature and stirring was applied since the results from a first test indicated incomplete dissolution of the test material in the test medium.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Strain: NIVA CHL 1

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

according to the test guidelines (no inividual values reported)

Test temperature:

23.1 ± 0.1 °C

pH:

The pH in the control flasks did not vary more than 1.5 units during the test (no inividual values reported).

Nominal and measured concentrations:

nominal: stock solution: 250 mg/L; test concentrations: 2.0, 5.0, 10, 20, 50, 100, and 200 mg/L
measured:
- stock solution: 76% of nominal
- test start: 76% of nominal
- test end: 81-86% of nominal

For details see Table 2

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 250 mL wide neck glass flasks, fill volume 100 mL
- Aeration: continuous shaking (approx. 120 RPM)
- Initial cells density: approx. 6000 cells/mL (corresponding to 10 fluorescence units (FU))
- Control end cells density: >1000 FU
- No. of vessels per concentration (replicates): 3 flasks at each each concentartion with test substance and algae
- No. of vessels per control (replicates): 6 flasks with algae but no test substance
- No. of vessels for analytical monitoring (replicates): 1 flask at each concentration with test substance but no algae

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Photoperiod: constant illumination
- Light intensity and quality: approx. 3.5-7 x 10E15 quanta x cm-2 x sec-1; provided from a panel of fluorescence light

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations:
- at test start: particle counter and in vivo fluorescence in the control mixture
- after 24, 48 and 72 hours of incubation: in vivo fluorescence in the triplicate test flasks and the six controls

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.0-2.5

Reference substance (positive control):

yes

Remarks:

potassium dichromat

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

35 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

other: total organic carbon (TOC)

Basis for effect:

growth rate

Remarks on result:

other: 95% confidence limits not calculable

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

17 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

other: total organic carbon (TOC)

Basis for effect:

growth rate

Remarks on result:

other: 95% confidence limits not calculable

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

15 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

other: total organic carbon (TOC)

Basis for effect:

growth rate

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50: 0.91 mg/L, 95% confidence limts 0.77-1.08 mg/L (in line with the results obtained in an international ring test in 1981 (ISO 8692, 2004): 1.12 mg/L, 95% confidence limts 0.62-1.73 mg/L)

Reported statistics and error estimates:

EC values wer calculated by use of the computer program TOXEDO, ver. 1.5; VKI 1999.
The NOEC was estimated by use of variance analysis according to Dunnett's procedure.

Table 1 Inhibition of growth

 

Nominal concentration (initially measured)	Replicate	Growth rate (h^-1)	% Inhibition
2* (-)	R1	0.077	4
2* (-)	R2	0.079	1
2* (-)	R3	0.085	0
5 (-)	R1	0.081	0
5 (-)	R2	0.081	0
5* (-)	R3	0.079	1
10 (-)	R1	0.080	0
10 (-)	R2	0.083	0
10 (-)	R3	0.082	0
20 (-)	R1	0.078	2
20 (-)	R2	0.080	0
20 (-)	R3	0.082	0
50 (38)	R1	0.009	89
50 (38)	R2	0.060	25
50 (38)	R3	0.043	46
100 (76)	R1	0.055	31
100 (76)	R2	0.000	100
100 (76)	R3	0.000	100
200 (152)	R1	0.000	100
200 (152)	R2	0.000	100
200 (152)	R3	0.000	100

* This results was not included in the statistical calculation of the EC values

(-): not analysed

 

In the study, the total organic carbon content (TOC) has been measured in the stock solution at test start and in the three highest test solutions showing an effect at test end. The results of the chemical analysis have been reported as mg TOC/L (the start concentrations of the test solutions have been calculated based on the measured TOC of the stock solution). The TOC values measured in the test solutions at test end were in the range of 107-113% of the initial values. Based on this stability determination, in the report the endpoints are reported on the basis of the nominal concentrations of the test material. Actual test material concentrations have not been calculated based on the carbon content of the test material (calculated to be 0.657 mg C/mg chemical).

 

However, when calculating the TOC of the test solutions based on the carbon content of the test material it is evident that only 76% of the expected TOC was determined in the stock solution (see Table 2).

 

For the risk assessment the endpoints EC50, EC10 and NOEC as presented in the report have been recalculated based on the recalculated initial test material concentrations presented in Table 2.

 

The lower content measured in the stock solution together with the slightly higher values measured at test end indicate that the test material has not been completely dissolved (although increased temperature and prolonged stirring has been applied).

 

 

Table 2 Analytical results

 

Nominal conc.	Test start			Test end
	TOC	Test substance conc.*	% of nominal	TOC	Test substance conc.**	% of nominal	Stability (%)
(mg/L)	(mg/L)	(mg/L)		(mg/L)	(mg/L)
50	-	38	76	27	41	81	107
100	-	76	76	57	86	86	113
200	-	152	76	110	167	84	109
250***	125	190	76	-	-	-	-

 *: Calculated based on the carbon content of the test material (0.657 g C/g chemical) and on the TOC as measured in the stock solution.

**: Calculated based on the carbon content of the test material (0.657 g C/g chemical) and on the TOC as measured in the test solutions.

***: stock solution

-: not analysed/not applicable

Validity criteria fulfilled:

yes

Remarks:

ISO 8692: control growth rate >1.4/day, variation coefficient of control growth rates <5%, variation of pH in control flasks <1.5 units

Description of key information

effect values for growth rates of Pseudokirchneriella subcapitata, 0-72 h, based on initial measured concentrations (OECD 201, EU C.3):

EC50: 35 mg/L, NOEC: 15 mg/L, EC10: 17 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:

35 mg/L