o-cresol

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

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:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

according to guideline

Guideline:

other: DEV L9

Principles of method if other than guideline:

cell multiplication inhibition test

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

a stock solution was prepared; to achive the test concentrations a defined amount of the stock solution was dissolved

Test organisms (species):

Microcystis aeruginosa

Details on test organisms:

blue-green algae = cyanobacteria

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

8 d

Test temperature:

27°C

pH:

initial pH 7.0

Details on test conditions:

-stock solution for test medium: 248 mg NaNO3, 19.5 mg K2HPO4, 750 mg MgSO4 x 7 H2O, 360 mg CaCl2 x 2 H2O,
400 mg NaSiO3, 580 mg Na2CO3, 30 mg citric acid, 30 mg ferric (III) citrate, 100 mg Na2EDTA x 2 H2O dissolved in 1 l double-distilled water containing the trace elements as H3BO3, MnCl2, ZnSO4, CuSO4, Na2MoO4 and CoCl2.
-incubation of 10 ml test solution
-the experiment was carried out in duplicate dilution series
-the concentration of the algal suspension was measured turbidimetrically

Duration:

8 d

Dose descriptor:

other: TGK

Effect conc.:

6.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: cell multiplication

Details on results:

TGK = Toxicity threshold, determined at 1% effect compared to control

In the cited literature, the experiments were conducted with the species Microcystis aeruginosa and Scenedesmus quadricauda. In the OECD/ICCA HPV programm it was stated that it is unclear whether the algae S. quadricauda are within the exponential growth throughout the whole exposure period of 8 days. Accordingly, the study was assessed to be not reliable (reliability 3). However, the bluegreen algae Microcystis aeruginosa have a lower rate of reproduction compared to green algae and are still in the exponential growth rate under the experimental conditions after 8 d.

Validity criteria fulfilled:

not specified

Conclusions:

The toxicity of o-cresol to the blue-green algae Microcystis aeruginosa (Cyanaophyceae) was determined in a cell multiplication inhibition test according to the guideline DEV L9. The relevant 8d-NOEC (EC3) is 6.8 mg/L.

Executive summary:

The toxicity of o-cresol to the blue-green algae Microcystis aeruginosa (Cyanaophyceae) was determined in a cell multiplication inhibition test according to the guideline DEV L9. Test conditions were as follows: continuous light, 27°C, with or without neutralization. The pH of the neutralized test solution was 7. For the endpoint biomass at the end of the test an 8 day-toxicity threshold value of 6.8 mg/l was obtained (nominal concentration). This toxicological threshold can also be regarded as a NOEC- or an EC3-value. For this reason the NOEC value can be given as 6.8 mg/l.

Reference 2

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:

other: Test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

other: NEN-6506 (1980)

GLP compliance:

not specified

Analytical monitoring:

no

Vehicle:

not specified

Test organisms (species):

Selenastrum sp.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

26 +/- 3°C

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

75 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Validity criteria fulfilled:

not specified

Conclusions:

With a growth inhibition test according to NEN-6506 (1980) on alga Selenastrum sp. a 96-hour EC50 of 100 mg/L based on nominal concentrations was determined for o-cresol.

Executive summary:

With a growth inhibition test according to NEN-6506 (1980) on alga Selenastrum sp. a 96-hour EC50 of 100 mg/L based on nominal concentrations was determined for o-cresol.

Description of key information

The toxicity of o-cresol to the blue-green algae Microcystis aeruginosa (Cyanaophyceae) was determined in a cell multiplication inhibition test according to the guideline DEV L9. The relevant 8d-NOEC (EC3) is 6.8 mg/L .

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

6.8 mg/L

Additional information

Concerning toxicity to aquatic algae there are several tests towards various species using o-cresol as test substance available.

The lowest toxicity value obtained with a blue-green algae is taken into account for further assessment.

The toxicity of o-cresol to the blue-green algae Microcystis aeruginosa (Cyanaophyceae) was determined in a cell multiplication inhibition test according to the guideline DEV L9. Test conditions were as follows: continuous light, 27°C, with or without neutralization. The pH of the neutralized test solution was 7. For the endpoint biomass at the end of the test an 8 day-toxicity threshold value of 6.8 mg/l was obtained (nominal concentration). This toxicological threshold can also be regarded as a NOEC- or an EC3-value. For this reason the NOEC value can be given as 6.8 mg/l.

With a growth inhibition test according to a dutch national standard method NEN-6506 (1980) on alga Selenastrum sp. a 96-hour EC50 of 100 mg/L based on nominal concentrations was determined for o-cresol.