Reaction mass of decyl acrylate and octyl acrylate

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:

2017-02-24 to

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Samples were taken from all test concentrations, from the control and from the satellite vessels at the start of the test and after 72 hours of exposure.

Vehicle:

no

Details on test solutions:

Due to the test item characteristics test solutions were prepared from a saturated stock solution prepared using slow-stirring conditions described in the OECD 123 guideline. This method used a special temperature-controlled glass-jacketed test vessel (around 1000 mL of capacity) with a sampling tap at the lower end and a magnetic stir bar at its bottom. A known volume of test medium (1000 mL) was first poured into the flask, then a known quantity of test item (11.36 µL) was gently added at the surface of medium. The solution was stirred at 20°C with a magnetic stir bar at a speed avoiding the formation of an emulsion. A speed of approximately 200/250 rpm was set up in order to create a vortex depth of around 0.5 cm: the aqueous phase was kept under stirring during approximately 24 hours, and then drawn off as a clear solution after a rest phase without agitation. Tests solutions were then prepared from dilutions of this saturated solution.

Test organisms (species):

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

Details on test organisms:

The test organism used for the study was Pseudokirchneriella subcapitata, Strain No. CCAP 278/4, supplied by the Culture Centre of Algae and Protozoa (Ambleside, UK).

Transfers of P. subcapitata were made regularly to provide suitable subcultures. The algae were cultivated under standardized conditions as described in Annex 2 of the OECD 201 guideline.

The quality of the stock culture was checked for the absence of micro-organisms and deformed or abnormal cells under microscopic observation before use.

Four days before the start of the exposure, two pre-cultures were prepared by inoculating sufficient cells from the algal stock culture to the growth medium to obtain a low cell density, e.g. 5*10^3 cells/mL to 10^4 cells/mL for pre-culturing, in order to maintain exponential growth until the start of the test. The pre-cultures were incubated under the same conditions as those used for the test cultures. Only one of the two pre-cultures was used to inoculate the test flasks for the study. The second one was only to be used if the first one was damaged.

At the beginning of the test, the cell density of the pre-culture was determined. The result was used to calculate the volume to be introduced into each test flask in order to obtain an initial cell concentration of 5*10^3 cells/mL as recommended in the OECD 201 guideline.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

Temperature was maintained at 23 ± 1°C: range from 22.9 to 23.3°C (mean: 23.1°C)

pH:

0h: 7.8 - 7.9
72h: 7.7 - 7.8

Dissolved oxygen:

0h: 8.5 - 8.9 mg/L
72h: 8.2 - 8.4 mg/L

Nominal and measured concentrations:

Nominal concentrations (% v/v saturated solution): 0 (Control), 5.0, 9.5, 17.0, 30.5, 55.5, 100.0
Geometric means of measured concentrations: 0 (Control), 0.01, 0.03, 0.04, 0.05, 0.07, 0.10

Details on test conditions:

The incubation was conducted in a phytoculture cabinet that allows test flasks to be incubated under precise conditions: temperature was set to 23 ± 1°C; flasks were continuously shaken with a rotation speed at around 100 rpm and constantly illuminated by fluorescent tubes between 6,000 and 10,000 lux.

Test vessels were made of glass bottles (120 mL capacity) capped with cellulose bungs. They were filled with a volume of 50 mL.

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.07 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

not determinable

Remarks:

Maximum observed effect: 21.1%

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.04 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Yield

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.09 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Yield

Results with reference substance (positive control):

The sensitivity of the test system and the methodology are evaluated every two months by performing an algal growth inhibition test on potassium dichromate. The latest value of ErC50 obtained in March 2017 was 1.41 mg/L.

According to the ISO 8692 standard, 72h-ErC50 obtained from an inter-laboratory exercise on potassium dichromate was in the range from 0.65 to 1.73 mg/L.

The appearance of the test solutions was visually checked at the beginning and at the end of the test. Solutions were found to be clear, no precipitation was observed at the end of the test.

 

Microscopic observation confirmed that the algae appeared "normal" at the end of the test: the normal shape of P. subcapitata algae is a crescent shaped cell with an average length of 5-10 µm.

 

Chemical analysis of test samples taken at 0 and 72 h indicated that concentrations of the test item were not maintained over the 72h test period (i.e. deviation > 20%). As a consequence, the stability of the substance was not confirmed over the test period; geometric means of measured concentrations were thus used to determine EC10 and EC50.

 

The results (growth rate) demonstrated that algal growth was inhibited from -1.68% at the lowest concentration (i.e. 5% of dilution) to 21.1% at the highest tested concentration (100% of saturation).

Validity criteria fulfilled:

yes

Conclusions:

This study was designed to determine the effects of the test item on the growth of Pseudokirchneriella subcapitata in a 72-hour test according to the OECD 201 Guideline.

Due to the test item characteristics test solutions were prepared from a saturated stock solution prepared using slow-stirring conditions described in the OECD 123 guideline.

Chemical analysis of the test item showed the instability of the substance over the 72-hour test period. Based on these results, the exposure concentrations were based on the geometric mean of measured concentrations.

GROWTH RATE INHIBITION:
72h-EC10 = 0.07 (95% Confidence Interval: 0.07 - 0.08)
72h-EC50 = Not determined due to mathematical reasons or inappropriate data
YIELD:
72h-EC10 = 0.04 (95% Confidence Interval: 0.04 - 0.05)
72h-EC50 = 0.09 (95% Confidence Interval: 0.08 - 0.09)

Executive summary:

This study was designed to determine the effects of the test item on the growth of Pseudokirchneriella subcapitata in a 72 -hour test according to the OECD 201 Guideline.

 

Due to the test item characteristics, test solutions were prepared from asaturated stock solution prepared using slow-stirring conditions described in the OECD 123 guideline.

 

The results are reported as growth rate and yield inhibitions. The concentrations that result in a 10 and 50% reduction in growth rate (72h-ErC10 and 72h-ErC50, respectively) and yield (72h-EyC10 and 72h-EyC50, respectively) were determined.

 

Chemical analysis of the test item showed the instability of the substance over the 72-hour test period. Based on these results, the exposure concentrations were based on the geometric mean of measured concentrations.

GROWTH RATE INHIBITION:

72h-EC10 = 0.07 (95% Confidence Interval: 0.07 - 0.08)

72h-EC50 = Not determined due to mathematical reasons or inappropriate data

YIELD:

72h-EC10 = 0.04 (95% Confidence Interval: 0.04 - 0.05)

72h-EC50 = 0.09 (95% Confidence Interval: 0.08 - 0.09)

The test met the validity criteria of the test guideline detailed as follows:

• The biomass in the control cultures increased exponentially by a factor of 99.9 within the 72-hour test period (required: at least 16-fold)
• The mean coefficients of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3) in the control cultures were less than or equal to 19.7% (required: < 35%)
• The coefficient of variation of average specific growth rates during the whole test period in the control cultures was 1.6% (required: < 7%)

Description of key information

The 72h-EC10 (growth rate inhibition) determined from data generated by a test performed according to OECD Test Guideline 201 was 0.04 mg/L for Pseudokirchneriella subcapitata.

The 72h-EC50 (growth rate inhibition) was not determined due to mathematical reasons and is considered to be greater than the highest tested rate (0.10 mg/L) as the maximum observed inhibition effect was 21.1% compared to the control. As a conservative approach, the EC50 value used for chemical safety assessment is considered to be equal to 0.10 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.1 mg/L

EC10 or NOEC for freshwater algae:

0.04 mg/L