2-naphthol

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:

05.02.2018 - 22.03.2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Remarks:

For the determination of the growth curve not the cell amount was used, but the fluorescence. In a pre-test the correlation of cell amount and fluorescence was confirmed.

GLP compliance:

no

Remarks:

accredited by DAkkS (Deutsche Akkreditierungsstelle)

Analytical monitoring:

no

Details on sampling:

A stock solution was prepared with the test item. Different dilutions with ultrapure water were prepared thereof.
50 mL-test preparations contained 40 ml of the related dilution as well as 5 ml algal medium and 5 ml algal culture (consisting of algal medium and Desmodesmus subspicatus CHODAT). The tests were performed in duplicate over a 72 h period of time.

Vehicle:

yes

Remarks:

water

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

20 – 22 °C

Nominal and measured concentrations:

3,0 mg/l, 6,0 mg/l, 12 mg/l, 24 mg/l and 30 mg/l

Details on test conditions:

In pre-tests it was found out that a direct correlation of growth rate and measurable fluorescence exists. Hence, the measurement of the fluorescence of all samples was performed using a fluorescence measuring device (Kontron) after 0, 24, 48 and 72 h.

Reference substance (positive control):

yes

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

5.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: fluorescence

Table 2: Fluorescence of all test samples with beta-naphthol and control (=0 mg/l) in 72 h

concentration [mg/l]	fluorescence
	0 h			24 h			48 h			72 h
	I	II	mean	I	II	mean	I	II	mean	I	II	mean
0	6,6	6,1	6,35	10,9	10,5	10,7	12,7	12,7	12,7	16,8	16,7	16,8
3	6,4	6,0	6,20	9,3	8,2	8,8	9,3	9,6	9,5	13,7	12,1	12,9
6	9,3	9,1	9,20	10,5	10,0	10,3	11,3	12,1	11,7	13,1	13,5	13,3
12	9,2	9,3	9,25	10,4	10,5	10,5	10,9	11,0	11,0	11,7	12,2	12,0
24	10,0	9,7	9,85	11,9	11,6	11,8	11,9	11,8	11,9	12,3	12,1	12,2
30	10,3	9,9	10,10	12,1	12,6	12,4	10,5	12,1	11,3	11,1	13,4	12,3

Table 3: growth rate of Desmodesmus subspicatus CHODAT at diffrerent concentrations of ß-Naphthol in relation to control samples (= 100%)

concentration of the sample [mg/l]	growth rate in 72 h Desmodesmus sub-spicatus [%]
3	62,55
6	54,99
12	34,36
24	9,02
30	0,00

Validity criteria fulfilled:

not specified

Conclusions:

The toxicity of 2-naphthol to algae was investigated in a study acc. to OECD Guideline 201 (Alga, Growth Inhibition Test). The 72 h EC50 was determined to be 5,8 mg/L (based on recalculated initial concentrations).

Executive summary:

The toxicity of beta-naphthol to algae was investigated in a study acc. to OECD Guideline 201 (Alga, Growth Inhibition Test).

For the hazard and risk assessment the effect concentration of EC₅₀ (72 h) = 5,8 mg/l based on the growth rate should be used.

Description of key information

A short-term toxicity study to determine the aquatic toxicity of 2-naphthol to freshwater unicellular algae (Desmodesmus subsoicatus) was performed in accordance with OECD Test Guideline 201.

In pre-tests it was found that a direct correlation of growth rate and measurable fluorescence exists.  Hence, the measurement of the fluorescence of all samples was performed using a fluorescence measuring device (Kontron) after 0, 24, 48 and 72 h.

The following concentrations were used in the definitive study: 0, 3, 6, 12, 24 and 30 mg/L.

The EC50 (72h) for 2-naphthol was 5.8 mg/L (based on recalculated initial concentrations).

 

Key value for chemical safety assessment

EC50 for freshwater algae:

5.8 mg/L