3-methyl-2-pent-2-enylcyclopent-2-enone

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:

March 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study done to guideline, in compliance with GLP

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

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Calibration solutions were injected in duplicate. Test samples and procedural recovery samples were analysed by single injection.

Vehicle:

no

Test organisms (species):

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

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Nominal and measured concentrations:

Nominal: 10, 18, 32, 56 and 100 mg/L

Details on test conditions:

Exposure was performed in airtight closed vessels as the test substance was possibly volatile. The growth medium (M2) was adjusted to prevent inhibition of growth due to the restriction of gaseous exchange. Additional sodium bicarbonate was added to the culture medium to provide a source of carbon dioxide for algal growth.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

38 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

18 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

19 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

8.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

The actual concentrations were at the level of nominal (96-108%) at the start of the test and remained stable during the test (90-100% of initial). Consequently, the effect parameters were reported in terms of nominal concentrations.
It should be noted that the NOEC for yield inhibition could not be determined because statistically and biologically significant effects were observed at all concentrations tested. Instead, the EC10 was calculated as an equivalent alternative.

Results with reference substance (positive control):

This reference test was carried out to check the sensitivity of the test system used by WIL Research Europe to Potassium dichromate (Merck, Art. 1.04864, Batch K44879664). Closed test vessels were used as to mimic testing a volatile test article and results were compared with standard ‘open’ systems.
The EC50 for growth rate inhibition (72h-ERC50) was 1.5 mg/l with a 95% confidence interval ranging from 1.4 to 1.7 mg/l. The historical ranges for growth rate inhibition using standard ‘open’ systems range between 0.82 and 2.3 mg/l. Hence, the 72h-ERC50 for the present test in closed systems is within the historical range.
The EC50 for yield inhibition (72h-EYC50) was 0.41 mg/l with a 95% confidence interval ranging from 0.38 to 0.44 mg/l. The historical ranges for yield inhibition using standard ‘open’ systems lie between 0.43 and 1.1 mg/l. Hence, the 72h-EYC50 for the present test in closed systems was just below this range.
It was concluded that the sensitivity of algae exposed in closed test systems towards Potassium dichromate was not significantly different from the sensitivity of algae exposed in standard ‘open’ reference studies during the past years.

The 72h-NOEC for yield inhibition could not be determined.

Validity criteria fulfilled:

yes

Executive summary:

Under the conditions of the present study with Pseudokirchneriella subcapitata, the EC50 for growth rate inhibition (72h-ERC50) was 38 mg/l with a 95% confidence interval ranging from 36 to 41 mg/l.

The EC10 for growth rate inhibition (72h-ERC10) was 18 mg/l with a 95% confidence interval ranging from 15 to 20 mg/l.

The EC50 for yield inhibition (72h-EYC50) was 19 mg/l with a 95% confidence interval ranging from 18 to 20 mg/l.

The EC10 for yield inhibition (72h-EYC10) was 8.8 mg/l with a 95% confidence interval ranging from 7.4 to 9.9 mg/l.

The 72h-NOEC for growth rate was 10 mg/l. The 72h-NOEC for yield inhibition could not be determined.

The preferred observational end point in this study is algal growth rate inhibition because it is not dependent on the test design (ECHA guidance Chapter R.7b v1.1). The EU CLP regulation (No 1272/2008 and its adaption 286/2011) also states that classification should be based on the ErC50. The preferred observational endpoint in long-term studies is the EC10 value because it is derived from the dose response curve. In contrast the NOEC depends on the experiment design (e.g. the concentrations used in the test). Thus the 72-h EC50 and EC10 based on growth rate are used for classification purposes.

Description of key information

ErC10 (72 h) 18.0 mg/L (nominal, OECD 201, P. subcapitata)

ErC50 (72 h) 38.0 mg/L (nominal, OECD 201, P. subcapitata)

Key value for chemical safety assessment

EC50 for freshwater algae:

38 mg/L

EC10 or NOEC for freshwater algae:

18 mg/L

Additional information

There is one GLP-study available, in which the toxicity of (Z)-3-methyl-2-(pent-2-en-1-yl)cyclopent-2-enone (CAS 488-10-8) to aquatic algae was assessed according to the OECD guideline 201.

In a static test, Pseudokirchneriella subcapitata at an initial cell density of 10^4 cells/mL was exposed to the nominal concentrations of 10, 18, 32, 56, and 100 mg/L test item for 72 h. The actual test item concentrations were analytically determined at the beginning and end of the test by GC analysis.

The measured test item concentrations were 96-108% of the nominal at the start of the test and remained stable throughout the test (90-100% of initial at test end). After 72 h growth inhibition was observed and resulted in an ErC10 (72 h) of 18.0 mg/L and an ErC50 (72 h) of 38.0 mg/L (nominal, OECD 201, P. subcapitata).