p-cresol

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:

1998-03-03 - 1998-03-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Samples were taken at the beginning (0 hours) and during the experiment (24 hours and 48 hours) until the end of trial (72 hours) of each concentration group triplicate.
Prior to analysis the algal cells were removed by centrifugation (2000rpm, 20 minutes).

Vehicle:

no

Details on test solutions:

Six concentrations: 5.3 mg/L, 9.5 mg/L, 17.1 mg/L, 30.9 mg/L, 55.6 mg/L and 100 mg/L were tested.

The test substance was dissolved in medium to prepare the α2% solution, which was sterilized by filtration to prepare a stock solution of the test substance. Each test solution was then prepared by adding the test substance stock solution to a filter-sterilized medium. Four test containers were used for each lighting area: One for pH measurement, analysis of test solution and cell number. Additionally medium was used as a control group. The test solution is colorless and transparent, and no precipitation is seen.

Test organisms (species):

Selenastrum sp.

Details on test organisms:

Selenastrum capricornutum unicellular green algae were used.
Strain ATCC-22662 was obtained from American Type Culture Collection, and aseptically subcultured in own research section.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

23 +/- 2°C

Temperature of algae culture test vessel during 72 hours of exposure period is 22.1 ~ 22.8 ° C, the average temperature was 22.3 ° C

pH:

Medium indicated in the OECD chemicals test guideline for pre-culture and testing of both were prepared and used in sterile. During the exposure period, the adjustment of pH was not carried out.

The pH of the test solution is a 7.3 to 7,6 during the beginning of the exposure, at the end of the study was 7.4 to 8.4.

Salinity:

not applicable

Nominal and measured concentrations:

5.3 mg/L, 9.5 mg/L, 17.1 mg/L, 30.9 mg/L, 55.6 mg/L and 100 mg/L (nominal concentration)

Details on test conditions:

Test container: 300 mL volume glass-made Erlenmeyer flask (with the air permeability of the silicon plug).
Algae culture test equipment: Ito Seisakusho AGP-150RL
Initial cell concentration: 1*10^4 cells/mL

Reference substance (positive control):

yes

Remarks:

Test with reference material (potassium dichromate, reagent grade) for a 72h growth inhibitory concentration (EbC50) was made. The retreived EbC50 = 41 mg/L.

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

23 mg/L

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

"area under the growth curve"

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

9.5 mg/L

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

"area under the growth curve"

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

17.1 mg/L

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

48.4 mg/L

Conc. based on:

test mat.

Basis for effect:

growth rate

Reported statistics and error estimates:

Probit method, equal variance test (Bartlett), ANOVA and Dunnet method were used. Oita Univ Yoshimasa Yoshioka Programming that has been developed in order to calculate the EC50, LC50, NOEC of ecological effects test by Manabu Faculty of Education Professor. We were using a ram [EcoTox-Statics (Version1.0β version RL4)].

A percentage of the nominal concentration (5.3 ~ 100.Omg / L), the exposure at the start is 88.7 to 106.0%, exposure for 72 hours was 92.5 to 103.7%. Since the measured concentration at the start of exposure was within ± 20% of nominal concentration the nominal concentration was used in the calculation of the test results.

Validity criteria fulfilled:

yes

Conclusions:

Toxicity to alga Pseudokirchnerella subcapitata (reported as Selenastrum capricornutum) was conducted according to OECD-Guideline 201. After 72 hours of exposure a NOEC (growth rate) of 17.1 mg/L and a ErC50 (growth rate) of 48.4 mg/L were obtained. Additionally, a NOEC (biomass, i.e. "area under growth curve") of 23.0 mg/L and a EbC50 (biomass, i.e. "area under growth curve") of 48.4 mg/L were determined.

Executive summary:

Toxicity to alga Pseudokirchnerella subcapitata (reported as Selenastrum capricornutum) was conducted according to OECD-Guideline 201. After 72 hours of exposure a NOEC (growth rate) of 17.1 mg/L and a ErC50 (growth rate) of 48.4 mg/L were obtained. Additionally, a NOEC (biomass, i.e. "area under growth curve") of 23.0 mg/L and a EbC50 (biomass, i.e. "area under growth curve") of 48.4 mg/L were determined.

Description of key information

The toxicity of p-cresol to the algae Pseudokirchnella subkapitata (former name Selenastrum capricornutum) was determined according to OECD TG 201 (1984) yielding an 72 h-EbC50 of 23 mg/l and an NOEC of 9.5 mg/l (both related to biomass) were determined.

Key value for chemical safety assessment

EC50 for freshwater algae:

23 mg/L

EC10 or NOEC for freshwater algae:

9.5 mg/L

Additional information

The effects of p-cresol on the the green alga Scenedemus subspicatus was also tested by a cell multiplication inhibition test (Kuehn and Pattard 1990). The experiment wass carried out according to a national standard procedure, DIN 38412, part 9. Based on nominal cincentrations a 48h-EC50 of 21 mg/l and an EC10 of 4.6 mg/l (both related to growth rate) were determined.