Ethoxyquin

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

Peer-reviewed assessment report (attached in section 13)

Qualifier:

according to guideline

Guideline:

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

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

not specified

GLP compliance:

yes

Test organisms (species):

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

Test type:

static

Water media type:

freshwater

Total exposure duration:

72 h

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

6.1 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 16 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

2.3 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

other: biomass and growth rate

Conclusions:

The study was conducted according to OECD Proposal for Updating Guideline 201 and EU Directive C.3 Guideline on ethoxyquin (CAS 91-53-2) itself. The study is specified in a draft assessment report and can be considered scientifically reasonable with no deficiencies in documentation or deviations from the guidelines. Hence, the validity criteria were met and the results can be considered as reliable to assess the toxicity of the test item towards pseudokirchneriella subcapitata.
Short term toxicity to algae was tested in a static test design, the 72-hour EC50 value for pseudokirchneriella subcapitata exposed to ethoxyquin was 6.1 mg/L, based on area under the growth curve (biomass).

Executive summary:

The 72-hour EbC50 value, based on area under the growth curve (biomass), was 6.1 mg/L, with a 95 % confidence interval of 4.7 and 7.9 mg/L. The 72-hour ErC50 value, based on growth rate, was > 16 mg/L, the highest concentration tested. The 72-hour NOEC, based on effects on biomass and growth rate, was 2.3 mg/L.

Description of key information

Toxicity to aquatic algae: NOEC (72 h) = 2.3 mg/L (biomass and growth rate), LOEC = 4.6 mg/L EbC50 (72 h) = 6.1 mg/L, (biomass), Er50 (72 h) > 16 mg/L (growth rate) for Pseudokirchnerella subcapitata (OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:

6.1 mg/L

EC10 or NOEC for freshwater algae:

2.3 mg/L

Additional information

There is a valid, peer-reviewed OECD 201 guideline study without relevant deviations on ethoxyquin available, assessed with Klimisch 2. In this study, the following values were determined: NOEC (72 h) = 2.3 mg/L (biomass and growth rate), LOEC = 4.6 mg/L EbC50 (72 h) = 6.1 mg/L, (biomass), Er50 (72 h) > 16 mg/L (growth rate) for Pseudokirchnerella subcapitata. The results can be considered as sufficiently reliable to assess the toxicity of ethoxyquin to aquatic algae. With regard to the CLP Regulation 1272/2008, the test item can be regarded as non-hazardous to the aquatic environment.